|Abstracts on Global Climate Change|
Day-to-day variation in sea-surface temperature reduces sooty tern Sterna fuscata foraging success on the Great Barrier Reef, Australia
Erwin, CA Congdon, BC
MARINE ECOLOGY-PROGRESS SERIES 331: 255-266
Many seabird species threatened by global climate change are found mainly or exclusively in tropical regions. A shortage of long-term data linking climatic variation, oceanography and tropical seabird reproductive biology at both within- and between-season temporal scales means that the potential impact of climate change on these species is largely unknown. The sooty tern Sterna fuscata, an almost ubiquitous tropical seabird, has been declining on the Great Barrier Reef (GBR), Australia, over the last 3 decades. We examined the relationship between sooty tern foraging success and sea-surface temperature (SST) at Michaelmas Cay over 2 consecutive breeding seasons. Consistent patterns were observed with significant negative relationships between day-to-day variation in SST and both the amount of food fed to chicks and the feeding frequency during the latter two-thirds of each breeding season. At the beginning of each breeding cycle, rapid changes in foraging success highlighted that other within-season mechanisms also influence sooty tern reproductive potential. Our results suggest a previously undescribed spatial and temporal link between SST and sooty tern reproduction. Combined with previous findings for the southern GBR, this suggests that SST variation can influence the foraging success of multiple tropical seabird species at a reef-wide scale and implies a significant negative effect of forecasted climatic changes on seabirds breeding on the GBR.
Sifting the future from the past: a personal assessment of trends impacting the Australian rangelands
RANGELAND JOURNAL 29:1 3-11
The fore-sighting exercise undertaken at the Australian Rangeland Society Conference at Port Augusta 10 years ago in 1996 developed four scenarios: ‘economic growth’, ‘best practice’, ‘extra green’ and ‘partial retreat’. These were later collapsed into two broad directions, ` looking out’ (the economic rewards generated by a full application of free market policies with rangeland enterprises having strong external linkages will result in production and management efficiencies which benefit the Australian economy) and ‘looking in’ (rangeland Australia and its human, economic and ecological resources will be best served by the development and maintenance of strong local communities in each rangeland region). It was anticipated that ` looking out’ would apply to only a few rangeland regions where pastoral production is highly valued and rangelands are resilient; ` looking in’ would apply to the majority of the rangelands where other values might outweigh pastoral production in the future and where the rangeland resource is considered less resilient. Given the world’s embrace of economic and trade globalisation, and the dominance in the federal sphere of one coalition government and one prime minister, it seems inevitable that across Australia the last 10 years were dominated by the ` looking out’ direction, while many marginal rangelands had few options but to ‘look in’. The 1996 discussions failed to appreciate fully the importance in shaping today’s world of singular issues such as terrorism, global climate change, potential disease pandemics, the emergence of China and India and, in an Australian rangelands context, the continuing success of the northern beef industry. In the interim, rangelands science has produced an impressive underpinning of integrative information led both by industry investment and government funding. However, long-term resilience is still not assured in many areas of Australia’s rangelands. It continues to be outpaced by those four horsemen of the ( rangelands) apocalypse: the need for growth, periodic droughts, personal gain and introduced organisms. During the next 2 decades the rangelands will be buffeted by many of the same old issues and well as obvious emerging ones. Important human-centric ones will be the tension between European and Aboriginal demographic trends, the increased economic dominance of mining, tourism and defence in the rangelands, and the ‘sponge effect’ of successful towns and particular enterprises. Ecological and bio-physical issues will include carbon trading, energy generation, water catchments, weeds and diseases and agricultural incursions into the northern rangelands. The broad directions of ‘looking out’ and ‘looking in’ still retain some currency for today’s rangeland decision makers but are now embedded in far stronger and shifting currents that are frequently determined by global and national dynamics, rather than local issues. A distinguishing feature of the Australian rangelands is that they are still essentially intact (apart from their fauna) in a world context and may gain future ecological and economic advantage by remaining so. How to retain this status remains one of the great challenges for the next generation of Australian rangelanders.
Namaqualand - A brief overview of the physical and floristic environment
JOURNAL OF ARID ENVIRONMENTS 70:4 570-587
This paper provides a brief introduction to the physical environment of Namaqualand as well as an overview of patterns of plant diversity. The diverse array of parent material and geological processes that have shaped the region since the break up of Gondwanaland have created a complex, and sometimes dynamic physical environment, that is partly responsible for the patterns and processes observed in the biota today. The contemporary climate is characterised by relatively reliable, albeit low (50-250 mm pa), winter rainfall (> 60% winter precipitation) arriving between May and September. East of the central mountains, tropical thunderstorms penetrate the region in late summer (February April). The presence of the cold Atlantic Ocean in the west not only moderates temperatures throughout Namaqualand (mean max summer temperature < 30 degrees C), but also provides alternative sources of moisture in the form of coastal fog and heavy dew experienced in winter months. Recent analyses show that the flora of the Succulent Karoo is part of the Cape Floral Kingdom, now termed the Greater Cape Floral Kingdom. It is one of only two desert regions recognised as a global biodiversity hot-spot and contains an estimated 6356 plant species in 168 families and 1002 genera. Namaqualand, which comprises about one quarter of the area of the Succulent Karoo, contains about 3500 species in 135 families and 724 genera, with about 25% of this flora endemic to Namaqualand. This remarkable diversity, however, is not distributed evenly throughout the region, but is concentrated in many local centres of endemism usually associated either with quartzite mountain complexes or lag-gravel plains (quartz-patches). A major exception to the general pattern of centres of diversity is the true Fynbos vegetation of the highest Kamiesberg peaks where rainfall exceeds 400 mm pa. Suggested determinants of the region’s exceptional floral diversity include the complex physical environment, a unique past and present climate and the region’s diverse fauna, most notably insects. The challenge for the current inhabitants and scientists working in the region is to develop a better understanding of this ecosystem so that they will be equipped to deal with the challenges posed by the demands for land and the prospect of global climate change. (c) 2007 Elsevier Ltd. All rights reserved.
Namaqualand’s climate: Recent historical changes and future scenarios
MacKellar, NC Hewitson, BC Tadross, MA
JOURNAL OF ARID ENVIRONMENTS 70:4 604-614
A brief outline of some issues concerning global climate change research is presented before discussing local-scale changes in Namaqaland’s rainfall. Using a gridded data set derived through interpolation of station records, trends in observed rainfall for the period 1950-1999 are discussed. To assess what changes may occur during the 21st century, the downscaled results of six different General Circulation Model projections are presented. The historical trends show some clear spatial patterns, which depict regions of wetting in the central coastal belt and the north-eastern part of the domain, and extensive drying along the escarpment. Reasonably good agreement is shown by the different downscaled projections. These suggest increased late summer convective precipitation in the north-east, but extensive drying along the coast in early and mid winter consistent with the poleward retreat of rain-bearing mid-latitude cyclones. (c) 2006 Elsevier Ltd. All rights reserved.
Coastal flood risk analysis using landsat-7 ETM+ imagery and SRTM DEM: A case study of Izmir, turkey
Demirkesen, AC Evrendilek, F Berberoglu, S Kilic, S
ENVIRONMENTAL MONITORING AND ASSESSMENT 131:1-3 293-300
The Intergovernmental Panel on Climate Change (IPCC) reports an acceleration of the global mean sea-level rise (MSLR) in the twentieth century in response to global climate change. If this acceleration remains constant, then some coastal areas are most likely to be inundated by the year 2100. The ability to identify the differential vulnerability of coastlines to future inundation hazards as result of global climate change is necessary for timely actions to be taken. Yildiz et al. (Journal of Mapping, 17, 1 75, 2003) reported that the local MSLR in the city of Izmir rose at a rate of 6.8 +/- 0.9 mm year(-1) between 1984 and 2002. In this study, the spatial distribution of the coastal inundation hazards of Izmir region was determined using not only land-use and land-cover (LULC) types derived from the maximum likelihood classification of Landsat-7 Enhanced Thematic Mapper Plus (ETM+) multi-spectral image set but also the classification of the digital elevation model (DEM) acquired by the shuttle radar topography mission (SRTM). Coastal areas with elevations of 2 and 5 m above mean sea-level vulnerable to inundation were found to cover 2.1 and 3.7% of the study region (6,107 km(2)), respectively. Our findings revealed that Menemen plain along Gediz river, and the settlements of Karsiyaka, Alacati, Aliaga, Candarli and Selcuk are at high risk in order of decreasing vulnerability to permanent and episodic inundation by 2100 under the high MSLR scenarios of 20 to 50 mm year(-1).
Experimental studies on homogeneous charge CI engine fueled with LPG using DEE as an ignition enhancer
Jothi, NKM Nagarajan, G Renganarayanan, S
RENEWABLE ENERGY 32:9 1581-1593
Producing and using renewable fuels for transportation is one approach for sustainable energy future for the world. A renewable fuel contributes lesser global climate change. The present work reports on the utilization of liquified petroleum gas (LPG) as a primary fuel with diethyl ether (DEE) as an ignition enhancer in a direct injection diesel engine. LPG has a simpler hydrocarbon structure than conventional fuels. DEE is recently reported as a renewable fuel and to be a low-emission high-quality diesel fuel replacement. A single cylinder, four-stroke, water-cooled naturally aspirated DI diesel engine having rated output of 3.7 kW at 1500 rpm was used for the experiments. Measurements were made to study the performance, combustion and emissions characteristics. From the results, it is observed that, the brake thermal efficiency lower by about 23% at full load with a reduction of about 65% NO emission than the diesel operation. The maximum reduction in smoke and particulate emissions is observed to be about 85% and 89%, respectively, when compared to that of diesel operation, however an increase in CO and HC emissions was observed. (c) 2006 Elsevier Ltd. All rights reserved.
Periodic solutions for soil carbon dynamics equilibriums with time-varying forcing variables
Martin, MP Cordier, S Balesdent, J Arrouays, D
ECOLOGICAL MODELLING 204:3-4 523-530
Numerical models that simulate the dynamics of carbon in soil are increasingly used to improve our knowledge and help our management of the carbon cycle. Calculation of the long-term behavior of these models is necessary in many applications but encounters the difficulty of managing the periodic forcing variables, e.g. seasonal variations, such as carbon inputs and decomposition rates. This calculation is conventionally done by running the model over large time durations or by assuming constant forcing variables. Two methods, which make it possible to rapidly compute periodic solutions taking into account the time variations of these variables, are proposed. The first one works on discrete-time models and the second one on continuous-time models involving Fourier transforms. Both methods were tested on the Rothamsted carbon model (RothC), a discrete-time model which has also been given a continuous approximation, using realistic and unrealistic sets of time-varying forcing functions. Both methods provided an efficient way to compute the periodic solutions of the RothC model within the application domain of the model. Compared to running the discrete model to the equilibrium, reduction in the computational cost was of up to 95% at the expense of a maximum absolute error of 1% for the estimation of carbon stocks. For specific distributions of the forcing variables the use of Fourier transform of zero order, which was equivalent to assume constant forcing variables, led to a maximum absolute error of SS% in the estimation of the long-term behavior of the model. There, a Fourier transform of order higher than zero is required. (C) 2007 Elsevier B.V. All rights reserved.
Storage and release of fossil organic carbon related to weathering of sedimentary rocks
Copard, Y Amiotte-Suchet, P Di-Giovanni, C
EARTH AND PLANETARY SCIENCE LETTERS 258:1-2 345-357
The biogeochemical carbon cycle, which plays an undeniable role in global climate change, is defined both by the size of carbon reservoirs (such as the atmosphere, biomass, soil and bedrock) and the exchange between them of various mineral and organic carbon forms. Among these carbon forms, fossil organic carbon (FOC) (i.e., the ancient organic matter stored in sedimentary rocks) is widely observed in modem environments but is not included in the supergene carbon budget. Using a digitized map of the world and an existing model of CO2 consumption associated with rock weathering, we establish the global distribution of FOC stored in the first meter of sedimentary rocks and a first estimation of annual FOC delivery to the modem environment resulting from chemical weathering of these rocks. Results are given for the world’s 40 major river basins and extended to the entire continental surface. With a mean value of I 100 10(9) t, mainly controlled by shale distribution, the global FOC stock is significant and comparable to that of soil organic carbon (1500 10(9) t). The annual chemical delivery of FOC, estimated at 43 10(6) t yr(-1) and controlled by the areal distribution of shales and runoff is of the same order of magnitude as the FOC output flux to oceans. Chemical weathering of bedrock within the Amazon basin produces one-quarter of the total global flux of FOC derived from chemical weathering, and thus is expected to govern FOC release on a global scale. These results raise important questions concerning the role of FOC in the modem carbon cycle as well as the origin and the budget of carbon in soils and rivers. (C) 2007 Elsevier B.V. All rights reserved.
Simulated changes in active/break spells during the Indian summer monsoon due to enhanced CO2 concentrations: assessment from selected coupled atmosphere-ocean global climate models
Mandke, SK Sahai, AK Shinde, MA Joseph, S Chattopadhyay, R
INTERNATIONAL JOURNAL OF CLIMATOLOGY 27:7 837-859
The simulations by ten coupled GCMs under the Intergovernmental Panel on Climate Change Assessment Report-4 are used to study the implication of possible global climate change on active/break spells of the Indian summer monsoon (ISM). The validation of the mean daily cycle of the summer monsoon precipitation over the Indian core region and the spatial pattern of the ISM precipitation climatology with observation suggest that six models simulate fairly well, whereas four models differ from observation. Thus, the identification of activelbreak spells is confined to six models. The sensitivity to climate change has been assessed from two experiments, namely, 1% per year CO2 increase to doubling and 1% per year CO2 increase to quadrupling. The changes in the daily mean cycle and the standard deviation of precipitation, frequency, and duration of active/break spells in future climate change are uncertain among the models and at times among two experiments. The break composite precipitation anomalies strengthen and spread moderately (significantly) in the doubled (quadrupled) CO2 experiment. Copyright (c) 2006 Royal Meteorological Society.
Simulation of seasonal precipitation and raindays over Greece: a statistical downscaling technique based on artificial neural networks (ANNs)
Tolika, K Maheras, P Vafiadis, M Flocasc, HA Arseni-Papadimitriou, A
INTERNATIONAL JOURNAL OF CLIMATOLOGY 27:7 861-881
A statistical downscaling technique based on artificial neural network (ANN) was employed for the estimation of local changes on seasonal (winter, spring) precipitation and raindays for selected stations over Greece. Empirical transfer functions were derived between large-scale predictors from the NCEP/NCAR reanalysis and local rainfall parameters. Two sets of predictors were used: (1) the circulation-based 500 hPa and (2) its combination along with surface specific humidity and raw precipitation data (nonconventional predictor). The simulated time series were evaluated against observational data and the downscaling model was found efficient in generating winter and spring precipitation and raindays. The temporal evolution of the estimated variables was well captured, for both seasons. Generally, the use of the nonconventional predictors are attributed to the improvement of the simulated results. Subsequently, the present day and future changes on precipitation conditions were examined using large-scale data from the atmospheric general circulation model HadAM3P to the statistical model. The downscaled climate change signal for both precipitation and raindays, partly for winter and especially for spring, is similar to the signal from the HadAM3P direct output: a decrease of the parameters is predicted over the study area. However, the amplitude of the changes was different. Copyright (c) 2006 Royal Meteorological Society
Strontium isotope tracing of terrigenous sediment dispersal in the Antarctic Circumpolar Current: Implications for constraining frontal positions
Hemming, SR van de Flierdt, T Goldstein, SL Franzese, AM Roy, M Gastineau, G Landrot, G
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS 8: -
 The vigor of the glacial Antarctic Circumpolar Current (ACC) and the locations of frontal boundaries are important parameters for understanding the role of the Southern Ocean in global climate change. Toward the goal of understanding the locations of currents we present a survey of Sr isotope ratios in terrigenous sediments around the perimeter of Antarctica. The pattern of the variations within the modern ACC is used to suggest that terrigenous sediment from Antarctica is injected into the ACC via the Ross and Weddell gyres in the south. North of the main ACC the Sr isotopes reflect continental contributions from Africa, Australia-New Zealand, and South America. Along a transect northward from the Ross Sea, Sr isotope ratios show a decrease from higher values in the south ( Antarctic provenance) to lower values in the north ( provenance from New Zealand). This otherwise monotonic decrease is interrupted within the ACC by a “zigzag” to lower and then higher values, which accompanies minimum terrigenous flux. This zigzag requires contributions from two additional sediment sources beyond the main Antarctic and New Zealand end-members. The lower Sr isotope ratios are attributable to greater contributions from basaltic sources within the current, a consistent pattern around the ACC. The samples with higher Sr isotope ratios point to an additional contributor, possibly a wind-transported component from Australia. During the LGM there is a systematic geographical variation in the Sr isotope ratios, similar to that of the Holocene. A small offset of the zigzag to the north ( approximately 1 degrees-2 degrees) may indicate a small northward shift of the southern boundary of the ACC. More highly resolved data are required to test whether this northward shift is really significant and whether it applies to other ACC fronts during the LGM.
Dominant factors controlling glacial and interglacial variations in the treeline elevation in tropical Africa
Wu, HB Guiot, J Brewer, S Guo, ZT Peng, CH
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 104:23 9720-9724
The knowledge of tropical palaeoclimates is crucial for understanding global climate change, because it is a test bench for general circulation models that are ultimately used to predict future global warming. A longstanding issue concerning the last glacial maximum in the tropics is the discrepancy between the decrease in sea-surface temperatures reconstructed from marine proxies and the high-elevation decrease in land temperatures estimated from indicators of treeline elevation. In this study, an improved inverse vegetation modeling approach is used to quantitatively reconstruct palaeoclimate and to estimate the effects of different factors (temperature, precipitation, and atmospheric CO2 concentration) on changes in treeline elevation based on a set of pollen data covering an altitudinal range from 100 to 3,140 m above sea level in Africa. We show that lowering of the African treeline during the last glacial maximum was primarily triggered by regional drying, especially at upper elevations, and was amplified by decreases in atmospheric CO2 concentration and perhaps temperature. This contrasts with scenarios for the Holocene and future climates, in which the increase in treeline elevation will be dominated by temperature. Our results suggest that previous temperature changes inferred from tropical treeline shifts may have been overestimated for low-CO2 glacial periods, because the limiting factors that control changes in treeline elevation differ between glacial and interglacial periods.
