Abstracts on Global Climate Change

Sep 2005

Changes of anti-oxidative enzymes and MDA content under soil water deficits among 10 wheat (Triticum aestivum L.) genotypes at maturation stage

Shao, HB Liang, ZS Shao, MA


Drought is a world-spread problem seriously influencing grain production and quality, the loss of which is the total for other natural disasters, with increasing global climate change making the situation more serious. Wheat is the staple food for more than 35% of world population, so wheat anti-drought physiology study is of importance to wheat production and biological breeding for the sake of coping with abiotic and biotic conditions. Much research is involved in this hot topic, but the pace of progress is not so large because of drought resistance being a multiple-gene-control quantitative character and wheat genome being larger (16,000 Mb). On the other hand, stress adaptive mechanisms are quite different, with stress degree, time course, materials, soil quality status and experimental plots, thus increasing the complexity of the issue in question. Additionally, a little study is related to the whole life circle of wheat, which cannot provide a comprehensive understanding of its anti-drought machinery. We selected 10 kinds of wheat genotypes as materials, which have potential to be applied in practice, and measured change of relative physiological indices through wheat whole growing-developmental circle (i.e. seedling, tillering and maturing). Here, we reported the anti-oxidative results of maturation stage (the results of seedling and tillering stage have been published) in terms of activities of POD, SOD, CAT and MDA content as follows: (1) 10 wheat genotypes can be grouped into three kinds (A-C, respectively) according to their changing trend of the measured indices; (2) A group performed better resistance drought under the condition of treatment level 1 (appropriate level), whose activities of anti-oxidative enzymes (POD, SOD, CAT) were higher and MDA lower; (3) B group exhibited stronger anti-drought under treatment level 2 (light-stress level), whose activities of anti-oxidative enzymes were higher and MDA lower; (4) C group expressed anti-drought to some extent under treatment level 3 (serious-stress level), whose activities of anti-oxidative enzymes were stronger, MDA lower; (5) these results demonstrated that different wheat genotypes have different physiological mechanisms to adapt themselves to changing drought stress, whose molecular basis is discrete gene expression profiling (transcriptom); (6) our results also showed that the concept and method accepted and adopted by most researchers [T.C. Hsiao, Plant response to water stress, Ann. Rev. Plant Physiol. 24 (1973) 519-570], that 75% FC is a proper supply for higher plants, was doubted, because this level could not reflect the true suitable level of different wheat genotypes. The study in this respect is the key to wheat anti-drought and biological-saving water agriculture; (7) our research can provide insights into physiological mechanisms of crop anti-drought and direct practical materials for wheat anti-drought breeding; (8) the physiological study of wheat is more urgent up-to-date and molecular aspects are needed, but cannot substitute this important part. The combination of both is an important strategy and a key and (9) POD, SOD and CAT activities and MDA content of different wheat genotypes had quite different changing trend at different stages and under different soil water stress conditions, which was linked with their origin of cultivation and individual soil water threshold. (c) 2005 Elsevier B.V. All rights reserved.

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Growing typhoon influence on east Asia

Wu, LG Wang, B Geng, SQ


Numerical model studies have suggested that the ongoing global climate change will likely affect tropical cyclone activity. Since the global warming has been underway, it is meaningful to ask: Are there evidences of observed changes in tropical cyclone activity? Using best-track data from 1965 to 2003, we show for the first time that over the past four decades the two prevailing typhoon tracks in the western North Pacific (WNP) have shifted westward significantly; thus the subtropical East Asia has experienced increasing typhoon influence; but the typhoon influence over the South China Sea has considerably decreased. Our trajectory model simulation indicates that the long-term shifts in the typhoon tracks result primarily from the changes in the mean translation velocity of typhoons or the large-scale steering flow, which is associated with the westward expansion and strengthening of the WNP subtropical high.

