The influence of water quality and macroinvertebrate colonization on the breakdown process of native and exotic leaf types in sub-alpine stream

Abstract

Most of the energy input of low-order lotic food webs derives from non-living sources of terrestrial organic matter. For this reason, many studies have examined patterns of leaf breakdown; most recently, interest has focused on the importance of water quality or the nature (native versus exotic) of plant material. In this study, we combined both aspects by analyzing the breakdown process and macroinvertebrate colonization of leaf bags containing leaves of different plant types in two nearby sites with different levels of water quality. We exposed a total of 600 leaf bags made of five leaf types (three native: Alnus incana, Populus alba and Quercus robur; and two exotic: Reynoutria japonica and Robinia pseudoacacia) at two sites of the Pellice River (northwestern Italy). Leaf bags were retrieved after 10, 20, 30, 40, 50 and 60 days, leaf mass loss determined and the associated macroinvertebrates quantified. Significant differences were found in the mass loss and in the colonization of leaf bags between sit...