Ni Haowei,Jing Xiaoyan,Xiao Xian,Zhang Na,Wang Xiaoyue,Sui Yueyu,Sun Bo,Liang Yuting
Understanding the effects of changing climate and long-term human activities on soil organic carbon (SOC) and the mediating roles of microorganisms is critical to maintain soil C stability in agricultural ecosystem. Here, we took samples from a long-term soil transplantation experiment, in which large transects of Mollisol soil in a cold temperate region were translocated to warm temperate and mid-subtropical regions to simulate different climate conditions, with a fertilization treatment on top. This study aimed to understand fertilization effect on SOC and the role of soil microorganisms featured after long-term community incubation in warm climates. After 12 years of soil transplantation, fertilization led to less reduction of SOC, in which aromatic C increased and the consumption of O-alkyl C and carbonyl C decreased. Soil live microbes were analyzed using propidium monoazide to remove DNAs from dead cells, and their network modulization explained 60.4% of variations in soil labile C. Single-cell Raman spectroscopy combined with D 2 O isotope labeling indicated a higher metabolic activity of live microbes to use easily degradable C after soil transplantation. Compared with non-fertilization, there was a significant decrease in soil α- and β-glucosidase and delay on microbial growth with fertilization in warmer climate. Moreover, fertilization significantly increased microbial necromass as indicated by amino sugar content, and its contribution to soil resistant C reached 22.3%. This study evidentially highlights the substantial contribution of soil microbial metabolism and necromass to refractory C of SOC with addition of nutrients in the long-term.
Microbial necromass is increasingly recognized as a major source of stable soil organic matter (SOM), and its persistence is often attributed to interactions with clay-sized minerals. However, the mechanisms underlying this mineral-mediated stabilization remain poorly understood. Here, we conducted an in situ dual-labeled ( 13 C and 15 N) microbial necromass experiment across a clay gradient to quantify how clay content and necromass origin (bacterial vs. fungal) regulate necromass persistence. We find that higher clay content markedly enhances necromass retention by strengthening mineral protection, suppressing microbial activity and diversity, and limiting leaching losses. NanoSIMS imaging shows that new necromass preferentially associates with organic matter coatings on the rough mineral surfaces, highlighting organo-organic interfaces as important stabilization pathways. Necromass origin exerts little effect on retention despite marked differences in C:N ratios and bulk chemical composition, indicating that finer-scale molecular features, rather than broad compositional differences, govern necromass stabilization in soils.
危险品化学品经营许可证（带存储）