Evidence for carbon sequestration by agricultural liming
Hamilton, SK Kurzman, AL Arango, C Jin, LX Robertson, GP
GLOBAL BIOGEOCHEMICAL CYCLES 21:2 -
 Agricultural lime can be a source or a sink for CO2, depending on whether reaction occurs with strong acids or carbonic acid. Here we examine the impact of liming on global warming potential by comparing the sum of Ca2+ and Mg2+ to carbonate alkalinity in soil solutions beneath unmanaged vegetation versus limed row crops, and of streams and rivers in agricultural versus forested watersheds, mainly in southern Michigan. Soil solutions sampled by tension indicated that lime can act as either a source or a sink for CO2. However, infiltrating waters tended to indicate net CO2 uptake, as did tile drainage waters and streams draining agricultural watersheds. As nitrate concentrations increased in infiltrating waters, lime switched from a net CO2 sink to a source, implying nitrification as a major acidifying process. Dissolution of lime may sequester CO2 equal to roughly 25 - 50% of its C content, in contrast to the prevailing assumption that all of the carbon in lime becomes CO2. The similar to 30 Tg/yr of agricultural lime applied in the United States could thus sequester up to 1.9 TgC/ yr, about 15% of the annual change in the U. S. CO2 emissions (12 Tg C/yr for 2002 - 2003). The implications of liming for atmospheric CO2 stabilization should be considered in strategies to mitigate global climate change.
Diversity and zonal distribution of arbuscular mycorrhizal fungi on the northern slopes of the Tianshan Mountains
Shi, ZY Chen, ZC Zhang, LY Feng, G Christie, P Tian, CY Li, XL
SCIENCE IN CHINA SERIES D-EARTH SCIENCES 50: Suppl. 1 135-141
The arbuscular mycorrhizal (AM) fungal status of the 20 most common plant species distributed in 4 vegetation types (meadow steppe, desert steppe, steppe desert and typical desert) on the northern slopes of the Tianshan Mountains was investigated. Samples of the plant species and their rhizosphere soils were collected from the 4 vegetation zones and examined to compare their mycorrhizal status, AM fungal spore densities, biovolumes, and community structures. 28 AM fungal species were isolated from the rhizosphere soils: of these, 5 belonged to Acaulospora, 1 to Archaeospora and 22 to Glomus. 5 AM fungi, Glomus aggregatum, G. claroideum, G. deserticola, G. etunicatum and G. sinuosum, were observed in all 4 zonal types. No significant differences were observed in mean proportion of root length colonized by AM fungi among the plant species within each zonal type. Comparing the 4 zonal types, Plantago minuta (84.5%) in steppe desert and Eremopyrum orientale (83.1%) in typical desert showed the highest root colonizatsion rates. AM fungal spore densities and biovolumes were significantly different in the different zonal types. AM fungal spore densities and biovolumes, species richness and diversity were highest in meadow steppe and lowest in typical desert.
Eustasy and sea water Sr composition: application to high-resolution Sr-isotope stratigraphy of Miocene shallow-water carbonates
Kroeger, KF Reuter, M Forst, MH Breisig, S Hartmann, G Brachert, TC
SEDIMENTOLOGY 54:3 565-585
Oceanic Sr-87/Sr-86-isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea-level change. The present study combines analysis of sequence stratigraphy and basin architecture with Sr-isotope stratigraphy in Miocene shallow-water sediments in southern Portugal and Crete (Greece). The common method is to use smoothed global sea water Sr-isotope reference curves but here a different approach is chosen. Instead, measured Sr-isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr. Transgressive intervals are characterized by increasing Sr-isotope ratios interpreted as corresponding to intensified silicate weathering as a consequence of deglaciation, while lowstand deposits have low Sr-isotope ratios. Comparison of Sr-isotope curves and sedimentary sequences in the studied basins with independent global delta O-18 data and data on global sea-level might suggest a general relationship, supporting a connection to global climate change. Because of these relationships, the method presented herein has a high potential for use in high-resolution age dating and is also applicable in shallow-water sediments.
The efficiency gap behind the Annex I parties under the Kyoto Protocol
INTERNATIONAL JOURNAL OF SUSTAINABLE DEVELOPMENT AND WORLD ECOLOGY 14:3 225-234
With the ratification of the Kyoto Protocol, an era of global efforts to combat climate change is beginning. Countries belonging to Annex I Parties are obligated to meet their target in reducing greenhouse gas (GHG) emissions. This paper broadens the scope of research to compare the performance between two groups, Annex 11 Parties and economies in transition (EIT) Parties (both of which are in the set of Annex I Parties), undertaking responsibilities for GHG emission reduction. This differs from the traditional application of evaluation and aims to identify inherent efficiency differences across systems, rather than separately from the potential inefficiency of individual countries. An efficiency gap was found between the group of Annex 11 Parties and the group of EIT Parties, by adjusting efficiency levels. Considering a reference set, efficient Annex 11 countries are referenced, both within their own group and within the EIT group; efficient EIT countries are only benchmarked within the group. The evidence provided can shed light on the function of joint implementation, that Annex I countries will cooperate to reduce GHG emissions, based on their common, but differentiated, responsibilities and capacity for global climate change.
Expert judgements on the response of the Atlantic meridional overturning circulation to climate change
Zickfeld, K Levermann, A Morgan, MG Kuhlbrodt, T Rahmstorf, S Keith, DW
CLIMATIC CHANGE 82:3-4 235-265
We present results from detailed interviews with 12 leading climate scientists about the possible effects of global climate change on the Atlantic Meridional Overturning Circulation (AMOC). The elicitation sought to examine the range of opinions within the climatic research community about the physical processes that determine the current strength of the AMOC, its future evolution in a changing climate and the consequences of potential AMOC changes. Experts assign different relative importance to physical processes which determine the present-day strength of the AMOC as well as to forcing factors which determine its future evolution under climate change. Many processes and factors deemed important are assessed as poorly known and insufficiently represented in state-of-the-art climate models. All experts anticipate a weakening of the AMOC under scenarios of increase of greenhouse gas concentrations. Two experts expect a permanent collapse of the AMOC as the most likely response under a 4xCO(2) scenario. Assuming a global mean temperature increase in the year 2100 of 4 K, eight experts assess the probability of triggering an AMOC collapse as significantly different from zero, three of them as larger than 40%. Elicited consequences of AMOC reduction include strong changes in temperature, precipitation distribution and sea level in the North Atlantic area. It is expected that an appropriately designed research program, with emphasis on long-term observations and coupled climate modeling, would contribute to substantially reduce uncertainty about the future evolution of the AMOC.
Thermal stress and coral cover as drivers of coral disease outbreaks
Bruno, JF Selig, ER Casey, KS Page, CA Willis, BL Harvell, CD Sweatman, H Melendy, AM
PLOS BIOLOGY 5:6 1220-1227
Very little is known about how environmental changes such as increasing temperature affect disease dynamics in the ocean, especially at large spatial scales. We asked whether the frequency of warm temperature anomalies is positively related to the frequency of coral disease across 1,500 km of Australia’s Great Barrier Reef. We used a new high-resolution satellite dataset of ocean temperature and 6 y of coral disease and coral cover data from annual surveys of 48 reefs to answer this question. We found a highly significant relationship between the frequencies of warm temperature anomalies and of white syndrome, an emergent disease, or potentially, a group of diseases, of Pacific reef- building corals. The effect of temperature was highly dependent on coral cover because white syndrome outbreaks followed warm years, but only on high (> 50%) cover reefs, suggesting an important role of host density as a threshold for outbreaks. Our results indicate that the frequency of temperature anomalies, which is predicted to increase in most tropical oceans, can increase the susceptibility of corals to disease, leading to outbreaks where corals are abundant.
Constructing regional scenarios for sustainable agriculture in European Russia and Ukraine for 2000 to 2070
Romanenko, IA Romanenkov, VA Smith, P Smith, JU Sirotenko, OD Lisovoi, NV Shevtsova, LK Rukhovich, DI Koroleva, PV
REGIONAL ENVIRONMENTAL CHANGE 7:2 63-77
This study estimates the consequences of climate change on cropland with and without implementation of adaptation measures, paying special attention to the maintenance of soil organic carbon (C) stocks. We examine the possibility for regional sustainable agricultural management practice that combines both maintenance and gain in soil carbon level with profit maximization. Future scenarios of Regional Agricultural Production Systems (RAPS) were constructed for 2000-2070 based on linking the effects of global climate change, predicted change in productivity parameters for the main agricultural crops, land-use and soil database parameters. The RAPS were used to examine profitability and feasibility of alternative agricultural scenarios, based on an economic model. A number of recommendations for decision making were proposed based on an assessment of the efficiency of adaptation in animal husbandry and in the crop production sector, after analysis of current percentage of perennial grass in rotation in comparison with future economic scenarios.
Modelling energy systems for developing countries
Urban, F Benders, RMJ Moll, HC
ENERGY POLICY 35:6 3473-3482
Developing countries’ energy use is rapidly increasing, which affects global climate change and global and regional energy settings. Energy models are helpful for exploring the future of developing and industrialised countries. However, energy systems of developing countries differ from those of industrialised countries, which has consequences for energy modelling. New requirements need to be met by present-day energy models to adequately explore the future of developing countries’ energy systems. This paper aims to assess if the main characteristics of developing countries are adequately incorporated in present-day energy models. We first discuss these main characteristics, focusing particularly on developing Asia, and then present a model comparison of 12 selected energy models to test their suitability for developing countries. We conclude that many models are biased towards industrialised countries, neglecting main characteristics of developing countries, e.g. the informal economy, supply shortages, poor performance of the power sector, structural economic change, electrification, traditional bio-fuels, urban-rural divide. To more adequately address the energy systems of developing countries, energy models have to be adjusted and new models have to be built. We therefore indicate how to improve energy models for increasing their suitability for developing countries and give advice on modelling techniques and data requirements. (c) 2007 Elsevier Ltd. All rights reserved.
Palau’s coral reefs show differential habitat recovery following the 1998-bleaching event
Golbuu, Y Victor, S Penland, L Idip, D Emaurois, C Okaji, K Yukihira, H Iwase, A van Woesik, R
CORAL REEFS 26:2 319-332
Documenting successional dynamics of coral communities following large-scale bleaching events is necessary to predict coral population responses to global climate change. In 1998, high sea surface temperatures and low cloud cover in the western Pacific Ocean caused high coral mortality on the outer exposed reefs of Palau (Micronesia), while coral mortality in sheltered bays was low. Recovery was examined from 2001 to 2005 at 13 sites stratified by habitat (outer reefs, patch reefs and bays) and depth (3 and 10 m). Two hypotheses were tested: (1) rates of change of coral cover vary in accordance with habitat, and (2) recovery rates depend on recruitment. Coral cover increased most in the sheltered bays, despite a low recruitment rate, suggesting that recovery in bays was primarily a consequence of remnant regrowth. Recruitment densities were consistently high on the wave-exposed reefs, particularly the western slopes, where recovery was attributed to both recruitment and regrowth of remnants. Recovery was initially more rapid at 10 m than 3 m on outer reefs, but in 2004, recovery rates were similar at both depths. Rapid recovery was possible because Palau’s coral reefs were buffered by remnant survival and recruitment from the less impacted habitats.
A maximum entropy method for combining AOGCMs for regional intra-year climate change assessment
Laurent, R Cai, XM
CLIMATIC CHANGE 82:3-4 411-435
This paper deals with different responses from various Atmosphere-Ocean Global Climate Models (AOGCMs) at the regional scale. What can be the best use of AOGCMs for assessing the climate change in a particular region? The question is complicated by the consideration of intra-year month-to-month variability of a particular climate variable such as precipitation or temperature in a specific region. A maximum entropy method (MEM), which combines limited information with empirical perspectives, is applied to assessing the probability-weighted multimodel ensemble average of a climate variable at the region scale. The method is compared to and coupled with other two methods: the root mean square error minimization method and the simple multimodel ensemble average method. A mechanism is developed to handle a comprehensive range of model uncertainties and to identify the best combination of AOGCMs based on a balance of two rules: depending equally on all models versus giving higher priority to models more strongly verified by the historical observation. As a case study, the method is applied to a central US region to compute the probability-based average changes in monthly precipitation and temperature projected for 2055, based on outputs from a set of AOGCMs. Using the AOGCM data prepared by international climate change study groups and local climate observation data, one can apply the MEM to precipitation or temperature for a particular region to generate an annual cycle, which includes the effects from both global climate change and local intra-year climate variability.
Response of macroinvertebrates to warming, nutrient addition and predation in large-scale mesocosm tanks
Feuchtmayr, H McKee, D Harvey, IF Atkinson, D Moss, B
HYDROBIOLOGIA 584: 425-432
There is increasing concern about the effect of climate change on aquatic systems. We examined changes in macroinvertebrate communities caused by increased temperature (3 degrees C above ambient during summer only and continuous 3 degrees C above ambient all year round), influences of fish (Gasterosteus aculeatus L.) and addition of nutrients ( nitrogen and phosphorus) in 48 large-scale (3000 l) tanks over a 2 year period. While numbers of Isopoda, Chaoborus, Corixidae, Ephemeroptera, Notonectidae and Odonata were reduced by the presence of fish, nutrient addition caused isopods, corixids, mayflies and odonates to increase in abundance. Impacts of temperature increase were surprisingly low, with only gastropods increasing in heated tanks, suggesting that, overall abundances of most macroinvertebrate taxa will not be severely affected by the predicted temperature rise. To determine if taxa were sampled representatively during the experiment, net sweep samples taken towards the end of the experiment were compared with final macroinvertebrate abundances when the complete contents of each tank were harvested. We found that net sweeping is an appropriate semi-quantitative method for most taxa in mesocosm tanks. However, mites, coleopteran adults and larvae, dipterans and Chaoborus were not adequately sampled. This might explain why we could not detect any treatment effects of temperature, fish or nutrients on mites, coleopterans and dipterans and calls for different sampling techniques for these taxa, especially in ponds with vegetation stands.
The evolution of climate change impact studies on hydrology and water resources in California
Vicuna, S Dracup, JA
CLIMATIC CHANGE 82:3-4 327-350
Potential global climate change impacts on hydrology pose a threat to water resources systems throughout the world. The California water system is especially vulnerable to global warming due to its dependence on mountain snow accumulation and the snowmelt process. Since 1983, more than 60 studies have investigated climate change impacts on hydrology and water resources in California. These studies can be categorized in three major fields: (1) Studies of historical trends of streamflow and snowpack in order to determine if there is any evidence of climate change in the geophysical record; (2) Studies of potential future predicted effects of climate change on streamflow and; (3) Studies that use those predicted changes in natural runoff to determine their economic, ecologic, or institutional impacts. In this paper we review these studies with an emphasis on methodological procedures. We provide for each category of studies a summary of significant conclusions and potential areas for future work.
Decade-centenary resolution records of climate changes in East Siberia from elements in the bottom sediments of lake Baikal for the last 150 kyr
Goldberg, EL Phedorin, MA Chebykin, EP Zolotarev, KB Zhuchenko, NA
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 575:1-2 193-195
High-resolution scanning Synchrotron Radiation X-ray Fluorescence Analysis (SRXFA) was applied to investigate the downcore distribution of elements in the sediments from Lake Baikal (East Siberia). The obtained multi-element time series reveal the presence of abrupt climate shifts in East Siberia which were synchronous with the abrupt warming events in the North Atlantic and Greenland (Dansgaard-Oeschges events (D/O) during the last ice age 24-75 kyr BP. We show here the set of climatic indicators reveals all globally known climate changes from dry and cool or glacial climates to humid and warm ones, which were recorded in Northern Atlantic and East Siberia both on the orbital and millennial time scales during the last 150 kyr. (c) 2007 Elsevier B.V. All rights reserved.
Peat archives from Siberia: Synchrotron beam scanning with X-ray fluorescence measurements
Phedorin, MA Bobrov, VA Zolotarevd, KV
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT 575:1-2 199-201
We used a new approach to measure the downcore distribution of some major and trace elements that record the Holocene history of peat-forming processes in peat from the Elovka mesotrophic swamp (West Siberia). The approach implies continuous non-destructive scanning of natural wet-core fragments under a sharp synchrotron beam combined with measurements of the excited X-ray fluorescence, in attempt to avoid errors due to the loss of volatiles abundant in peat. The obtained data are in good agreement with the results of the certified methods of neutron activation gamma-spectrometry (INAA) and classical SR XRF, though, as we expected, there is some discrepancy in the contents of volatiles (Br, Zn) which are most probably lost in INAA and/or in ignition. The precision of the suggested SR XRF scanning resolved the variability of 18 elements in the peat-core deposited during 0-8 kyr bp at no worse than 30 years in most cases. The distribution of the measured elements provided a clue to the evolution of peat deposition environments that controlled biogenic production, aerosol input, post-depositional processes, and Ca mineralization associated with pore water circulation in soil during the non-mesotrophic stages of the swamp history. (c) 2007 Elsevier B.V. All rights reserved.
Remote monitoring of spatial and temporal surface soil moisture in fire disturbed boreal forest ecosystems with ERS SAR imagery
Bourgeau-Chavez, LL Kasischke, ES Riordan, K Brunzell, S Nolan, M Hyer, E Slawski, J Medvecz, M Walters, T Ames, S
INTERNATIONAL JOURNAL OF REMOTE SENSING 28:10 2133-2162
Due to the large volume of carbon currently stored in boreal regions and the high frequency of wildfire, the prospects of a warming climate would have important implications for the ecology of boreal forests which in turn would have significant feedbacks for carbon cycling, fire frequency, and global climate change. Since ecological studies and climate change models require routine information on surface soil moisture, the ability to remotely sense this variable is highly desirable. Toward this end research was conducted on developing methods for the retrieval of spatially and temporally varying patterns of soil moisture from recently bumed boreal forest ecosystems of Alaska using C-band satellite radar data. To do this we focused on both individual date and temporal SAR datasets to develop techniques and algorithms which indicate how moisture varies across a recently burned boreal forest. For each of the methods developed we focused on reducing errors of SAR-derived soil moisture estimates due to confounding factors of variations in vegetative biomass and surface roughness. For the individual date soil moisture monitoring, we grouped test sites by a measurable biophysical variable, burn severity, and then developed algorithms relating moisture to SAR backscatter for each bum severity group. The algorithms developed had high coefficients of determination (0.56-0.82) and the moisture maps produced had high accuracy (3.61 rms error) based on the minimal validation conducted. For the seasonal soil moisture mapping we used principal component analysis to capture the time-variant feature of soil moisture and minimize the relatively time-invariant features that confound SAR backscatter. This resulted in good agreement between the drainage maps produced and our limited in situ observations and weather data. However, further validation, with larger sample sizes, is needed. While this study focuses on Alaska, research indicates that the techniques developed should be applicable to boreal forests worldwide.
