Changes in the soil microbial community with a pine plantation restoration in a dry valley of the upper reaches of the Minjiang River, southwest China.

The objective of this study was to investigate the changes in soil microbial biomass C, microbial metabolic activity, functional diversity, and metabolic diversity pattern during the restoration process of a pine (Pinus tabulaeformis) plantation. In this study, a chronosequence approach was adopted. Three sites of pine plantations along a restoration chronosequence (12 years old (PF12), 25 years old (PF25), 35 years old (PF35)), and their paired reference sites of natural shrub community (Shrub1, Shrub2, and Shrub3) were selected. Soil microbial biomass C increased and microbial quotient declined with pine plantation age. Microbial metabolic activity, as measured by average well color development (using Biolog GN(2) plates), exhibited a decline along the restoration chronosequence with values ranked as PF12 > PF35 > PF25 in topsoil and PF12 > PF25 > PF35 in subsoil. Functional diversity, as estimated by substrate diversity and substrate richness, exhibited a pattern similar to the metabolic activity. Principal component analysis indicated that metabolic diversity followed recognized patterns along the restoration chronosequence with PF12 significantly different from PF25 and PF35. There was an apparent reduction of microbial metabolic activity and functional diversity during pine plantation restoration, which can be explained by a general decline in soil nutrient availability, particularly C availability, and soil pH associated with the establishment of a coniferous species.