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Watershed Scale and the Importance of Riparian Zones in Modifying Solute Inputs from Land to Streams

Christopher Neill, MBL, cneill@mbl.edu (Presenting)
Helmut Elsenbeer, Unviersity of Potsdam, helsenb@rz.uni--potsdam.de
Alex V. Krusche, CENA/USP, alex@cena.usp.br
Joaquin Chaves, MBL, jchaves@mbl.edu

The conversion of large areas of the Amazon Basin from natural vegetation to human uses is intimately linked to the movement of water and materials from land to water. There is growing evidence that near-stream riparian zones contribute different amounts of water to streams and that the hydrological importance of riparian influences varies with watershed scale. Riparian zones can also exhibit strong control over the concentrations of solutes reaching streams. Deforestation has the obvious potential to alter these relationships by increasing the total volume of water arriving from hillslopes in surficial flowpaths. We use hydrological measurements and chemical techniques to examine the flowpaths by which water reaches streams across different soils watershed scales and land uses in watersheds in Rond˘nia and within a lager set of watershed studies within LBA. The influence of flowpaths through riparian zones increases with stream size and extent of riparian development. For some solutes, for example nitrate, the influence of riparian zones on stream concentrations is higher in forest than in pasture because conversion to pasture tends to decrease and homogenize the large variability in solute concentrations among flowpaths that existed in the former forest. Because each landscape element has different areal extent and hydrologic and geomorphic characteristics that can be assessed through field investigations and remote sensing, this approach of quantifying flowpaths provides a new way of linking plot and reach scale process information on hydrology and biogeochemistry to whole catchments in the Amazon. It also indicates that management practices that maintain riparian zones can be effective in moderating the influence of watershed land use change on stream chemistry and physical characteristics.

Science Theme:  ND (Nutrient Dynamics)

Session:  1B: Nutrient Cycling in Terrestrial and Aquatic Systems

Presentation Type:  Oral

Abstract ID: 130

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