Modeling data with multiple time dimensions
COMPUTATIONAL STATISTICS & DATA ANALYSIS 51:9 4761-4785
A large class of problems in time series analysis can be represented by a set of overlapping time series with different starting times. These time series may be treated as different probes of the same underlying process. Such probes may follow a characteristic lifecycle as a function of the time since the series began. They may also be subject to environmental shocks according to calendar time. In addition, the calibration of each probe may be unknown such that each series may show a different magnitude of response to the underlying lifecycles and environmental impacts. This paper describes an approach to analyzing these multiple time series as a single set such that the underlying lifecycles and calendar-based shocks may be measured. Simultaneously, the individual calibrations of the time series are also measured. This technique is referred to as dual-time dynamics, and it applies to many important business problems. Applications to tree ring analysis, the SETI@home project, and retail loan portfolio forecasting are provided. Other areas of possible application include digital media services, insurance, human resource management, health care, and biological systems to name a few. (c) 2007 Elsevier B.V. All rights reserved.
Drought sensitivity shapes species distribution patterns in tropical forests
Engelbrecht, BMJ Comita, LS Condit, R Kursar, TA Tyree, MT Turner, BL Hubbell, SP
NATURE 447:7140 80-U2
Although patterns of tree species distributions along environmental gradients have been amply documented in tropical forests(1-7), mechanisms causing these patterns are seldom known. Efforts to evaluate proposed mechanisms have been hampered by a lack of comparative data on species’ reactions to relevant axes of environmental variation(1). Here we show that differential drought sensitivity shapes plant distributions in tropical forests at both regional and local scales. Our analyses are based on experimental field assessments of drought sensitivity of 48 species of trees and shrubs, and on their local and regional distributions within a network of 122 inventory sites spanning a rainfall gradient across the Isthmus of Panama. Our results suggest that niche differentiation with respect to soil water availability is a direct determinant of both local- and regional-scale distributions of tropical trees. Changes in soil moisture availability caused by global climate change and forest fragmentation are therefore likely to alter tropical species distributions, community composition and diversity.
Spatio-temporal patterns of juvenile marine turtle occurrence in waters of the European continental shelf
Witt, MJ Penrose, R Godley, BJ
MARINE BIOLOGY 151:3 873-885
We present data spanning approximately 100 years regarding the spatial and temporal occurrence of marine turtle sightings and strandings in the northeast Atlantic from two public recording schemes and demonstrate potential signals of changing population status. Records of loggerhead (n = 317) and Kemp’s ridley (n = 44) turtles occurring on the European continental shelf were most prevalent during the autumn and winter, when waters were coolest. In contrast, endothermic leatherback turtles (n = 1,668) were most common during the summer. Analysis of the spatial distribution of hard-shell marine turtle sightings and strandings highlights a pattern of decreasing records with increasing latitude. The spatial distribution of sighting and stranding records indicates that arrival in waters of the European continental shelf is most likely driven by North Atlantic current systems. Future patterns of spatial-temporal distribution, gathered from the periphery of juvenile marine turtles habitat range, may allow for a broader assessment of the future impacts of global climate change on species range and population size.
Potential changes in weed competitiveness in an agroecological system with elevated temperatures
Tungate, KD Israel, DW Watson, DM Rufty, TW
ENVIRONMENTAL AND EXPERIMENTAL BOTANY 60:1 42-49
Increases in temperature due to global climate changes could significantly impact weed competitiveness and crop-weed interactions. Factors contributing to the responsiveness of a plant species to increasing temperature include the inherent genetic limitations of the species and the ability to acquire water and nutritional resources. The purpose of this study was to examine the temperature responses of selected species from a model agronomic system in the Southeastern U.S.: soybean (Glycine max), sicklepod (Senna obtusifolia) and prickly sida (Sida spinosa). We also determined temperature effects on mycorrhizal colonization and development of the soybean N-2-fixation system, two below-ground associations critical for resource acquisition. The species were grown at 42/37 (day/night), 36/31, 32/27, 28/23, or 23/18 degrees C for 30 days in a field soil with naturally low fertility. Growth of the weed species was maximized at a higher temperature than that for soybean, 36/31 degrees C versus 32/27 degrees C, probably reflecting different geographical origins. At the optimal temperature, weeds had higher root:shoot mass ratios (1.3-1.5 versus 0.9) than soybean, and greater mycorrhizal colonization. In soybean, nodule weights, numbers, and total nitrogenase activity were highest at the growth temperature optimum but decreased considerably at higher temperatures. The results collectively indicate that increases in aerial temperatures above similar to 32 degrees C would enhance weed competitiveness. Increased interference with soybean growth and yields should be expected. (c) 2006 Elsevier B.V. All rights reserved.
Impact of predicted climate change on landslide reactivation: case study of Mam Tor, UK
Dixon, N Brook, E
LANDSLIDES 4:2 137-147
Global change is expected to result in worldwide increases in temperature and alteration of rainfall patterns. Such changes have the potential to modify stability of slopes, both natural and constructed. This paper discusses the potential effect of global climate change on reactivation of landslides through examination of predicted changes in rainfall pattern on the active landslide at Mam Tor, Derbyshire, UK. This landslide is of Pleistocene origin and is crossed by a road that is now abandoned. Damaging winter movement is known to occur when precipitation reaches both 1-month triggering and 6-month antecedent thresholds. Return periods for threshold exceedence is modelled statistically, and the climate change data from the UKCIP 2002 report (Hulme et al. 2002) is applied to this model. For the predicted changes in precipitation, it is shown that the instability threshold could decrease from 4 to 3.5 years by the 2080s for the medium-high climate change scenario. However, predicted temperature changes could influence the response of the landslide through increased evapotranspiration leading to a change in the triggering precipitation thresholds, and this will help counter the impact of changes in precipitation. Analysis of sources of uncertainty in the model has been used to establish the factors that contribute to the predicted changes in stability. Assessment of these factors can provide an indication of the potential impact of climate change on landslides in other areas of the UK.
Short-rotation forestry of birch, maple, poplar and willow in Flanders (Belgium) I - Biomass production after 4 years of tree growth
Walle, IV Van Camp, N Van de Casteele, L Verheyen, K Lemeur, R
BIOMASS & BIOENERGY 31:5 267-275
During the last three decades, oil crises, agricultural surpluses and global climate change enhanced the interest in short-rotation forestry (SRF). In this study, the biomass production of birch (Betula pendula Roth), maple (Acer pseudoplatanus L.-Tintigny), poplar (Populus trichocarpa x deltoides -Hoogvorst) and willow (Salix viminalis-Orm) growing under a short-rotation (SR) management system were compared after a 4 years period. The plantation was established on former agricultural land. The sandy soil had a mean pH of 4.5 and a mean carbon content of 1.0%. Survival rates after 4 years were 75.8%, 96.8%, 86.3% and 97.6% for birch, maple, poplar and willow, respectively. The mean actual annual biomass production for these four species amounted to 2.6, 1.2, 3.5 and 3.4 t DM ha(-1) yr(-1), respectively. The large variation in biomass production at the different plots of the plantation could not be explained by the measured soil parameters. Biomass production results found here were in the lower range of values reported in literature. However, in contrast to most other studies, no weed control, fertilisation or irrigation was applied in this experiment. As marginal agricultural soils are suboptimal for the growth of poplar and willow, birch can be considered as a very interesting alternative for the establishment of SR plantations in Flanders. (c) 2007 Elsevier Ltd. All rights reserved.
Groundwater influence on alpine stream ecosystems
Brown, LE Milner, AM Hannah, DM
FRESHWATER BIOLOGY 52:5 878-890
1. Spatial and temporal variability of relative snow-melt, glacier-melt and groundwater contributions to streams play important roles in shaping alpine freshwater ecosystems. Although meltwater (particularly glacier-fed) streams have received much attention in recent years, the influence of groundwater on alpine freshwater ecosystems remains poorly understood. 2. This study tested the hypotheses that increased groundwater contributions to meltwater-dominated alpine streams would yield increases in water temperature, channel stability, electrical conductivity and particulate organic matter (POM) and decreases in suspended sediment concentration (SSC). These more favourable habitat conditions were hypothesised to result in increased macroinvertebrate abundance and diversity. 3. Groundwater contributions, physicochemical habitat variables and benthic macroinvertebrates were sampled throughout the 2002 and 2003 summer-melt seasons in three streams in the French Pyrenees. 4. Increased groundwater contributions were significantly correlated with higher discharge, water temperature, electrical conductivity, POM and channel stability, but lower SSC. 5. Macroinvertebrate total abundance, taxonomic richness, number of Ephemeroptera, Plecoptera and Trichoptera genera, and per cent Plecoptera all increased significantly with greater groundwater contributions to streamflow. However, beta diversity and Trichoptera relative abundance decreased. 6. Abundance of most macroinvertebrate taxa was highest under groundwater-dominated conditions but a gradient of optimum groundwater preferences was evident across all taxa. Some taxa were found only where groundwater contributions were low (i.e. in predominantly meltwater-fed streams). 7. This study provides evidence that water source, physicochemical habitat and stream biota are strongly linked. Therefore, an interdisciplinary approach is necessary for future studies aiming to develop conservation strategies or predict the response of alpine river ecosystems to global climate change.
A new chronology for the age of Appalachian erosional surfaces determined by cosmogenic nuclides in cave sediments
Anthony, DM Granger, DE
EARTH SURFACE PROCESSES AND LANDFORMS 32:6 874-887
The relative chronology of landscape evolution across the unglaciated Appalachian plateaus of Kentucky and Tennessee is well documented. For more than a century, geomorphologists have carefully mapped and correlated upland erosional surfaces inset by wide-valley straths and smaller terraces. Constraining the timing of river incision into the Appalachian uplands was difficult in the past due to unsuitable dating methods and poorly preserved surface materials. Today, burial dating using the differential decay of cosmogenic Al-26 and Be-10 in clastic cave sediments reveals more than five million years of landscape evolution preserved underground. Multilevel caves linked hydrologically to the incision history of the Cumberland River contain in situ sediments equivalent to fluvial deposits found scattered across the Eastern Highland Rim erosional surface. Cave sediments correlate with: (1) thick Lafayette-type gravels on the Eastern Highland Rim deposited between c. 5 center dot 7 and c. 3 center dot 5 Ma; (2) initial incision of the Cumberland River into the Eastern Highland Rim after c. 3 center dot 5 Ma; (3) formation of the Parker strath between c. 3 center dot 5 Ma and c. 2 center dot 0 Ma; (4) incision into the Parker strath at c. 2 Ma; (5) formation of a major terrace between c. 2 center dot 0 Ma and c. 1 center dot 5 Ma; (6) shorter cycles of accelerated incision and base level stability beginning at c. 1 center dot 5 Ma; and (7) regional aggradation at c. 0 center dot 85 Ma. Initial incision into the Appalachian uplands is interpreted as a response to eustasy at 3 center dot 2-3 center dot 1 Ma. Incision of the Parker strath is interpreted as a response to eustasy at 2 center dot 5-2 center dot 4 Ma. A third incision event at c. 1 center dot 5 Ma corresponds with glacial reorganization of the Ohio River basin. Widespread aggradation of cave passages at c. 0 center dot 85 Ma is interpreted as the beginning of intense glacial-interglacial cycling associated with global climate change. (C) Copyright 2006 John Wiley & Sons, Ltd.
Vulnerability: A generally applicable conceptual framework for climate change research
GLOBAL ENVIRONMENTAL CHANGE-HUMAN AND POLICY DIMENSIONS 17:2 155-167
The term `vulnerability’ is used in many different ways by various scholarly communities. The resulting disagreement about the appropriate definition of vulnerability is a frequent cause for misunderstanding in interdisciplinary research on climate change and a challenge for attempts to develop formal models of vulnerability. Earlier attempts at reconciling the various conceptualizations of vulnerability were, at best, partly successful. This paper presents a generally applicable conceptual framework of vulnerability that combines a nomenclature of vulnerable situations and a terminology of vulnerability concepts based on the distinction of four fundamental groups of vulnerability factors. This conceptual framework is applied to characterize the vulnerability concepts employed by the main schools of vulnerability research and to review earlier attempts at classifying vulnerability concepts. None of these one-dimensional classification schemes reflects the diversity of vulnerability concepts identified in this review. The wide range of policy responses available to address the risks from global climate change suggests that climate impact, vulnerability, and adaptation assessments will continue to apply a variety of vulnerability concepts. The framework presented here provides the much-needed conceptual clarity and facilitates bridging the various approaches to researching vulnerability to climate change. (c) 2006 Elsevier Ltd. All rights reserved.
Effects of carbon dioxide, temperature and ultraviolet-B radiation and their interactions on soybean (Glycine max L.) growth and development
Koti, S Reddy, KR Kakani, VG Zhao, D Gao, W
ENVIRONMENTAL AND EXPERIMENTAL BOTANY 60:1 1-10
Genetic modifications of agronomic crops will likely be necessary to cope with global climate change. Projected changes in global climate include increasing atmospheric carbon dioxide concentration ([CO2]), temperatures (T) and ultraviolet-B (UV-B) radiation which have significant effects on plants, however, their interactions are not clearly known to date. In this study we tested the hypothesis that soybean genotypes differ in growth and physiology with exposure to treatments of [CO2] [360 and 720 mu mol mol(-1) (+[CO2])], temperature [30/22 and 38/30 degrees C (+T)] and UV-B radiation [0 and 10 kJ m(-2) d(-1) (+UV-B)] and their interactions. Six soybean genotypes (D 88-5320, D 90-9216, Stalwart III, PI 471938, DG 5630 RR, and DP 4933 RR) representing five maturity groups were grown in eight sunlit, controlled environment chambers in which control treatment had 360 mu mol mol(-1) [CO2] at 30/22 degrees C temperatures and 0 kJ UV-B. Results showed that elevated C02 levels compensated the damaging effects caused by negative stressors such as high temperature and high UV-B radiation levels on most of the growth and physiological parameters studied. Total stress response index (TSRI) for each genotype was developed from the cumulative sum of response indices of vegetative and physiological parameters such as plant height, leaf area, total biomass, net photosynthesis, total chlorophyll content, phenolic content, relative injury and wax content. Based on TSRI, the genotypes were classified as tolerant (PI 471938 and D 88-5320), intermediate (DG 5630 RR and D 90-9216) and sensitive (DP 4933 RR and Stalwart 111). The disruption of growth and physiology was significantly reduced in tolerant genotypes compared to sensitive genotypes. Strong correlations between total response of relative injury (RI), an indicator of cell membrane thermo stability and TSRI developed in this study show that RI could be used to predict the overall vegetative performance of the crop. However, the total response of RI did not show any linear correlation with TSRI of our previous study (which was developed with responses of reproductive traits). This suggests that there is a need to develop better screening tools and/or breeding strategies in developing genotypes suitable to cope future climates at both vegetative and reproductive stages. (c) 2006 Elsevier B.V. All rights reserved.
Depth-mediated reversal of the effects of climate change on long-term growth rates of exploited marine fish
Thresher, RE Koslow, JA Morison, AK Smith, DC
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 104:18 7461-7465
The oceanographic consequences of climate change are increasingly well documented, but the biological impacts of this change on marine species much less so, in large part because of few long-term data sets. Using otolith analysis, we reconstructed historical changes in annual growth rates for the juveniles of eight long-lived fish species in the southwest Pacific, from as early as 1861. Six of the eight species show significant changes in growth rates during the last century, with the pattern differing systematically with depth. Increasing temperatures near the ocean surface correlate with increasing growth rates by species found in depths < 250 m, whereas growth rates of deep-water I(> 1,000 m) species have declined substantially during the last century, which correlates with evidence of long-term cooling at these depths. The observations suggest that global climate change has enhanced some elements of productivity of the shallow-water stocks but also has reduced the productivity, and possibly the resilience, of the already slow-growing deep-water species.
Reconstruction of solar total irradiance since 1700 from the surface magnetic flux
Krivova, NA Balmaceda, L Solanki, SK
ASTRONOMY & ASTROPHYSICS 467:1 335-346
Context. Total solar irradiance changes by about 0.1% between solar activity maximum and minimum. Accurate measurements of this quantity are only available since 1978 and do not provide information on longer-term secular trends. Aims. In order to reliably evaluate the Sun’s role in recent global climate change, longer time series are, however, needed. They can only be assessed with the help of suitable models. Methods. The total solar irradiance is reconstructed from the end of the Maunder minimum to the present based on variations of the surface distribution of the solar magnetic field. The latter is calculated from the historical record of the sunspot number using a simple but consistent physical model. Results. Our model successfully reproduces three independent data sets: total solar irradiance measurements available since 1978, total photospheric magnetic flux since 1974 and the open magnetic flux since 1868 empirically reconstructed using the geomagnetic aa-index. The model predicts an increase in the solar total irradiance since the Maunder minimum of 1.3(-0.4)(+0.2) Wm(-2).
Anthropogenic and natural disturbance effects on a macrobenthic estuarine community over a 10-year period
Dolbeth, M Cardoso, PG Ferreira, SM Verdelhos, T Raffaelli, D Pardal, MA
MARINE POLLUTION BULLETIN 54:5 576-585
For some decades, the Mondego estuary has been under severe ecological stress, mainly caused by eutrophication. The most visible effect was the occurrence of macroalgal blooms and the concomitant decrease of the area occupied by Zostera noltii beds. Since the end of 1998, mitigation measures were implemented in the estuary to promote the recovery of the seagrass beds and the entire surrounding environment. The present study offers a unique opportunity to evaluate the impact of disturbance and the success of the initial recovery process (before and after implementation of the management measures), over a 10-year period, having secondary production as the descriptor. Before the implementation of the mitigation measures, in parallel with the decrease of the Z. noltii beds, species richness, mean biomass and production also decreased, lowering the carrying capacity of the whole Mondego’s south arm. Yet, after the introduction of management measures, the seagrass bed seemed to recover. Consequently, the biomass and production also increased substantially, for the whole intertidal area. Nevertheless, even after the mitigation measures implementation, natural-induced stressors, such as strong flood events induced a drastic reduction of annual production, not seen before the implementation of those measures. This shows that the resilience of the populations may have been lowered by a prior disturbance history (eutrophication) and consequent interactions of multiple stressors. (C) 2006 Elsevier Ltd. All rights reserved.
Phenological responses of plants to climate change in an urban environment
Luo, ZK Sun, OJ Ge, QS Xu, WT Zheng, JY
ECOLOGICAL RESEARCH 22:3 507-514
Global climate change is likely to alter the phenological patterns of plants due to the controlling effects of climate on plant ontogeny, especially in an urbanized environment. We studied relationships between various phenophases (i.e., seasonal biological events) and interannual variations of air temperature in three woody plant species (Prunus davidiana, Hibiscus syriacus, and Cercis chinensis) in the Beijing Metropolis, China, based on phenological data for the period 1962-2004 and meteorological data for the period 1951-2004. Analysis of phenology and climate data indicated significant changes in spring and autumn phenophases and temperatures. Changes in phenophases were observed for all the three species, consistent with patterns of rising air temperatures in the Beijing Metropolis. The changing phenology in the three plant species was reflected mainly as advances of the spring phenophases and delays in the autumn phenophases, but with strong variations among species and phenophases in response to different temperature indices. Most phenophases (both spring and autumn phenophases) had significant relationships with temperatures of the preceding months. There existed large inter- and intra-specific variations, however, in the responses of phenology to climate change. It is clear that the urban heat island effect from 1978 onwards is a dominant cause of the observed phenological changes. Differences in phenological responses to climate change may cause uncertain ecological consequences, with implications for ecosystem stability and function in urban environments.
