Rhizosphere effects on soil organic carbon processes in terrestrial ecosystems: A meta-analysis

Rhizosphere processes are one of the most important ways in which plants affect carbon (C) cycling in terrestrial ecosystems. However, how rhizosphere processes related to C cycling are regulated by microorganisms is still poorly understood. Here, using a meta-analysis based on data compiled from 110 published articles and our measured data, we quantified the magnitudes of the rhizosphere effects on soil organic C (SOC), microbial biomass C (MBC), respiration (Rs), microbial biomass and enzymes involved in C acquisition, and discovered the linkages between the rhizosphere effect on Rs and microbial characteristics. This study provided a global-scale assessment in which positive rhizosphere effects on SOC, MBC, and Rs were observed across terrestrial ecosystems worldwide. We also found that the positive rhizosphere effects on microbial biomass and enzyme activities were likely widespread phenomena in terrestrial ecosystems. The results of the structural equation model also indicated that the rhizosphere effects on SOC and total nitrogen had positive effects on the rhizosphere effect on Rs, but the rhizosphere effects on fungal and bacterial biomass showed negative effects. Our findings highlight the importance of microbial-mediated rhizosphere Rs in global SOC cycling and suggest that the consideration of the rhizosphere effects on C cycling processes in Earth system models may improve the accuracy of predicting global SOC dynamics.

Automated summary

Rhizosphere processes are important for plant-mediated carbon cycling in terrestrial ecosystems, but the role of microorganisms in regulating these processes is not well understood. This study conducted a meta-analysis of 110 published articles and measured data to quantify the effects of the rhizosphere on soil organic carbon, microbial biomass carbon, respiration, and enzyme activities. Positive effects of the rhizosphere on these parameters were observed globally, indicating the widespread importance of the rhizosphere in carbon cycling. The results also showed that the rhizosphere effects on microbial biomass and enzyme activities were likely common phenomena. Structural equation modeling revealed that the rhizosphere effects on soil organic carbon and total nitrogen had positive effects on respiration, while effects on fungal and bacterial biomass were negative. This study highlights the significance of microbial-mediated rhizosphere respiration in global soil organic carbon cycling and suggests that incorporating rhizosphere effects in Earth system models can improve predictions of carbon dynamics.