The National Natural Science Foundation of China
土壤表层及深层的微生物互作对土壤养分循环和物质转化等具有重要意义。为揭示典型红壤水稻土剖面微生物分子生态网络特征，通过16S rRNA和18S rRNA高通量测序技术，运用CoNet分析方法，构建上层（0～20 cm）、中层（20～60 cm）和下层（60～100 cm）土壤细菌、真菌分子生态网络。结果表明，土壤全碳和全氮含量、细菌和真菌的丰富度沿土壤剖面显著降低（P<0.05）。微生物网络拓扑参数，如连通度、群聚系数和网络密度等均明显增加，表明微生物互作随深度增加而增强。与细菌和真菌界内网络互作特征相反，界间的网络互作随深度减弱。进一步利用随机森林模型和方差分解分析，表明土壤碳氮是影响微生物分子生态网络的关键因素；沿土壤剖面碳对微生物互作的贡献逐渐增加，由上层的3.58%增加到下层的32.67%。
[Objective] Soil environmental factors are highly spatially heterogeneous, especially soil pH, nutrient availability, soil temperature and soil microbes, which vary with soil depth, and hence affect the distribution of soil microbial communities. Soils in deep soil layers may have microbial communities that have adapted to the environments of deep soil layers, and consequently are different in structure from those in topsoil layers. Microbial communities decrease in biomass and diversity with depth in the soil profile, which alters structures of the soil microbial communities and affects their functions. Microbes in deep soil play an important role in soil formation, biogeochemical reactions and pollutant degradation. So deep soil has significant influences on quality indices of the soil and hence productivity of the vegetation on the surface. Interactions between species of the microbes may be more important than richness and diversity to ecosystem function of the microbial community, especially in complex ecosystems. Interactions between microbial communities are a part of the microbial network of a terrestrial ecosystem, and the basis of biochemical cycles. Ecological network analysis is a new analysis method to visualize interactions between microbial communities and explore co-existence patterns of the species in microhabitats and their main influencing factors. Network analysis can be used to explore mechanisms of microbial interactions driving biogeochemical coupling of important elements in soil, and hence is an important means to improve service functions of a soil ecosystem. However, most of the previous studies on soil microbial communities focused on those in the topsoil (0-20 cm) layer or on abundance of microbial species. Therefore, the information available in the literature about potential relationships between microbial interactions and soil depth, and their determining environmental factors.[Method] After late rice was harvested, soil samples were collected from a paddy field in Yingtan (116°54' E, 28°13' N, 34-62 m in elevation), South China. For the sampling, five sampling sites were set randomly as five replicates. At each site, a soil sample was collected from each of the five soil layers, 0-10, 10-20, 20-40, 40-60, 60-80 and 80-100 cm with an auger, making up a total of 30 samples for analysis, separately, of soil geochemical properties and DNAs.[Result] Contents of soil nutrients, including total nitrogen (TN), total carbon (TC) and NH4+-N, and species richness of soil microbes decreased significantly with soil depth. Network analysis shows that with increasing soil depth, the average. number of neighbors, clustering coefficient and Network density of the microbial interaction network increased, indicating that the associations between microbial communities became more complex in the microbial co-existence network with positive interactions intensified, and interactions within the bacterial community and within the fungal community enhanced, but the interactions between bacteria and fungi communities reduced. TC and TN were the main factors contributing to soil microbial interactions according to the random forest analysis. Variance partitioning analysis of the soil microbial network shows that microbial interactions were affected by carbon (TC + DOC) and nitrogen (TN + NO3--N+NH4+-N). Moreover, the effect of C intensified with soil depth.[Conclusion] The interactions between soil microbes become more intensive, more complicated and more modular with soil depth. The interactions within soil microbial communities are positively related to soil depth, and so were the interactions between bacterial and fungal communities. With the soil going down in depth, the contribution of soil C increased from 3.58% to 32.67% for the microbial interaction network.
黄兰婷,倪浩为,李新宇,孙波,梁玉婷.典型红壤水稻土剖面细菌和真菌分子生态网络特征研究[J].土壤学报,2021,58(4):1018-1027. DOI:10.11766/trxb202001170025 HUANG Lanting, NI Haowei, LI Xinyu, SUN Bo, LIANG Yuting. Molecular Ecological Network of Bacteria and Fungi in Paddy Soil Profile of Typical Red Soil[J]. Acta Pedologica Sinica,2021,58(4):1018-1027.复制