The effects of precipitation variability on C4 photosynthesis, net primary production and soil respiration in a Chihuahuan Desert grassland

Although the Earth's climate system has always been inherently variable, the magnitude and rate of anthropogenic climate change is subjecting ecosystems and the populations that they contain to novel environmental conditions. Because water is the most limiting resource, arid-semiarid ecosystems are likely to be highly responsive to future climate variability. The goal of my dissertation is to understand how precipitation variability affects primary productivity and soil respiration in desert grassland ecosystems. Initially, I reviewed the literature to understand how climate change affects net ecosystem exchange (NEE) across the warm deserts of North America (Chapter 2). Next, I examined the effects of precipitation frequency and intensity on soil moisture (&thetas;), leaf-level photosynthesis (Anet), predawn leaf water potential (Ψpd), aboveground net primary productivity (ANPP), and soil respiration (Rs) (Chapter 3). Last, I studied how large (10 mm) and extreme (30 mm) rainfall events with extended dry periods affected the ecophysiological response of two co-occurring dominant perennial C4 grasses, Bouteloua eriopoda and B. gracilis across an arid-semiarid ecotone (Chapter 4).