1.School of Applied Meteorology, Nanjing University of Information Science & Technology;2.Institute of Applied Ecology, Chinese Academy of Sciences
Supported by the National Natural Science Foundation of China (Nos. 42077085 and 41977025) and the Startup Foundation for Introducing Talent of NUIST of China (No. 2018r101)
Microorganisms are the engine driving the biogeochemical cycling of soil elements and play an important role in the transformation of soil organic matter (SOM). They decompose SOM and release CO2 into the atmosphere through mineralization on the one hand and transform SOM into their cell components through assimilation on the other hand. These cell components can be accumulated in the soil as microbial residues after their death. There is increasing recognition that microbial residues are important precursors of SOM formation and contribute significantly to long-term SOM stabilization. Therefore, this paper calls for scientists to pay more attention and study the role of microbial residues in the accumulation, turnover and stabilization of SOM, and possible underlying mechanisms. To achieve this objective, this paper first explains the processes of how microorganisms continuously produce microbial residues in soils via assimilation and emphasizes the extent to which microbial residues contribute to soil stable carbon (C) pool. Subsequently, this paper introduces the (i) quantification of microbial residues using amino sugar analysis, (ii) conversion of amino sugar data into microbial residue C data to account for the proportion of microbial-derived C in soil organic C and (iii) distinction of original- and newly-formed microbial residues with isotopic labelling techniques to indicate the turnover of microbial residues in soil. Furthermore, this paper summarizes the key external factors influencing the accumulation and turnover of microbial residues. These factors include: (1) nutrition management that can directly influence substrate availability for soil microorganisms and consequently the production and accumulation of microbial residues, even though soil fungi and bacteria may respond differently to substrate addition; (2) tillage practices which generally reduce the accumulation of microbial residues through the destruction of fungal hyphae and breakdown of soil aggregates; (3) land-use change that can permanently impact the contribution of microbial-derived C to soil organic C; and (4) climate change factors which include temperature elevation, elevated CO2 concentration and nitrogen deposition. The fourth section of this paper summarizes the potential stabilization mechanisms of microbial residues in soil, which include chemical protection by attaching to soil mineral surfaces, physical protection by occluding in soil aggregates and delayed decomposition due to the chemical structure of microbial residues. In the last section, some perspectives are provided for the scientific issues that need to be further studied regarding microbial residue contribution to SOM: (a) combine microbial residues with living microbial communities to link with the processes of microbial assimilation from both instantaneous and continuous perspectives; (b) explore the distribution process and stabilization mechanism of microbial residues with soil minerals; (c) investigate the accumulation and turnover of microbial residues in subsurface soils as soil physicochemical properties and microbial community composition change substantially with increase in depth. These discussions will provide a clue to clarify the role of microbial anabolism driving and involving SOM formation and stabilization as well as the underlying relationship between SOM turnover and microbial process in terrestrial ecosystem.
张 彬,陈 奇,丁雪丽,何红波,张旭东.微生物残体在土壤中的积累转化过程与稳定机理研究进展[J].土壤学报,DOI:10.11766/trxb202012270705,[待发表]
ZHANG Bin, CHEN Qi, DING Xueli, HE Hongbo, ZHANG Xudong. Research Progress on Accumulation, Turnover and Stabilization of Microbial Residues in Soil[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202012270705,[In Press]