Monsoon Precipitation Extremes and Soil Water Dynamics Across a Semiarid Grassland Ecotone
In keeping with the Intergovernmental Panel on Climate Change (2007) global climate projections, this study aims to determine how a shift towards more extreme precipitation events punctuated with longer dry intervals will affect the ecophysiological response of two arid-semiarid grassland species, Bouteloua eriopoda and Bouteloua gracilis. Both species are dominants in their respective ecosystems (Chihuahuan Desert Grassland and Great Plains Short Grassland Prairie, respectively) and co-occur at an ecotone located at the Sevilleta National Wildlife Refuge (SNWR) in central New Mexico. Knowing how these dominant grassland species differentially respond to altered precipitation regimes is critical to understanding potential shifts in ecotone boundaries due to increased climate variability. I hypothesize that large, infrequent rainfall events will increase photosynthesis and stomatal conductance and decrease leaf water potential in both species. However, B. eriopoda will maintain higher rates of photosynthesis, stomatal conductance and lower leaf water potentials during dry intervals, which will increase aboveground net primary productivity (ANPP) when compared with B. gracilis. Thus, giving B. eriopoda an advantage and potentially shifting the ecotone boundary northward under proposed climate scenarios.