Modeling the potential effects of climate change on leaf pack processing in central Appalachian streams

A computer simulation model was constructed to evaluate some of the projected impacts of climate change, including elevated temperatures and increased frequency and magnitude of floods and droughts, on leaf pack processing in central Appalachian streams. The model simulated microbial processing, invertebrate consumption, and transport along a 1-km second-order stream. We examined the effects of wet and dry years with and without a 2°C temperature increase. Both invertebrates and microbes processed more leaf material under the elevated temperature scenarios; however, the invertebrate response was greater than the microbial response. In the model, microbial processing is represented as a linear function of temperature; a nonlinear response might produce different results. Invertebrates processed a greater percentage of the inputs in wet than in dry years, while microbial processing rates were unaffected. A 20-year flood event occurring in November, January, or March caused more than 50% of the leaf inputs to be exported, leaving little detrital material available for invertebrate consumption. The timing of the flood event made little difference to the simulation results. All climate change scenarios resulted in decreases, sometimes substantial, in coarse particulate organic matter availability to shredders during the summer months.