PARENT SESSION
Oral Session #42: Decomposition.
Presiding: K. Gross
Tuesday, August 6. 1:00 PM to 4:45 PM. Apache Meeting Room, TCC.
Mixed-litter effects on decomposition, litter quality, microbial metabolism and invertebrate colonization in a stream ecosystem.
Swan, Christopher*,1, Palmer, Margaret1, 1 Department of Biology, College Park, MD
ABSTRACT- Studies of litter decomposition in aquatic and terrestrial ecosystems have revealed that species-specific differences in litter chemistry mediate complex interactions between community and ecosystem processes. Litter species with refractory chemical attributes and low nutrient concentrations tend to slow microbial activity, alter decomposition rates, and adversely affect the growth and abundance of detritivorous invertebrates. While research in terrestrial ecosystems has revealed that mixing litter can further alter these patterns and processes, often in non-additive ways, such studies in aquatic ecosystems remain rare. We performed a field experiment where we placed packs of leaves from five species of common riparian trees as single-species and four-species mixtures in a Piedmont stream. We documented strong differences among single species treatments in C processing, N accumulation, microbial respiration, decomposition rates, and invertebrate abundance. Among mixed treatments, N accumulation rates were greater than could be predicted from averaging single-species estimates in two of our mixed treatments. Furthermore, decomposition rates were slower than predicted in one instance, and microbial respiration was lower than predicted in another. Certain species combinations, especially those with highly labile, high N attributes, resulted in higher than expected estimates than would be predicted by simply averaging single-species effects, while refractory species in mixtures tended to lower estimates. Given the extent to which riparian habitats are being altered, it is evident that not just the number, but also the composition of tree species present are important to stream ecosystem properties.
KEY WORDS: decomposition, mixed-litter, streams, non-additivity