Efeitos de alterações na zona ripária sobre a integridade de igarapés amazônicos no Baixo rio Teles Pires, Norte de Mato Grosso

Abstract

In the Amazon basin there are many streams, locally called streams, embedded in heterogeneous landscapes, considering the natural variations of geomorphological conditions, rainfall periods and degradation promoted by deforestation, mainly on the southern Amazon basin. Therefore, the aim of this study was to evaluate the impacts of the riparian forest cover changes on the structure streams in the lower Teles Pires River, north of Mato Grosso. Ten sites in the basin of the Teles Pires River, tributary of the Tapajos river, and each of them two headwater streams were selected; a stream located in area with riparian forest preserved (pristine stream) and another stream with the riparian zone disturbed with changes in the riparian forest cover (altered stream). As changes in the riparian zone of the streams, partial or total removal of the forest were considered. Indicator variables of habitat integrity (proportion of forest buffer zones, habitat integrity index), hydromorphological variables streams, physico-chemical parameters, and the autochthonous primary production (algae and aquatic herbaceous) were evaluated in drought, rain/begin and rain/end (hydrological periods). The variation between the hydrological periods and spatial heterogeneity in the structure of pristine headwater streams were recorded. Changes in riparian forest cover affected the variability in habitat structure of the streams between the hydrological periods, making them more homogeneous, and contributing to a lower availability of organic material in benthic substrate. In addition, the absence of forest cover in the riparian zone contributed to the rise of primary production allochthonous in headwater streams in southern Amazonia, although aquatic plants and algal biomass have responded differently to periods of drought and rainy. From the comparison between pristine and altered streams indicators of changes in the headwaters were identified, which can be used in the assessment of environmental impacts in these environments as well as in monitoring and rehabilitation of degraded streams actions in the southern Amazon.