Contrasting responses of fungal and bacterial communities to biogas slurry addition in rhizospheric soil of poplar plantations

Abstract

Rhizosphere microorganisms can affect the nutrient uptake of plant roots, and therefore contribute significantly to plant growth and nutrient cycling in forest ecosystems. Our previous studies revealed that the application of biogas slurry, an available organic fertilizer, increased the signal intensity and diversity of functional microbial genes in bulk soil. Further study of the response of rhizosphere soil microbial community structure to biogas slurry fertilization is of great significance for elucidating the mechanisms of nutrient cycling in forest ecosystems. In this study, our aim was to investigate the effects of biogas slurry application at different concentrations (Control, no treatment; Low, 250 m3 ha−1 yr−1; High, 375 m3 ha−1 yr−1) on the microbial community structures in the rhizospheric soil of poplar plantations. We found that the treatments with the highest biogas slurry concentration had the greatest fungal community Shannon diversity and richness. Among these, the Shannon diversity of rhizospheric soil fungal communities increased significantly with the high-concentration biogas slurry treatment compared with the control. However, the Shannon index of bacterial communities in rhizospheric soil exhibited negligible changes with the addition of biogas slurry. Further analyses revealed that the relative abundance of the fungal community in rhizospheric soil significantly changed in response to the quantity of biogas slurry. In particular, the abundance of several functional fungi, that play important roles in plant growth, significantly altered with the application of biogas slurry. These may be due to the changes of rhizosphere soil physicochemical properties, such as C/N ratio and available P, caused by biogas slurry application. Our results suggest that fertilization with biogas slurry can elevate fungal community diversity, but not bacterial diversity, in rhizospheric soil.