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ND-03 Abstract

Key Connections in Amazonian Stream Corridors

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

Deforestation in the

Amazon has the potential to alter the biogeochemistry of carbon and major

nutrients over large regions and to alter the movements of these materials among

adjoining ecosystems. Small streams dominate the total length of stream channels

in the landscape. They receive material from adjacent uplands and contribute

material to larger rivers. Because of their position, small streams and their

associated riparian zones thus play a key role in the landscape as links and

regulators of material fluxes between terrestrial ecosystems and larger rivers

of the Amazon Basin.



Our goal is to develop an

understanding of how C and nutrients are transformed as water moves from uplands

through small streams to larger rivers in forested and deforested landscapes of

the Amazon. We will do this by: 1) focusing on carbon and nutrient

transformations in riparian zones and small stream channels--key points in the

landscape where these transformations are potentially of major importance but

very poorly known in tropical landscapes; 2) comparing these transformations in

drainage basins with forest and pasture land use and in streams of different

sizes, and; 3) coupling our process level work with information on land use and

riparian zone structure derived from remote sensing and models of stream channel

processing to predict transfers of organic matter and nutrients to larger rivers

in stream networks. The work will be focused in central Rond˘nia.



In riparian

zones, we will determine the spatial variability of water entering and leaving

the riparian zones of forest and pasture streams of different sizes using

surveys of ground water characteristics. We will use 15N, nutrient

and conservative tracer additions to identify key processes and rates of

transformation in the groundwater of forest and pasture riparian zones.



In stream

channels, we will use 15N tracer additions in forest and pasture

streams to determine key processes and rates of transformation, and production

and consumption of dissolved organic carbon and dissolved inorganic carbon. We

will use the isotopes of 13C in dissolved organic carbon and

dissolved inorganic carbon and different particulate and dissolved constituents

to trace the sources of C to streams. We will extend this work to a regional

basis with surveys of nutrients and organic matter in 2-5th order

streams in forest and pasture land use on different soil types within the

region.



At the regional

scale, satellite images will be used to classify areas to land use type,

riparian zone type and extent and length of stream channels of different stream

orders in forest and pasture. A multi-compartment stream biogeochemistry model

will be used to predict the transformations of C and N and their downstream

transport in streams of different sizes and land uses. We will integrate

watershed land use area and stream channel length in different land use types to

estimate regional impacts of land use change on biogeochemical cycles in small

streams and transport from small streams to larger rivers.



This project will bring

together studies of land and water biogeochemistry and link them together with

an understanding of changes in processes that occur in key points in the

landscape. It will provide new information on how these processes change when

forest is replaced by pasture and it will put this information in a framework to

predict the effects of forest-to-pasture conversion on stream water quality and

C and nutrient transport to larger rivers.

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