Lee, Z. and T.M. Schmidt
Presented at the All Scientist and GLBRC Sustainability Meeting (2009-05-05 to 2009-05-07 )
Heterotrophic bacteria in soil converts plant residues and other soil organic matter into microbial biomass and carbon dioxide. The efficiency of transforming the carbon substrates into microbial biomass is known as bacterial growth efficiency (BGE). BGE is measured as the proportion of carbon incorporated into microbial biomass out of the total amount of carbon assimilated. BGE can be influenced by intrinsic factors such as the use of ATP-dependent transporters, and environmental factors such as the availability of carbon substrates and nutrients. In aquatic system, BGE is known to decrease along with the productivity of the environment, where oligotrophic lakes have bacterial communities with low carbon utilization efficiency, leading to the increased transformation of organic matter to carbon dioxide. This study is to determine if a similar pattern is observed for the bacterial community from soil with different management practice and to specifically determine if agricultural activities affect BGE. BGE is measured as the amount of tritiated leucine incorporated into trichloroacetic acid-precipitable biomass per µmol oxygen consumed. Soil samples were collected from a conventional agricultural plot (T1) and an early successional plot (T8). The agricultural plot has the highest rates of carbon dioxide emission, while T8 has the greatest carbon mitigation potential among all the treatments at the KBS LTER site. Mitigation potential can be affected by physical processes such as aggregate formation that decrease access to labile carbon substrate hence decreasing the overall decomposition rate. It can also be influenced by the efficiency with which microbes incorporate labile carbon into biomass. This study will assess the relative contributions of microbial communities to differences in mitigation potential and seek to identify factors influencing BGE in these treatments.
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