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IMPACTS OF LAND USE CHANGE AND FIRE ON NUTRIENT AND CARBON CYCLES AND TRACE GAS EXCHANGE IN SOILS OF THE CERRADO IN CENTRAL BRAZIL
Citation:
Pinto, A., R. Varella, G. Nardoto, L. Viana, L. Andrade, R. Chiba, R. Santos, M. Bustamante, R A. Burke Jr., M Molina, R G. Zepp, K. Kisselle, AND S. P. Opsahl. IMPACTS OF LAND USE CHANGE AND FIRE ON NUTRIENT AND CARBON CYCLES AND TRACE GAS EXCHANGE IN SOILS OF THE CERRADO IN CENTRAL BRAZIL. Presented at First Large Scale Biosphere-Atmospheric Experiment in Amazonia (LBA) Scientific Conference, Belem, Brazil, June 26-30, 2000.
Impact/Purpose:
The overall objective of this task is to develop quantitative relationships for assessing the vulnerability of aquatic resources to global change. The task will contribute experimental and modeling tools for assessments of the interactions of global climate and UV changes with coral reefs and selected watersheds and estuaries in the U.S. These activities are contributing primarily to two APGs in the ecosystems component of the Global Change Research Multiyear Plan: the 2006 APG (APG 3) on building the capacity to assess global change impacts on coastal aquatic ecosystems, including coral reefs and estuaries and the 2004 APG (APG 2) on building capacity to assess and respond to global change impacts on selected watersheds. One major task objective is to assess interactions of global warming and UV exposure that are contributing to the observed coral bleaching and disease. Our lab is working with scientists at the NHEERL Gulf Ecology Lab to characterize UV exposure and effects at several coral reef sites. Other research in this task is examining the interactions between UV-induced breakdown of refractory organic matter in estuaries and coastal areas that enhance UV penetration into the water and concurrently form biologically-labile nitrogen-, phosphorus- and carbon-containing substances that stimulate productivity and microbial activity. This task also involves research in central Brazil that is part of the Large Scale Biosphere Atmosphere Experiment (LBA). The objectives of this project are to assess the impacts of land use and climatic changes on soil nutrient cycles and microbiota, trace gas exchange and water quality in the Brazilian cerrado. This work involves a close collaboration between EPA and a group of scientists from the Department of Ecology, University of Brasilia, Brazil. Other objectives of this task are to assess the interactions of land use and climate changes with the ecological functioning of streams in watersheds of the Piedmont region of the southestern U.S.
Description:
The Brazilian cerrado is experiencing rapid land use changes that are often accompanied by fire. Here we report initial studies of the effects of fire and land use change on the composition and persistence of litter and soil organic carbon and nitrogen and related changes in the soil-atmosphere fluxes of selected trace gases (C02, CO, N20, NO). The studies are focusing on two classes of cerrado, cerrado stricto senso (20-50% canopy cover) and campo sujo (open, grass-dominated), located in the research and ecological reserve operated by IGBE, located 35 km south of Brasilia and in a 20-year-old cattle pasture at an EMBRAPA Cerrados field research site located 25 km northwest of Brasilia. Variation in N-mineralization rates were determined in both dry and wet season. Pronounced increases were observed at the beginning of the wet season. N-mineralization rates were lowest in the camp sujo and pasture sites. Significant immobilization of N immediately following fire at both classes of cerrado at IBGE. These variations in mineralization indicate that significant changes in soil-atmosphere trace gas fluxes, especially of nitrogen oxides, may occur at the sites. To determine the size and diversity of the soil microbial community at the sites, we are measuring the amount and composition of biomarker compounds in the litter and soil organic matter, particularly phosopholipid ester-linked fatty acids (PLFA) and ergosterol.