Coniferous-Broadleaf Mixture Increases Soil Microbial Biomass and Functions Accompanied by Improved Stand Biomass and Litter Production in Subtropical China

Abstract

Although the advantages of multi-species plantations over single-species plantations have been widely recognized, the mechanisms driving these advantages remain unclear. In this study, we compared stand biomass, litter production and quality, soil properties, soil microbial community, and functions in a Pinus massoniana Lamb. and Castanopsis hystrix Miq. mixed plantation and their corresponding mono-specific plantations after 34 years afforestation in subtropical China. The results have shown that a coniferous-broadleaf mixture created significantly positive effects on stand biomass, litter production, soil microbial biomass, and activities. Firstly, the tree, shrub and herb biomass, and litter production were significantly higher in the coniferous-broadleaf mixed plantation. Secondly, although the concentrations of soil organic carbon (SOC) and total nitrogen (TN) were lower in the mixed stand, the concentrations of soil microbial biomass carbon (MBC), and nitrogen (MBN), along with MBC-to-SOC and MBN-to-TN ratio, were significantly higher in mixed stands with markedly positive admixing effects. We also found higher carbon source utilization ability and β−1, 4−N−acetylglucosaminidase, urease and acid phosphatase activities in mixed stands compared with the mono-species stands. Our results highlight that establishment of coniferous-broadleaf mixed forests may be a good management practice as coniferous-broadleaf mixture could accumulate higher stand biomass and return more litter, resulting in increasing soil microbial biomass and related functions for the long term in subtropical China.