Do Leaves from Native and Non-Native Trees Decompose at Different Rates in Streams?

Abstract

Organic matter decomposition is an important ecological process in stream ecosystems. Decaying leaves in particular constitute an important source of food and habitat for microorganisms and macroinvertebrate “shredders,” two groups that play a critical role in leaf breakdown. Bacteria and fungi decompose leaves and macroinvertebrates break the leaves apart as they feed on these microorganisms. Shredder feeding accounts for 50-74% of leaf decomposition in streams; however, leaves may differ in their nutritional quality and toughness. Leaves from non-native plants may support different microbial communities and/or be of different nutritional quality for shredders, and this may alter leaf decomposition rates. Little Niagara Creek receives leaves from both native and non-native trees. To study the importance of leaf type, microbial decomposition and shredders on leaf breakdown rates, we examined leaves from three native (slippery elm, maple and oak) and two non-native trees (buckthorn and ginkgo). We hypothesized that native species would be colonized by greater numbers of macroinvertebrate shedders than non-native leaves and would also decompose more rapidly.