Deforestation affects biogeographical regionalization: a case study contrasting potential and extant distributions of Mexican terrestrial mammals
Escalante, T Sanchez-Cordero, V Morrone, JJ Linaje, M
JOURNAL OF NATURAL HISTORY 41:13-16 965-984
We used ecological niche modelling projected as species’ potential ( based on the original vegetation map) and extant ( based on the 2000 land use and vegetation map) distributions to analyse changes on patterns of endemism of terrestrial mammals occurring in Mexico. Based on the biogeographic method of Parsimony Analysis of Endemicity, we obtained cladograms under scenarios of species’ potential distribution ( t1) and extant distributions ( t2). We found that the resolution of consensus cladogram in t2 was poorer, while there were more geographic synapomorphies in t1, and more autapomorphies in t2 due to a reduction of species’ distributions as a consequence of deforestation. We defined a hierarchical regionalization with two regions with the cladogram of t1; a transitional zone, two subregions, five dominions, and 15 provinces. Conversely, the consensus cladogram of t2 had a basal trichotomy, and the position of the Sierra Madre Occidental changed compared with t1. In t1 and t2, the Yucatan Peninsula+ Chiapas+ Isthmus of Tehuantepec clade was maintained, although in t2 it was separated from the remaining areas of the country. The impact of deforestation on species distributions strongly affected the biogeographic regionalization of terrestrial mammals in Mexico.
Impact of climate change on water resources in Yongdam Dam Basin, Korea
Kim, BS Kim, HS Seoh, BH Kim, NW
STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT 21:4 355-373
The main purpose of this study is to investigate and evaluate the impact of climate change on the runoff and water resources of Yongdam basin, Korea. First, we construct global climate change scenarios using the YONU GCM control run and transient experiments, then transform the YONU GCM grid-box predictions with coarse resolution of climate change into the site-specific values by statistical downscaling techniques. The downscaled values are used to modify the parameters of a stochastic weather generator model for the simulation of the site-specific daily weather time series. The weather series is fed into a semi-distributed hydrological model called SLURP to simulate the streamflows associated with other water resources for the condition of 2CO(2). This approach is applied to the Yongdam dam basin in the southern part of Korea. The results show that under the condition of 2CO(2), about 7.6% of annual mean streamflow is reduced when it is compared with the current condition. Seasonal streamflows in the winter and autumn are increased, while streamflow in the summer is decreased. However, the seasonality of the simulated series is similar to the observed pattern
An estimate of biogenic emissions of volatile organic compounds during summertime in China
Wang, QG Han, ZW Wang, TJ Higano, Y
ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH 14:1 69-75
Background and Aim. An accurate estimation of biogenic emissions of VOC (volatile organic compounds) is necessary for better understanding a series of current environmental problems such as summertime smog and global climate change. However, very limited studies have been reported on such emissions in China. The aim of this paper is to present an estimate of biogenic VOC emissions during summertime in China, and discuss its uncertainties and potential areas for further investigations. Materials and Methods. This study was mainly based on field data and related research available so far in China and abroad, including distributions of land use and vegetations, biomass densities and emission potentials. VOC were grouped into isoprene, monoterperies and other VOC (OVOC). Emission potentials of forests were determined for 22 genera or species, and then assigned to 33 forest ecosystems. The NCEP/NCAR reanalysis database was used as standard environmental conditions. A typical summertime of July 1999 was chosen for detailed calculations. Results and Discussion. The biogenic VOC emissions in China in July were estimated to be 2.3x 10(12)gC, with 42% as isoprene, 19% as monoterpenes and 39% as OVOC. About 77.3% of the emissions are generated from forests and woodlands. The averaged emission intensity was 4.11 MgC M-2 hr(-1) for forests and 1.12 MgC M-2 hr(-1) for all types of vegetations in China during the summertime. The uncertainty in the results arose from both the data and the assumptions used in the extrapolations. Generally, uncertainty in the field measurements is relatively small. A large part of the uncertainty mainly comes from the taxonomic method to assign emission potentials to unmeasured species, while the ARGR method serves to estimate leaf biomass and the emission algorithms to describe light and temperature dependence. Conclusions. This study describes a picture of the biogenic VOC emissions during summertime in China. Due to the uneven spatial and temporal distributions, biogenic VOC emissions may play all important role in the tropospheric chemistry during summertime. Recommendations and Perspectives. Further investigations are needed to reduce uncertainties involved in the related factors such as emission potentials, leaf biomass, species distribution as well as the mechanisms of the emission activities. Besides ground measurements, attention should also be placed on other techniques such as remotesensing and dynamic modeling. These new approaches, combined with ground measurements as basic database for calibration and evaluation, can hopefully provide more comprehensive information in the research of this field.
The impact of water resources development projects on water vapor pressure trends in a semi-arid region, Turkey
Tonkaz, T Cetin, M Tulucu, K
CLIMATIC CHANGE 82:1-2 195-209
The aim of this study was to investigate long-term seasonal trends and decadal change patterns of monthly mean water vapor pressure (WVP) observation series at 16 meteorological stations scattered point-wisely over the Southeastern Anatolian Project (GAP) area in Turkey, where large-scale soil and water development projects have been put into practice since the 1970s. The record length of WVP observation series of each station varied between 31- and 41-years between 1962 and 2002. The monthly mean WVP observation series of each station was rearranged on seasonal basis. Sequential Mann-Kendall trend test, Sen’s slope estimator, and Spearman’s rank-order correlation tests were employed for detection of likely trends, and Kruskall-Wallis test was used to detect decadal variations in WVP series of each observation station. A possible area of representation for each meteorological station was determined by using the Thiessen polygons technique in a geographical information systems media. It was found that 15 seasonal WVP series have a positive trend covering 97% of the GAP area in the summer season; although one WVP series has a negative trend direction. However, in the spring season, 33% of the area had a positive trend, and a negative trend did not appear in any stations. WVP records in the winter season showed an increasing trend over 19% of the GAP area, whereas a decreasing trend prevailed in 9% of the area. The study results led us to conclude that the substantial increase of WVP observations in summer season could be attributed to both the shift from rain-fed agriculture to irrigated agriculture being made increasingly spacious year by year and building large water reservoirs in the GAP located in a semi-arid region. The results also indirectly suggested that the historical trends in the WVP parameters might be related to global climate change phenomenon.
Causes of lineage decline in the Aplodontidae: Testing for the influence of physical and biological change
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY 246:2-4 331-353
This study documents diversity decline in a once-speciose rodent clade, the family Aplodontidae, and evaluates the potential influence of three commonly suggested controls on diversity: climate change, floral change, and competitive interactions. Aplodontids first appeared in the late Eocene, diversified during the early Oligocene, declined precipitously at the end of the Oligocene such that standing diversity was only about 5 species during the early Miocene, peaked again in the early middle Miocene, then declined through the late Miocene, and are entirely absent from the Pliocene and early Pleistocene fossil record. This long term pattern culminated in the survival of a single extant species, Aplodontia rufa, the mountain beaver. The species’ richness and body size distribution through time were compared with the timing of climatic changes as inferred from global oxygen isotope curves, with the rise of grasslands as inferred from phytolith and other stable isotope studies, and with fluctuating diversity of potential competitors as inferred from published stratigraphic and geographic distributions. The timing of global climate change is decoupled from the diversity fluctuations and seems not to have been a proximate cause. Rise of grasslands and the increasing dominance Of C-4 vegetation correlates with diversity decline in the late Oligocene and late Miocene, but data are sparse, and more work will be required to determine the mechanism driving this relationship. Examination of potential mammalian competitors (sciurids and castorids) finds no evidence for competitive replacement of aplodontids. It is difficult to ascribe the fluctuations in aplodontid diversity to a single cause. The explanation likely involves vegetation changes associated with the spread of grasslands, but there is some variation in diversity that cannot be explained by the vegetation, at least using the proxies employed here. Climate and competition are less consistent with the available data. The reasons for the decline of aplodontids in the late Oligocene and the late Miocene apparently involved the interaction of multiple physical and biological causes, coupled with the chance events that underlie any evolutionary process. (c) 2006 Elsevier B.V. All rights reserved.
Environmental hazard analysis and effective remediation of highway seepage
Yuan, RM Yang, YS Qiu, X Ma, FS
JOURNAL OF HAZARDOUS MATERIALS 142:1-2 381-388
Risk assessment and minimisation of environmental hazards are critical issues to consider in the geotechnical engineering projects. A case of highway pavement seepage induced by groundwater, at a locality along the section of Hua-Qing Highway of Guangdong Province, China, is presented for environmental hazard analysis and effective remediation. The environmental hazard analyses were based on in situ hydrogeologic investigation, rock-soil testing and integrated environmental understanding. The analyses indicate that the highway seepage was caused by elevation of groundwater hydraulic pressure in low permeable strata near the highway pavement, which was controlled by landform, hydrology, weather and road structure. The risk source of groundwater ‘flooding’ was the groundwater and surface water in the ring-like valley around Fenshui Village. A blind-ditch system for effective remediation of the pavement seepage hazard was proposed and successfully implemented by declining groundwater table near the highway based on the comprehensive assessment of various conditions. This geotechnical accident shows that the role of groundwater is an essential factor to consider in the geotechnical and environmental engineering studies and multidisciplinary effort for risk assessment of environmental hazards is important under current global climate change condition. (c) 2006 Elsevier B.V. All rights reserved.
Long-term changes in the geographic distribution and population structures of Osilinus lineatus (Gastropoda : Trochidae) in Britain and Ireland
Mieszkowska, N Hawkins, SJ Burrows, MT Kendall, MA
JOURNAL OF THE MARINE BIOLOGICAL ASSOCIATION OF THE UNITED KINGDOM 87:2 537-545
Since the rate of global climate change began to accelerate in the 1980s, the coastal seas of Britain have warmed by tip to l degrees C. Locations close to the northern range edges of a southern trochid gastropod Osilinus lineatus in Britain previously surveyed in the 1950s and 1980s were resurveyed during 2002-2004 to determine whether changes in the success of near-limit populations had occurred during the period of climate warming. Between the 1980s and the 2000s, the range limits had extended by up to 55 krn. Populations sampled over a latitudinal extent of 4 degrees from northern limits towards the centre of the range showed synchronous increases in abundance throughout the years sampled, suggesting a large-scale factor such as climate was driving the observed changes. These increases in abundance and changes in range limits are likely to have occurred via increased recruitment success in recent years.
Construction of a novel economy-climate model
Chou, JM Dong, WJ Ye, DZ
CHINESE SCIENCE BULLETIN 52:7 1006-1008
An attempt has been made to construct a novel economy-climate model by combining climate change research with agricultural economy research to evaluate the influence of global climate change on grain yields. The insertion of a climate change factor into the economic C-D (Cobb-Dauglas) production function model yields a novel evaluation model, which connects the climate change factor to the economic variation factor, and the performance and reasonableness of the novel evaluation model are also preliminarily simulated and verified.
Evolutionary aspects of climate-induced changes and the need for multidisciplinarity
Pertoldi, C Bach, LA
JOURNAL OF THERMAL BIOLOGY 32:3 118-124
An integrated view on the possible effects of global climate change is provided while taking into account that not only the rising average temperature is likely to impact natural populations but also that increased variation around the mean and higher frequency of extreme events will be important. We propose that complex genetic effects in concert with demographic patterns may affect how focal populations react to the environmental challenge in an adaptive way (if they can). In order to aim for an inclusive picture of the ongoing environmental change we argue for a synthesis of knowledge from a range of ‘classical’ disciplines such as quantitative genetics, conservation genetics and population ecology. A hereto little exposed concern is the importance of the increase in amplitude of environmental fluctuations and how the corresponding evolutionary and ecological reactions are expected to occur. Due to the complex interactions between the ecological and genetic mechanisms in the response to climate-induced impacts interdisciplinary approaches are the most promising path in seeking knowledge about the present and future changes in the biosphere. (c) 2007 Elsevier Ltd. All rights reserved.
Irrigation and enhanced soil carbon input effects on below-ground carbon cycling in semiarid temperate grasslands
Xiao, CW Janssens, IA Liu, P Zhou, ZY Sun, OJ
NEW PHYTOLOGIST 174:4 835-846
Global climate change is generally expected to increase net primary production, resulting in increased soil carbon (C) inputs. To gain an understanding of how such increased soil C inputs would affect C cycling in the vast grasslands of northern China, we conducted a field experiment in which the responses of plant and microbial biomass and respiration were studied. Our experiment included the below-ground addition of particulate organic matter (POM) at rates equivalent to 0, 60, 120 and 240 g C m(-2), under either natural precipitation or under enhanced precipitation during the summer period (as predicted for that region in recent simulations using general circulation models). We observed that addition of POM had a large effect on soil microbial biomass and activity and that a major part of the added C was rapidly lost from the system. This suggests that microbial activity in the vast temperate grassland ecosystems of northern China is energy-limited. Moreover, POM addition (and the associated nutrient release) affected plant growth much more than the additional water input. Although we performed no direct fertilization experiments, the response of plant productivity to POM addition (and associated release of nutrients) leads us to believe that plant productivity in the semiarid grassland ecosystems of northern China is primarily limited by nutrients and not by water.
Population trends and spatial synchrony in peripheral populations of the endangered Lesser grey shrike in response to environmental change
Giralt, D Valera, F
BIODIVERSITY AND CONSERVATION 16:4 841-856
Regional synchronization in species dynamics as well as particular ecological and demographic characteristics of peripheral populations poses special challenges for conservation purposes, particularly under the current scenario of global climate change. Here, we study the population trend and spatial synchrony of several peripheral populations of the endangered Lesser grey shrike Lanius minor at the western limit of its breeding range (southern France and northeast Spain). In an attempt to ascertain the effect of environmental change on the decline of the species we also look for evidence of climate changes in the breeding and wintering area of this shrike and related effects on vegetation by using the normalized difference vegetation index (NDVI). We found that the interannual fluctuations of the peripheral populations in France and Spain are strongly correlated, therefore suggesting that their decline can be under the influence of a common factor. We obtained clear evidence of climatic change (an increased thermal oscillation) in one peripheral population that could have resulted in a decrease of the NDVI index in the area. Our study finds correlational evidence that climatic variables in the breeding area may account for fluctuations in abundances of some populations and that environmental conditions experimented by some population could influence the fate of the neighboring populations. Our results indicate that the studied peripheral populations are spatially synchronized, so that conservation efforts should be applied at a large-scale encompassing all the isolated populations at the western border of the range of the species in the Mediterranean area.
Combining airborne photographs and spaceborne SAR data to monitor temperate glaciers: Potentials and limits
Trouye, E Vasile, G Gay, M Bombrun, L Grussenmeyer, P Landes, T Nicolas, JM Bolon, P Petillot, I Julea, A Valet, L Chanussot, J Koehl, M
IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING 45:4 905-924
Monitoring temperate glacier activity has become more and more necessary for economical and security reasons and as an indicator of the local effects of global climate change. Remote sensing data provide useful information on such complex geophysical objects, but they require specific processing techniques to cope with the difficult context of moving and changing features in high-relief areas. This paper presents the first results of a project involving four laboratories developing and combining specific methods to extract information from optical and synthetic aperture radar (SAR) data. Two different information sources are processed, namely: 1) airborne photography and 2) spaceborne C-band SAR interferometry. The difficulties and limitations of their processing in the context of Alpine glaciers are discussed and illustrated on two glaciers located in the Mont-Blanc area. The results obtained by aerial triangulation techniques provide digital terrain models with an accuracy that is better than 30 cm, which is compatible with the computation of volume balance and useful for precise georeferencing and slope measurement updating. The results obtained by SAR differential interferometry using European Remote Sensing Satellite images show that it is possible to measure temperate glacier surface velocity fields from October to April in one-day interferograms with approximately 20-m ground sampling. This allows to derive ice surface strain rate fields required to model the glacier flow. These different measurements are complementary to results obtained during the summer from satellite optical data and ground measurements that are available only in few accessible points.
The agricultural impact of global climate change: How can developing-country farmers cope?
GEOTIMES 52:4 30-34
Ecophysiological response and morphological adjustment of two Central Asian desert shrubs towards variation in summer precipitation
Xu, H Li, Y Xu, GQ Zou, T
PLANT CELL AND ENVIRONMENT 30:4 399-409
As part of global climate change, variation in precipitation in arid ecosystems is leading to plant adaptation in water-use strategies; significant interspecific differences in response will change the plant composition of desert communities. This integrated study on the ecophysiological and individual morphological scale investigated the response, acclimation and adaptation of two desert shrubs, with different water-use strategies, to variations in water conditions. The experiments were carried out on two native dominant desert shrubs, Tamarix ramosissima and Haloxylon ammodendron, under three precipitation treatments (natural, double and no precipitation, respectively), in their original habitats on the southern periphery of Gurbantonggut Desert, Central Asia, during the growing season in 2005. Changes in photosynthesis, transpiration, leaf water potential, water-use efficiency, above-ground biomass accumulation and root distribution of the two species were examined and compared under the contrasting precipitation treatments. There were significant interspecific differences in water-use strategy and maintenance of photosynthesis under variation in precipitation. For the phreatophyte T. ramosissima, physiological activity and biomass accumulation rely on the stable groundwater, which shields it from fluctuation in the water status of the upper soil layers caused by precipitation. For the non-phreatophyte H. ammodendron, efficient morphological adjustment, combined with strong stomatal control, contributes to its acclimation to variation in precipitation. On account of its positive responses to increased precipitation, H. ammodendron is predicted to succeed in interspecific competition in a future, moister habitat.
Tension wood formed in Fagus sylvatica and Alnus glutinosa after simulated mass movement events
Heinrich, I Gartner, H Monbaron, M
IAWA JOURNAL 28:1 39-48
Due to the likelihood of global climate change, the frequency and magnitude of natural hazards such as mass movements may likewise change, thus favouring the refinement of methods to detect and quantify geomorphic events when precise records are not available. Geomorphic events typically have a significant effect on tree growth, e.g., reaction wood marked by changes in ring widths and wood density. To date, several dendroecological techniques have been developed to document the occurrence of these events but it rarely has been possible to retrieve additional information from reaction wood concerning the precise kind and intensity of geomorphic events. Additional qualitative information inferred from reaction wood of trees holds the potential to not only document but also estimate important characteristics of natural hazard events. To refine the methods already used in dendrogeornorpology, experiments simulating various geomorphic events were used to monitor subsequent wood anatomical responses of Fagus sylvatica and Alnus glutinosa. The preliminary results indicate that these two common broadleaf tree species show variations in their reactions to different experimental treatments.
