Nutrient and sediment fluxes in microbasins with different conservation states in the northeastern Brazil
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Nutrient and sediment fluxes in microbasins with different conservation states in the northeastern Brazil Felipe de Souza Pimenta & Maria Eugênia Bruck de Moraes & Daniela Mariano Lopes da Silva & Roberto Ferreira Machado Michel
Received: 1 October 2019 / Accepted: 22 October 2020 # Springer Nature Switzerland AG 2020
Abstract The implications of land use change in small watersheds through the conversion of forests to agropastoral areas have altered the natural nutrient cycle, intensifying exports under freshwater ecosystems. This study aimed to investigate the land use effects on nutrient and sediment exports in two small watersheds in northeastern Brazil to understand if anthropogenic disturbance alters the structure end functioning of these systems. Thus, land use mapping and hydrological treatment of a digital elevation model were made to characterize the basins. Water samples were collected monthly from Aug. 2016 to Jan. 2017 to evaluate suspended − sediments and dissolved nutrient fluxes (NHþ 4 , NO3 , NO−2 , PO3− 4 , and dissolved organic nitrogen and phosphorus). The results indicated that land use change had a greater influence on exports from the most disturbed basin, where the nutrient and sediment increments were F. de Souza Pimenta (*) : M. E. B. de Moraes : R. F. M. Michel Departamento de Ciências Agrárias e Ambientais, Universidade Estadual de Santa Cruz (UESC), Ilhéus, BA 45662-900, Brazil e-mail: [email protected]
M. E. B. de Moraes e-mail: [email protected] R. F. M. Michel e-mail: [email protected] D. M. L. da Silva Departamento de Ciências Biológicas, Universidade Estadual de Santa Cruz (UESC), Ilhéus, BA 45662-900, Brazil e-mail: [email protected]
respectively an average 6.61 and 5.81 times higher than the most preserved basin. Thus, the conservation status of the forest cover has influenced the assimilation capacity of diffuse loads, highlighting the differences between the microbasins of this study. Keywords Nutrient export . Forest coverage . Fluvial hydrochemistry . Erosion . Biogeochemistry
Introduction Nutrient concentration and flow measurements in rivers have been widely used to assess forest ecosystem responses to a wide range of environmental stress such as atmospheric deposition of acidifying substances, climate change, forest management practices, and land use conversion (Meybeck 1982; Chaves et al. 2009; Creed and Beall 2009; Germer et al. 2009; Martinelli et al. 2010; Parron et al. 2011; Silva et al. 2012; Chen et al. 2015; Salemi et al. 2015; Santos et al. 2015; Silva et al. 2015). The implications of land use change due to the conversion of forests into agricultural areas have altered the natural nutrient cycle, intensifying exports under freshwater ecosystems. Studies conducted in the tropical and subtropical zone indicated that landscape changes such as the conversion of forests to more intensive land uses have altered the biogeochemistry of nutrients, increasing concentrations and promoting greater variability of these materials in the hydrological pathways
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