不同有机物料培肥下土壤团粒结构形成及相关有机碳转化的微生物驱动机制

Applications of different organic materials is an important way to improve the soil fertility of low-yield farmlands and exploring the microbial community has become an important method to study the soil functionality and fertility on soil aggregate level. However, the mechanisms of soil granular structure formation and organic carbon turnover driven by microorganisms under the applications of different organic materials need to be further studied. In this project, we designed an incubation experiment using low-yield farmland soils. The soils were combusted in a muffle furnace, added different sterilized organic materials in and inoculated with soil microbial suspension before incubation. Soil samples were taken periodically during the period of incubation. Using the technologies of soil granular structure grading, organic carbon composition analyzing and high through pyrosequencing to study: i) the processes of combusted soil reagglomeration under the application of different organic materials; ii) the microbial community succession during soil granular structure formation; iii) the transformation and distribution of organic carbon in varied soil granular structures during microbial community succession. Thus, by exploring the coupling relationships of soil reagglomeration, microbial community succession and organic carbon transformation and distribution under the application of different organic materials, we could elucidate the effect of microorganisms in the processes of soil agglomeration. Additionally, we could explain the mechanism of microbial droved organic carbon turnover in varied soil granular structures. The previous conclusions could be proved by another incubation experiment: adding stable isotope (13C) labeled organic materials to fresh soils. This research will lay a good foundation for further exploring the soil functionality and soil biological and chemical processes, provide scientific basis for improving low-yield farmlands or increasing soil fertility, and ensure the food security in China.

有机物料培肥是提高我国中低产田土壤肥力的重要途径，从土壤团粒结构层面研究微生物区系已成为探究土壤功能及肥力演变的重要方法，但土壤团粒结构形成及有机碳转化的微生物驱动机制仍有待深入研究。本项目以我国典型的中低产土壤为研究对象，将经马弗炉充分灼烧后的土壤用灭菌的有机物料培肥，再接种微生物培育，采用土壤团粒结构分级、有机碳组分分析和高通量测序相结合的技术手段，研究土壤颗粒的重新团聚过程，分析土壤团粒结构形成过程中的微生物区系演变特征，探究有机碳的转化及分配过程。试图通过研究三者之间的耦联关系，从微生物作用的角度来揭示团粒结构形成过程，阐明土壤新添加有机物料中有机碳转化的微生物驱动机制，再通过向未灼烧的土壤中添加稳定同位素13C标记的有机物料进行原位培育加以印证。从而为深入探究土壤功能和相关生物化学过程奠定良好的理论基础，也为迅速进行中低产田改造、提高土壤肥力提供科学依据，保证我国粮食安全。

本项目通过土壤培育，结合高通量测序手段和信息学分析，先通过比较三组有机碳含量水平的土壤细菌群落生态学网络差异，表明高有机碳含量水平的细菌群落互作网络是一个组织有序化程度最高的网络。可以推断高有机碳含量水平的细菌群落是一个高效运作，资源利用有序化的生态系统。通过比较中低有机碳含量水平细菌群落中的种群和拓扑结构作用变化表明可以通过合理的施肥方式促进细菌生态网络有序化，有利于土壤养分循环，提升耕地质量。不同细菌种群的拓扑结构作用表明富营养细菌类群中某些特殊的细菌类群可以作为土壤肥力的指示菌微生物。再通过土壤不同形态碳磷源输入阐明了农田土壤不同施肥管理方式会显著影响土壤不同粒径中的有机碳水平以及其他各种养分组成和含量水平，同时会显著影响土壤中有机碳分解和固氮相关类群的组成和相对丰度。最后通过整体群落演替规律阐明土壤微生物群落的装配机制，发现稀释显著降低了细菌群落的物种多样性和功能多样性，影响了群落的装配过程，特殊性功能在土壤微生物群落随机性装配、保证群落多功能性和土壤生产力中具有十分重要的作用。因此，经过本项目研究，已初步阐明了不同土壤肥力下的微生物群落演替特征，揭示了细菌群落的互作网络模型，发现了一些可以作为肥力指示的指标微生物类群；同时通过土壤团粒分级分析，阐明了不同有机物料培肥下土壤团粒结构形成过程及微生物区系演变特征，揭示了不同碳氮比物料添加对土壤团粒中的有机碳分布的影响，阐明了其中有机碳分解的微生物类群和自生固氮类群的组成和偶联驱动机制，这对今后继续深入探讨农田土壤养分物质输入的形式和比例，并在不影响土壤正常功能的情况下提高土壤有机碳库含量和自生固氮效能，实现可持续农业发展提供重要的理论指导。