Seasonal Emissions of N 2 O, NO, CO and CO 2 in Brazilian Savannas Subjected to Prescribed Fires. Alexandre Pinto, Mercedes Bustamante, Laura Viana, Universidade de Brasília, BRAZIL. Richard Zepp, Roger Burke, Keith Kisselle, Marirosa Molina, U.S. Environmental Protection Agency.
Seasonal Emissions of N2O, NO, CO and CO2 in Brazilian Savannas Subjected to Prescribed Fires
Alexandre Pinto, Mercedes Bustamante, Laura Viana, Universidade de Brasília, BRAZIL
Richard Zepp, Roger Burke, Keith Kisselle, Marirosa Molina, U.S. Environmental Protection Agency
Rainfall distribution (1980-1999)
LBA - Large Scale Biosphere-Atmosphere Experiment in Amazonia
NASA - National Aeronautics and Space Administration
N-inorganic availability, net mineralization and net nitrification
(mg kg-1 30 days-1) rates in cerrado ss and campo sujo and soils
Seasonal CO flux
Savanna ecosystems are controlled by the interactions between water and nutrient availability. In recent times the use of burning has become much more intensive and extensive areas of Brazilian Savanna (Cerrado) have been converted to pastures and grasslands by frequent burning or clearing. Nitrification and denitrification are key processes for the production of nitrogen oxides. Biological production of CO2 in soils is derived from the decomposition of soil organic matter and from root respiration. The net CO flux results from a competition between thermal and photochemical oxidation of standing dead grasses, litter, and soil organic matter (SOM) to produce CO, and biological oxidation of CO by soil microorganisms to consume this gas. These trace gases have an important role on atmosphere chemistry and/or could contribute to greenhouse effect. Our objective was evaluate the effects of burning and seasonality on soil emissions of NO, N2O, CO and CO2 under different vegetation types of Cerrado.
MATERIAL AND METHODS
The studies are focusing on two classes of Cerrado, cerrado stricto sensu and campo sujo (see poster left), in the research and ecological reserve operated by IGBE, located 35 km south of Brasilia, D.F (15 56’S, 47 51’W). We are measuring trace gases soil emissions (N2O, NO, CO2 and CO) on plots burned and unburned. The burned areas have been subjected to prescribed fires every two years since 1992 at the end of the dry season (late September). The unburned areas have been protected from fire since 1974. Soil respiration and NO flux have been measured by dynamic chamber method, awhile N2O and CO by static chamber technique. Four rings were installed on soil of each plot at 5 cm deep. The measurements were made monthly since February 2000. To assess the effect of soil moisture on CO2 and NO fluxes, water was added on the 6 different rings installed on campo sujo unburned at middle of dry season (July). It was simulated 2 cm and 18 cm of accumulated rain. The effect of fire was studied measuring trace gases flux on plots with different periods of prescribed burning (middle-dry season (August), end-dry season (September). The precipitation data was acquired from meteorological station located in the ecological reserve.
Water addition experiment
Seasonal soil respiration
Seasonal NO fluxes