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RELATIONSHIP OF MICROBIAL COMMUNITY STRUCTURE AND CARBON DYNAMICS IN SOILS FROM BRAZILIAN SAVANNAS
Citation:
MOLINA, M., R. G. ZEPP, A. KOZOVITS, J. BRESOLIN, AND M. BUSTAMANTE. RELATIONSHIP OF MICROBIAL COMMUNITY STRUCTURE AND CARBON DYNAMICS IN SOILS FROM BRAZILIAN SAVANNAS . Presented at 11th International Symposium on Microbial Ecology, Vienna, AUSTRIA, August 20 - 25, 2006.
Impact/Purpose:
The objective of the proposed study is to evaluate and apply fast and reproducible DNA-based technology that can detect and track fecal contamination back to its source in complex environmental matrices, including recreational and drinking water resources.
Description:
Fertilization is a widespread management practice in savanna areas of central Brazil (Cerrado) that are undergoing rapid agricultural land use changes. We conducted field and laboratory studies in soils with added fertilizers to determine the effect that fertilization of native areas have on microbial composition and decomposition rates of soil organic matter (SOM) pools. We compared microbial communities from native (savanna and forest) and managed (pasture and N, P, N+P, Ca-fertilized savanna) areas using phospholipid fatty acid analysis (PLFAs) and fungal to bacterial ratios. The structure of the microbial community varied as a function of the fertilization treatment and management practice (p<0.000l). Calcium and the control treatment exhibited the same community structure and had a higher concentration of Gram negative biomarkers, while N, P, and N+P treatments had a higher concentration of Gram positive biomarkers and similar microbial communities. Phosphorus amendments produced the highest fungal:bacterial ratio after 10 days of fertilization. The effect of added fertilizers was further studied in the laboratory using gas-tight jars containing soils amended with N and P. Results from a two-compartment model indicated that although N and P treatments produced very similar decay constants for the labile C, P addition enhanced CO2 evolution from the more refractory SOM. CO was taken up by the soil cores in all cases. CO deposition velocities were enhanced by the addition of fertilizer with particularly large effects observed with soil cores amended by P. This study indicates that the presence of fertilizers significantly affects the amount and type of C that is recycled by the microbial community in Cerrado soils.