Wednesday, November 7, 2007
292-9
Effect of Land Management on Soil Bacterial Community Composition and Diversity in the Southern Peidmont, USA.
Kamlesh Jangid1, Mark A. Williams2, Alan J. Franzluebbers3, Michael B. Jenkins4, Dinku Endale3, David Coleman1, and William B. Whitman1. (1) Microbiology, University of Georgia, Athens, GA 30606, (2) Plant and Soil Sciences, Mississippi State University, Rm 117 Dorman Hall, Stone Bldvd, MSU, MS State, MS 39762, (3) USDA-ARS, 1420 Experiment Station Road, Watkinsville, GA 30677, (4) J. Phil Campbell, Sr., Natural Resource Conservation Center, USDA-ARS, 1420 Experiment Station Rd., Watkinsville, GA 30677-2373
The effects of agricultural land management practices on prokaryotic diversity are not well described. We investigated seven management systems at the J. Phil Campbell, Sr., Natural Resource Conservation Center near Watkinsville, Georgia . Community DNA was extracted from soil, and the prokaryotic community composition and diversity were assessed using 16S rRNA gene clone libraries and phospholipid fatty acid (PLFA) analyses. The resulting 3706 sequences formed 1335 operational taxonomic units (OTUs) with a Chao1 estimated total richness of 3104 OTUs at 97 % sequence similarity. Specific associations between certain OTUs and soil types were noted. The Acidobacteria and the Firmicutes were the two most abundant taxa in all soil libraries. The forest soils contained the highest numbers of Acidobacteria, the poultry-litter treated croplands and pasture soils contained the least. The LIBSHUFF analyses indicated that the bacterial communities from soils under all seven treatments were significantly different. However, those from the forest were clearly distinct from the others. Statistical modeling revealed that the β-, Δ- and γ-Proteobacteria were abundant in ungrazed and cropped soils, whereas the numbers of γ-Proteobacteria decreased in the cropped soils. With the addition of inorganic fertilizer, the Acidobacteria and γ-Proteobacteria increased in abundance. In contrast the β- and Δ-Proteobacteria were significantly decreased. Similarly, the relative abundance of the Gemmatimonadetes and the Δ- and γ-Proteobacteria, was higher in the summer than in the winter. Analyses of the mol % PLFA indicated that the fungi were relatively more abundant in the forest. Bacteria dominated the grazed and cropped soils. Seasonal effects on mol % PLFA were also observed. The microbial biomass was 1.3-2 folds in winter than in the summer. These results suggest that agricultural land management practices such as inorganic fertilizer, poultry-litter amendments, grazing or season affect the microbial community structure.