Breeding distributions of north American bird species moving north as a result of climate change
Hitch, AT Leberg, PL
CONSERVATION BIOLOGY 21:2 534-539
Geographic changes in species distributions toward traditionally cooler climes is one hypothesized indicator of recent global climate change. We examined distribution data on 56 bird species. If global warming is affecting species distributions across the temperate northern hemisphere, these data should show the same northward range expansions of birds that have been reported for Great Britain. Because a northward shift of distributions might be due to multidirectional range expansions for multiple species, we also examined the possibility that birds with northern distributions may be expanding their ranges southward. There was no southward expansion of birds with a northern distribution, indicating that there is no evidence of overall range expansion of insectivorous and granivorous birds in North America. As predicted, the northern limit of birds with a southern distribution showed a significant shift northward (2.35 km/year). This northward shift is similar to that observed in previous work conducted in Great Britain: the widespread nature of this shift in species distributions over two distinct geographical regions and its coincidence with a period of global warming suggests a connection with global climate change.
What environmental fate processes have the strongest influence on a completely persistent organic chemical’s accumulation in the Arctic?
Meyer, T Wania, F
ATMOSPHERIC ENVIRONMENT 41:13 2757-2767
Fate and transport models can be used to identify and classify chemicals that have the potential to undergo long-range transport and to accumulate in remote environments. For example, the Arctic contamination potential (ACP), calculated with the help of the zonally averaged global transport model Globo-POP, is a numerical indicator of an organic chemical’s potential to be transported to polar latitudes and to accumulate in the Arctic ecosystem. It is important to evaluate how robust such model predictions are and in particular to appreciate to what extent they may depend on a specific choice of environmental model input parameters. Here, we employ a recently developed graphical method based on partitioning maps to comprehensively explore the sensitivity of ACP estimates to variations in environmental parameters. Specifically, the changes in the ACP of persistent organic contaminants to changes in each environmental input parameter are plotted as a function of the two-dimensional hypothetical “chemical space” defined by two of the three equilibrium partition coefficients between air, water and octanol. Based on the patterns obtained, this chemical space is then segmented into areas of similar parameter sensitivities and superimposed with areas of high default ACP and elevated environmental bioaccumulation potential within the Arctic. Sea ice cover, latitudinal temperature gradient, and macro-diffusive atmospheric transport coefficients, and to a lesser extent precipitation rate, display the largest influence on ACP-values for persistent organic contaminants, including those that may bioaccumulate within the polar marine ecosystems. These environmental characteristics are expected to be significantly impacted by global climate change processes, highlighting the need to explore more explicitly how climate change may affect the long-range transport and accumulation behavior of persistent organic pollutants. (C) 2006 Elsevier Ltd. All rights reserved.
Influence of elevated CO2 concentrations on thermal tolerance of the edible crab Cancer pagurus
Metzger, R Sartoris, FJ Langenbuch, M Portner, HO
JOURNAL OF THERMAL BIOLOGY 32:3 144-151
Current trends of global climate change affect marine ectothermal animals not only through the increase in ambient temperature. Synergistic effects of carbon dioxide and temperature changes as well as more frequent hypoxia events must also be considered. As a first attempt, the combined effects of warming and elevated CO2 concentrations were investigated in the edible crab (Cancer pagurivs). Arterial oxygen tension (PaO2) in the haemolymph was recorded on-line during a progressive warming scenario from 10 to 22 degrees C and cooling back to 10 degrees C. Hypercapnia (1% CO2) caused a significant reduction of oxygen partial pressure in the haemolymph as well as a large, 5 degrees C downward shift of upper thermal limits of aerobic scope. The present findings are the first to show that hypercapnia causes enhanced sensitivity to heat and thus, a narrowing of the thermal tolerance window of a marine ectotherm. Such interactions of ambient temperature and anthropogenic increases in ambient CO2 concentrations will need to be considered during future investigations of the effects of climate change on ecosystems. (c) 2007 Elsevier Ltd. All rights reserved.
Spatial and temporal effects of pre-seeding plates with invasive ascidians: Growth, recruitment and community composition
JOURNAL OF EXPERIMENTAL MARINE BIOLOGY AND ECOLOGY 342:1 30-39
Many shallow water subtidal habitats in Massachusetts, USA have recently been invaded by five non-indigenous ascidian species: Ascidiella aspersa, Botrylloides violaceus, Didemnum sp., Diplosoma listerianum and Styela clava. This study examined the effects of seawater temperature, as a proxy for climate change, on B. violaceus and D. listerianum and the impact these ascidians have on native sessile fouling communities. Field experiments were conducted over a four month period at two locations (Lynn and Woods Hole, MA) to examine growth dynamics over regional thermal and geographic ranges. Invasive ascidians occupied as much as 80% of the primary substratum and accounted for the majority of species richness. B. violaceus and D. listerianum growth were similar at both study sites, but initial colony growth of D. listerianum was positively affected by temperature. B. violaceus and D. listerianum exhibited rapid two-week growth rates during the summer months with more rapid growth at the warmer Woods Hole site. Competition for space between B. violaceus and D. listerianum typically resulted in neutral borders between colonies. Overgrowth occurred if the colony of one species was disproportionably larger than the colony of the other species. Recruitment and growth of native species influenced the long-term composition of experimental communities more than the pre-seeding with B. violaceus or D. listerianum colonies. Elevated temperatures, however, increased initial growth of B. violaceus and D. listerianum and may have facilitated the species success to invade the communities during crucial periods of introduction. With projected global climate change, a rise in sea surface temperatures may exacerbate the cumulative impacts of invasions on benthic communities and facilitate the invasion of other non-native ascidian species. (c) 2006 Elsevier B.V. All rights reserved.
Biogenic secondary organic aerosol over the United States: Comparison of climatological simulations with observations
Liao, H Henze, DK Seinfeld, JH Wu, SL Mickley, LJ
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES 112:D6 -
Understanding the effects of global climate change on regional air quality is central in future air quality planning. We report here on the use of the Goddard Institute for Space Studies ( GISS) general circulation model ( GCM) III to drive the GEOS-CHEM global atmospheric chemical transport model to simulate climatological present-day aerosol levels over the United States. Evaluation of model predictions using surface measurements from the Interagency Monitoring of Protected Visual Environments ( IMPROVE) network indicates that the GISS GCM III/GEOS-CHEM model is a suitable tool for simulating aerosols over the United States in the present climate. The model reproduces fairly well the concentrations of sulfate ( mean bias of -0.36 mu g m(-3), normalized mean bias ( NMB) of -25.9%), black carbon ( -0.004 mu g m(-3), -1.9%), organic carbon that comprises primary and secondary components ( -0.56 mu g m(-3), -34.2%), and PM2.5 (-0.87 mu g m(-3), -20.4%). Nitrate concentrations are overpredicted in the western United States ( west of 95 degrees W) with a NMB of +75.6% and underestimated in the eastern United States with a NMB of -54.4%. Special attention is paid to biogenic secondary organic aerosol ( SOA). The highest predicted seasonal mean SOA concentrations of 1-2 mu g m(-3) and 0.5-1.5 mu g m(-3) are predicted over the northwestern and southeastern United States, respectively, in the months of June-July-August. Isoprene is predicted to contribute 49.5% of the biogenic SOA burden over the United States, with the rest explained by the oxidation of terpenes. Predicted biogenic SOA concentrations are in reasonable agreement with inferred SOA levels from IMPROVE measurements. On an annual basis, SOA is predicted to contribute 10-20% of PM2.5 mass in the southeastern United States, as high as 38% in the northwest and about 5-15% in other regions, indicating the important role of SOA in understanding air quality and visibility over the United States.
A new economic assessment index for the impact of climate change on grain yield
Dong, WJ Chou, JM Feng, GL
ADVANCES IN ATMOSPHERIC SCIENCES 24:2 336-342
The impact of climate change on agriculture has received wide attention by the scientific community. This paper studies how to assess the grain yield impact of climate change, according to the climate change over a long time period in the future as predicted by a climate system model. The application of the concept of a traditional “yield impact of meteorological factor (YIMF)” or “yield impact of weather factor” to the grain yield assessment of a decadal or even a longer timescale would be suffocated at the outset because the YIMF is for studying the phenomenon on an interannual timescale, and it is difficult to distinguish between the trend caused by climate change and the one resulting from changes in non-climatic factors. Therefore, the concept of the yield impact of climatic change (YICC), which is defined as the difference in the per unit area yields (PUAY) of a grain crop under a changing and an envisaged invariant climate conditions, is presented in this paper to assess the impact of global climate change on grain yields. The climatic factor has been introduced into the renowned economic Cobb-Douglas model, yielding a quantitative assessment method of YICC using real data. The method has been tested using the historical data of Northeast China, and the results show that it has an encouraging application outlook.
Impact of changes in rainfall amounts predicted by climate-change models on decomposition in a deciduous forest
Lensing, JR Wise, DH
APPLIED SOIL ECOLOGY 35:3 523-534
Climate-change models predicta more intense hydrological cycle, with both increased and decreased amounts of rainfall in areas covered with temperate deciduous forests. These changes could alter rates of litter decomposition, with consequences for rates of nutrient cycling in the forest ecosystem. To examine impacts of predicted changes in precipitation on the rate of decay of canopy leaves, we placed litterbags in replicated, fenced 14 m(2) low-rainfall and high-rainfall plots located under individual rainout shelters. Unfenced, open plots served as an ambient treatment. Litter in the high-rainfall and ambient plots decayed 50% and 78% faster, respectively, than litter in the low-rainfall plots. Litter in the ambient plots disappeared 20% faster than in the high-rainfall treatment, perhaps via greater leaching during heavy rainfall events. Ambient rainfall during the experiment was similar in total amount to the high-rainfall treatment, but was more variable in intensity and timing. We used litterbags of different mesh sizes to examine whether changes in rainfall might alter the impacts of major categories of the fauna on litter decay. However, we found no consistent evidence that excluding arthropods of different sizes affected litter decay rate within any of the three rainfall treatments. This research reveals that changes in rainfall predicted to occur with global climate change will likely strongly alter rates of litter decay in deciduous forests. (c) 2006 Elsevier B.V. All rights reserved.
Impact of local temperature increase on the early development of biofilm-associated ciliate communities
Norf, H Arndt, H Weitere, M
OECOLOGIA 151:2 341-350
Indications of global climate change and associated unusual temperature fluctuations have become increasingly obvious over the past few decades. Consequently, the relevance of temperature increases for ecological communities and for whole ecosystems is one of the major challenges of current ecological research. One approach to investigating the effects of increasing temperatures on communities is the use of fast-growing microbial communities. Here we introduce a river bypass system in which we tested the effect of temperature increases (0, 2, 4, 6 degrees C above the long-term average) on both the colonization speed and the carrying capacity of biofilm-associated ciliate communities under different seasonal scenarios. We further investigated interactions of temperature and resource availability by cross-manipulations in order to test the hypothesis that temperature-mediated effects will be strongest in environments that are not resource-limited. Strong seasonal differences in both tested parameters occurred under natural conditions (no resource addition), and the effects of temperature increase at a given time were relatively low. However, increasing temperature can significantly accelerate the colonization speed and reduce the carrying capacity in particular seasons. These effects were strongest in winter. Simultaneous manipulation of temperature and of resource availability amplified the response to temperature increase, adumbrating strong interactive control of populations by temperature and resource availability. Our results show that the response of communities to local temperature increases strongly depends on the seasonal setting, the resource availability and the stage of succession (early colonization speed vs. carrying capacity).
Climate change and the emergence of Vibrio vulnificus disease in Israel
Paz, S Bisharat, N Paz, E Kidar, O Cohen, D
ENVIRONMENTAL RESEARCH 103:3 390-396
In 1996, a major unexplained outbreak of systemic Vibrio vulnificus infection erupted among Israeli fish market workers. The origins of this emergent infectious disease have not been fully understood. A possible link between climate change and disease emergence is being investigated. Meteorological service data from 1981, the earliest detection and reporting of V vulnificus for the time in Israel, to 1998 for two stations located within the main inland fish farm industry were analyzed. The 1996-1998 summers were identified as the hottest ever recorded in Israel in the previous 40 years. Time series of monthly minimum, maximum, and mean temperatures showed significant increase in the summer temperatures along the 18 years. The highest minimum temperature value was recorded in summer 1996. Lag correlation analysis revealed significant correlations between temperature values and hospital admission dates. The eruption appeared 25-30 days after the extreme heat conditions in summer 1996, at a lag of 3 weeks in summer 1997 while the results for 1998 were at a lag of less than a week. Higher significant results were detected for the daily minimum temperatures in summer 1996 compatible with the disease eruption. These findings suggest that high water temperature might have impacted the ecology of our study area and caused the emergence of the disease, as an effect of global climate change. (c) 2006 Elsevier Inc. All rights reserved.
Kiln-drying lumber quality of hybrid poplar clones
Kang, KY Bradic, S Avramidis, S Mansfield, SD
HOLZFORSCHUNG 61:1 65-73
Hybrid poplars are currently used in North America primarily for the production of pulp fibre and in the manufacture of engineered solid wood products. Recently, the deployment of poplars as a short-rotation fibre crop has been of interest to mitigate the increasing amount of plantation-grown short fibre resources (hardwoods) derived from the Southern Hemisphere, as well as in the context of global climate change, both as a means to rapidly sequester carbon and as a feedstock for potential bioenergy production. Knowledge on the utility of hybrid poplars in the value-added secondary wood-processing sector, however, is very limited. To improve this situation, the variation in kiln-drying quality of five hybrid poplar genotypes of similar age, harvested from a common site in British Columbia, Canada, was evaluated for three different kiln-drying schedules. The results clearly demonstrate that the drying schedule has a greater effect on grade recovery and the degree of deformation than the hybrid poplar genotype. Furthermore, it was shown that many of the deformations inherently associated with wood derived from fast-grown trees can be reduced or removed with drying, in particular with an aggressive drying schedule.
Analysis and prognosis of tropical cyclone genesis over the western North Pacific on the background of global warming
Li, YP Wang, XF Yu, RL Qin, ZH
ACTA OCEANOLOGICA SINICA 26:1 23-34
As revealed by the observational study, there are more tropical cyclones generated over the western North Pacific from the early 1950s to the early 1970s in the 20th century and less tropical cyclones from the mid-1970s to the present. The decadal change of tropical cyclones activities are closely related to the decadal changes of atmospheric general circulation in the troposphere, which provide favorable or unfavorable conditions for the formation of tropical cyclone. Furthermore, based on the simulation of corresponding atmospheric general circulation from a coupled climate model under the schemes of Intergovernmental Panel on Climate Change (IPCC) special report on emission scenarios (SRES) A2 and B emissions scenarios an outlook on the tropical cyclone frequency generated over the western North Pacific in the coming half century is presented. It is indicated that in response to the global climate change the general circulation of atmosphere would become unfavorable for the formation of tropical cyclone as a whole and the frequency of tropical cyclones formation would likely decrease by 5% within the next half century, although more tropical cyclones would appear during a short period in it.
Scientists’ perceptions of threats to Coral Reefs: Results of a survey of Coral Reef researchers
Kleypas, JA Eakin, CM
BULLETIN OF MARINE SCIENCE 80:2 419-436
Prior to the 10(th) International Coral Reef Symposium in Okinawa, Japan, in June 2004, symposium participants and members of the International Society for Reef Studies were surveyed to obtain their opinions about the major threats facing coral reef ecosystems. Responses from 286 participants were analyzed and compared to results obtained in a similar survey conducted in 1993. Respondents tended to rank highest those threats associated with human population growth, coastal development, and overfishing. While coral bleaching was ranked much more highly than in the 1993 survey, about two-thirds of the respondents felt that direct human impacts were worse threats than those associated with global climate change.
Temperature sensitivity of vertical distributions of zooplankton and planktivorous fish in a stratified lake
Helland, IP Freyhof, J Kasprzak, P Mehner, T
OECOLOGIA 151:2 322-330
Recent studies have indicated that temporal mismatches between interacting populations may be caused by consequences of global warming, for example rising spring temperatures. However, little is known about the impact of spatial temperature gradients, their vulnerability to global warming, and their importance for interacting populations. Here, we studied the vertical distribution of two planktivorous fish species (Coregonus spp.) and their zooplankton prey in the deep, oligotrophic Lake Stechlin (Germany). The night-time vertical centre of gravity both of the fish populations and of two of their prey groups, daphnids and copepods, were significantly correlated to the seasonally varying water temperature between March and December 2005. During the warmer months, fish and zooplankton occurred closer to the surface of the lake and experienced higher temperatures. The Coregonus populations differed significantly in their centre of gravity; hence, also, the temperature experienced by the populations was different. Likewise, daphnids and copepods occurred in different water depths and hence experienced different temperatures at least during the summer months. We conclude that any changes in the vertical temperature gradient of the lake as a result of potential future global warming may impact the two fish populations differently, and may shape interaction strength and timing between fish and their zooplankton prey.
Using dynamical downscaling to close the gap between global change scenarios and local permafrost dynamics
Stendel, M Romanovsky, VE Christensen, JH Sazonova, T
GLOBAL AND PLANETARY CHANGE 56:1-2 203-214
Even though we can estimate the zonation of present-day permafrost from deep-soil temperatures obtained from global coupled atmosphere-ocean general circulation models (GCMs) by accounting for heat conduction in the frozen soil, it is impossible to explicitly resolve soil properties, vegetation cover and ice contents in great details. On the local scale, descriptions of the heterogeneous soil structure in the Arctic exist only for limited areas. Semi-empirical approaches, e.g. based on the Stefan [Stefan, J., 1891. Uber die Theorie der Eisbildung, insbesondere uber Eisbildung im Polarmeere. Ann. Phys. 42, 269-286] formula, give a more realistic depiction of permafrost temperatures and active layer thicknesses while at the same time avoiding problems inevitably associated with the explicit treatment of soil freezing and thawing. The coarse resolution of contemporary GCMs models that prevents a realistic description of soil characteristics, vegetation, and topography within a model grid box is the major limitation for use in permafrost modelling. We propose to narrow the gap between typical GCMs on one hand and local permafrost models on the other by introducing as an intermediate step a high resolution regional climate model (RCM) to downscale surface climate characteristics to a scale comparable to that of a detailed permafrost model. Forcing the permafrost model with RCM output results in a more realistic depiction of present-day mean annual ground temperature and active layer depth, in particular in mountainous regions. By using global climate change scenarios as driving fields, one can obtain permafrost dynamics in high temporal resolution on the order of years. For the 21st century under the IPCC SIZES scenarios A2 and B2, we find an increase of mean annual ground temperature by up to 6 K and of active layer depth by up to 2 m within the East Siberian transect. According to these simulations, a significant part of the transect will suffer from permafrost degradation by the end of the century. (C) 2006 Elsevier B.V. All rights reserved.
