Microbial Community Response to Burning, Fertilization and Seasonal Variations in Prairie Grassland Soil.

Microorganisms drive soil nutrient cycles and are sensitive to environmental changes. Grasslands have been historically managed by fires, but the effect on below ground processes mediated by soil microbes are yet to be fully understood. Prescribed burning and nutrients (N, P) impact the size and composition of soil microbial community, hence nutrient cycling. Microbial PLFA can be used to assess the response of the microbial community to soil management and seasonal variations. Study location was Konza Prairie Biological Station. The experimental design was a split plot with main plots (annually burned vs. unburned) arranged in a randomized complete block. Subplots were N (10g N/m2 /y) and P (1g P/m2 /y) treatments with seasonal sampling (June 2008, October 2008 and February 2009). Soils were sampled at two depths (0-5 and 5-15 cm). Microbial categories identified were Gram –ve and Gram +ve bacteria, fungi, AMF, and actinomycetes. Individual microbial groups varied with significant seasonal response. Total microbial biomass was similar for October and February but higher than June. Burning reduced Gm –ve bacteria in June but not in October nor February, while Gm +ve bacteria was higher at 0-5 cm depth in June and February but not in October. Although actinomycetes were higher at 0-5 cm depth; it was not significant in October and February. AMF and fungal biomass responded to P and N although this response varied with season. Soil microbial groups responded to burning and nutrient (N and P) application with seasonal influence in prairie grassland soil. This response is critical to understanding biogeochemical cycles and microbial ecology.