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Changes in tropical cyclone number, duration, and intensity in a warming environment

Webster, PJ Holland, GJ Curry, JA Chang, HR

SCIENCE 309:5742 1844-1846

We examined the number of tropical cyclones and cyclone days as well as tropical cyclone intensity over the past 35 years, in an environment of increasing sea surface temperature. A large increase was seen in the number and proportion of hurricanes reaching categories 4 and 5. The largest increase occurred in the North Pacific, Indian, and Southwest Pacific Oceans, and the smallest percentage increase occurred in the North Atlantic Ocean. These increases have taken place while the number of cyclones and cyclone days has decreased in all basins except the North Atlantic during the past decade.

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The contribution of sulfuric acid and non-volatile compounds on the growth of freshly formed atmospheric aerosols

Wehner, B Petaja, T Boy, M Engler, C Birmili, W Tuch, T Wiedensohler, A Kulmala, M


The formation of atmospheric aerosol particles ( homogeneous nucleation, forming of stable clusters similar to 1 nm in size), their subsequent growth to detectable sizes (> 3 nm), and to the size of cloud condensation nuclei, remains one of the least understood atmospheric processes upon which global climate change critically depends. However, a quantitative model explanation for the growth of freshly formed aerosols has been missing. In this study, we present observations explaining the nucleation mode ( 3 - 25 nm) growth. Aerosol particles typically grow from 3 nm to 60 - 70 nm during a day, while their non-volatile cores grow by 10 - 20 nm as well. The total particle growth rate is 2 - 8 nm/h while the non-volatile core material can explain 20 - 40%. According to our results, sulfuric acid can explain the remainder of the growth, until the particle diameter is around 10 - 20 nm. After that secondary organic compounds significantly take part in growth process.

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The role of plants and land management in sequestering soil carbon in temperate arable and grassland ecosystems

Rees, RM Bingham, IJ Baddeley, JA Watson, CA

GEODERMA 128:1-2 130-154

Global climate change and concerns about soil quality have led to a widespread interest in the opportunities that are available to sequester carbon in soils. To achieve a better understanding of the changes in C storage, we need to be able to accurately measure and model inputs and losses of C from soils. This in turn requires a thorough understanding of the biological processes involved and the way in which they are influenced by the soil’s physical and chemical environment. The amount of C present in a soil is determined by the difference between C addition and C loss. Because these fluxes are large relative to changes in C storage, net storage can be very difficult to measure, particularly in the short term. Carbon is added to soil from plant and animal materials deposited on the soil surface. It is known that approximately 50% of C assimilated by young plants can be transferred below ground; some is used for root construction and maintenance as well as root respiration; some organic C is lost to the soil through exudation and root turnover. A comparison of eight studies has shown that the input to the soil of root derived organic C during a growing season can range between 0.1 and 2.8 t C ha(-1). Quantifying inputs from different processes has proved difficult and the relative importance of exudation and root death under field conditions remains uncertain. The chemical composition of substrates released by exudation and root death is known to be very different. Exudates contain high concentrations of soluble organic substrates and as a consequence are highly labile, whereas additions of C from root death have structural organic substrates with lower potential decomposition rates. Losses of C from soil occur as a consequence of plant and microbial respiration. However, identifying the source of evolved CO2, whether it be from root or microbial respiration, is much more difficult. Some new methods using isotopic labelling and pool dilution have been developed to separate plant and microbial respiration, and despite difficulties, these promise to provide valuable information on the processes of C input and loss from soils.At a field scale measurements and models would suggest that soil and crop management can play a significant role in determining the extent of C sequestration by soils and the proportion of labile C present. A comparison of 11 field studies showed that soil respiration varies between 4 and 26 t C ha(-1) year(-1), with management such as tillage, drainage, grazing and manure application exerting a strong influence on the magnitude of fluxes. Net ecosystem exchange of C has been shown to be at least an order of magnitude lower than respiratory losses in comparable studies, but land management is important in determining the direction and magnitude of the C flux. Recent studies have suggested that although the overall quantity of C stored in European soils is increasing, this increase is confined largely to forested areas and that many cropped soils are losing soil organic matter. It is has been suggested that that the biological potential for C storage in European cropland lies between 9 and 120 Mt C year(-1). In order to take advantage of this potential and to develop management systems that promote C storage we need to achieve a better understanding of the processes of C input and loss, and develop improved models using pools that coincide with measurable soil C fractions. (c) 2004 Elsevier B.V. All rights reserved.