Diurnal temperature range and daily mortality in Shanghai, China
Kan, HD London, SJ Chen, HL Song, GX Chen, GH Jiang, LL Zhao, NQ Zhang, YH Chen, BH
ENVIRONMENTAL RESEARCH 103:3 424-431
Although the relationship between temperature level and mortality outcomes has been well established, it is still unknown whether within-day variation in temperature, e.g. diurnal temperature range (DTR), is a risk factor for death independent of the corresponding temperature. Moreover, DTR is a meteorological indicator associated with global climate change which may be related to a variety of health outcomes. We hypothesized that large diurnal temperature change might be a source of additional environmental stress and therefore a risk factor for death. We used daily weather and mortality data from Shanghai, China to test this hypothesis. We conducted a time-series study to examine the association between DTR and mortality outcomes from 2001 to 2004. A semi-parametric generalized additive model (GAM) was used to assess the acute effect of DTR on mortality after controlling for covariates including time trend, day of the week (DOW), temperature, humidity, and outdoor air pollution. We found a strong association between DTR and daily mortality after adjustment for those potential confounders. A 1 degrees C increment of the 3-day moving average of DTR corresponded to a 1.37% (95% Cl 1.08-1.65%) increase in total non-accidental mortality, a 1.86% (95% CI 1.40-2.32%) increase in cardiovascular mortality, and a 1.29% (95% Cl 0.49-2.09%) increase in respiratory mortality. The effects of DTR on total non-accidental and cardiovascular mortality were significant on both “cold” (below 23 degrees C) and “warm” (at least 23 degrees C) days, although respiratory mortality was only significantly associated with DTR on “cold” days. This study suggests within-day variation in temperature may be a novel risk factor for death. (c) 2006 Elsevier Inc. All rights reserved.
Daytime, temporal, and seasonal variations of N2O emissions in an upland cropping system of the humid tropics
Khalil, MI Van Cleemput, O Rosenani, AB Schmidhalter, U
COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 38:1-2 189-204
Nitrous oxide (N2O) contributes to global climate change, and its emission from soil-crop systems depend on soil, environmental, and anthropogenic factors. Thus, we evaluated the variability of N2O emissions measured by microchambers (cross section: 184 cm(2)) from a groundnut-fallow-maize-fallow cropping system of the humid tropics. The crops received inorganic nitrogen (N) plus crop residues (NC), inorganic N alone as ammonium sulfate (RN), and half of the inorganic N along with crop residues and chicken manure (N1/2CM), amounting for the crop rotation to 322, 180, and 400 kg N ha(-1) yr(-1), respectively. The N2O fluxes during the groundnut-maize crop rotation were log-normally distributed, and the frequency distributions were positively skewed. Daytime changes in N2O fluxes were inconsistent, and the 50% of total N2O emission during the 12 h measurement periods was attained earlier under maize (-11 : 00 h) than groundnut covers (- 13: 00 h). Spatial variability in each treatment with eight gas chambers was large but smaller during the cropping periods than the fallow, indicating masking efficiency of crop covers for the soil heterogeneity that was accelerated presumably by antecedent climatic variables. The temporal variability of N2O emissions was also large (coefficients of variation, CV, ranged from 60 to 81%), involving both input differences between treatments and measurement periods. As such, the relative deviation from the annual mean of total N2O emission was high during the period after a large N application with a maximum of +480%, due to addition of chicken manure. The seasonal contribution of summer and monsoon to N2O emissions was insignificant. However, intensive rainfall negatively (-0.65**) and the amount of added N from either source positively (0.83***) correlated with the integrated N2O emissions, and those were exponential. Results suggest that around noon (12: 00 h) gas collection could represent well the daily N2O fluxes, increasing the number or size of the gas chambers could minimize the large variability, and mainly the rainfall and N inputs regulated its emissions in the humid tropics of Malaysia.
Resurrection ecology and global climate change research in freshwater ecosystems
JOURNAL OF THE NORTH AMERICAN BENTHOLOGICAL SOCIETY 26:1 12-22
The complex effects of global climate change on freshwater ecosystems limit our ability to predict biological responses in a standard way and may compromise ecosystem management with respect to potential changes. I present a theoretical framework that shows the usefulness of resurrection ecology for standardizing cross-system comparisons of ecological responses to global climate change. Resurrection ecology makes use of plant seed and animal resting-egg (propagule) banks that integrate past environmental histories in the gene pools of their organisms. Resurrected organisms that have undergone different periods of dormancy can be studied comparatively using evolutionary/genetic and experimental approaches. Both approaches combined can provide insights into how the dimensions of species’ ecological niches have shifted over time and could help reveal whether direct effects of climate change (increased temperatures and CO2 concentrations and hydrological alterations) or other anthropogenic stressors (e.g., contamination, landuse change) have caused microevolution. Insights gained from resurrection ecology could be used to manage gene flow between populations and to help prevent extinctions of threatened populations. These insights could be used to help manage ecosystem structure and function and maintain ecological sustainability. However, our ability to apply results from resurrection ecology to organisms that do not have long-term dormancy stages in their life cycles may be limited, and the usefulness of resurrection ecology will have to be evaluated along gradients of hydroperiod and flood frequency, which may determine rates of microevolution in aquatic ecosystems.
Regional land surface energy fluxes by satellite remote sensing in the Upper Xilin River Watershed (Inner Mongolia, China)
Fan, L Liu, S Bernhofer, C Liu, H Berger, FH
THEORETICAL AND APPLIED CLIMATOLOGY 88:3-4 231-245
The Inner Mongolia grassland of China is representative of semi-arid grasslands in temperate zones. Studying land surface processes in this region will improve the understanding of regional climate formation and the feedback with global climate change. Satellite remote sensing provides an excellent opportunity to study land-atmosphere interactions at the regional scale. It is necessary to develop feasible and reasonable remote sensing-based methods to map surface energy fluxes for a specific study area. In this paper, previously published algorithms and empirical formulae were tested with Landsat 7 ETM+ data to derive the regional distributions of land surface reflectance, surface temperature, NDVI and land surface energy fluxes (net radiation, soil heat flux, sensible heat flux and latent heat flux) over the upper Xilin River watershed in Inner Mongolia, China. A new land use/land cover classification was developed and applied for regionalization analysis. Validation of remote sensing derived surface reflectance, surface temperature, net radiation and sensible heat flux with field measurements shows differences of about 13, 4, 1, and 28%, respectively. This study provides valuable guidance for further investigation of the whole watershed.
Past and future changes in climate and hydrological indicators in the US Northeast
Hayhoe, K Wake, CP Huntington, TG Luo, LF Schwartz, MD Sheffield, J Wood, E Anderson, B Bradbury, J DeGaetano, A Troy, TJ Wolfe, D
CLIMATE DYNAMICS 28:4 381-407
To assess the influence of global climate change at the regional scale, we examine past and future changes in key climate, hydrological, and biophysical indicators across the US Northeast (NE). We first consider the extent to which simulations of twentieth century climate from nine atmosphere-ocean general circulation models (AOGCMs) are able to reproduce observed changes in these indicators. We then evaluate projected future trends in primary climate characteristics and indicators of change, including seasonal temperatures, rainfall and drought, snow cover, soil moisture, streamflow, and changes in biometeorological indicators that depend on threshold or accumulated temperatures such as growing season, frost days, and Spring Indices (SI). Changes in indicators for which temperature-related signals have already been observed (seasonal warming patterns, advances in high-spring streamflow, decreases in snow depth, extended growing seasons, earlier bloom dates) are generally reproduced by past model simulations and are projected to continue in the future. Other indicators for which trends have not yet been observed also show projected future changes consistent with a warmer climate (shrinking snow cover, more frequent droughts, and extended low-flow periods in summer). The magnitude of temperature-driven trends in the future are generally projected to be higher under the Special Report on Emission Scenarios (SRES) mid-high (A2) and higher (A1FI) emissions scenarios than under the lower (B1) scenario. These results provide confidence regarding the direction of many regional climate trends, and highlight the fundamental role of future emissions in determining the potential magnitude of changes we can expect over the coming century.
Estimating organic carbon from loss-on-ignition in northern Arizona forest soils
Abella, SR Zimmer, BW
SOIL SCIENCE SOCIETY OF AMERICA JOURNAL 71:2 545-550
Many studies in ecology, soil science, and global climate change require accurate estimates of soil organic C (SOC). When calibrated with direct SOC determinations, loss-on-ignition (LOI) has been proposed as a rapid, inexpensive, and accurate method for estimating SOC. We collected 0- to 15- and 15- to 50-cm mineral soil samples from 102 plots within a 110000-ha ponderosa pine (Pinus ponderosa P & C. Lawson) landscape to develop regression equations between LOI and SOC measured with an elemental C analyzer. We tested nine LOI temperature-duration combinations ranging from 300 to 600 C and 2 to 6 h to discern optimal combinations for estimating SOC, used the optimal combination to develop regressions for 100 samples each of 0- to 15- and 15- to 50-cm depths, and assessed whether stratifying samples into ecosystem types improved LOI-SOC equations. Pearson r(2) values between LOI and SOC did not exceed 0.74 for any LOI temperature-duration combination. These values showed no consistent trend to change with increasing duration, but tended to be slightly higher at the lowest temperature (300 degrees C). Multiple regressions, including LOI and clay concentration, explained only 78 (0-15 cm) and 64% (15-50 cm) of the variation in SOC. Relationships between LOl and SOC found in this study are among the weakest reported in the soil literature, and it remains unclear precisely why observed relationships were weak. Our results suggest that LOI may be useful for roughly estimating SOC in this region, but other methods or modifications to LOI are needed when more accurate SOC measurements are required.
Global cooling forced increase in marine strontium isotopic ratios: Importance of mica weathering and a kinetic approach
Li, GJ Chen, J Ji, JF Liu, LW Yang, JD Sheng, XF
EARTH AND PLANETARY SCIENCE LETTERS 254:3-4 303-312
The knowledge of how and why marine Sr-87/Sr-86 ratios changed helps understand the impacts of many processes on the global biogeochemical cycle in the geological past. Here we examine the possible influence of global cooling on the evolution of marine Sr-87/Sr-86 curve by a kinetic approach. The importance of mica weathering is emphasized due to its high content of radiogenic strontium and low activation energy in weathering reaction. Since the activation energy determines the sensitivity of weathering rate in response to temperature changes, global cooling will increase the Sr-87/Sr-86 ratio of continental flux by relatively preferential weathering of mica. Based on the average strontium contents and Sr-87/Sr-86 ratios of the mica minerals in the exposed upper continental crust, a kinetic model is established to survey the response of riverine Sr-87/Sr-86 to the changes of global temperatures. The model result indicates that the increase of riverine Sr-87/Sr-86 caused by global cooling can solely account for most of the increase in seawater Sr-87/Sr-86 since 3.4 Myr B.P. This finding emphasizes that the weathering kinetics is an important mechanism relating the global climate change to marine Sr-87/Sr-86 curve; and the marine Sr-87/Sr-86 curve should be used with great care in the climate-weathering-tectonic connections. (c) 2006 Elsevier B.V All rights reserved.
Inverse flood risk modelling under changing climatic conditions
Cunderlik, JM Simonovic, SP
HYDROLOGICAL PROCESSES 21:5 563-577
One of the most significant anticipated consequences of global climate change is the increased frequency of hydrologic extremes. Predictions of climate change impacts on the regime of hydrologic extremes have traditionally been conducted using a top-down approach. The top-down approach involves a high degree of uncertainty associated with global circulation model (GCM) outputs and the choice of downscaling technique. This study attempts to explore an inverse approach to the modelling of hydrologic risk and vulnerability to changing climatic conditions. With a focus targeted at end-users, the proposed approach first identifies critical hydrologic exposures that may lead to local failures of existing water resources systems. A hydrologic model is used to transform inversely the main hydrologic exposures, such as floods and droughts, into corresponding meteorological conditions. The frequency of critical meteorological situations is investigated under present and future climatic scenarios by means of a generic weather generator. The weather generator, linked with GCMs at the last step of the proposed methodology, allows the creation of an ensemble of different scenarios, as well as an easy updating, when new and improved GCM outputs become available. The technique has been applied in Ontario, Canada. The results show significant changes in the frequency of hydro-climatic extremes under future climate scenarios in the study area. Copyright (c) 2007 John Wiley & Sons, Ltd.
Changes in biotic interactions and climate determine recruitment of Jeffrey pine along an elevation gradient
Gworek, JR Wall, SBV Brussard, PF
FOREST ECOLOGY AND MANAGEMENT 239:1-3 57-68
The mechanisms by which climate affects recruitment and loss of plants and the interactions between those plants and other organisms (e.g., pathogens, granivores, seed dispersers) have seldom been studied in the context of plant response to climate change. We examined how climate influences Jeffrey pine (Pines jeffreyi) recruitment, mortality, and species interactions at three elevation zones (low, mid, high) across its elevation range (1550-2470 m) in the semi-arid Carson Range of western Nevada. Local climate was correlated with several aspects of stand structure, including smaller trees, slower growth rates, greater predation by seed insects, and higher tree mortality at low elevation. Cone crop was not affected by elevation, but there were more mature trees and more filled seeds per cone at mid- and high elevations. Populations of seed-caching rodents were largest at mid-elevation, but sufficient rodents were present at all elevations to cause rapid removal and dispersal of pine seeds. Seedling emergence from rodent caches was greatest at low and middle elevation, but seedling survival was best at middle and high elevations. The number of saplings was greatest at mid-elevation sites. These results suggest a retracting population at low elevation (high adult tree mortality and low recruitment), a rapidly expanding population at mid-elevation (low adult tree mortality and high recruitment), and a slowly expanding population at high elevation (low adult tree mortality and low recruitment). These demographic patterns foreshadow a shift in distribution upslope over future decades, driven by changes in climate and facilitated by biotic interactions. (c) 2006 Elsevier B.V. All rights reserved.
On the sensitivity of radiative forcing from biomass burning aerosols and ozone to emission location
Naik, V Mauzerall, DL Horowitz, LW Schwarzkopf, MD Ramaswamy, V Oppenheimer, M
GEOPHYSICAL RESEARCH LETTERS 34:3 -
Biomass burning is a major source of air pollutants, some of which are also climate forcing agents. We investigate the sensitivity of direct radiative forcing due to tropospheric ozone and aerosols (carbonaceous and sulfate) to a marginal reduction in their ( or their precursor) emissions from major biomass burning regions. We find that the largest negative global forcing is for 10% emission reductions in tropical regions, including Africa (- 4.1 mWm(-2) from gas and - 4.1 mWm(-2) from aerosols), and South America (- 3.0 mWm(-2) from gas and - 2.8 mWm(-2) from aerosols). We estimate that a unit reduction in the amount of biomass burned in India produces the largest negative ozone and aerosol forcing. Our analysis indicates that reducing biomass burning emissions causes negative global radiative forcing due to ozone and aerosols; however, regional differences need to be considered when evaluating controls on biomass burning to mitigate global climate change.
Effects of climate change on water resources in Tarim River Basin, Northwest China
Chen, YN Li, WH Xu, CC Hao, XM
JOURNAL OF ENVIRONMENTAL SCIENCES-CHINA 19:4 488-493
Based on hydrology, temperature, and precipitation data from the past 50 years, the effects of climate change on water resources in Tarim River Basin in Northwest China were investigated. The long-term trends of the hydrological time series were detected using both parametric and nonparametric techniques. The results showed that the increasing tendency of the temperature has a 5% level of significance, and the temperature increased by nearly VC over the past 50 years. The precipitation showed a significant increase in the 1980s and 1990s, and the average annual precipitation exhibited an increasing trend with a magnitude of 6.8 mm per decade. A step change occurred in both the temperature and precipitation time series around 1986. The streamflow from the headwater of the Tarim River exhibited a significant increase during the last 20 years. The increase in temperature, precipitation, and streamflow may be attributed to global climate change.
Exploring linkages between abiotic oceanographic processes and a top-trophic predator in an Antarctic ecosystem
Proffitt, KM Garrott, RA Rotella, JJ Siniff, DB Testa, JW
ECOSYSTEMS 10:1 119-126
Climatic variation affects the physical and biological components of ecosystems, and global-climate models predict enhanced sensitivity in polar regions, raising concern for Antarctic animal populations that may show direct responses to changes in sea-ice distribution and extent, or indirect responses to changes in prey distribution and abundance. Here, we show that over a 30-year period in the Ross Sea, average weaning masses of Weddell seals, Leptonychotes weddellii, varied strongly among years and were correlated to large-scale climatic and oceanographic variations. Foraging success of pregnant seals (reflected by weaning mass the following pupping season) increased during summers characterized by reduced sea-ice cover and positive phases of the southern oscillation. These results demonstrate a correlation between environmental variation and an important life history characteristic (weaning mass) of an Antarctic marine mammal. Understanding the mechanisms that link climatic variation and animal life history characteristics will contribute to understanding both population dynamics and global climatic processes. For the world’s most southerly distributed mammal species, the projected trend of increasing global climate change raises concern because increasing sea-ice trends in the Ross Sea sector of Antarctica will likely reduce populations due to reduced access to prey as expressed through declines in body condition and reproductive performance.
Consistency of interdecadal variation in the summer monsoon over eastern China and heterogeneity in springtime surface air temperatures
Xu, XD Shi, XH Xie, L Wang, YF
JOURNAL OF THE METEOROLOGICAL SOCIETY OF JAPAN 85A: 311-323
This study investigates the consistency of interdecadal variations in the East Asian summer monsoon (EASM) and changes in the heterogeneous structure of sea/land springtime surface air temperature (SAT) over eastern China and the adjacent ocean (including the South China Sea and part of the Western Pacific Ocean). A profile of the summer mean meridional wind over eastern China for the past 40 years shows a coherent interdecadal weakening trend for the EASM. The decadal-scale (11-year running mean) summertime (June-August) wind and springtime (March-May) SAT fields are decomposed using the empirical orthogonal function (EOF) method. The results indicate that both the leading eigenvector of the decadal-scale meridional wind and that for the SAT over East Asia account for more than 70% of the total variance. Their time coefficients show a similar trend, with the transition from negative to positive values occurring around 1978; i.e., the EASM turned from a stronger phase to a weaker phase around 1978. The springtime sea/land SAT distribution before and after 1978 also showed a shift in interdecadal trends. Therefore, the south-low/north-high nature of the principal component of springtime SAT over eastern China is closely related to the progressive weakening of the EASM. Our results suggest that within the context of the regional impact of global climate change, heterogeneous changes in the regional springtime sea/land SAT in eastern Asia might in part have led to a weakening of the effect of sea/land thermal driving on the EASM.
