Invertebrate and microbial colonisation in native and exotic leaf litter species in a mountain stream

Decomposition of three leaf species (Alnus glutinosa, Eucalyptus globulus and Quercus robur) were examined in a headstream. During two months decomposing leaves were periodically analysed for nutrient content, soluble sugars, phenols, protein precipitation capacity, total fiber, weight loss, microbial and macroinvertebrate colonisation. The leaves of the three species showed similar patterns in dynamics of soluble sugars, tannins and phenols. Bacteria numbers per foliar dry mass were constant in oak during the experiment, but increased linearly in eucalyptus. Total heterotrophic colony forming units (bacteria and fungi) were similar in eucalyptus and oak and constant during incubation, whereas in alder, they became more abundant. The analysis of invertebrate assemblages revealed differences between alder and the other two species related to nitrogen and microbial abundance.