Riparian land use and the relationship between invertebrate communities and litter decomposition in a tropical highland stream

Abstract

The relationships between catchment land use and stream processes have been widely studied in temperate regions, however, effects of land use on litter processing in tropical streams are less well known. Leaf breakdown and benthic invertebrate colonization of artificial leaf packs in nine tropical highland streams in three differing land uses. Leaf packs were added to nine second order streams (three in each of rainforest, tea plantation and maize fields) in order to determine leaf breakdown and the contribution of benthic invertebrates  o litter processing. Break-down rates over the six weeks of the study did not differ between land uses and was primarily by microbial activity. Significantly lower densities of invertebrates were found in leaf bags incubated in streams draining tea plantation and maize fields than in forest streams (ANOVA, F₂, ₁₅ = 8.399; P = 0.003). The most abundant shredders colonizing bags at all sites were larvae of Tipulidae (Diptera) and Calamoceratidae (Trichoptera). Shredder abundance and diversity were significantly higher in forest streams little evidence was found for invertebrates feeding on leaves. This may have been because leaves remained tough and microbial communities had not softened leave sufficiently over the six weeks of the study.