Soil carbon and nitrogen stores and storage potential as affected by land-use in an agro-pastoral ecotone of northern China
Zhou, ZY Sun, OJ Huang, JH Li, LH Liu, P Han, XG
BIOGEOCHEMISTRY 82:2 127-138
Equilibrium carbon stock is the result of a balance between inputs and outflows to the pool. Changes in land-use are likely to alter such balance, resulting in different carbon stores under different land-use types in addition to the impacts of global climate change. In an agro-pastoral ecotone of Inner Mongolia, northern China, we investigated productivity and belowground carbon and nitrogen stores under six different types of land-uses, namely free grazing (FG), grazing exclusion (GE), mowing (MW), corn plantation (CP), fallow (FL), and alfalfa pasture (AP), and their impacts on litter and fine roots in semiarid grassland ecosystems. We found that there were great variations in aboveground net primary production (ANPP) across the six land-use types, with CP having markedly high ANPP; the FG had significantly reduced soil organic carbon (SOC) and nitrogen stores (SON) to 100 cm depth compared with all other types of land uses, while very little litter accumulation was found on sites of the FG and CP. The top 20 cm of soils accounted for about 80% of the root carbon and nitrogen, with very little roots being found below 50 cm. About 60% of SOC and SON were stored in the top 30 cm layer. Land-use change altered the inputs of organic matters, thus affecting SOC and SON stores accordingly; the MW and GE sites had 59 and 56% more SOC and 61% more SON than the FG. Our estimation suggested that restoring severely degraded and overgrazed grasslands could potentially increase SOC and SON stores by more than 55%; conversion from the native grasses to alfalfa could potentially double the aboveground biomass production, and further increase SOC and SON stores by more than 20%. Our study demonstrated significant carbon and nitrogen storage potential of the agro-pastoral ecotone of northern China through land-use changes and improved management in the context of mitigating global climate change.
The potential bioavailability of organic C, N, and P through enzyme hydrolysis in soils of the Mojave Desert
Nadeau, JA Qualls, RG Nowak, RS Blank, RR
BIOGEOCHEMISTRY 82:3 305-320
Increases in the growth rate of plants and microbes in the Mojave Desert in response to predicted increases in precipitation and CO2 due to global climate change may induce nutrient limitations. This study was designed to measure the pool of potentially bioavailable nutrients in soils of the Mojave Desert. Soils were collected from shrub and interspace microsites and then subjected to amendment with buffered solutions of an excess of various enzymes. The products of each enzyme reaction were then measured and the maximum quantity of hydrolyzable substrates was calculated. In interspace and shrub microsite soils, respectively, 14.5 and 9.7% of the organic C in the form cellulose, 60.0-97.8% and 61.2-100.0% of the organic N in the form protein, and 44.0 and 57.5% of the organic P was hydrolyzable. There were significant differences between microsites for hydrolyzable substrate using all enzyme amendments, except protease. We propose that accumulations of hydrolyzable organic C, N, and P in the Mojave Desert could be a result of the persistently dry soil conditions often found in desert ecosystems and the immobilization of enzymes, which may result in low diffusivity of soil substrates and enzymes and, accordingly, little degradation of organic C, N, and P. Alternatively, rapid nutrient cycling and immobilization by soil microorganisms could account for accumulations of organic C, N, and P. Further refinement of the methods used in this study could lead to a valuable tool for the assessment of potential bioavailability of nutrients in a variety of soils.
The cost of postponing biodiversity conservation in Mexico
Fuller, T Sanchez-Cordero, V Illoldi-Rangel, P Linaje, M Sarkar, S
BIOLOGICAL CONSERVATION 134:4 593-600
Though Neotropical countries are the most species rich in the world, their biodiversity is threatened by the loss of native vegetation. Land conversion in Mexico during the last 30 years has been extensive and is representative of that of other developing countries. However, the effects of land use change on the required size and configuration of an adequate biological conservation area network are largely unknown. It is shown here that endemic mammals in Mexico could have been protected considerably more economically if a conservation plan had been implemented in 1970 than is possible today due to extensive conversion of primary habitats. Analysis of the distributions of 86 endemic mammal species in 1970, 1976, 1993, and 2000 indicates that the distributions of 90% of the species shrank during this 30-year period. At each time step, optimal conservation area networks were selected to represent all species. 90% more land must be protected after 2000 to protect adequate mammal habitat than would have been required in 1970. In addition, under a realistic conservation budget, 79% fewer species can be represented adequately in a conservation area network after 2000 compared to 1970. This provides an incentive for rapid conservation action in Mexico and other biodiversity hotspots with comparable deforestation rates, including Burma, Ecuador, Indonesia, the Philippines, and Sri Lanka. Due to ongoing habitat degradation, the efficiency of a conservation plan decreases with delays in its implementation. (c) 2006 Elsevier Ltd. All rights reserved.
The Arctic as a trigger for glacial terminations
Martinson, DG Pitman, WC
CLIMATIC CHANGE 80:3-4 253-263
We propose a hypothesis to explain the very abrupt terminations that end most of the glacial episodes. During the last glaciation, the buildup and southerly expansion of large continental ice-sheets in the Northern Hemisphere and extensive cover of sea ice in the N. Pacific and the N. Atlantic imposed a much more zonal climatic circulation system than exists today. We hypothesize that this, in combination with the frigid (dry) polar air led to a significant decrease in freshwater runoff into the Arctic Ocean. In addition the freshwater contribution of the fresher Pacific water was completely eliminated by the emergence of the Bering Strait (sill depth 50 m). As the Arctic freshwater input was depleted, regions of the Arctic Ocean lost surface stability and eventually overturned, bringing warmer deep water to the surface where it melted the overlying sea ice. This upwelled water was quickly cooled and sank as newly formed deep water. For sustained overturn events, such as might have occurred during the peak of very large glacial periods (i.e. the last glacial maximum), the voluminous deep water formed would eventually overflow into the Nordic Seas and North Atlantic necessitating an equally voluminous rate of return flow of warmer surface waters from the North Atlantic thus breaking down the Arctic’s zonal isolation, melting the expansive NA sea ice cover and initiating oceanic heating of the atmosphere over the ice-sheets bordering the NA. We suggest that the combined effect of these overturn-induced events in concert with a Milankovitch warming cycle, was sufficient to drive the system to a termination. We elaborate on this proposed sequence of events, using the model for the formation of the Weddell Sea polynya as proposed by Martinson et al. (1981) and various, albeit sparse, data sets from the circum-Arctic region to apply and evaluate this hypothesis to the problem of glacial terminations.
The California current system during the last 136,000 years: response of the North Pacific High to precessional forcing
Yamamato, M Yamamuro, M Tanaka, Y
QUATERNARY SCIENCE REVIEWS 26:3-4 405-414
Alkenone sea surface temperature (SST) records were generated from the Ocean Drilling Program’s (ODP) Sites 1014 and 1016 to examine the response of the California Current System to global climate change during the last 136ka. The temperature differences between these sites (Delta SSTNEP = SSTODP10144-SSTODP1016) reflected the intensity of the California Current and varied between 0.4 and 6.1 degrees C. A high ASSTNEP (weaker California Current) was found for late marine isotope stage (MIS) 2 and early MIS 5e, while a low ASSTNEP (stronger California Current) was detected for mid-MIS 5e and MIS 1. Spectral analysis indicated that this variation pattern dominated 23- (precession) and 30-ka periods. Comparison of the Delta SSTNEP and SST based on data from core MD01-2421 at the Japan margin revealed anti-phase variation; the high ASSTNEP (weakening of the California Current) corresponded to the low SST at the Japan margin (the southward displacement of the NW Pacific subarctic boundary), and vice versa. This variation was synchronous with a model prediction of the tropical El Nino-Southern Oscillation behavior. These findings suggest that the intensity of the North Pacific High varied in response to precessional forcing, and also that the response has been linked with the changes of tropical ocean-atmosphere interactions. (c) 2007 Elsevier Ltd. All rights reserved.
Relative importance of estuarine flatfish nurseries along the Portuguese coast
Cabral, HN Vasconcelos, R Vinagre, C Franca, S Fonseca, V Maia, A Reis-Santos, P Lopes, M Ruano, M Campos, J Freitas, V Santos, PT Costa, MJ
JOURNAL OF SEA RESEARCH 57:2-3 209-217
The relative importance of nursery areas and their relationships with several environmental variables were evaluated in nine estuarine systems along the Portuguese coast based on trawl surveys. Historical data were used to outline changes and trends in the nursery function of some of these estuaries over the past decades. The dominant flatfish species in Portuguese estuaries were Platichthys flesus (Linnaeus, 1758), Solea solea (Linnaeus, 1758), Solea senegalensis Kaup, 1858 and Monochirus hispidus Rafinesque, 1814, but their occurrence differed among the estuaries, R flesus only occurred in estuaries north of the Tejo estuary (39 degrees N), S. solea was quite rare along the southern Portuguese coast (south of 37 degrees 30’N), S. senegalensis occurred in estuaries throughout the coast, but its abundance varied considerably, and the occurrence of M. hispidus was limited to the Sado estuary and Ria Formosa. A Correspondence Analysis was performed to evaluate the relationships between flatfish species abundance and geomorphologic and hydrologic characteristics of estuaries (latitude, freshwater flow, estuarine area, intertidal area, mean depth and residence time). Abiotic characteristics (depth, temperature, salinity, sediment type) of nursery grounds of each flatfish species were also evaluated. Results showed that some estuaries along the Portuguese coast have nursery grounds used by several flatfish species (e.g. Ria de Aveiro, Sado, estuary), while in other systems a segregation was noticed, with juveniles of different species occurring in distinct estuarine areas (e.g. Minho and Mondego estuaries). This emphasizes the relevance of niche overlap, but the potential for competition may be considerably minimized by differences in resource use patterns and by an extremely high abundance of resources. Peak densities of flatfishes recorded in nurseries areas along the Portuguese coast were within the range of values reported for other geographical areas. Inter-annual abundance variability of all the species in the Tejo and Sado estuaries was extremely high, with a drastic decrease in P flesus in the Tejo estuary, probably related to higher water temperature in recent years due to global climate change. (c) 2006 Elsevier B.V. All rights reserved.
Climatological aspects of convective parameters from the NCAR/NCEP reanalysis
Brooks, HE Anderson, AR Riemann, K Ebbers, I Flachs, H
ATMOSPHERIC RESEARCH 83:2-4 294-305
Annual cycles of convectively important atmospheric parameters have been computed for a variety of from the National Center for Atmospheric Research (NCAR)/National Centers for Environmental Prediction (NCEP) global reanalysis, using 7 years of reanalysis data. Regions in the central United States show stronger seasonality in combinations of thermodynamic parameters than found elsewhere in North America or Europe. As a result, there is a period of time in spring and early summer when climatological mean conditions are supportive of severe thunderstorms. The annual cycles help in understanding the large-scale processes that lead to the combination of atmospheric ingredients necessary for strong convection. This, in turn, lays groundwork for possible changes in distribution of the environments associated with possible global climate change. (c) 2006 Elsevier B.V. All rights reserved.
Do elevated temperature and CO2 generally have counteracting effects on phenolic phytochemistry of boreal trees?
Veteli, TO Mattson, WJ Niemela, P Julkunen-Tiitto, R Kellomaki, S Kuokkanen, K Lavola, A
JOURNAL OF CHEMICAL ECOLOGY 33:2 287-296
Global climate change includes concomitant changes in many components of the abiotic flux necessary for plant life. In this paper, we investigate the combined effects of elevated CO2 (720 ppm) and temperature (+2 K) on the phytochemistry of three deciduous tree species. The analysis revealed that elevated CO2 generally stimulated increased carbon partitioning to various classes of phenolic compounds, whereas an increase in temperature had the opposite effect. The combined effects of both elevated CO2 and temperature were additive, i.e., canceling one another’s individual effects. Obviously, the effects of global climate change on leaf chemistry must simultaneously consider both temperature and CO2. If these results are generally applicable, then the counteracting effect of the temperature is likely to play a major role in alpine, boreal, and arctic zones in determining the balance between populations of plants and herbivores.
Carbon sources and sinks in high-elevation spruce-fir forests of the Southeastern US
Van Miegroet, H Moore, PT Tewksbury, CE Nicholas, NS
FOREST ECOLOGY AND MANAGEMENT 238:1-3 249-260
This paper examines carbon (C) pools, fluxes, and net ecosystem balance for a high-elevation red spruce-Fraser fir forest [Picea rubens Sarg./ Abies fraseri (Pursh.) Poir] in the Great Smoky Mountains National Park (GSMNP), based on measurements in fifty-four 20 m x 20 m permanent plots located between 1525 and 1970 m elevation. Forest floor and mineral soil C was determined from destructive sampling of the 0 horizon and incremental soil cores (to a depth of 50 cm) in each plot. Overstory C pools and net C sequestration in live trees was estimated from periodic inventories between 1993 and 2003. The CO2 release from standing and downed wood was based on biomass and C concentration estimates and published decomposition constants by decay class and species. Soil respiration was measured in situ between 2002 and 2004 in a subset of eight plots along an elevation gradient. Litterfall was collected from a total of 16 plots over a 2-5-year period. The forest contained on average 403 Mg C ha(-1) almost half of which stored belowground. Live trees, predominantly spruce, represented a large but highly variable C pool (mean: 126 Mg C ha(-1), CV = 39%); while dead wood (61 Mg C ha(-1)), mostly fir, accounted for as much as 15% of total ecosystem C. The 10-year mean C sequestration in living trees was 2700 kg C ha(-1) year(-1), but increased from 2180 kg C ha(-1) year(-1) in 1993-1998 to 3110 kg C ha(-1) year(-1) in 1998-2003, especially at higher elevations. Dead wood also increased during that period, releasing on average 1600 kg C ha(-1) year(-1). Estimated net soil C efflux ranged between 1000 and 1450 kg C ha(-1) year(-1), depending on the calculation of total belowground C allocation. Based on current flux estimates, this old-growth system was close to C neutral. (c) 2006 Elsevier B.V. All rights reserved.
Plant water sources in the cold semiarid ecosystem of the upper Kherlen River catchment in Mongolia: A stable isotope approach
Li, SG Romero-Saltos, H Tsujimura, M Sugimoto, A Sasaki, L Davaa, G Oyunbaatar, D
JOURNAL OF HYDROLOGY 333:1 109-117
In the cold semiarid region of northeastern Mongolia, we used stable isotopes (180 and D) to determine potential plant water sources during the 2003 growing season (June to September) in two habitats: montane forest and an elevation gradient from the forest to Kherten river bank. The forest is dominated by larch (Larix sibirica) with patches of cinquefoil shrubs (Potentilla fruticosa). The latter also grow throughout the elevation gradient, while the Larch grows only on the top slope. Poplar (Populus spp.) and willow (Salix spp.) trees grow only on the river bank. All plant and soil samples showed isotopic signatures similar to summer precipitation, which is isotopically heavier in summer than winter. In July and August, [arch trees in the forest tended to shift their water uptake to shallow depths in response to recent rainfall, but during the remaining months (June and September), depths of water uptake were unclear. Further, both the larch trees and cinquefoil shrubs in the forest used water at similar depths, suggesting potential competition for water. Plants along the elevation gradient showed different patterns of water use: (1) in July, larch used recent rainfall only, but in other months, the pattern was unclear; (2) cinquefoil depended on rainfall from recent weeks (as in August), but sometimes used antecedent rainwater from one month prior; and (3) poplar and willow seemed to use water from the river (as in August) or from precipitation that felt a few weeks prior (as in September), but the factors controlling this unusual shift are unknown. This study contributes to our understanding of plant water use strategies in cold semiarid ecosystems, and provides baseline data for models designed to understand large-scale hydrological effects of global climate change. (c) 2006 Elsevier B.V. All rights reserved.
Evidence of methane release from Blake Ridge ODP Hole 997A during the Plio-Pleistocene: Benthic foraminifer fauna and total organic carbon
Bhaumik, AK Gupta, AK
CURRENT SCIENCE 92:2 192-199
Methane is a powerful greenhouse gas and may have played a significant role in global climate change in the geological past. Destabilization of gas hydrates, frozen methane stored within the ocean floor sediment and in permafrost, may have provided an important source of methane to the atmosphere. Ocean Drilling Program Hole 997A (water depth 2770 m), situated on the crest of the Blake Outer Ridge, is a potentially large reservoir of gas hydrate. Methane emissions from the Blake Outer Ridge have been reported previously, which has been suggested as a driver for global climate change. Methane at this site is of biogenic origin, produced by the bacterial decomposition of organic matter. We used benthic foraminifer faunal assemblages (> 125 mu m size fraction) and species diversity, combined with total organic carbon data from Hole 997A, to identify intervals of methane releases during the late Neogene (last 5.4 Ma). We identified a group of benthic foraminifera, which were taken to indicate methane fluxes based on previous work on seep-related benthic foraminifera. We then classified ‘seep-related’ benthic foraminifera, as well as high organic carbon taxa independent of deep-sea oxygenation. We recognized five intervals of increased abundance of the seep-related benthic foraminifera since last 3.6 Ma representing intervals of methane release, which coincide with intervals of lowered sea level. Changes in benthic foraminifera are more abrupt over the past 3.6 Ma when the northern hemisphere glaciation began to intensify and climate switched to a 41-kyr cycle world.
Rapid evolution of flowering time by an annual plant in response to a climate fluctuation
Franks, SJ Sim, S Weis, AE
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 104:4 1278-1282
Ongoing climate change has affected the ecological dynamics of many species and is expected to impose natural selection on ecologically important traits. Droughts and other anticipated changes in precipitation may be particularly potent selective factors, especially in and regions. Here we demonstrate the evolutionary response of an annual plant, Brassica rapa, to a recent climate fluctuation resulting in a multiyear drought. Ancestral (predrought) genotypes were recovered from stored seed and raised under a set of common environments with descendant (postdrought) genotypes and with ancestor x descendant hybrids. As predicted, the abbreviated growing seasons caused by drought led to the evolution of earlier onset of flowering. Descendants bloomed earlier than ancestors, advancing first flowering by 1.9 days in one study population and 8.6 days in another. The intermediate flowering time of ancestor x descendant hybrids supports an additive genetic basis for divergence. Experiments confirmed that summer drought selected for early flowering, that flowering time was heritable, and that selection intensities in the field were more than sufficient to account for the observed evolutionary change. Natural selection for drought escape thus appears to have caused adaptive evolution in just a few generations. A systematic effort to collect and store propagules from suitable species would provide biologists with materials to detect and elucidate the genetic basis of further evolutionary shifts driven by climate change.
