Biogeochemical dynamics in meso-scale rivers of the Amazon Basin and their response to anthropogenic change

Abstract

Very little is known about the biogeochemistry of micro and meso scale rivers in the amazon region. Even less is known about the possible changes in the biogeochemical cycles resulting from the conversion of pastures to forests, which is the most common land use change in the region. Therefore, the main objective of this proposal is to study and understand how the conversion of forests into pastures change the distribution of carbon and nutrients (nitrogen and phosphorous), the primary production and its limiting factors, and the biodiversity in micro and micro scales of tropical rivers in the Amazon. The major questions to be answered are: question 1 - how are the quantity and composition of the organic matter and nutrients that are delivered to and processed within a river changed when the watershed land cover is changed from forest to pasture ? question 2 - does the primary production and its limiting factors change with the changes in land cover, and what are the effects of such changes in the dynamics of the organic matter? question 3 - what are the changes in the benthonic macroinvertebrate fauna in small streams when land use changes from forest to pasture? question 4 - are there detectable and persistent changes in the storage and flux of organic matter, nutrients and associated elements when evolving from micro to meso scale basins, and how is it related to changes in land use? To answer these questions we propose to compare pristine and deforested watersheds, at two scales: rnicro scale (~10km2) at the Fazenda Nova Vida, and meso scale using the Ji-Paraná river (~104km2). Emphasis will be given to the spatial and temporal variations of carbon, nitrogen and phosphorous. Changes in primary production related to the conversion of forest into pastures and also its abiotic (light) and nutritional (nitrogen and phosphorous) limiting factors will be studied. As for the biodiversity, changes in the population of macroinvertebrates along land use change gradients will be addressed. Finally, patterns of biogeochemical signatures will be followed along the micro and meso scales to access their spatial and temporal variations. Considering that water is one of the major driving forces of the biogeochemical cycles in drainage basins, parallel studies of key hydrological processes within the watersheds will be also addressed. The following products are expected as results of this project: a) a georeferenced data base on the structural attributes of the studied watersheds; b) increased knowledge ... (AU)