Characteristics of soil microbial biomass and community composition in three types of plantations in southern subtropical area of China

By using fumigation-extraction method and phospholipid fatty acids(PLFAs) analysis,this paper studied the characteristics of soil microbial biomass and community composition in the Erythrophleum fordii,Castanopsis hystrix,and Pinus massoniana plantations in south subtropical China.The soil microbial biomass,total PLFAs,bacterial PLFAs,and fungal PLFAs in the plantations were significantly affected by the plantation type and season,and the soil microbial biomass,total PLFAs,and individual PLFA signatures were higher in dry season than in rainy season.The C.hystrix plantation had the highest soil microbial biomass carbon and total PLFAs,while the E.fordii plantation had the highest soil microbial biomass nitrogen.There was a significant positive correlation between the soil pH and arbuscular mycorrhizal fungal(AMF) PLFA(16:1ω5c).The soil total PLFAs,gram-positive bacterial PLFAs,saprophytic fungal PLFA(18:2ω6,9c),and the ratio of gram-positive to gram-negative bacterial PLFAs were significantly positively correlated with soil organic carbon,total nitrogen,and total phosphorus,suggesting that the soil organic carbon,total nitrogen,and total phosphorus contents were the most important nutrient factors affecting the numbers and types of the soil microorganisms.In addition,the ectomycorrhizae fungal PLFA(18:1ω9c) and AMF PLFA were significantly correlated with the soil C/N ratio.