Climatic constraints on high-elevation aboveground net primary production

Abstract

Life in high-elevation ecosystems is hard. Ecosystem functions such as aboveground net primary production (ANPP) are constrained by short growing seasons and patchy resource availability. I quantified ANPP responses to changes in these variables by combining global, regional, and local observations with simple models. I observed a consistent, linear increase in ANPP with growing season length (4 g/m2/d) at local and regional scales. I also found a nonlinear, asymptotic increase in ANPP with soil moisture across sites, despite variation in space, time, and plant species composition. I hypothesized that this soil moisture limitation may be partially mediated by nitrogen availability based on leaf-level observations from Niwot Ridge, CO. Finally, I compared a set of competing models relating ANPP to growing season length and soil moisture. I found that the combined influence of these variables was modeled best with a cumulative limitation by soil moisture. This model offers a simple basis for predicting the response of high-elevation ANPP to changes in these climatic constraints.