Root exudates, as an important form of material input from plants to the soil, regulate the carbon input and efflux of plant rhizosphere soil and play an important role in maintaining the carbon and nutrient balance of the whole ecosystem. Root exudates are notoriously difficult to collect due to their underlying characteristics (e.g., low concentration and fast turnover rate) and the associated methodological challenges of accurately measuring root exudates in native soils. As a result, up until now, it has been difficult to accurately quantify the soil organic carbon input from root exudates to the soil in most studies. In recent years, the contribution and ecological effects of root exudates to soil organic carbon input and efflux have been paid more and more attention. However, the ecological mechanism of soil organic carbon input and efflux mediated by root exudates are rarely analyzed comprehensively. In this review, the main processes and influencing factors of soil organic carbon input and efflux mediated by root exudates are demonstrated. Soil minerals and soil microbes play key roles in the processes. The carbon allocation from plants to soil is influenced by the relationship between root exudates and root functional traits. Compared with the quantity of root exudates, the response of root exudate quality to environmental changes affects soil carbon function more. In the future, the contribution of root exudates in different plants to soil carbon turnover and their relationship with soil nutrient availability will be accurately quantified, which will be helpful to understand the mechanism of soil organic carbon sequestration.

Soil moisture content (SWC) can change the diversity and composition of soil fungal communities by affecting soil texture and soil nutrients. To explore the response of soil fungal communities to moisture in the grassland ecosystem on the south shore of Hulun Lake, we set up a natural moisture gradient that was subdivided into high (HW), medium (MW), and low (LW) water contents. Vegetation was investigated by quadrat method, and aboveground biomass was collected by the mowing method. Soil physicochemical properties were obtained by internal experiments. The composition of the soil fungal community was determined using high-throughput sequencing technology. The results showed significant differences in soil texture, nutrients, and fungal species diversity under the moisture gradients. Although there was significant clustering of fungal communities in different treatments, the fungal community composition was not significantly different. According to the phylogenetic tree, the Ascomycota and Basidiomycota were the most important branches. The fungal species diversity was smaller when SWC was higher, and in this environment (HW), the fungal-dominant species were significantly related to SWC and soil nutrients. At this time, soil clay formed a protective barrier for the survival of the dominant classes Sordariomycetes and Dothideomycetes and increased their relative abundance. In summary, the fungal community responded significantly to SWC on the southern shore of the Hulun Lake ecosystem in Inner Mongolia, China, and the fungal community composition of the HW group was stable and easier to survive.

Soil moisture is one important factor affecting ecosystem function, controlling the diffusion and transport of soil nutrients, maintaining soil microbial activities, and altering soil microbial diversity. To explore the response of soil microbial to soil moisture in the grassland ecosystem along the south shore of Hulun Lake in Inner Mongolia, China, we established a study area covering a natural soil moisture gradient which was subdivided into high (HW), medium (MW) and low water content (LW). Aboveground and belowground properties were measured by field investigation and laboratory analyses, respectively. Soil prokaryotic community composition was determined by high-throughput sequencing techniques. Soil moisture content as a dominant controlling factor, and soil organic nutrients as a secondary controlling factor, significantly affected the diversity of prokaryotic communities. The relative abundance and diversity of prokaryotic microbial were highest under MW, indicating a high heterogeneity of prokaryotes. However, the number of differential ASVs decreased, indicating that the structure and composition of the community stabilized under MW. Therefore, the prokaryotic community was more suitable to survive under MW. Although the relative abundance and diversity of microorganisms were lower under HW and LW than MW, phenotypic predictions showed that the prokaryotic community was more tolerant. We believe that either too high or too low soil water content will reduce the relative abundance and diversity of prokaryotic communities, and the communities will gradually become resistant to stress. Soil microbial community characteristics of the south shore of Hulun Lake in Inner Mongolia, China, respond significantly to soil moisture.