秸秆还田条件下模拟增温对水稻土碳氮矿化的影响机制研究

To explore the characteristics of soil organic carbon and nitrogen mineralization plays an important role in controlling soil nutrients and greenhouse gas emissions. Straw returning contributes significantly to increasing soil carbon sequestration and alleviating global warming. However, straw returning would accelerate carbon and nitrogen mineralization, and thus increase greenhouse gas emissions which lead to global warming. Therefore, it is uncertain that whether increased soil carbon sequestration can mitigate greenhouse gas emissions due to straw returning. In this study, paddy soil samples will be collected from rice-green manure cropping rotation system in hilly area of Southern Jiangsu Province. Incubation experiments will be conducted to study the responses of CO2 efflux and net nitrogen mineralization to stimulated warming in paddy soils with straw returning, to analyze the temperature dependence of carbon mineralization, and to assess the contributions of greenhouse gas emissions and soil carbon sequestration to global warming after field straw residue incorporation. Furthermore, this study will discuss the correlation between CO2 efflux and net nitrogen mineralization, as well as their relationships with soil environmental factors. Above all, the investigation of this study will be helpful to ensure the rational use of straw, increase the sequestration of carbon in paddy soil, and reduce its contribution of CO2 release in the atmosphere.

揭示土壤有机质的矿化规律对土壤养分、温室气体排放的有效管理具有重要的理论和实践意义。秸秆还田作为目前重要的农田资源利用措施，在土壤固碳、减缓全球变暖方面具有突出贡献，而施加秸秆会加速有机质矿化，增加土壤温室气体的排放，所以，秸秆还田后温室气体增排的增温潜力对土壤固碳减缓全球变暖的贡献的抵消作用还存在不确定性。因此，本项目选取苏南丘陵地区水稻-绿肥轮作区水稻土，采用室内培养方法，重点研究秸秆还田条件下，水稻土CO2释放量与净氮矿化对模拟增温的响应特征，分析秸秆还田后水稻土碳矿化速率的温度敏感性（Q10），综合评估秸秆还田后温室气体排放与土壤固碳对全球变暖的贡献；研究水稻土CO2释放量与净氮矿化之间关系，及两者与土壤因子之间的相互关系，探讨水稻土土壤碳氮矿化规律及其控制机制，为科学合理利用秸秆资源，增加土壤碳固持，减少土壤温室气体排放，以及进一步研究农田土壤碳氮矿化对气候变化的响应提供理论依据

秸秆还田作为目前重要的农田资源利用措施，在土壤固碳、减缓全球变暖方面具有突出贡献，而施加秸秆会加速有机质矿化，增加土壤温室气体的排放，所以，秸秆还田后温室气体增排的增温潜力对土壤固碳减缓全球变暖的贡献的抵消作用还存在不确定性。因此，本项目选取苏南丘陵地区水稻-绿肥轮作区水稻土，采用室内培养方法，重点研究秸秆还田条件下，水稻土CO2释放量与净氮矿化对模拟增温的响应特征，分析秸秆还田后水稻土碳矿化速率的温度敏感性（Q10），综合评估秸秆还田后温室气体排放与土壤固碳对全球变暖的贡献；研究水稻土CO2释放量与净氮矿化之间关系，及两者与土壤因子之间的相互关系，探讨水稻土土壤碳氮矿化规律及其控制机制。主要研究结果如下：.1.秸秆还田会增强水稻土C矿化，不受温度影响，而净N矿化速率只有在低温环境下（5℃）会随着秸秆还田量的增加而提高；增温会显著加快水稻土C矿化释放CO2-C与净N矿化，CO2释放量随温度增加呈指数增长；秸秆全量还田处理下C矿化的Q10值显著高于半量还田与对照处理。.2.秸秆还田下水稻土C、N矿化后的土壤有机碳（SOC）、可溶性有机氮（DON）不受温度变化的影响；温度对微生物量碳（MBC）有显著影响，温度升高，MBC含量降低。.3.水稻秸秆还田土壤C矿化对增温的响应主要受到秸秆CN含量的影响，与秸秆C含量、N含量、C:N比均显著正相关，与土壤初始CN养分含量无关。N矿化与土壤CN养分含量、秸秆CN含量均无关。.水稻秸秆还田土壤C矿化速率与净N矿化速率之间存在线性正相关关系，不随秸秆还田量的变化而变化，但会随着温度的变化而变化，5℃时，两者之间存在线性正相关关系，温度升高时，两者无相关关系。