Abstracts on Global Climate Change

Mar 2007

Spatial and temporal effects of pre-seeding plates with invasive ascidians: Growth, recruitment and community composition

Agius, BP


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.

| /unclassified/todo | 083

Biogenic secondary organic aerosol over the United States: Comparison of climatological simulations with observations

Liao, H Henze, DK Seinfeld, JH Wu, SL Mickley, LJ


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.

| /unclassified/todo | 067

A new economic assessment index for the impact of climate change on grain yield

Dong, WJ Chou, JM Feng, GL


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.

| /unclassified/todo | 081

Impact of changes in rainfall amounts predicted by climate-change models on decomposition in a deciduous forest

Lensing, JR Wise, DH


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.

| /unclassified/todo | 097

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).

| /unclassified/todo | 089

Climate change and the emergence of Vibrio vulnificus disease in Israel

Paz, S Bisharat, N Paz, E Kidar, O Cohen, D


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.

| /unclassified/todo | 072

Kiln-drying lumber quality of hybrid poplar clones

Kang, KY Bradic, S Avramidis, S Mansfield, SD


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.

| /unclassified/todo | 099

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


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.

| /unclassified/todo | 091

Scientists’ perceptions of threats to Coral Reefs: Results of a survey of Coral Reef researchers

Kleypas, JA Eakin, CM


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.

| /unclassified/todo | 044

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.

| /unclassified/todo | 088

Using dynamical downscaling to close the gap between global change scenarios and local permafrost dynamics

Stendel, M Romanovsky, VE Christensen, JH Sazonova, T


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.

| /unclassified/todo | 078

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


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.

| /unclassified/todo | 073

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


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.

| /unclassified/todo | 090

Resurrection ecology and global climate change research in freshwater ecosystems

Angeler, DG


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.

| /unclassified/todo | 098

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


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.

| /unclassified/todo | 085

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


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.

| /unclassified/todo | 111

Estimating organic carbon from loss-on-ignition in northern Arizona forest soils

Abella, SR Zimmer, BW


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.

| /unclassified/todo | 066