The Role of Photodegradation in Grassland Ecosystems.

Patterns of decomposition in grassland ecosystems are not well predicted by models, suggesting that our understanding of the controls on decomposition in these systems is incomplete. We are investigating the influence of solar radiation on rates of decomposition of plant litter through a combination of field, laboratory, and modeling studies. Our results indicate that ultraviolet radiation may play an important role in plant litter decomposition under dry conditions. Field measurements show that the presence of ultraviolet radiation results in decomposition rates that are 25% higher than those measured in the absence of ultraviolet radiation. We also find that photodegradation of sterilized plant litter can result in measurable emissions of carbon dioxide. These controlled experiments show that photodegradation occurs in the presence of ultraviolet radiation or in the presence of short wavelengths of visible light (< 500 nm). We are investigating methods by which the influence of photodegradation can be incorporated into biogeochemical models to predict carbon and nitrogen cycling with photodegradation.