Changes in Soil Microbial and Denitrifying Bacterial Community Structure in Adjacent Native Forest and Agricultural Soils.

The transition of microbial communities from forests to farm lands in coastal regions of Georgia was studied.  Three vegetation types including forest, agricultural, and transitional lands were selected at three different locations (Acacia Farm, Strickland Farm, and Honeydew Farm) of operational crop-producing farms in the coastal plain of Georgia. Five soil samples from each soil at each location were collected. Length Heterogeneity PCR (LH-PCR) and fragment analysis based on bacterial 16S rRNA genes, fungal ITS-1, and animal 18S rRNA genes were performed for microbial diversity and community analyses. Denitrifier bacterial genes were detected using Denaturing Gradient Gel Electrophoresis (DGGE).  Fungal communities showed distinct grouping by different vegetation types. Forest samples displayed lower degrees of fungal community similarity than agricultural samples. This may be due to a higher number of unique species or less number of common species in forest soils compared to agricultural soils. Distinct grouping of soil bacterial and nitrate reducing bacterial communities was detected under forest and agricultural management practices. Transitional soils shared high similarity with several forest samples. Agricultural soils significantly decreased the diversity of denitrifying bacteria. Grouping of soil animal communities by vegetation type was less distinct than grouping of bacteria or fungi.