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Abstract

Hoilett, N.O., N.V. Nkongolo, R. J. Kremer, F. Eivazi, S.J. Adisa, R. M. Paro, and K. Schmidt. 2008. Understanding the relationships between microbial biomass, enzymes and greenhouse gas efflux in a secondary forest in Missouri. JEMREST 5:190-199.

Carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) concentrations are increasing at annual rates of 0.5%, 0.75% and 0.75% respectively. Documented research has established links between soil physical and chemical properties and efflux of greenhouse gasses; however a need exists for closer examination of the relationship among soil microbial properties, management practices, and greenhouse gas efflux. This study investigated the relationship between the spatial distribution of greenhouse gases, soil microorganisms and microbial activity within a secondary forest in central Missouri. Laboratory assessments of field samples included determination of gas flux rate, microbial biomass by total organic carbon (TOC) and chloroform fumigation extraction; and enzyme activity by beta-glucosidase assay. Results showed a slight but not significant decrease in CO2 efflux, and significantly higher efflux of N2O and CH4 in 2007 versus 2006. The higher efflux in N2O and CH4 may be related to similar changes in some soil biological and thermal properties from 2006 to 2007. For example ß-glucosidase activity significantly increased from 228.5 µg PNP g-1 soil h-1 in June 2006 to 421.2 µg PNP g-1 soil h-1 in June 2007. Soil microbial biomass carbon (MBC) was correlated with soil thermal conductivity (K) (r = 0.4785; p < 0.05), and K was also correlated with CO2 (r = -0.4577; p < 0.05). These correlations would suggest an indirect influence of soil biological indices on greenhouse gas efflux.