Response of bacterial compositions to soil biochemical properties under mulching-intensive management in a Phyllostachys edulis forest

Abstract

Phyllostachys edulis (Moso bamboo) is of great significance to forestry in China. Increased attention has been paid to exploring the role of underground ecology, especially soil microorganisms, in the cultivation and ecology of Moso bamboo. Mulching-intensive management can benefit Moso bamboo forests with low yields. However, the response of soil bacteria to changes in soil biochemical properties after intensive mulching is still unclear. In this study, the responses of the soil bacterial composition to changes in soil biochemical properties under different management conditions were analysed by sampling a bamboo forest under four management conditions: control, mulching, alternation and long-term mulching. The results showed that mulching and alternation could improve the diversity of soil bacteria at the phyla and genera levels, while long-term mulching had the opposite result. The relative abundances of Proteobacteria, Actinomycetes, TM7 and Bacteroides were lower in the control plots than in the other plots, while those of AD3, Verruca and GAL15 were higher. The results also showed that C (carbon), N (nitrogen) and P (phosphorus) accumulated rapidly in the mulching, alternation and long-term mulching plots due to the extensive application of organic and compound fertilizer. Soil acidification became obvious with the extension of mulching time. An increase in the C/N led to a decrease in substrate soil quality. Large amounts of total phosphorus (TP) and NO3−-N accumulated under long-term mulching, while the amounts of available phosphorus (AP) and NH4+-N decreased. The change in the microbial biomass carbon (MBC) content was consistent with that in the MBC/microbial biomass nitrogen (MBN), which decreased significantly in both the mulching plots and the long-term mulching plots, and alternation ameliorated the trend. MBC/MBN and pH were positively correlated with the bacterial composition at the genus level, while TP, NO3−-N, soil organic carbon (SOC) and water-soluble organic carbon (WSOC) were negatively correlated. The results showed that the soil bacteria did not benefit from the availability of relatively low-quality (high C/N) substrates, which was reflected by an imbalance in the soil bacteria composition under long-term mulching. Therefore, mulching is beneficial to the improvement of soil biochemical properties and the development of bacterial communities in a short period, but long-term mulching results in a significant decline compared with the other three management conditions. The soil biochemical environment and bacterial composition of Moso bamboo forest can be properly elevated by alternation, which is a necessary supplement to mulching and long-term mulching.