Fire Alters Vegetation and Soil Microbial Community in Alpine Meadow

Grassland fire, as an important ecological factor, is quite influential in determining the structural and functional stability of ecosystem. In this work, the fire-induced changes on the vegetation and soil microbial community were studied in alpine meadow. Microbial community composition was assessed by phospholipid fatty acid (PLFA) analysis, and functional diversity was determined by Biolog EcoPlate method. Our results showed that burning caused a significant increase in plant functional group coverage, biomass of grasses, soil bulk density and the ratio of roots to soils. Fire also caused an increase in soil pH and a decrease in total soil nutrient contents and soil moisture. The average well colour development of soil microorganism, the microbial functional diversity and the number of carbon source utilisation were also significantly affected by fire. Total bacteria PLFA, Gram-positive bacteria (G⁺) PLFA, Gram-negative bacteria (G⁻) PLFA and total PLFA of the burnt sites all increased significantly in burnt soil. The BACT/FUNG, SAT/MONO and G⁺/G⁻ ratio also appeared to be higher in burnt sites. The total PLFA, G⁺ PLFA and G⁻ PLFA are closely related to the plant community quantitative characteristics and soil nutrients. The total PLFA, bacteria and G⁺ PLFA are significantly correlated with the soil total nutrients and available nutrients. These results suggest that the ability of soil microorganisms to use a single-carbon substrate was increased after a fire event. Grassland fire not only has direct impacts on plant community structure and function but also indirectly alters the soil microbial properties because of fire-induced changes in plant community.