冻融循环增加土壤N2O产生和排放的机理研究

Nitrous oxide (N2O) is an important greenhouse gas and the soil N2O emission during the freeze-thaw cycle period is an important source of N2O gas. However, few studies have been done on the mechanism of increasing soil N2O production and emission by the freeze-thaw cycle. A lab-simulated soil column experiment combined with 15N stable isotope tracer technology will be implemented to explore the mechanism of increased soil N2O production and emissions during the freeze-thaw cycle period in a temperate forest of Changbai Mountain in northeast China. We will address the following questions: (1) the release of NH4+ from soil lattice in the freeze-thaw cycle and its contribution to soil N2O production; (2) the migration and transformation of dead microbial residues in the freeze-thaw cycle and its contribution to soil N2O production; (3) the contribution rate of plant roots to soil N2O production during the freeze-thaw cycle; (4) the contribution rate of physical release and new microbial release to soil N2O emission during the freezing-thawing cycle; (5) the contribution rate of surface soil and bottom soil to soil N2O emission during the freeze-thaw cycle. The study will reveal the intrinsic mechanism of increasing soil N2O production and emissions by the freeze-thaw cycle. Therefore, it will provide a scientific basis for better understanding, simulation, and prediction of N2O emissions from ecosystems.

氧化亚氮（N2O）是一种重要的温室气体，冻融时期土壤N2O排放是N2O气体的重要排放源。然而，目前冻融循环增加土壤N2O内在的机理尚不明确。本项目拟以东北地区长白山典型温带森林土壤为研究对象，采用室内模拟土柱的方法，并结合同位素技术，探究冻融循环期间增加的土壤N2O产生和排放的内在作用机理。主要包括以下几个内容：（1）冻融循环期间土壤晶格中NH4+释放规律及其对土壤N2O产生的贡献；（2）冻融循环中死亡微生物残体迁移转化规律及其对土壤N2O产生的贡献；（3）冻融循环期间植物根系对于土壤N2O产生的贡献率；（4）冻融循环期间物理释放和微生物作用下即刻产生释放对土壤N2O排放的贡献率；（5）冻融循环期间表层土壤和底层土壤对土壤N2O排放的贡献率。研究成果将揭示冻融循环期间增加的土壤N2O产生和排放的真正内在作用机理，为更好地认识、模拟及预测生态系统N2O排放提供科学依据。

全球气候变化可能会改变冻融循环的强度和频率，从而可能会显著影响土壤N2O排放。N2O是一种重要的温室气体，但目前冻融循环增加N2O的内在机理尚不明确。本研究以吉林省长白山典型温带森林为研究对象，采用室内模拟土柱的方法，并结合稳定性同位素双氮标记技术，揭示了在冻融循环期间土壤N2O产生和排放的内在作用机理。主要研究结果表明：（1）在冻融循环期间土壤晶格中铵态氮的释放对于土壤N2O产生的贡献较小；（2）在冻融循环期间，死亡的微生物残体氮主要变成土壤有机氮和微生物量氮，死亡微生物残体释放的养分可为活着的微生物提供大量养分，并且对于土壤N2O气体的排放贡献率较大；（3）在冻融循环过程中，因植物根系死亡释放的养分对于活着的微生物贡献占比较大，对于土壤N2O气体的排放贡献率较大，并且随着冻结强度的增加，植物根系对于土壤N2O排放的气体贡献率越大；（4）在第一次冻融循环期间，土壤N2O气体排放增加的原因主要以物理释放占主导地位，随着冻融循环次数的增加，微生物作用释放的机理占主导地位；（5）在冻融循环过程中，表层土壤对于土壤N2O气体的排放贡献率较大，并且随着冻融循环次数的增加，底层土壤对于土壤N2O气体排放占比表现出减小趋势。该研究结果有助于更好地理解土壤N2O对冻融循环的响应及其影响因素，为更准确地预测未来全球气候变化对N2O排放影响提供科学数据支撑。