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Climatic Change Scenarios (climatic + change_scenario)
Selected AbstractsAssessing forest growth across southwestern Oregon under a range of current and future global change scenarios using a process model, 3-PGGLOBAL CHANGE BIOLOGY, Issue 1 2001N. C. Coops Summary With improvements in mapping regional distributions of vegetation using satellite-derived information, there is an increasing interest in the assessment of current limitations on forest growth and in making projections of how productivity may be altered in response to changing climatic conditions and management policies. We utilised a simplified physiologically based process model (3-PG) across a 54 000 km2 mountainous region of southwestern Oregon, USA, to evaluate the degree to which maximum periodic mean annual increment (PAI) of forests could be predicted at a set of 448 forest inventory plots. The survey data were pooled into six broad forest types (coastal rain forest, interior coast range forest, mixed conifer, dry-site Douglas-fir, subalpine forest, and pine forest) and compared to the 3-PG predictions at a spatial resolution of 1 km2. We found good agreement (r2 = 0.84) between mean PAI values of forest productivity for the six forest types with those obtained from field surveys. With confidence at this broader level of integration, we then ran model simulations to evaluate the constraints imposed by (i) soil fertility under current climatic conditions, (ii) the effect of doubling monthly precipitation across the region, and (iii) a widely used climatic change scenario that involves modifications in monthly mean temperatures and precipitation, as well as a doubling in atmospheric CO2 concentrations. These analyses showed that optimum soil fertility would more than double growth, with the greatest response in the subalpine type and the least increase in the coastal rain forests. Doubling the precipitation increased productivity in the pine type (> 50%) with reduced responses elsewhere. The climate change scenario with doubled atmospheric CO2 increased growth by 50% on average across all forest types, primarily as a result of a projected 33% increase in photosynthetic capacity. This modelling exercise indicates that, at a regional scale, a general relationship exists between simulated maximum leaf area index and maximum aboveground growth, supporting the contention that satellite-derived estimates of leaf area index may be good measures of the potential productivity of temperate evergreen forests. [source] Projecting future N2O emissions from agricultural soils in BelgiumGLOBAL CHANGE BIOLOGY, Issue 1 2007CAROLINE ROELANDT Abstract This study analyses the spatial and temporal variability of N2O emissions from the agricultural soils of Belgium. Annual N2O emission rates are estimated with two statistical models, MCROPS and MGRASS, which take account of the impact of changes in land use, climate, and nitrogen-fertilization rate. The models are used to simulate the temporal trend of N2O emissions between 1990 and 2050 for a 10, latitude and longitude grid. The results are also aggregated to the regional and national scale to facilitate comparison with other studies and national inventories. Changes in climate and land use are derived from the quantitative scenarios developed by the ATEAM project based on the Intergovernmental Panel on Climate Change-Special Report on Emissions Scenarios (IPCC-SRES) storylines. The average N2O flux for Belgium was estimated to be 8.6 × 106 kg N2O-N yr,1 (STD = 2.1 × 106 kg N2O-N yr,1) for the period 1990,2000. Fluxes estimated for a single year (1996) give a reasonable agreement with published results at the national and regional scales for the same year. The scenario-based simulations of future N2O emissions show the strong influence of land-use change. The scenarios A1FI, B1 and B2 produce similar results between 2001 and 2050 with a national emission rate in 2050 of 11.9 × 106 kg N2O-N yr,1. The A2 scenario, however, is very sensitive to the reduction in agricultural land areas (,14% compared with the 1990 baseline), which results in a reduced emission rate in 2050 of 8.3 × 106 kg N2O-N yr,1. Neither the climatic change scenarios nor the reduction in nitrogen fertilization rate could explain these results leading to the conclusion that N2O emissions from Belgian agricultural soils will be more markedly affected by changes in agricultural land areas. [source] Global potential distribution of an invasive species, the yellow crazy ant (Anoplolepis gracilipes) under climate changeINTEGRATIVE ZOOLOGY (ELECTRONIC), Issue 3 2008Youhua CHEN Abstract Changes to the Earth's climate may affect the distribution of countless species. Understanding the potential distribution of known invasive species under an altered climate is vital to predicting impacts and developing management policy. The present study employs ecological niche modeling to construct the global potential distribution range of the yellow crazy ant (Anoplolepis gracilipes) using past, current and future climate scenarios. Three modeling algorithms, GARP, BioClim and Environmental Distance, were used in a comparative analysis. Output from the models suggest firstly that this insect originated from south Asia, expanded into Europe and then into Afrotropical regions, after which it formed its current distribution. Second, the invasive risk of A. gracilipes under future climatic change scenarios will become greater because of an extension of suitable environmental conditions in higher latitudes. Third, when compared to the GARP model, BioClim and Environmental Distance models were better at modeling a species' ancestral