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Transient future climate over the western United States using a regional climate model

Snyder, MA Sloan, LC


Regional climate models (RCMs) have improved our understanding of the effects of global climate change on specific regions. The need for realistic forcing has led to the use of fully coupled global climate models (GCMs) to produce boundary conditions for RCMs. The advantages of using fully coupled GCM output is that the global-scale interactions of all components of the climate system ( ocean, sea ice, land surface, and atmosphere) are considered. This study uses an RCM, driven by a fully coupled GCM, to examine the climate of a region centered over California for the time periods 1980 - 99 and 2080 - 99. Statistically significant increases in mean monthly temperatures by up to 7 degrees C are found for the entire state. Large changes in precipitation occur in northern California in February ( increase of up to 4 mm day(-1) or 30%) and March ( decrease of up to 3 mm day(-1) or 25%). However, in most months, precipitation changes between the cases were not statistically significant. Statistically significant decreases in snow accumulation of over 100 mm (50%) occur in some months. Temperature increases lead to decreases in snow accumulation that impact the hydrologic budget by shifting spring and summer runoff into the winter months, reinforcing results of other studies that used different models and driving conditions.

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Irradiance models

Solanki, SK Krivova, NA Wenzler, T


Measurements of solar irradiance have revealed variations at all the sampled time scales (ranging from minutes to the length of the solar cycle). One important task of models is to identify the causes of the observed (total and spectral) irradiance variations. Another major aim is to reconstruct irradiance over time scales longer than sampled by direct measurements in order to consider if and to what extent solar irradiance variations may be responsible for global climate change. Here, we describe recent efforts to model solar irradiance over the current and the previous two solar cycles. These irradiance models are remarkably successful in reproducing the observed total and spectral irradiance, although further improvements are still possible. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

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Plant growth and water use efficiency of four Chinese conifer tree species under different air humidity

Zheng, Y Shimizu, H


Air humidity is an important controlling factor for the establishment of tree seedlings. It is predicted that the annual amount of rainfall will decline in some parts of China due to the global climate change in the foreseeable future. There is limited information on the potential responses of this region’s forest to the global climate change. Our study investigated the responses of four major Chinese conifer tree species to air humidity variations. Seedlings of Pinus massoniana Lamb. var. massoniana, Pinus tabulaeformis Carr. var. tabulaeformis, Platycladus orientalis (Linn.) Franco cv. Sieboldii and Cunninghamia lanceolata (Lamb.) Hook were grown in controlled environment chambers under four different air humidity (RH: 40, 50, 60 and 70% or VPD: 2.4, 2.0, 1.6 and 1.2 kPa). Results showed that the growth of these four species responded to air humidity differently. P. massoniana was the most sensitive species, P. tabulaeformis and P. orientalis were less sensitive and C. lanceolata was the least sensitive species. However, the biomass increment (Delta biomass) and the relative growth rate (RGR) over the experimental period were higher under the RH 70% treatment than that under the 40% treatment for all the four species. Delta biomass and RGR were reduced by 54% and 47%, respectively, under the RH 40% treatment compared with those under the RH 70% treatment for P. massoniana, 24% and 12% for P. tabulaeformis, 22 % and 16 % for P. orientalis, 9% and 5% for C. lanceolata. The decreased growth under drier air conditions was partially due to the closure of leaf stomata and subsequently the depression of photosynthesis. Plants under higher humidity conditions had higher water use efficiency (WUE). There was a positive linear relationship between WUE and RH in all the four species. Our results may suggest that if air humidity becomes lower in some regions of China in the future, the area of distribution for the humidity sensitive species P. Massoniana may become smaller or this species may move to higher humidity region while the other three species will be less affected by this change.

