Supported by the Geological Survey Project of China Geological Survey (No. DD20190305) and the National Natural Science Foundation of China (No. 31930070)
微生物对土壤有机质（SOM）转化和形成具有重要作用，然而微生物残体对SOM贡献的评估仍是目前的热点。以长白山5个森林次生演替序列（20 a、80 a、120 a、200 a和≥300 a ）和2个土壤深度（0～5 cm有机质层和5～15 cm矿质层）为对象，利用氨基糖和中红外光谱技术，探究森林次生演替过程中微生物残体变化及其对土壤有机碳（SOC）的贡献。森林次生演替序列80~200 a显著增加了有机质层和矿质层微生物残体含量及其对SOC的贡献，而在演替300 a均显著降低。森林演替80～200 a有机质层和矿质层土壤芳香族碳组分/多糖较低，有利于微生物生物量碳（MBC）产生和微生物碳利用（高的MBC/SOC），促进微生物残体积累及其对SOC的贡献；而演替300 a芳香族碳组分/多糖较高，抑制MBC产生和微生物碳利用，导致微生物残体及其对SOC贡献的下降。SOC含量差异导致不同土壤深度微生物残体含量的变化，有机质层高的SOC产生高的MBC，进而刺激微生物残体积累；此外，有机质层难利用SOM组分高于矿质层，导致真菌残体对SOC的贡献比例下降，而细菌残体的贡献增加。
[Objective] Soil microbes are an important factor driving turnover of soil organic matter (SOM), through participating in SOM formation, linking aboveground and underground ecosystems in evolution process, and influencing the structure and function of ecosystems. However, it is still a hard nut to evaluate the contribution of soil microbes (especially microbial residues) to SOM, and a hotspot of research in this aspect, due to limitation in technology. In this study, efforts were dedicated to examining (1) how forest secondary succession influences the content of microbial residues and its contribution to soil organic carbon (SOC); (2) how soil depth affects content of microbial residues and its contribution to SOC; and (3) how fungal and bacterial residues regulate the contribution of microbial residues to SOC.[Method] To explore changes in the content of microbial residues and contribution of microbial residues to SOC, soil samples were collected from the topsoil (0-5 cm) and subsoil (5-15 cm) in five plots of secondary forests with different age or succession (i.e. 20 years, 80 years, 120 years, 200 years and ≥ 300 years) in the Changbai Mountain National Nature Reserve, Jilin, Northeast China for analysis of amino sugars, including glucosamine, galactoamine, and muramic acid, as biomarkers for microbial residues. Based on the analysis, contents of fungal and bacterial residues were worked out. Besides, soil organic matter in the sample was analyzed for composition (i.e. aromatic C, aliphatic C and polysaccharides) with fourier transform mid-IR spectroscopy.[Result] Our study showed significant increases in content of microbial residues and contribution of the residues to SOC in both topsoil and subsoil during the period of 80-200 years of the succession, whereas a reverse trend was found after 300 years. Path analysis showed that content of microbial residues was positively related to microbial biomass carbon (MBC) in the two soil layers during the succession, indicating that changes in MBC influence the accumulation of microbial residues. In the soils under secondary forests 80-200 years old, labile SOM (low in aromatic C/polysaccharides ratio) was relatively higher, which was beneficial to utilization of microbial carbon (high in MBC/SOC ratio) and accumulation of microbial residues, and promoted contribution of the residues to SOC, while in the soils under secondary forests >300 years old, recalcitrant SOM (high in aromatic C/polysaccharides ratio) was relatively higher, which inhibited utilization of microbial C, thus leading to decline in content of microbial residues and contribution of the residues to SOC. Content of microbial residues varied with soil depth, being higher in the topsoil than in the subsoil as SOC did. Higher content of SOC in the topsoil induced generation of more microbial biomass, thus leading to higher accumulation of microbial residues, whereas the existence of higher contents of recalcitrant fractions of SOM in the topsoil caused decrease in contribution of the residues to SOC. In addition, the variation of SOM utilization rate from low in the topsoil to high in the subsoil caused decline of fungal residue contribution to SOC, but a reverse trend with bacterial residues.[Conclusion] In summary, changes in availability of carbon resources (i.e. SOC concentration and SOM components) trigger variation of content and accumulation of microbial residues in SOC. All the findings in this study may provide certain theoretical support for us in exploring effects of microbial metabolites on SOM formation from the perspective of microbial ecology. Therefore, this study suggests that the anabolic pathways of soil microbes be integrated into the current terrestrial ecosystem carbon models, which will sure facilitate better prediction and evaluation of SOC response to ecosystem managements.
邵鹏帅,解宏图,鲍雪莲,梁超.森林次生演替过程中有机质层和矿质层土壤微生物残体的变化[J].土壤学报,2021,58(4):1050-1059. DOI:10.11766/trxb201912210508 SHAO Pengshuai, XIE Hongtu, BAO Xuelian, LIANG Chao. Variation of Microbial Residues during Forest Secondary Succession in Topsoil and Subsoil[J]. Acta Pedologica Sinica,2021,58(4):1050-1059.复制