Grassland sensitivity to climate change at local to regional scales: assessing the role of ecosystem attributes vs. environmental context

Although we have learned much in the past 20 years about how individual ecosystems are likely to respond to climate change, extending this knowledge to regional and continental scales has been a far greater challenge. At these larger spatial scales, both the environment and the attributes of ecosystems expected  to influence their response to climate change vary dramatically. For example, in the central US, there are strong temperature and rainfall gradients from Texas to North Dakota and the dry plains of Colorado to eastern Kansas, and the types of grasslands differ as well (from short grasslands in the west to tall grasslands in the east). In order to better forecast how entire regions will respond to expected climatic changes, there is a pressing need to understand how and why ecosystems differ in their sensitivity to changes in climate.  This project is designed to answer a question of fundamental importance for advancing knowledge of biological processes at large scales:  How important are the attributes of ecosystems per se vs. the environmental context in which climate is changing in determining ecological responses to climate change at regional scales?  To answer this question, a geographically distributed field experiment will be conducted at six sites in NM, CO, WY and KS and the results from this experiment will be used to strengthen an existing process-based terrestrial ecosystem model. With this model, the relative importance of ecosystem attributes versus the environment for determining responses to climate change will be evaluated and then scaling rules for extending site-based knowledge to regional scales will be developed.  The experiment imposed will be a severe multi-year drought in grasslands arrayed along a rainfall gradient (from desert grassland to mesic tallgrass prairie).  Key responses measured will include many related to carbon cycling and budgets and plant biodiversity.