The role of forest fragments in controlling water quality and ecosystem functioning of streams draining agricultural catchments

Abstract

Natural forest ecosystems are potentially the best land use to protect water resources, while agricultural practices tend to change physical, chemical and biological properties of waters. The use of forests as a management toll will only be consolidated in Brazil when we improve our understanding of the influence of land use change on stream water quality, as well as on the role that forests play in determining stream ecosystem functioning. Moreover, the interaction between forests and hydrologically sensitive areas (HSA) must be better understood. Therefore, we propose to investigate the role of forests over hydrologically sensitive areas in controlling the water quality of tropical streams, draining catchments with intensive agriculture. Three studies will be conducted simultaneously in the Corumbatai Watershed in the State of Sao Paulo. First, we intend to analyze the influence of forest fragments of different sizes and stages of succession on the water quality of streams draining areas under pasture and sugarcane agriculture. We will also investigate the direct influence of riparian forests on ecological functions of streams, such as ecosystem metabolism, in order to understand how agricultural practices in sugarcane fields may or may not be mitigated by the presence of riparian forest. Finally, we intend to understand the importance of having forests over the HSA in order these HSA perform the expected ecosystem functions that determine water quality. We expect that the results of this project will show that denser and older forest fragments that overlap almost entirely with HSA can be powerful tools for managing water quality in aquatic systems of regions with intensive agricultural activities, especially in areas of sugar cane plantations. This type of information is highly relevant to ensure the sustainable use of water resources in Brazil, given the ongoing scenario of expansion of intensive agriculture and production of renewable energy, and may corroborate the hypothesis of actively induced riparian areas recovery as HSA. (AU)