Can land use changes alter carbon, nitrogen and major ion transport in subtropical brazilian streams?

Abstract

Several studies in tropical watersheds have evaluated the impact of urbanization and agricultural practices on water quality. In Brazil, savannas (known regionally as Cerrados) represent 23% of the country's surface, representing an important share to the national primary growth product, especially due to intense agriculture. The purpose of this study is to present a comprehensive evaluation, on a yearly basis, of carbon, nitrogen and major ion fluxes in streams crossing areas under different land use (natural vegetation, sugar cane and eucalyptus) in a savanna region of SE Brazil. Eucalyptus and sugar cane alter the transport of the investigated elements in small watersheds. The highest concentration of all parameters (abiotic parameters, ions, dissolved organic carbon -DOC -and dissolved inorganic carbon -DIC) were found in Sugar Cane Watersheds (SCW). The observed concentrations of major cations in Eucalyptus Watersheds (EW) (Mg, Ca, K, Na), as well as DIN and DOC, were found frequently to be intermediate values between those of Savanna Watersheds (SW) and SCW, suggesting a moderate impact of eucalyptus plantations on the streamwater. Same trends were found in relation to ion and nutrient fluxes, where the higher values corresponded to SCW. It is suggested that sugar cane plantations might be playing an important role in altering the chemistry of water bodies.

Influence of land use changes on water chemistry in streams in the State of São Paulo, southeast Brazil

“…in pastures watersheds compared to forest watersheds. Same trend were found by Silva et al (2007) that found higher concentrations of inorganic nitrogen and carbon in sugar cane crops compared to silviculture and savanna.…”

“…The values found in stream 6 (located at Santa Rita do Passa Quatro) were lower if compared to other streams in state parks since this area is located under savanna region with presents highly weathered soils and poor nutrient concentrations (Markewitz et al 2006) that reflected in all parameters of water chemistry evaluated in this work (see above). Silva et al (2007) evaluating undisturbed stream in this area reported that land use changes such as sugar cane and eucalyptus contribute to a decrease of physicochemical conditions in savanna watersheds.…”

Métodos e técnicas de pesquisa em bacias hidrográficas

“…A cultura de cana-de-açúcar é uma cultura anual que necessita de uma alta demanda de nitrogênio (KRUSCHE et al, 2003), e a aplicação de fertilizantes nitrogenados pode aumentar a mineralização e as taxas de nitrifi cação, aumentando a concentração de nitrogênio nos corpos d'água (SILVA et al, 2007), especialmente no período seco. De fato, as microbacias agrícolas 230 da bacia do rio Corumbataí são compostas por uma mistura de cultivo de cana-de-açúcar e pastagem; assim, as altas concentrações de nitrato observadas devem ocorrer devido ao uso de fertilizantes que são carreados para os corpos d'água (HUNTER; WALTON, 2008).…”

Perspectives on biodiversity science in Brazil

“…In a recent paper in Conservation Biology, although acknowledging the relevance of production of knowledge on biodiversity, he argued that biological studies are often of reduced effect on restraining harmful natural-resource development and that effective solutions are generally related to economic changes and adoption of alternative land uses (Valladares-Pádua, 2006). Interestingly, this Special Issue brings two papers that discuss ecological consequences of land use changes (Silva et al, 2007a;2007c). …”

“…Martins et al (2006) argue that the comparatively good performance of the country in aspects such as global responsibility, quality of water of soil (see Silva et al, 2007c, for a discussion about the relationship between soil loss and habitat quality), and available biodiversity, compensates for low income and educational problems and bring the country into a better ranking at the Environmental HDI.…”