不同施肥制度土壤有机碳矿化对温度的响应及微生物驱动机制

Understanding the mechanisms of soil carbon mineralization's feedbacks to climate changes is critical to project future climate warming because of its significant relationships with soil quality and Green House Gas emission. The temperature responses to soil carbon mineralization under different fertilization regimes are uncertain so far and little is known about the mechanisms of soil microbes' dynamics although they play crucial roles in regulating carbon mineralization. In order to answer these questions, we use a long-term fertilization experiment as platform, firstly to investigate temperature responses to soil carbon mineralization, secondly to study the effects of temperature on soil microbial community composition and rate-limiting enzymes to analysis the relationships between changes in microorganisms/enzymes and soil carbon mineralization kinetics under warming, and then find out the microbial dynamic mechanisms of regulating temperature sensitivity of soil carbon mineralization. Meanwhile, we want to identify the microorganisms which control the added 13C-labelled carbon mineralization processes using DNA stable isotope probing technology, and study the dynamic processes of the added carbon mineralization which they participant in. Finally, we try to find the roles of shifts in specific functional microbial groups and enzymes which control the soil carbon mineralization under long-term fertilizer regimes and their contributions to soil carbon mineralization under warming and to elucidate microbial mediated feedbacks to temperature changes, which is fundamental to understanding the responses of different fertilized soils to climate warming.

土壤有机碳矿化与土壤质量和温室气体排放密切相关，明确其对气候变化的反馈是应对未来气候变暖的重要手段。不同施肥土壤有机碳矿化不同，微生物起着重要作用。目前对不同施肥土壤有机碳矿化与温度变化的响应关系研究不够深入，微生物的调控机制还不明确。故本项目以长期定位施肥试验为平台，首先研究不同施肥土壤有机碳矿化对温度响应的差异，其次监测微生物群落和限速酶的变化，通过分析有机碳矿化与微生物群落特征、限速酶的对应关系，探寻调控有机碳矿化温度敏感的微生物学机制。同时，利用13C-DNA-SIP技术，鉴定参与外源碳矿化的微生物种群，研究其参与外源碳矿化温度响应的动态过程。最后，通过综合评价不同施肥制度土壤微生物群落、酶类及参与外源碳矿化的关键微生物种群特征变化对土壤有机碳矿化温度响应的贡献，揭示土壤有机碳矿化对温度响应的微生物驱动机制，为预测不同施肥土壤对气候变暖的反馈提供理论依据。

本研究以始建于1986年的长期定位施肥试验为平台，利用常规化学分析和分子生态学方法，系统研究了（1）长期施肥农田旱地土壤活性碳氮组分的变化特征；（2）长期施肥土壤微生物群落多样性及结构变化；（3）参与土壤养分循环的关键功能酶活性；(4) 长期施肥土壤有机碳矿化及酶活性对温变的响应机制；（5）添加牛粪对长期施肥土壤有机碳矿化的影响及机制。具体研究结果如下： . 1、28年长期施肥尤其是施有机肥显著提高了潮土养分含量，降低了pH值；长期施肥显著增加了潮土微生物量碳氮、可溶性有机碳氮、颗粒有机碳氮和易氧化有机碳含量，提高了土壤碳库管理指数，且随有机肥施用量的增加而增加；长期施肥特别是施有机肥显著增加了土壤水解酶活性和过氧化物酶活性，降低了土壤酚氧化酶活性。可溶性有机碳是关键环境影响因子。. 2、长期施肥改变了土壤细菌群落组成及丰富度，高量有机肥处理最高；微生物量碳（MBC）是主要环境影响因子。基因组学与转录组学高通量测序研究发现，土壤细菌在DNA水平和RNA水平上分异显著；在RNA水平上，芽孢杆菌纲为高量施有机肥处理（DM）区别于其他处理的关键菌群。. 3、温度和施肥及其交互作用显著影响不同施肥制度潮土总有机碳含量、活性有机碳库组分含量及土壤酶活性。温度升高显著降低了不同施肥土壤活性碳库组分含量；土壤水解酶活性一般随温度的升高而降低，过氧化物酶和酚氧化酶活性表现相反。随着温度的升高，调控土壤酶活性变化的关键活性有机碳库因子发生显著变化。. 4、添加牛粪对不同施肥潮土活性有机碳、氮库组分的影响存在显著差异。且牛粪的添加对长期施用常量有机肥及常量有机无机配施土壤的影响小于其对长期不施肥及常量化肥的处理。. 5、添加牛粪提高了长期不同施肥潮土有机碳矿化量；牛粪对长期不施肥及施用常量化肥土壤有机碳矿化的正激发效应显著高于长期施用常量有机肥和常量有机无机配施，且受长期不同施肥土壤养分含量及活性有机碳库组分碳氮比的影响显著。