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The quantitative effects of population density and winter weather on the body condition of white-tailed deer (Odocoileus virginianus) in Nova Scotia, Canada

Garroway, CJ Broders, HG


Understanding the underlying mechanisms that cause variation in survival and the reproductive success of animals is essential for predicting variation in population parameters. To gain an understanding of the effects of density and winter weather severity on white-tailed deer, Odocoileus virginianus (Zimmermann, 1780), we examined the effects of current-year deer density and cumulative weekly average values for snow depth, rainfall, and the number of degrees below -15 degrees C until the time of death, as well as cumulative effects of density and snow depth over the previous one and two winters, on the body condition of adult females, adult males, and fawns. Model selection using Akaike’s Information Criterion and multi-model inference suggested that snow depth was the best predictor of body condition for all three age/sex groups. Winter rainfall was the next most influential predictor for adult females and adult males but was not important in determining fawn body condition. Temperature had the least influence on the body condition of all three age/sex groups. Deer density during the winter of death had minimal effects for all groups and we found no evidence that cumulative multiyear variables influenced body condition. We hypothesize that cohort variation may better explain previous findings showing effects of multiyear variables. A model for estimating the proportion of animals in poor body condition for each age/sex group is presented.

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A hydrologic contribution to risk assessment for the Caspian Sea

Helms, M Evdakov, O Ihringer, E Nestmann, F

LIMNOLOGICA 35:3 114-122

The Caspian Sea (CS), the world’s largest inland sea, may also be considered as large-scale limnic system. Due to strong fluctuations of its water level during the 20th century and the flooding of vast areas in a highly vulnerable coastal zone, economic and environmental risk potentials have to be considered. Since the major water input into the CS is attributed to the Volga river, the understanding of its long-term flow process is necessary for an appropriate risk assessment for the CS and its coastal area. Therefore, a top-down approach based on statistical analyses of long-term Volga flow series is pursued. For the series of annual mean flow (MQ) of the Volga river basin during the 20th century, a complex oscillation pattern was identified. Analyses for multiple gauges in the Volga river basin and Eurasian reference basins revealed that this oscillation pattern resulted from the superposition of oscillations with periods of similar to 30 years (MQ) in the western part of the Volga river basin, and similar to 14 years (flow volume of snowmelt events) and similar to 20 years (flow volume of summer and autumn) in the eastern part of the Volga river basin (Kama river basin). Almost synchronous minima or maxima of these oscillations occurred just in the periods of substantial changes of the Caspian Sea level (CSL). It can thus be assumed that the described mechanism is fundamental for an understanding of the CSL development during the 20th century. Regarding the global climate change, it is still difficult to predict reliably the development of the CSL for the 21st century. Consequently, we suggest an ongoing, interdisciplinary research co-operation among climatology, hydrology, hydraulics, ecology and spatial data management. (c) 2005 Elsevier GmbH. All rights reserved.

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Characterization of microsatellite loci in Schoenoplectus americanus (Cyperaceae)

Blum, MJ McLachlan, JS Saunders, CJ Herrick, JD


Schoenoplectus americanus is a model organism for studying ecological and ecosystem responses of salt marsh plant communities to global climate change. Here we characterize 16 microsatellite loci in S. americanus to facilitate studies on the genetic basis of phenotypic responses to changing climate conditions such as elevated atmospheric carbon dioxide. Most loci also amplified in the morphologically similar sister species, Schoenoplectus pungens. Five loci exhibited species-specific alleles or distinct allelic size distributions that discriminate S. americanus from S. pungens.