distribution. These findings are discussed in light of the predictive accuracy of these models. [source] Effects of elevated ozone on photosynthesis and stomatal conductance of two soybean varieties: a case study to assess impacts of one component of predicted global climate changePLANT BIOLOGY, Issue 2009E. Singh Abstract Global climatic change scenarios predict a significant increase in future tropospheric ozone (O3) concentrations. The present investigation was done to assess the effects of elevated O3 (70 and 100 ppb) on electron transport, carbon fixation, stomatal conductance and pigment concentrations in two tropical soybean (Glycine max L.) varieties, PK 472 and Bragg. Plants were exposed to O3 for 4 h·day,1 from 10:00 to 14:00 from germination to maturity. Photosynthesis of both varieties were adversely affected, but the reduction was higher in PK 472 than Bragg. A comparison of chlorophyll a fluorescence kinetics with carbon fixation suggested greater sensitivity of dark reactions than light reactions of photosynthesis to O3 stress. The O3 -induced uncoupling between photosynthesis and stomatal conductance in PK 472 suggests the reduction in photosynthesis may be attributed to a factor other than reduced stomatal conductance. An increase in internal CO2 concentration in both O3 -treated soybean varieties compared suggests that the reduction in photosynthesis was due to damage to the photosynthetic apparatus, leading to accumulation of internal CO2 and stomatal closure. The adverse impact of O3 stress increased at higher O3 concentrations in both soybean varieties leading to large reductions in photosynthesis. This study suggests that O3 -induced reductions in photosynthesis in tropical and temperate varieties are similar. [source] Evaluation of habitat sustainability and vulnerability for beech (Fagus crenata) forests under 110 hypothetical climatic change scenarios in JapanAPPLIED VEGETATION SCIENCE, Issue 3 2009Tetsuya Matsui Abstract Questions: Are there any sustainable or vulnerable habitats in which beech (Fagus crenata) forests could survive in Japan under 110 hypothetical climate change scenarios? Location: Six islands of Japan on which beech grows naturally. Methods: An ecological habitat model was used to simulate the potential habitat shifts of beech forests under 110 climate change scenarios. The amount of suitable habitat loss and gain was calculated with three migration options and risk surfaces. Vulnerable and sustainable habitats were identified to evaluate the potential risks and survival of beech forests. Results: The total areas of potential suitable habitats differed considerably depending on the future temperature and precipitation changes. Some areas on the Sea of Japan (SOJ) side showed higher probability of maintaining suitable habitats, whereas there were wider areas in which suitable habitats could not persist under any of the 110 climate change scenarios. Conclusions: The risk surfaces of the suitable habitats showed that decreases in precipitation along with increases in temperature reduced the total areas of suitable habitats. Increases in precipitation with increases in temperature of more than or equal to 2°C always reduce the areas of suitable habitats. Under increased precipitation with a temperature increase of <2°C, the areas of suitable habitats showed an increase, maintenance of the status quo or a decrease, depending on the size of the increase in precipitation. Beech forests in western Japan are predicted to be vulnerable to climate change, whereas some mountains on the SOJ side are predicted to be possible future refugia. [source] Soil microbial activity along an arctic-alpine altitudinal gradient from a seasonal perspectiveEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 5 2008U. C. M. Löffler Summary The knowledge on dynamics of soil microbial activity and its correlation to climate and vegetation is still poor but essential for predicting climatic changes scenarios. Seasonal dynamics of soil microbial activity and cell counts were studied along an arctic-alpine altitudinal gradient. The gradient comprised 12 ridges from 1000 to 1600 m altitude. Soil samples were collected during March, May, July and September 2005. The effect of temperature, snow depth and vegetation, all of which changed with altitude, on soil microbial activity and bacterial cell counts was analysed. The potential activities of phosphatase and chitinase were determined using fluorescent 4-methylumbelliferyl labelled analogues. Total and live bacterial cell counts were determined by live-dead-staining. We detected marked differences in soil microbial variables along the altitudinal gradient, forming three major clusters: a low alpine belt, a middle alpine belt, and an intermediate transition zone. Our results demonstrated that more frequent occurrence of shrubs and bryophytes would also increase microbial activity. Furthermore, we detected a clear relation (R2 = 0.6; P < 0.02) between high soil temperatures and greater soil microbial activity during summer. As higher temperatures are predicted to promote shrubs and higher humidity to promote bryophytes we expect microbial activity in dry heath tundra soils will increase with anticipated warmer, and in the case of Scandinavia, more humid climates. We did not find winter microbial activity to be less at snow-free sites than at sites covered by snow up to depths of 30 cm; hence, possible future decreases in snow depth will not result in reduced winter microbial activity. We demonstrate that shrubs support winter microbial activity not only by trapping snow but also directly by increasing the amount of organic carbon. [source] | |||||||||||||