SEASONAL EFFECTS IN SOIL MICROBIAL COMMUNITIES ALONG A PRECIPITATION GRADIENT IN THE NORTHEASTERN TIBETAN PLATEAU

Seasonal changes in soil microbial communities along an annual precipitation were investigated by using phospholipid fatty acids (PLFA) analysis from samples collected in summer and winter in 2009 from the northeastern Tibetan Plateau. Total PLFA concentration, which is indicative of microbial biomass, was high in summer and low in winter suggest that seasonal changes have significant effects on soil microbial biomass, mainly affected by precipitation other than temperature. What's more, bacteria, Gram-positive bacteria, Gram-negative bacteria and actinomycetes biomass was significant high in summer than that in winter suggest that precipitation had various effects on soil microbial communities in different seasons. In different soil depths, precipitation had different effects on microbial communities. Precipitation had significantly positively correction with bacteria, Gram-positive bacteria, Gram-negative bacteria and actinomycetes biomass in four soil depths (0-5, 5-10, 10-20, 20-40 cm) in summer. But in winter, precipitation had a long-term effect on soil microbial communities, and it was only strongly positive with the bacteria and fungi-PLFAs in the 0-10 cm soil surface, and not significantly correlation with precipitation in 10-40 cm.