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Rates of soil creep, worldwide: weak climatic controls and potential feedback

Oehm, B Hallet, B


The rate of soil creep sets the tempo at which material is transferred from hill-slopes to fluvial systems over major portions of terrestrial landscapes. Hence, soil creep rates affect the rates of landscape evolution and delivery of terrigenous material to floodplains and eventually to the oceans. Herein, we compile data from all sources worldwide that arc readily available in the literature, and derive common, quantitative characteristics of soil creep from digitized soil displacement profiles that permit estimates of soil flux and comparison between diverse studies. We also search for systematic variations of creep rates with climate and explore potential feedbacks between creep rates and climate. Significant creep is found in a range of environments worldwide and is fueled by diverse physical and biological processes. The considerable inter-site variability overwhelms the dependence of creep rates on hillslope gradient and obscures, but does not conceal, the climate influence. We speculate that the general tendency for rapid creep to be associated with colder climates could exacerbate global climate change. A global rise in temperature, for example, could slow the sequestration of atmospheric CO2 as creep rates decrease by slowing two distinct pedogcnic processes: mineral weathering, which is sensitive function of processes that create and freshen mineral surfaces, and the subaerial delivery of organic carbon stored in soils to rivers and long-lived reservoirs.

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Animal-borne sensors successfully capture the real-time thermal properties of ocean basins

McMahon, CR Autret, E Houghton, JDR Lovell, P Myers, AE Hays, GC


Climate change is perhaps the most pressing and urgent environmental issue facing the world today. However our ability to predict and quantify the consequences of this change is severely limited by the paucity of in situ oceanographic measurements. Marine animals equipped with sophisticated oceanographic data loggers to study their behavior offer one solution to this problem because marine animals range widely across the world’s ocean basins and visit remote and often inaccessible locations. However, unlike the information being collected from conventional oceanographic sensing equipment, which has been validated, the data collected from instruments deployed on marine animals over long periods has not. This is the first long-term study to validate in situ oceanographic data collected by animal oceanographers. We compared the ocean temperatures collected by leatherback turtles (Dermochelys coriacea) in the Atlantic Ocean with the ARGO network of ocean floats and could find no systematic errors that could be ascribed to sensor instability. Animal-borne sensors allowed water temperature to be monitored across a range of depths, over entire ocean basins, and, importantly, over long periods and so will play a key role in assessing global climate change through improved monitoring of global temperatures. This finding is especially pertinent given recent international calls for the development and implementation of a comprehensive Earth observation system ( see http://iwgeo.ssc.nasa.gov/documents.asp?s=review) that includes the use of novel techniques for monitoring and understanding ocean and climate interactions to address strategic environmental and societal needs.

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Prediction of expected global climate change by forecasting of galactic cosmic ray intensity time variation in near future based on solar magnetic field data

Belov, AV Dorman, LI Gushchina, RT Obridko, VN Shelting, BD Yanke, VG


A method of prediction of expected part of global climate change caused by cosmic ray (CR) by forecasting of galactic cosmic ray intensity time variation in near future based on solar activity data prediction and determined parameters of convection-diffusion and drift mechanisms is presented. This gave possibility to make prediction of expected part of global climate change, caused by long-term cosmic ray intensity variation. In this paper, we use the model of cosmic ray modulation in the Heliosphere, which considers a relation between long-term cosmic ray variations with parameters of the solar magnetic field. The later now can be predicted with good accuracy. By using this prediction, the expected cosmic ray variations in the near Earth space also can be estimated with a good accuracy. It is shown that there are two possibilities: (1) to predict cosmic ray intensity for 1-6 months by using a delay of long-term cosmic ray variations relatively to effects of the solar activity and (2) to predict cosmic ray intensity for the next solar cycle. For the second case, the prediction of the global solar magnetic field characteristics is crucial. For both cases, reliable long-term cosmic ray and solar activity data as well as solar magnetic field are necessary. For solar magnetic field, we used results of two magnetographs (from Stanford and Kitt Peak Observatories). The obtained forecasting of long-term cosmic ray intensity variation we use for estimation of the part of global climate change caused by cosmic ray intensity changing (influenced on global cloudiness covering). (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

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Estimation of long-term cosmic ray intensity variation in near future and prediction of their contribution in expected global climate change

