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ND-31 Abstract

Quantifying and Scaling Land-Water Connections and River-Channel Biogeochemistry in Amazon River Networks

Linda Ann Deegan — Marine Biological Laboratory (US-PI)
Reynaldo Luiz Victoria — CENA - Centro de Energia Nuclear na Agricultura (USP) (SA-PI)

Quantifying and Scaling Land-Water Connections and River-Channel Biogeochemistry in Amazon River Networks



Deforestation in the Brazilian Amazon has important effects on the functioning of streams and rivers. As the extent of deforestation increases, the transport of material downstream in large river basins can also be affected. We will use remote sensing, combined with our field data collected in the Large Scale Biosphere-Atmosphere Experiment (LBA) in Amazonia on how deforestation has influenced the structure and chemistry of streams in forested and deforested areas, to estimate the extent of drainage basin networks that have been influenced by forest clearing over time. We will do this for the Ji-Parana River watershed and its 14 sub-basins, a total area of 75,260 km2 in Rondonia, where deforestation has increased rapidly since the 1980s.

We will also apply an ecosystem model, the Terrestrial Ecosystem Model, to estimate the movement of carbon and nutrients from forest and pasture into small streams. These estimates will be used as input to a model that calculates carbon and nutrient retention and transport in river channels, to estimate the movement of carbon and nutrients downstream in the Ji-Parana River and its sub-basins. We will calibrate these models with our data, collected in our small watersheds studies in Rondonia as part of LBA, on the fluxes of carbon and nutrients move from land to small streams in forest and pasture. We will validate our estimates of material fluxes at the large river basin scale by comparing our model results with LBA data on water chemistry and material flux measured in the Ji-Parana River basins.

This project will advance our understanding of how changes in land cover influence the ecological and biogeochemical functioning of Amazon rivers and how these changes are altering the fluxes of carbon and nutrient fluxes at the regional scale in the Amazon basin. It will improve understanding of carbon and nutrient dynamics of the Amazon and specifically the question of the transport of carbon and nutrients from terrestrial ecosystems to stream and rivers. Our estimates of the extent of stream channel altered by deforestation, linked with our field measurements that have documented major changes to stream function caused by deforestation, will contribute to understanding the magnitude of the effects of deforestation on the aquatic life, fisheries and biological diversity of the Amazon and the sustainability of the goods and services that streams and rivers provide to Amazon residents.

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