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

Decomposition of three leaf species (Alnus glutinosa, Eucalyptus globulus a nd Quercus robur) were examined in a headstream. During two months decompos ing leaves were periodically analysed for nutrient content, soluble sugars, phenols, protein precipitation capacity, total fiber, weight loss, microbi al and macroinvertebrate colonisation. The leaves of the three species show ed similar patterns in dynamics of soluble sugars, tannins and phenols. Bac teria numbers per foliar dry mass were constant in oak during the experimen t, 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 analys is of invertebrate assemblages revealed differences between alder and the o ther two species related to nitrogen and microbial abundance.