不同母质水稻土中有机碳转化和功能微生物类群演变及相互关系

Both soil physical-chemical property and microbial community assembly derive from soil parent material. Distribution of decomposed organic carbon in soil organic carbon pools is the key to soil fertility development. However, it remains unclear that the microbial process of carbon cycling in paddy soils derived from different parent materials. In this project, paddy soils developed from different parent materials are taken as the research object. Samples including three soil layers are collected to quantify the characteristic of carbon sequestration and microbial community assembly process. A flooded soil experiment is conducted in which 13C-labeled straw is added to assess the variations of organic carbon transformation in different soil types. The δ13C method is used to evaluate the distribution of soil organic fractions. The variations of functional microbial communities involved in organic carbon transformation are analyzed by means of SIP technology and bioinformatics. The contributions of soil physic-chemical and microbial factors on organic carbon transformation are calculated by using statistic method; the results are helpful to gain a deeper understanding of the process of carbon cycling and provide a theoretical basis for the scientific management of regional farmland ecosystems.

成土母质是土壤理化与微生物群落构建的物质基础，外源有机碳被微生物分解后在土壤碳库中的分配去向是影响土壤肥力演变的关键，然而不同母质发育的水稻土中有机碳转化的微生物过程特征及驱动因素并不明确。本项目以不同母质发育的水稻土为研究对象，采集不同土层样品，分析不同母质发育水稻土中有机碳变化特征与微生物群落构建过程；并以13C标记秸秆为碳源，室内淹水培育土壤，运用δ13C方法定量分析新/老有机碳转化过程；借助SIP技术与生物信息学探明参与有机碳转化的功能微生物类群的响应规律；结合统计学手段分析驱动有机碳转化的土壤理化及微生物因子的贡献率；结果可为深入认识土壤有机碳转化的微生物学过程提供理论依据，并对区域农田养分管理具有重要的理论指导意义。

成土母质是土壤理化与微生物群落构建的物质基础，外源秸秆碳被微生物分解后在土壤碳库中的分配去向是影响土壤肥力演变的关键，而不同母质发育的水稻土中有机碳转化的微生物调控机制并不清楚。本项目以我国亚热带典型红壤水稻土为研究对象，选择第三纪红砂岩风化物（红砂岩）、第四纪红黏土（红黏土）及河流冲积物（河积物）母质发育的红壤水稻土，采集 0‒10 cm、10‒20 cm和20‒40 cm土层样品。探明不同母质发育水稻土碳库的时空演变特征及微生物群落构建机制。以13C标记秸秆为碳源，室内培育土壤，分别在秸秆降解的第7 d、30 d、90 d和180 d时破坏性取样，运用 δ13C方法定量分析新/老有机碳转化过程；借助高通量测序技术与生物信息学分析手段探明有机碳转化过程中相关微生物类群的演变规律。结果发现，与2002年背景资料对比，0~10 cm土层有机碳、全氮及速效钾的增幅分别达35%、40%和34%，而pH显著降低。0‒10 cm土层细菌群落构建主要是随机过程，水稻土长期淹水，微生物随水流迁徙，导致微生物群落结构相对均一化。随土层深度增加，微生物扩散限制愈加明显，尤其是下表层土，微生物群落结构与形成土壤的母质关联更为紧密。养分及微生物互作是影响微生物群落构建的关键因子。室内培养实验表明，秸秆降解半年后，红砂岩母质土壤秸秆残留碳占60.17%，显著高于红黏土和河积物母质土壤。秸秆碳的0.16%和1.14%分别进入可溶性有机碳和微生物生物量碳。红砂岩母质土壤中秸秆源有机碳对活性碳组分的贡献值最小，显著低于红黏土与河积物母质土壤。秸秆降解前期主要是放线菌和子囊菌门，随秸秆降解进行，担子菌门相对含量逐渐增加。秸秆降解前期，膜转运、糖代谢及氨基酸代谢功能基因含量最高，随秸秆降解的进行而降低，细胞代谢及信号转导相关基因丰度增加。不同母质发育土壤的土壤碳库、养分、及微生物学特性是调控有机碳转化过程的关键。依托该项目，累积发表4篇 SCI 论文，相关研究结果不仅丰富了微生物生态学理论，同时也为水稻土碳库培育及地力提升提供理论支撑。