Cross-Site: Analysis of Past and Current Changes in Grassland Ecosystem Dynamics in Asia and North America

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We propose a three year project to investigate the role and consequences of changes in climate, land use, vegetation, and soils of the temperate grassland ecosystems of Asia and North America. The objective of this study is to characterize the factors controlling ecosystem integrity relative to changes in climate and land use of North American and Asian grasslands, and to understand these changes relative to the presence and distribution of C3 and C4 species in these two regions. Although plant productivity tends to be greater for the same amount of rainfall in the Asian continent, the occurrence of C4 species in the Asian grasslands is greatly reduced compared to the North American grasslands. They will incorporate isotopic analysis of soils and vegetation across a gradient of rainfall and temperature in Asia and compare these to similar analyses collected in North America. This information will be integrated using the CENTURY ecosystem model to investigate climate-soil-land use interactions on soil and vegetation dynamics. Isotopic signature 813C will be compared across sim ilar topo-edaphic positions of plant communities in different regions of the two continents. Remote sensing will provide the land cover template to evaluate the degree of changes from natural vegetation. These differences will be used in conjunction with the CENTURY model to evaluate net changes in ecosystem properties at the regional scale and the susceptibility of these grasslands to climate change and human activities.