Soil Microbial Population Dynamics along a Chronosequence of Moist Evergreen Broad-leaved Forest Succession in Southwestern China

Little is known about whether soil microbial population dynamics are correlated with forest succession.To test the hypotheses that(1) soil microbial composition changes over successional stages,and(2) soil microbial diversity is positively correlated with plant species diversity,we determined the soil microbial populations,community composition,and microflora diversity in evergreen broad-leaved forests along a chronosequence of vegetation succession from 5 to 300 years in southwestern China.The soil microbial community was mainly composed of bacteria(87.1-98.7% of the total microorganisms and 10 genera identified),fungi(0.3-4.0%,7 genera),and actinomycetes(2.1-9.1%,8 species and 1 genus).There were significant differences in soil microbial populations among different successional stages and within the four seasons.The seasonal variations of the soil microbial community may be associated with the seasonal changes in environmental conditions.The changes in soil microbial diversity(Shannon-Wiener index) with successional time followed one-humped,convex curves peaked at-100 years since restoration,which is identical with the trends of the aboveground plant diversity.Higher plant diversity resulting in enhanced nutrient flow and root exudation may contribute to positive relationships between the soil microbial diversity and plant diversity.Hence,decreases in soil microbial diversity in the late-successional stages appear to be related to the net loss in species richness that occurs after 100 years since restoration.Our findings confirm the intermediate disturbance hypothesis that suggests diversity peaks at midsuccessional stages.