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EFFECTS OF LAND USE CHANGES ON THE FUNCTIONING OF SOILS AND WATERSHEDS OF CENTRAL BRAZIL SAVANNAS: PHASE 2, IMPACTS ON NUTRIENT AND CARBON CYCLES AND TRACE GAS EXCHANGE
Impact/Purpose:
This project is a part of Phase 2 the Large-Scale Biosphere-Atmosphere Experiment in Amazonia (LBA), a multi-investigator study that is planned for 2003 - 2005 in Brazil. LBA, which is an international initiative lead by Brazil in cooperation with the U.S. and European countries, is examining how changes in land use and climate affect the biological, chemical, and physical functions of Amazonia and the Brazilian cerrado, including sustainability of development in the region. Such interactions are believed to have an important influence on global climate change. LBA is examining carbon storage, nutrient dynamics, trace gas fluxes, and the prospect for sustainable land use in Amazonia and the Brazilian cerrado. This agreement includes research to be accomplished by the U.S. EPA/ORD, in collaboration with scientists from the University of Brasilia, as a part of LBA. The project was selected by the LBA competitive peer-review process. The research will be conducted at sites located in the Cerrado near Brasilia, Brazil.
Description:
This research is funded through an interagency agreement with NASA. The research in this project is contributing to assessments of the effects of land use in central Brazil on: 1) the stocks and cycling rates of carbon and nutrient cycling; 2) the function and structure of soil and sedimentary microbial communities; 3) soil-atmosphere fluxes of trace carbon and nitrogen gases (CO2, CO, N2O, and NO); and 4) the composition and quantity of nutrients and organic matter entering small streams via gallery forests. Our native study sites will continue to include native cerrado stricto sensu and campo sujo and will expand to include gallery forests. Added converted Cerrado sites will include croplands and recently converted pastures. We will quantify rates of carbon and nutrient cycling and characterize soil organic matter (SOM) and litter quality at both native and converted sites. We plan to study the influence of fertilization and management practices (tillage, no-tillage and cover crops) on the carbon balance in pastures and cropland. These experiments will include measurements of different SOM fractions, microbial biomass and characterization, litter quality, N cycling, and P fractions. We will measure soil-atmosphere fluxes of trace carbon and nitrogen gases (CO2, CO, N2O, NO) from soils under different land uses. To provide data and relationships needed for regional trace gas models we will measure relevant ancillary data along with the trace gas fluxes, including changes in soil temperature, moisture, and incident solar radiation. To assess land use changes on gallery forests and aquatic systems, streams that drain watersheds dominated by natural vegetation, agriculture, and urban lands, will be selected. Chemical analyses of water collected from surface runoff collectors, soil lysimeters, and groundwater piezometer located within the gallery forest, and directly from the stream, will be used to evaluate nutrient cycling within the forest buffers and the stream. The goal will be to develop predictive models that relate the landscape metrics, determined by analysis of spatial land cover databases, to the various chemical and physical parameters.