Increasing inputs of invasive N?fixing Acacia litter decrease litter decomposition and associated microbial activity in streams

Nitrogen (N)-fixing Acacia species are often aggressive invaders outside their native range. When invading riparian temperate forests, they can decrease tree diversity, alter the quality of litter inputs to streams and increase water N concentration. Although effects diversity nutrient enrichment on decomposition associated microbial decomposers have been widely studied, individual combined remain poorly understood, especially in flowing through forests invaded by species. Here, we assessed (species evenness) concentration litter, activity community structure decomposers. Litter Castanea sativa (C) melanoxylon (A) was enclosed fine-mesh bags a total five evenness treatments (100%C, 75%C + 25%A, 50%C 50%A, 25%C 75%A 100%A), immersed stream forest (native stream) (invaded stream). rates decomposer differed among treatments, generally decreasing as proportion A. increased. considered individually, C. did not differ treatments. For melanoxylon, whereas lower with higher or even proportions sativa. had (small) antagonistic streams. However, affected between streams, suggesting that be modulated were than stream, probably consequence former stream. magnitude small owing fact still oligothrophic range Overall, our results suggest increasing N-fixing deciduous will affect activity, aquatic hyphomycete structure, most result decreases increases resulting from input (due contribution) into larger those concentration, thus overall decrease. These impacts possibly cycles food webs depend detritus, implications for functioning.