Efeitos das mudanças do uso da terra na biogeoquímica dos corpos d'água da bacia do rio Ji-Paraná, Rondônia

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

Este trabalho discute os efeitos das mudanças do uso do solo na biogequímica dos rios da bacia de drenagem do rio Ji-Paraná (Rondônia). Nesta região, a distribuição espacial do desmatamento e das propriedades do solo resultam em sinais diferentes, possibilitando a divisão dos sistemas fluviais em três grupos: rios com águas pobres em íons e baixo impacto; rios com conteúdo iônico intermediário e impacto médio e rios com elevados conteúdo iônico e impacto antropogênico. As características biogeoquímicas dos rios têm relação significativa com a área de pasto, melhor parâmetro para prever a condutividade elétrica (r² = 0,87) e as concentrações de sódio (r² = 0,75), cloreto (r² = 0,69), potássio (r² = 0,63), fosfato (r² = 0.78), nitrogênio inorgânico (r² = 0.52), carbono inorgânico (r² = 0.81) e carbono orgânico (rain ² = 0.51) dissolvidos. Cálcio e magnésio tiveram sua variância explicada pelas características do solo e pastagem. Nossos resultados indicam que as mudanças observadas na micro-escala constituem "sinais biogeoquímicos" gerados pelo processamento do material nas margens dos rios. A medida em que os rios evoluem para ordens superiores, os sinais persistentes nos canais fluviais estão mais associdados às características da bacia de drenagem (solos e uso da terra). Apesar dos efeitos das mudanças observadas no uso do solo não serem ainda detectáveis na macro-escala (bacia amazônica), a disrupção da estrutura e funcionamento dos ecossistemas é detectável nas micro e meso escalas, com alterações significativas na ciclagem de nutrientes nos ecossistemas fluviais.

Translated abstract

In this article we present the results of the effects of land use change on the river biogeochemistry of the Ji-Paraná basin (Rondônia). In this region, the spatial distribution of deforestation and soil properties result in different biogeochemical signals, allowing the division of the fluvial systems into three groups: rivers with low ionic concentration and low impact; rivers with intermediate ionic content and medium impact; and rivers with high ionic content and anthropogenic impact. River biogeochemical characteristics present a significant correlation with pasture area, the best predictor for electric conductivity (r² = 0,87), sodium (r² = 0,75), chloride (r² = 0,69), potassium (r² = 0,63), phosphate (r² = 0,78), and dissolved inorganic nitrogen (r² = 0,52), inorganic carbon (r² = 0,81) and organic carbon (r² = 0,51). For calcium and magnesium, both soil properties and pasture explained most of the observed variability. Our results indicate that the changes observed at the micro-scale constitute "biogeochemical signals" generated by the material processing at the riparian zones. As the rivers evolve to higher orders, the persistent signals in the fluvial channels are very closely related to the drainage basin characteristics (soils and land use), which, in turn, become the determinant of these systems dynamics. While at the macro-scale (the whole basin) the effects of land use changes are not yet detectable in the Amazon, the disruption of the structure and functioning is occuring at the micro and meso scales, with significant alterations of nutrient cycling in fluvial ecosystems

Related collections

Most cited references 45

Record: found
Abstract: found
Article: not found

Outgassing from Amazonian rivers and wetlands as a large tropical source of atmospheric CO2.

Jeffrey Richey, John Melack, Anthony K Aufdenkampe … (2002)

Terrestrial ecosystems in the humid tropics play a potentially important but presently ambiguous role in the global carbon cycle. Whereas global estimates of atmospheric CO2 exchange indicate that the tropics are near equilibrium or are a source with respect to carbon, ground-based estimates indicate that the amount of carbon that is being absorbed by mature rainforests is similar to or greater than that being released by tropical deforestation (about 1.6 Gt C yr-1). Estimates of the magnitude of carbon sequestration are uncertain, however, depending on whether they are derived from measurements of gas fluxes above forests or of biomass accumulation in vegetation and soils. It is also possible that methodological errors may overestimate rates of carbon uptake or that other loss processes have yet to be identified. Here we demonstrate that outgassing (evasion) of CO2 from rivers and wetlands of the central Amazon basin constitutes an important carbon loss process, equal to 1.2 +/- 0.3 Mg C ha-1 yr-1. This carbon probably originates from organic matter transported from upland and flooded forests, which is then respired and outgassed downstream. Extrapolated across the entire basin, this flux-at 0.5 Gt C yr-1-is an order of magnitude greater than fluvial export of organic carbon to the ocean. From these findings, we suggest that the overall carbon budget of rainforests, summed across terrestrial and aquatic environments, appears closer to being in balance than would be inferred from studies of uplands alone.