Response of soil bacterial communities to organic carbon input under soil freeze-thaw in forest ecosystems

The soil microbial community controls the biogeochemical cycle of elements critical to plant growth. Different carbon input modes have different effects on soil carbon storage and the microbial community, but the effects of carbon input control on soil microbial diversity and community structure in temperate forests remain unclear. We used high-throughput 16SrRNA gene sequencing and ecological network analysis methods to analyze the soil bacterial community, symbiotic network, and key species of three different carbon input treatments (litter removal, root removal, litter and root removal) in temperate natural secondary forests during the freeze-thaw season and growing season. The results showed that the change in the carbon source input led to a change in the way in which soil bacteria used carbon, which was mainly manifested as follows: (1) The relative abundance of Acidobacteria, which was oligotrophic bacteria, significantly decreased in the sample plots where the root system was removed. (2) In the litter removal treatment, the abundance of bacteria with functions related to the absorption of CH4 decreased. (3) The correlation between the module characteristic genes in the bacterial network analysis and the physical and chemical properties of soil, CK modules were grouped separately, and the change in the correlation may also indicate the change in the way soil bacteria use carbon. Second, the influence of belowground roots on the soil bacterial community structure was more significant than that of aboveground litter. The root system had a greater influence on the soil bacterial community. Third, the decrease of organic carbon input reduced the stability of the soil bacterial network, and the proportion of positive connections in the bacterial network for litter removal and root treatment increased significantly, indicating that these bacterial communities had the same change trend as the fluctuation of the environment. Finally, the freeze-thaw season had a greater impact than the growing season on bacterial diversity, community structure, and function. The freeze-thaw process allowed the bacterial community to respond to root removal more significantly, and the structural changes were mainly due to changes in temperature, water content, dissolved organic carbon, and nitrate nitrogen.

Automated summary

The soil microbial community plays a crucial role in plant growth by controlling the biogeochemical cycle of essential elements. Different carbon input methods affect soil carbon storage, microbial diversity, and community structure. Changes in carbon input alter the way soil bacteria utilize carbon, with underground roots having a greater impact on bacterial community structure than aboveground litter.