Energy and water availability are fundamental controls on ecosystem properties such as ecosystem type, water use, phenology, and carbon uptake, allocation, and turnover. How availability of energy and water interact to produce stepwise changes in ecosystem properties across linear climate gradients remains an important question for ecology and predicting impacts of climate change. Previous work has focused on the climatic factors that determine individual species’ mortality or locations of individual ecotones, but research is lacking that examines role of energy and water availability in controlling patterns of ecosystem trait shifts across a broad climatic gradient. We studied a 2600-m elevation gradient along the western slope of the Sierra Nevada Mountains in the Southern Sierra Critical Zone Observatory (SSCZO) to understand how water and energy availability interact to influence ecosystem properties across a broad range of climate conditions and ecosystem types. Eddy covariance, vegetation type, forest biomass and production, sap flux, and soil moisture were measured to understand nonlinear ecosystem responses to gradients in energy and water availability. We describe the small differences in temperature and water availability that produce sharp transitions in ecosystem type, productivity, water use, and phenology. Conversely, we describe how broad ranges of temperature and water availability produce stability in ecosystem properties and demonstrate ecosystem resilience to climate change. These findings can better inform predictions of impacts of a changing climate on ecosystem range shifts, mortality, seasonality, carbon cycling, and water use.
Kelly, A.E., Goulden, M., Bales, R.C., Meadows, M.W., and G. Winston (2012): Water and energy gradients produce resilience and thresholds in ecosystem function in the western Sierra Nevada Mountains. Fall Meeting, American Geophysical Union, December 2012. Abstract B51C-0559..