Land use effect on aquatic macroinvertebrates diversity in subtropical highland grasslands streams

Resum

Spatial distribution of macroinvertebrates helps to understand the impacts and drive conservation actions on aquatic systems. We evaluated the α and β diversity of macroinvertebrates in streams at four different phytophysiognomies of the subtropical region (highland grasslands with riparian vegetation, grasslands without riparian vegetation, mixed ombrophilous forest and silviculture). In addition, we verified how environmental factors influence the α diversity. We sampled macroinvertebrates community (by surber sampler), litter input (by nets) and physicochemical variables of water (by multiparameter and chemical analysis) in 10 sites in riparian zones of a highland system. A total of 2,124 individuals were identified, among 41 taxa, showing the high α and β diversity of mixed ombrophilous forest indicating that environmental heterogeneity allows for a high food resources availability, increases the diversity of macroinvertebrates community. Also, the disconnected streams increase the β diversity by the distance. Silviculture areas show the highest density values compared to other sampled areas due high organic material bedding in soil. Therefore, higher system productivity may decrease the toxicity effect compared at environments with low systemic productivity, such as highland grasslands. The presence of riparian vegetation drives the canopy opening, water temperature, dissolved oxygen, and orthophosphate on the streams that control the frequency and occurrence of benthic macroinvertebrates communities. The highland grasslands, as they are naturally more homogeneous, and the high canopy openness showed the lowest richness and density. These results may be an important guideline for legislation, management, and conservation of highland grassland stream areas in Subtropical zones.