DISSOLVED ORGANIC CARBON CONCENTRATIONS AND BALANCES IN TWO WATERSHEDS OF RONDÔNIA: COMPARASION BETWEEN FOREST AND PASTURE / "Concentrações e balanços de carbono orgânico dissolvido em duas bacias do Estado de Rondônia: uma comparação entre floresta e pastagem"

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Dissolved Organic Carbon (DOC) is one of the main fractions of organic carbon exported in rivers and other flow paths in watersheds. In the Amazon, studies of DOC in waters focus mainly on the large basins of the central region, with few analyses of changes in its dynamics after the replacement of forests by pastures, one of the most important land use changes in the region. This objective of this study was to obtain more information about these processes, by comparing dynamics in several flowpaths, exports and budgets of DOC during rain events in two first-order watersheds, one with forest and another with pasture. The study was conducted near city of Cacaulândia in the State of Rondônia. Samples were collected in the transition from dry to wet (August to November of 2004) and in the wet seasons (January to April of 2005). The results demonstrate that during the transition from dry to wet seasons, statistically significant differences in DOC concentrations between forest and pasture occur only in the inputs from precipitation in pasture and throughfall in forest and in the outputs in streams and groundwater. During the wet season the remaining flowpaths analyzed, soil solution at 20 and 100cm depth and overland flow, also showed statistically significant differences in DOC concentrations between forest and pasture. In terms of the periods of the year, in both watersheds DOC concentrations were higher during the transition from dry to wet seasons. The only exception to this pattern was observed in forest groundwater, with higher concentrations during the wet season. In the pasture, increases in discharge resulted in higher DOC export than in forest. As a consequence of this, DOC budgets, both in individual events and annually, showed a larger retention in the latest. Although in this study it was not possible, among others, to quantify the fluxes of DOC in groundwater, the results demonstrate that the conversion of forest into pasture causes a significant increase of DOC export in streams, both in individual rain events and on an annual basis.

ASSUNTO(S)

ciclo do carbono precipitação atmosférica vias hidrológicas deforestation balanço hídrico biogeochemistry desmatamento flowpaths precipitation water balance biogeoquímica carbon cycle

ACESSO AO ARTIGO

Documentos Relacionados