Interactive effects of consumer exclusion and leaf litter composition on patterns of litter decomposition in a stream ecosystem

Abstract

The decomposition of leaf litter in streams is an ecosystem process influenced by a multitude of factors including invertebrate consumers and leaf litter composition. This field experiment measured the effect of functional and taxonomic diversity of leaf species and the exclusion of consumers on the rate of leaf litter decomposition in a first order stream on the Patapsco River in Baltimore, Maryland (USA). This experiment manipulated different levels of leaf diversity by using single or mixed species in leaf packs, as well as coarse and fine mesh to exclude consumers. After 42 days in the stream, leaf packs were removed to determine mass loss for each pack and the interaction between mesh size and diversity on decomposition. As predicted, significant differences were observed between variability (taken as CV) and diversity levels, as well as shredder (consumer) abundance and mass loss. A hypothesis was also tested to determine if a family of shredders, Limnephilidae, was observed to prefer high or low diversity leaves. Although this prediction did not show a trend supporting a higher abundance of Limnephilidae linked to higher diversity leaves, it serves as a foundation for future studies to determine if other shredder families prefer different species of leaf litter. These results can be used to further enhance existing literature on freshwater ecology as well as provide knowledge to expand opportunities for riparian habitat conservation.