摘要：Allochthonous material from riparian forest is an important source for detritivore food chain in streams. This study aimed to: i) estimate the leaf mass loss of Salix humboldtiana Willd., ii) analyze the changes in the detritus chemical composition during mass loss, and iii) analyze the invertebrate colonizers assemblage of a sandy stream in south coastal plain of the Rio Grande do Sul state (Brazil). We hypothesized that S. humboldtiana debris constitute favorable habitat for colonization by invertebrates, which in turn contribute to debris degradation. Twenty eight bags were incubated on the sediment surface of the stream in seven sampling dates. During the decomposition process we analyzed changes of detritus chemical composition and the abundance, richness and functional trophic groups of invertebrates. After 184 days we recorded an average loss of 70% of debris (k=0.0066 day-1) and counted a total of 14197 invertebrate individuals, distributed in 36 taxa. Oligochaeta (43.6%), Hydrobiidae (16.6%), Chironominae (11.3%) and Hydracarina (6.6%) were the most representative. The biofi lm development, observed through increased concentrations of total phosphorus and nitrogen in the debris, may have favored colonization by scrapers at the end of the decomposition period. The initial hypothesiswas partially corroborated as the abundance of potential shredders was low, the contribution of invertebrates assemblage to litter decomposition was low, and the gathering-collectors were the most abundant group.
