Influence of summer drought on spatial patterns of resource availability and detritus processing in Mediterranean stream sub-basins (Sardinia, Italy)

We studied the variation patterns of Phragmites australis detritus decomposition and derived patterns of field resource availability in three Mediterranean-type sub-basins exposed to varying degrees to summer drought events. The study was carried out during spring-summer 1998 and fall-winter 1998-1999, in 1(st) to 4(th) order streams. Detritus processing and macroinvertebrate body-condition were measured. Decomposition rates were significantly higher in spring-summer than in fall-winter, in relatively unperturbed than in perturbed sub-basins, and in high-order than low-order streams. The influence of disturbance decreased with increasing stream order, suggesting that higher order streams have greater resilience to drought events than lower order streams. The body condition of macroinvertebrates suggested patterns of field resource availability spatially covariant with those of detritus decay and ecosystem resilience.