High temperature acclimation of C-4 photosynthesis is linked to changes in photosynthetic biochemistry
Dwyer, SA Ghannoum, O Nicotra, A Von Caemmerer, S
PLANT CELL AND ENVIRONMENT 30:1 53-66
With average global temperatures predicted to increase over the next century, it is important to understand the extent and mechanisms of C-4 photosynthetic acclimation to modest increases in growth temperature. To this end, we compared the photosynthetic responses of two C-4 grasses (Panicum coloratum and Cenchrus ciliaris) and one C-4 dicot (Flaveria bidentis) to growth at moderate (25/20 degrees C, day/night) or high (35/30 degrees C, day/night) temperatures. In all three C-4 species, CO2 assimilation rates (A) underwent significant thermal acclimation, such that when compared at growth temperatures, A increased less than what would be expected given the strong response of A to short-term changes in leaf temperature. Thermal photosynthetic acclimation was further manifested by an increase in the temperature optima of A, and a decrease in leaf nitrogen content and leaf mass per area in the high-relative to the moderate-temperature-grown plants. Reduced photosynthetic capacity at the higher growth temperature was underpinned by selective changes in photosynthetic components. Plants grown at the higher temperature had lower amounts of ribulose-1,5-bisphosphate carboxylase/oxygenase and cytochrome f and activity of carbonic anhydrase. The activities of photosystem II (PSII) and phosphenolpyruvate carboxylase were not affected by growth temperature. Chlorophyll fluorescence measurements of F. bidentis showed a corresponding decrease in the quantum yield of PSII (Phi(PSII)) and an increase in non-photochemical quenching (Phi(NPQ)). It is concluded that through these biochemical changes, C-4 plants maintain the balance between the various photosynthetic components at each growth temperature, despite the differing temperature dependence of each process. As such, at higher temperatures photosynthetic nitrogen use efficiency increases more than A. Our results suggest C-4 plants will show only modest changes in photosynthetic rates in response to changes in growth temperature, such as those expected within or between seasons, or the warming anticipated as a result of global climate change.
Erosion in northwest Tibet from in-situ-produced cosmogenic Be-10 and Al-26 in bedrock
Kong, P Na, CG Fink, D Ding, L Huang, FX
EARTH SURFACE PROCESSES AND LANDFORMS 32:1 116-125
Concentrations of in-situ-produced cosmogenic nuclides Be-10 and Al-26 in quartz were measured by accelerator mass spectrometry for bedrock basalts and sandstones located in northwest Tibet. The effective exposure ages range between 23 and 134 ka (Be-10) and erosion rates between 4.0 and 24 mm ka(-1). The erosion rates are significantly higher than those in similarly and Antarctica and Australia, ranging between 0.1 and 1 mm ka(-1), suggesting that precipitation is not the major control of erosion of landforms. Comparison of erosion rates in and regions with contrasting tectonic activities suggests that tectonic activity plays a more important role in controlling long-term erosion rates. The obtained erosion rates are, however, significantly lower than the denudation rate of 3000-6000 mm ka(-1) beginning at c. 53 Ma in the nearby Godwin Austen (K2) determined by apatite fission-track thermochronology. It appears that the difference in erosion rates within different time intervals is indicative of increased tectonic activity at c. 5-3 Ma in northwest Tibet. We explain the low erosion rates determined in this study as reflecting reduced tectonic activity in the last million years. A model of localized thinning of the mantle beneath northwest Tibet may account for the sudden increased tectonic activity at c. 5-3 Ma and the later decrease. Copyright (c) 2006 John Wiley & Sons, Ltd.
Geographic variation in the immunoglobulin levels in pygoscelid penguins
Barbosa, A Merino, S Benzal, J Martinez, J Garcia-Fraile, S
POLAR BIOLOGY 30:2 219-225
Antarctic organisms, including penguins, are susceptible to parasites and pathogens. Effects of infestation could differ in different locations along a geographical gradient from north to south consistent with conditions that affect the prevalence and virulence of parasites and pathogens. The immune system, including immunoglobulins as the main component of the humoral immune response, is the major way by which organisms confront infestation. We investigated the variation in immunoglobulin levels in three species of antarctic penguins (Pygoscelis antarctica, Pygoscelis papua, and Pygoscelis adeliae) along a geographical gradient from King George Island (62 degrees 15’S) to Avian Island (67 degrees 46’S). We found that immunoglobulin levels increased northwards in all the three species. This could indicate a higher impact of parasites and/or pathogens relative to the existing gradient in temperatures along this coast. Changing temperatures, consistent with global climate change, could be altering the ecology of parasite or pathogen infestation within the biota of northern Antarctica. We have also found marginal differences in immunoglobulin levels between sexes in both chinstrap and gentoo penguins.
Clean development mechanism and off-grid small-scale hydropower projects: Evaluation of additionality
ENERGY POLICY 35:1 714-721
The global climate change mitigation policies and their stress on sustainable development have made electrification of rural mountainous villages, using small hydro, an attractive destination for potential clean development mechanism (CDM) projects. This invariably involves judging the additionality of such projects. The paper suggests a new approach to judge the additionality of such stand-alone small hydropower projects. This has been done by breaking up additionality into two components: external and local. The external additionality is project developer dependent. For determining the local additionality, the paper takes into account the probability of a village getting electrified over a period of time, which is kept equal to the possible crediting period. This is done by defining an electrification factor (EF) whose value depends on the degree of isolation, financial constraints and institutional constraints encountered while electrifying a mountainous village. Using this EF, the additionality of a CDM project can be judged in a much easier and accurate way. The paper is based on the data and inputs gathered during site visits to many isolated villages located in the eastern Indian Himalayas. (c) 2006 Elsevier Ltd. All rights reserved.
Nonlinear effects of climate change on phosphorus stability in wetlands: Concept and estimation
JOURNAL OF FOOD AGRICULTURE & ENVIRONMENT 5:1 295-301
Effects of climate change on ecosystems like freshwater wetlands cannot be understood without focusing research on getting sense of vulnerability and resiliency at the systemic level, involving tipping points, rapid changes in events and states, because of the interdependency of various components that are subject to nonlinear changes even though they may exert significant inertia to short-term hydro-climatic fluctuations. Depending on resilience, threshold and lag times, hydro-climatic changes brought upon by global climate change may cause nonlinear and/or irreversible changes in phosphorus (P) dynamic, and instigate P enrichment in freshwater wetlands. Thus, the studies of the influence of expected global climate change and its direct and indirect effects on bioavailability/stability of organic P in wetlands are in critical need to help manage or increase the resilience of wetland ecosystem against any abrupt or irreversible changes that may adversely affect the ecosystem and its services. Phosphorus dynamic in freshwater wetland system is likely to behave nonlinearly due to expected changes in temperature, and sediment/soil and water acidity and redox status because of global climate change in the decades to come, thereby freshwater wetland, a sensitive ecosystem that plays critical role ranging from water quality management to atmospheric CO2 removal, could face irreversible or hysteretic adverse changes. The overall objectives of this paper are to provide consolidated information on identification and estimation of any nonlinear behaviors in the stability/bioavailability of various P forms, which are present in water columns, detritus and soils/sediments, at different levels of stressors in light of changing global climate. Addressing how stable organic P is, and at what threshold level and lag time would organic P behave nonlinearly and release back into the water column, in turn, exacerbate eutrophic conditions, are crucial. Learning the resilience, threshold level and lag times allows us to gauge the strengths and weaknesses of our technological advances and policies that may help us to cope with nonlinear impacts of global climate change on ecosystems such as wetlands. The relationships developed between P mobilization processes, stressors’ levels and lag time can provide invaluable insights for the formulation of management strategies that could increase resilience in freshwater wetlands, which may be subjected to nonlinear ecological responses.
Carbon emission control strategies for China: A comparative study with partial and general equilibrium versions of the China MARKAL model
Chen, WY Wu, ZX He, JK Gao, PF Xu, SF
ENERGY 32:1 59-72
China’s carbon dioxide emissions from fossil fuel combustion had increased with an annual growth rate of 4.36% since 1980, hitting 1 GtC in 2003. The global climate change issue is becoming more and more important and hence to be the fourth challenge for China’s future energy development, following energy supply shortages, energy security, and local environmental protection. This paper used three MARKAL (MARKet ALlocation) family models, that is, MARKAL, MARKAL-ED (MARKAL with elastic demand), and MARKAL-MACRO, to study China energy system’s carbon mitigation strategies and corresponding impacts on the economy. The models’ structures and the economic feedback formulations used in MARKAL-MACRO and MARKAL-ED are briefly described. The endogenous demands in MARKAL-MACRO and MARKAL-ED enable them to partly satisfy carbon abatement constraints via energy service demand reductions, and the reduction levels for the 30 demand sectors from these two kinds of models for given carbon emission constraints are presented and compared. The impact of carbon mitigation on social welfare from MARKAL and MARKAL-ED, and on GDP, investment and consumption from MARKAL-MACRO are evaluated. The changes in both final and primary energy mix, changes in technology development, as well as marginal abatement costs for given carbon constraints from the three models, are analyzed. (c) 2006 Elsevier Ltd. All rights reserved.
Does the El Nino-Southern Oscillation control the interhemispheric radiocarbon offset?
Turney, CSM Palmer, JG
QUATERNARY RESEARCH 67:1 174-180
Since the 1970s it has been recognised that Southern Hemisphere samples have a lower radiocarbon content than contemporaneous material in the Northern Hemisphere. This interhemispheric radiocarbon offset has traditionally been considered to be the result of a greater surface area in the southern ocean and high-latitude deepwater formation. This is despite the fact that the El Nino-Southern Oscillation (ENSO) is known to play a significant role in controlling the interannual variability of atmospheric carbon dioxide by changing the flux of ‘old’ CO2 from the tropical Pacific. Here we demonstrate that over the past millennium, the Southern Hemisphere radiocarbon offset is characterised by a pervasive 80-yr cycle with a step shift in mean values coinciding with the transition from the Medieval Warm Period to the Little Ice Age. The observed changes suggest an ENSO-like role in influencing the mterhemispheric radiocarbon difference, most probably modulated by the Interdecadal Pacific Oscillation, and supports a tropical role in forcing centennial-scale global climate change. (c) 2006 University of Washington. All rights reserved.
Pathways of anaerobic carbon cycling across an ombrotrophic-minerotrophic peatland gradient
Keller, JK Bridgham, SD
LIMNOLOGY AND OCEANOGRAPHY 52:1 96-107
Peatland soils represent globally significant stores of carbon, and understanding carbon cycling pathways in these ecosystems has important implications for global climate change. We measured aceticlastic and autotrophic methanogenesis, sulfate reduction, denitrification, and iron reduction in a bog, an intermediate fen, and a rich fen in the Upper Peninsula of Michigan for one growing season. In 3-d anaerobic incubations of slurried peat, denitrification and iron reduction were minor components of anaerobic carbon mineralization. Experiments using C-14-labeled methanogenic substrates showed that methanogenesis in these peatlands was primarily through the aceticlastic pathway, except early in the growing season in more ombrotrophic peatlands, where the autotrophic pathway was dominant or codominant. Overall, methane production was responsible for 3-70% of anaerobic carbon mineralization. Sulfate reduction accounted for 0-26% of anaerobic carbon mineralization, suggesting a rapid turnover of a very small sulfate pool. A large percentage of anaerobic carbon mineralization (from 29% to 85%) was unexplained by any measured process, which could have resulted from fermentation or possibly from the use of organic molecules (e.g., humic acids) as alternative electron acceptors.
Species richness of migratory birds is influenced by global climate change
Lemoine, N Schaefer, HC Bohning-Gaese, K
GLOBAL ECOLOGY AND BIOGEOGRAPHY 16:1 55-64
Aim Global climate change is increasingly influencing ecosystems. Long-term effects on the species richness and composition of ecological communities have been predicted using modelling approaches but, so far, hardly demonstrated in the field. Here, we test whether changes in the composition of bird communities have been influenced by recent climate change. Location Europe. Methods We focus on the proportion of migratory and resident bird species because these groups are expected to respond differently to climatic change. We used the spatial relationship between climatic factors and bird communities in Europe to predict changes in 21 European bird communities under recent climate change. Results Observed changes corresponded significantly to predicted changes and could not be explained by the effects of spatial autocorrelation. Alternative factors such as changes in land use were tested in a first approximation as well but no effects were found. Main Conclusions This study demonstrates that global climate change has already influenced the species richness and composition of European bird communities.
The influence of major dams on hydrology through the drainage network of the Sacramento River basin, California
RIVER RESEARCH AND APPLICATIONS 23:1 55-72
This paper reports basinwide patterns of hydrograph alteration via statistical and graphical analysis from a network of long-term streamflow gauges located various distances downstream of major dams and confluences in the Sacramento River basin in California, USA. Streamflow data from 10 gauging stations downstream of major dams were divided into hydrologic series corresponding to the periods before and after dam construction. Pre- and post-dam flows were compared with respect to hydrograph characteristics representing frequency, magnitude and shape: annual flood peak, annual flow trough, annual flood volume, time to flood peak, flood drawdown time and interarrival time. The use of such a suite of characteristics within a statistical and graphical framework allows for generalising distinct strategies of flood control operation that can be identified without any a priori knowledge of operations rules. Dam operation is highly dependent oil the ratio of reservoir capacity to annual flood Volume (impounded runoff index). Dams with high values of this index generally completely cut off flood peaks thus reducing time to peak, drawdown time and annual flood volume. Those with low values conduct early and late flow releases to extend the hydrograph, increasing time to peak, drawdown time and annual flood Volume. The analyses reveal minimal flood control benefits from foothill dams in the lower Sacramento River (i.e. dissipation of the down-valley flood control signal). The lower part of the basin is instead reliant on a weir and bypass system to control lowland flooding. Data from a control gauge (i.e. with no upstream dams) suggest a background signature of global climate change expressed as shortened flood hydrograph failing limbs and lengthened flood interarrival times at low exceedence probabilities. This research has implications for flood control, water resource management, aquatic and riparian ecosystems and for rehabilitation strategies involving flow alteration and/or manipulation of sediment Supplies. Copyright (c) 2006 John Wiley & Sons, Ltd.
Insect development under predation risk, variable temperature, and variable food quality
Logan, JD Wolesensky, W Joern, A
MATHEMATICAL BIOSCIENCES AND ENGINEERING 4:1 47-65
We model the development of an individual insect, a grasshopper, through its nymphal period as a function of a trade-off between prey vigilance and nutrient intake in a changing environment. Both temperature and food quality may be variable. We scale up to the population level using natural mortality and a predation risk that is mass, vigilance, and temperature dependent. Simulations reveal the sensitivity of both survivorship and development time to risk and nutrient intake, including food quality and temperature variations The model quantifies the crucial role of temperature in trophic interactions and development, which is an important issue in assessing the effects of global climate change on complex environmental interactions.
Multi-scale analysis of global temperature changes and trend of a drop in temperature in the next 20 years
Zhen-Shan, L Xian, S
METEOROLOGY AND ATMOSPHERIC PHYSICS 95:1-2 115-121
A novel multi-timescale analysis method, Empirical Mode Decomposition (EMD), is used to diagnose the variation of the annual mean temperature data of the global, Northern Hemisphere (NH) and China from 1881 to 2002. The results show that: (1) Temperature can be completely decomposed into four timescales quasi-periodic oscillations including an ENSO-like mode, a 6-8-year signal, a 20-year signal and a 60-year signal, as well as a trend. With each contributing ration of the quasi-periodicity discussed, the trend and the 60-year timescale oscillation of temperature variation are the most prominent. (2) It has been noticed that whether on century-scale or 60-year scales, the global temperature tends to descend in the coming 20 years. (3) On quasi 60-year timescale, temperature abrupt changes in China precede those in the global and NH, which provides a denotation for global climate changes. Signs also show a drop in temperature in China on century scale in the next 20 years. (4) The dominant contribution of CO2 concentration to global temperature variation is the trend. However, its influence weight on global temperature variation accounts for no more than 40.19%, smaller than those of the natural climate changes on the rest four timescales. Despite the increasing trend in atmospheric CO2 concentration, the patterns of 20-year and 60-year oscillation of global temperature are all in falling. Therefore, if CO2 concentration remains constant at present, the CO2 greenhouse effect will be deficient in counterchecking the natural cooling of global climate in the following 20 years. Even though the CO2 greenhouse effect on global climate change is unsuspicious, it could have been excessively exaggerated. It is high time to re-consider the trend of global climate changes.
Temperature-dependent effects of cadmium and purine nucleotides on mitochondrial aconitase from a marine ectotherm, Crassostrea virginica: a role of temperature in oxidative stress and allosteric enzyme regulation
Cherkasov, AA Overton, RA Sokolov, EP Sokolova, IM
JOURNAL OF EXPERIMENTAL BIOLOGY 210:1 46-55
Temperature and heavy metals such as cadmium (Cd) are important environmental stressors that can strongly affect mitochondrial function of marine poikilotherms. In this study, we investigated the combined effects of temperature (20 degrees C and 30 degrees C) and Cd stress on production of reactive oxygen species (ROS) and oxidative stress in a marine poikilotherm Crassostrea virginica (the eastern oyster) using mitochondrial aconitase as a sensitive biomarker of oxidative damage. We also assessed potential involvement of mitochondrial uncoupling proteins (UCPs) in antioxidant protection in oyster mitochondria using purine nucleotides (GDP, ATP and ADP) as specific inhibitors, and free fatty acids as stimulators, of UCPs. Our results show that exposure to Cd results in elevated ROS production and oxidative damage as indicated by aconitase inactivation which is particularly pronounced at elevated temperature. Unexpectedly, oyster mitochondrial aconitase was inhibited by physiologically relevant levels of ATP (IC50 = 1.93 and 3.04 mmol l(-1) at 20 degrees C and 30 degrees C, respectively), suggesting that allosteric regulation of aconitase by this nucleotide may be involved in regulation of the tricarboxylic acid flux in oysters. Aconitase was less sensitive to ATP inhibition at 30 degrees C than at 20 degrees C, consistent with the elevated metabolic flux at higher temperatures. ADP and GDP also inhibited mitochondrial aconitase but at the levels well above the physiological concentrations of these nucleotides (6-11 mmol l(-1)). Our study shows expression of at least three UCP isoforms in C. virginica gill tissues but provides no indication that UCPs protect mitochondrial aconitase from oxidative inactivation in oysters. Overall, the results of this study indicate that temperature stress exaggerates toxicity of Cd leading to elevated oxidative stress in mitochondria, which may have important implications for survival of poikilotherms in polluted environments during seasonal warming and/or global climate change, and suggest a novel temperature-dependent mechanism of allosteric regulation of TCA flux in oyster mitochondria.