Significant Effects of Dead Trees on Active Organic Carbon Components and Microbial Communities in Subtropical Forests

Abstract As a vital component of the forest ecosystem, dead wood plays an important role in forest regeneration, species variety, water conservation, soil erosion avoidance, and the carbon cycle. At the moment, dead wood research is mostly concerned with the storage of dead wood in forests and the change of nutritional components throughout the decomposition process. There have been few investigations on the changes in soil active organic carbon components and bacterial community structure during the breakdown of dead wood. To investigate the impact of dead wood on soil active organic carbon components and the structure of microbial communities. we selected the soil under three different decay grades of Castanopsis eyrei dead wood and the forest soil without dead wood as the control. The basic physical and chemical indexes of soil, the composition of soil active organic carbon and the structure of microbial community were measured. Compared with the control group, dead wood mulching significantly increased the content of soil organic carbon and total nitrogen (P < 0.05), and dead wood significantly affected the content of soil active organic carbon (P < 0.05). The easily oxidized organic carbon, microbial biomass carbon and organic carbon under the severe decay dead wood were significantly higher than those in the control (P < 0.05), and the content of activated carbon increased with the increase of decay grade. The relative abundance of Actinobacteria, Chloroflexi, WPS-2, Patescibacteria and Bacteroidetes increased with the increase of decay grade of dead wood, and the relative abundance of soil bacteria under dead wood was higher than that of the control. Through the redundancy analysis of environmental factors and soil microbial community, we found soil total nitrogen and pH are the key factors driving microbial community. The distribution of soil bacterial community under light rotten dead wood is similar to that soil without dead wood, which is significantly different from that under moderate and severe rotten dead wood. The abundance of soil bacterial community and soil active organic carbon components are most affected by heavy rotten dead wood. Soil active organic carbon was significantly negatively correlated with Acidobacteria(P < 0.01), and positively correlated with Ktedonobacteria, Bacteroidia, Saccharimonadia and TK10(P < 0.05). The above research results show that dead wood has a great impact on soil physical and chemical properties and microbial community structure. Our study improves the impact of dead wood on soil activated carbon components and microbial community, and provides a theoretical basis for sustainable forest management.