Como remanescentes florestais influenciam o funcionamento e a diversidade em um córrego exposto à fragmentação da vegetação ripária?

Abstract

Low-order streams are systems especially vulnerable to riparian vegetation fragmentation. However, the understanding of the importance of forest remnants in streams exposed to anthropogenic impacts and the estimation of forest length necessary to maintain the integrity of these systems remain imprecise. Our study aims to investigate the role of riparian vegetation remnants in maintaining functioning and biodiversity in a stream exposed to fragmentation. To this end, we sampled 20 points along a continuous forest-pasture-forest fragment type transition, in which we analyzed periphytic growth, leaf decomposition and benthic invertebrate diversity. We observed that algal biomass and periphyton diatoms showed a consistent delay response in relation to land cover transitions, taking between 300-400 meters into the pasture to reach the highest biomasses. Within the forest fragment we found that algal biomass gradually diminished with distance from the fragment edge. Decomposition, in general, did not change with the land cover transitions. Benthic invertebrates increased within the forest fragment. In this stretch, we identified an increase in some families and a tendency towards increased EPT abundance, Shannon index and the representativeness of different functional groups within the community. The forest fragment, although not returning some metrics to the pre-disturbance state, was able to dampen several altered characteristics along the pasture. In view of these results, we are in agreement with growing evidence in the literature of the importance of forest remnants in maintaining stream integrity and functioning