Partitioning of Evapotranspiration in a Chihuahuan Desert Grassland

Abstract

Recent invasions of woody plants into semiarid grasslands are a world-wide phenomena with potential ramifications for global-scale carbon cycling. An understanding of how biological and non-biological processes within ecosystems influence water loss to the atmosphere is important to evaluating the consequences of woody plant encroachment on carbon and water cycling in semiarid lands. Accordingly, evapotranspiration in a Chihuahuan Desert grassland was partitioned into its component fluxes for the 2005 summer growing season using a combination of microlysimeters, to quantify soil evaporation, and eddy covariance, to quantify evapotranspiration and net ecosystem exchange of CO2 (NEE). While some of the results of this study (e.g., the ratio of T to ET) are expected to be highly dependent on the particular characteristics of the 2005 summer rainy season, many of them reveal a more general picture about the timing and magnitude of the biological and non-biological water and carbon cycling responses for a warm-season semiarid grassland. This will be important for trying to understand what happens to the carbon and water cycling processes as grasslands are invaded by shrubs.