Impacts of recent droughts on North American terrestrial ecosystems

Tuesday, 16 December 2014
Jingfeng Xiao1, Scott V Ollinger1, Feng Li1, Changsheng Li1, Steve E Frolking1, George C Hurtt2, Rossella Guerrieri1, Lucie C Lepine1 and Heidi Asbjornsen3, (1)University of New Hampshire, Earth Systems Research Center, Durham, NH, United States, (2)University of Maryland, College Park, MD, United States, (3)University of New Hampshire, Durham, NH, United States
The frequency and severity of droughts have been increasing, and their impacts on terrestrial ecosystems have received growing attention. There has been limited research on the responses of carbon fluxes, evapotranspiration (ET), and water use efficiency (WUE) to severe and extended droughts at regional to continental scales. Here we combine a gridded carbon and water flux dataset (EC-MOD), Palmer Drought Severity Index (PDSI), a process-based ecosystem model, and agricultural statistics to examine the impacts of recent droughts on North American terrestrial ecosystems. The gridded flux dataset was upscaled from eddy covariance flux observations across North America through a data-driven approach. We assess the responses of ecosystem carbon fluxes, ET, and WUE to severe and extended droughts at the continental scale using EC-MOD. Drought can lead to significant declines in ET and subsequent decreases in carbon fluxes. The responses of WUE to drought are assessed at the annual scale. Simulations from a process-based ecosystem model and crop yield statistics are also used to assess the effects of drought on agricultural productivity and WUE. Drought is one of the main sources of the interannual variability of carbon and water fluxes in North America. Drought is expected to become more frequent and more severe during the remainder of the 21st century and therefore will likely have larger impacts on terrestrial ecosystems.