Série histórica de uso e cobertura do solo e determinantes ambientais locais e de paisagem na concentração da clorofila-a em riachos de uma bacia do Cerrado

Abstract

The unplanned land use is a main cause of biodiversity loss, the conversion of vegetation affects not only the terrestrial environments, but also aquatic ecosystems. The monitoring environments such as streams can be done using the variable chlorophyll-a which is a good representative of algae and cyanobacteria. The general aim of this work was to evaluate the changes in vegetation cover and land use over 28 years and see which site environmental determinants and/or landscape that affect the concentration of chlorophyll-a directly and indirectly in streams in the river basin Santa Teresa. For the analysis of land cover and use through a historical series in the basin, the satellite images were obtained, these were processed using ENVI 4.7 and ArcGIS 10.0. To check which determine the concentration of chlorophyll-a were collected site environmental variables and water samples to obtain the chlorophyll-a in 30 sample units. In addition, landscape data were obtained for each sub-basin. Through remote sensing analysis we found that the soil cover has changed over the time, from 1985 until 2013 there was a reduction of 17.22% of the natural vegetation, in addition, grazing areas, bare soil and burned has increased over the time. The values of the concentration of chlorophyll-a, nutrients, pH, dissolved oxygen and conductivity indicates that the sampled streams are oligotrophic. The main determinants of the concentration of chlorophyll-a was sites factors, among them the conductivity was the most important variable, furthermore there was little effect of the landscape, however, despite the low landscape effect, the soil cover affects aquatic environments indirectly through other variables, such as conductivity, pH and turbidity. The analysis of coverage and land use in the sub-basins demonstrated that the environments are still quite preserved. About 99.66% of the sub-basins is the predominant coverage represented by remaining, the main use is intended for grazing. The work was the first to characterize the vegetation cover and land use and evaluate the determinants of primary productivity in the survey area. However, we emphasize that the ongoing assessment of landscape and studies using chlorophyll-a to assess the impacts on streams, because although occur slowly, the land cover has changed over the time.