Dorman, LI


On the basis of results obtained in our paper [Dorman, L.I. Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays, Paper D2.1/C2.2/E3.1-0097-04. Adv. Space Res., 2004 (accepted)], we determine: the dimension of the Heliosphere (modulation region), radial diffusion coefficient and other parameters of convection-diffusion; drift mechanisms of long-term variations of cosmic ray (CR) dependence on particle energy; level of solar activity (SA); and generally, the solar magnetic field. We obtain this important information on the basis of CR and SA data in the past, taking into account the theory of convection-diffusion and global drift modulation of galactic CR in the Heliosphere. By using these results and other regularly published predictions of expected SA variation in the near future, as well as predictions of the next SA cycle, we may make predictions of long-term cosmic ray intensity variation expected in the near future (up to 10-12 years). In [Dorman, L.I. Long-term cosmic ray intensity variation and part of global climate change, controlled by solar activity through cosmic rays, Paper D2.1/C2.2/E3.1-0097-04. Adv. Space Res., 2004 (accepted)], properties of connections between long-term variation in CR intensity and some part of a global climate change were estimated, controlled by solar activity through CR. We show that in this way we may make predictions of some part of a global climate change expected in the near future (up to 10-12 years and maybe more, depending upon the period during which definite predictions of SA can be made), controlled by solar activity through CR. In this case, estimations of expected long-term changes in the planetary distribution of cutoff rigidities, which also influence CR intensity, as well as CR-influenced effects on global climate variation, become important. (c) 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

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Model of the net primary productivity of terrestrial ecosystems in china and its response to climate change

Zheng, YR Xie, ZX Jiang, LH Chen, LJ Yu, YJ Zhou, GS Shimizu, H


The present study proposed to distinguish agricultural vegetation from natural vegetation when modelling net primary productivity (NPP), and developed a NPP model specifically for agricultural vegetation in China. The new model and the ZHOU & ZHANG model 1996 were then used to simulate NPP for agricultural land and natural ecosystems in China, respectively. The results showed that the overall accuracy improved when simulating the present NPP. As a general trend, NPP declined from southeast to northwest, with the lowest NPP in the Xinjiang Autonomous region. Except in extremely and or extremely humid areas, agricultural NPP was usually lower than natural NPP, especially in northeastern China and the North China plain. The two models were also used to simulate NPP in China under three climatic change scenarios. The results demonstrated that if air temperature increased by 2 degrees C and rainfall decreased by 20 %, both low NPP and high NPP area would decrease, resulting in an increase of medium NPP area. The other two scenarios, characterized by a temperature increase of 2 degrees C, combined with precipitation increase of 20 % and with precipitation unchanged, showed a decrease in low NPP area and a increase in medium and high NPP area, however, the former resulted in a greater medium NPP increase. In conclusion, our approach supplied better predictions than those based on only a natural NPP model.

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Sensitivity analysis of the tree distribution model PHENOFIT to climatic input characteristics: implications for climate impact assessment

Morin, X Chuine, I


Species distributions are already affected by climate change. Forecasting their long-term evolution requires models with thoroughly assessed validation. Our aim here is to demonstrate that the sensitivity of such models to climate input characteristics may complicate their validation and introduce uncertainties in their predictions. In this study, we conducted a sensitivity analysis of a process-based tree distribution model PHENOFIT to climate input characteristics. This analysis was conducted for two North American trees which differ greatly in their distribution and eight different types of climate input for the historic period which differ in their spatial (local or gridded data) and temporal (daily vs. monthly) resolution as well as their type (locally recorded, extrapolated or simulated by General Circulation Models). We show that the climate data resolution (spatial and temporal) and their type, highly affect the model predictions. The sensitivity analysis also revealed, the importance, for global climate change impact assessment, of (i) the daily variability of temperatures in modeling the biological processes shaping species distribution, (ii) climate data at high latitudes and elevations and (iii) climate data with high spatial resolution.

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