Effects of riparian forest management on Chilean mountain in-stream characteristics

Abstract

We assessed the effect of forest management practices on temporal differences in riparian litterfall input and autumnal leaf litter processing of 3 evergreen plant species, using independently 2 mesh sizes (for two of the three species), between two contrasting headwater streams draining (a) near-pristine and (b) harvested evergreen old-growth forests in Chile (39°S). Additionally, we compared rainfall, streamflow, suspended sediment concentration, and the in-stream invertebrate community, collected two years after logging in the harvested microcatchment. The harvested forested stream had higher runoff, suspended sediment concentration and input of litter (3377kgha−1yr−1) than the pristine stream (3166kgha−1yr−1). However, leaf-litter decay rates were faster for the pristine (ranging from k=−0.0120 to −0.0024day−1) than for the harvested forest stream (k=−0.0049 to −0.0023day−1) depending on leaf species and litterbag type. Likewise, the pristine stream revealed higher shredder taxa richness than harvested stream, suggesting a higher correlation with the decomposition rate and leaf mass losses. Therefore, the results of our study suggest that despite the implementation of best management practices on riparian forests, there are detectable shifts in the structure and functioning of aquatic invertebrate community in the Andean streams of south-central Chile.