Photodegradation of Plant Litter in Grassland Ecosystems: A Mechanism for Uncoupling C and N Biogeochemistry

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Decomposition is the basic ecosystem process by which carbon and nutrients in dead organic matter are recycled, yet knowledge of this process is incomplete, as evidenced by the fact that current biogeochemical models of carbon and nutrient cycling cannot reliably estimate rates of decomposition. Photodegradation, the photochemical oxidation of organic matter by ultraviolet radiation, may play an important role in determining rates of decomposition in highly exposed areas such as grassland systems. This project will address the current lack of understanding about the contribution of photodegradation to decomposition rates. A multi-year, multi-site field decomposition experiment and a series of laboratory studies will be used to measure the direct and indirect effects of photodegradation on overall element cycling. These results will be integrated into a biogeochemical model that can be applied more generally. This study addresses the complexity of decomposition as a process controlled by both biological and non-biological factors. The results will enable better estimates of carbon and nitrogen cycling rates as well as improved ability to predict how cycling rates may change under differing environmental conditions. The project will have far-reaching impact through collaboration between three LTER sites and integration of research and educational opportunities for undergraduates, graduate students, and the general public.