IMPACTS OF CLIMATE CHANGE AND DROUGHT OCCURRENCE ON CPOM DEGRADATION IN PREVIOUSLY PERENNIAL ALPINE STREAMS (NW ITALY)

Stream ecosystems have been recognized as extremely sensitive to climate change, because of the raising of water temperatures and the disruption of hydrologic cycles. In particular, mountain streams are known to be particularly fragile since highest rates of climate change are occurring above the treeline. The aim of the study was to investigate the functional impact of droughts in three Alpine streams (Po, Pellice and Varaita - NW Italy), which are becoming increasingly intermittent. In particular, using leaf litter bags of chestnut and oak we investigated the CPOM degradation process in both perennial and recently intermittent reaches, by measuring the following: i) mass loss variations; ii) macroinvertebrate colonisation patterns; iii) microbiota communities (fungi and bacteria) involved in the process. We hypothesized that the CPOM decomposition in sites with permanent flow would be driven by a relevant contribution of both macro- and micro-consumers. On the contrary, we expected that CPOM degradation in intermittent sites would be explained primarily by the role of microconsumers. With continued drought conditions and changing CPOM subsidies, the biodiversity, richness and density of colonizer communities could result in altered Alpine stream ecosystems.