The Effects of Forest Management Practices on the Community Structure of Chemolithotrophic Bacteria.

The effects of forest management practices on soil microbial diversity are currently being studied in the Bankhead National Forest (BNF), which is located in Franklin and Winston Counties, Alabama. Prescribed fires and logging treatments have significantly altered bacterial communities that are central to soil biogeochemical nutrient cycling processes and essential for long-term soil sustainability. Forest management practices can affect the natural carbon (C) cycle in forest ecosystems which may in turn, impact C sequestration. In addition to destroying C stored in organic plant material on the forest surface, forest fires and thinning may affect the soil physical and chemical characteristics which influence soil C mineralization and CO₂ emissions processes. It is, therefore, important to study how forest management practices in BNF affect soil C mineralization, CO₂ emission and C sequestration and their potential impact on global climate change. Because C is central to global climate change, we focused on chemolithotrophic bacteria, which obtain their energy from the oxidation of chemical compounds and fixed CO₂ for cell biosynthesis. The aim of this research was to quantify the genetic potential for ribulose-1,5-bisphophate carboxylase/oxygenase (RubisCO) large subunit coding genes in soils from the BNF that have experienced thinning and prescribed burning.  We hypothesized that burning and thinning will produce measureable changes in the community structure of chemolithotrophic bacteria. Soils were sampled from the upper 0-10 cm soil layers and analyzed for microbial activity by genomic DNA analysis, and chemistry including pH, and microbial biomass carbon. Results show that the controls have very minimal DNA. Soils from thinned plots have more microbial activity than the controls, but with no significant change in soil pH. Soils that had no thinning and was burned showed the highest amount of microbial activity. Also, our results indicate a direct correlation between pH and prescribed burning.