Land use change and stand age regulate soil respiration by influencing soil substrate supply and microbial community

Abstract

Land use change and forest stand age are important factors in regulating soil respiration (Rs) in terrestrial ecosystems. However, the responses of Rs to these factors and the underlying mechanisms are not well understood, especially in fields converted from rice paddies (RPs) to upland cultivation. In this study, the characteristics of Rs and soil microbial community responses to land use changes from RPs to citrus orchards (ORs) with different stand ages (3, 10, 22, and 30 years) were investigated using static chamber/gas chromatography and phospholipid fatty acid (PLFA) analyses. The results showed that Rs rates significantly decreased by 28.2% during the first 3 years after a land use change from RPs to ORs and then substantially increased with increasing stand age. Converting RPs to ORs substantially decreased the total, bacterial and AMF PLFAs but significantly increased the fungal PLFAs and the F/B PLFA ratio. The microbial community composition was significantly influenced by the land use change but slightly changed during the growth of ORs. Soil moisture and the C/N ratio were the main factors related to the variances in the soil microbial community composition. Moreover, soil temperature coupled with soil C/N ratio and the abundance of fungi could explain 96% of the spatial variability in the Rs. The results indicated that linking the soil microbial community and substrate supply could improve our understanding of the responses of Rs to land use changes and plant succession.