Trends in soil microbial communities in afforestation ecosystem modulated by aggradation phase

Abstract

Afforestation may alter soil microbial community structure and function, but its effects on trends of microbial abundance and activities has not been analyzed globally. The objectives of this study was to investigate how soil microbial community abundance and activities change as stand age increases and illustrate the factors affecting these changes after afforestation. We conducted a comprehensive meta-analysis from 45 articles to evaluate global patterns and controls of soil microbial change following afforestation. Our results showed that during aggradation, all microbial biomass carbon (Cmic), microbial biomass nitrogen (Nmic), bacterial, and fungal abundance significantly increased during the early stage (0–10 years) but decreased for late-stage sites (>30 years). Microbial activities were also changed with stand age. In particular, Cmic: Nmic and microbial respiration to biomass ratio (Rmic:Cmic) significantly decreased during the late stages, but Nmic: Nitrogen (Nsoil), microbial respiration (Rmic), and Rmic:Cmic significantly increased during the early stage. These trends highlighted the importance of stand age in regulating the response of soil microbial abundance and activities to change. In addition, we found soil microbial community abundance was positively correlated with soil water content (SWC), pH, Bulk density (BD), Csoil, Nsoil, and Csoil:Nsoil, but negatively correlated Psoil, which suggested that the trend in soil properties following afforestation should be considered when implementing soil microbes as proxies of soil nutrients cycling. More importantly, response ratio of soil bacterial, fungi, and microbial community abundance was negatively correlated with response ratio of aridity index. This correlation indicated that the sensitivity of response ratio of microbial abundance to increases in precipitation can be greater in arid areas relative to humid areas. Overall, our findings highlight a broad understanding of the responses of microbial community abundance and activities to afforestation, which provides the background needed to form novel methods that accurately model ecosystem functions.