黄土高原干旱区冬小麦田土壤有机碳固定机制及高光谱定量监测研究

The drought will become the main natural disaster in next years to continuously affect the production of winter wheat on the Loess Plateau region and it will definitely cause the emission of soil organic carbon (SOC), which will transform the soil function from the soil carbon sequestration to the soil carbon source. Thus, the study on the mechanism of SOC sequestration and monitored by using the hyperspectral technology in the winter wheat field on arid of Loess Plateau, China, is of significance. In study, the plot experiments of water pool and the regional field experiment will be combined to analyzes the quantitative contribution of soil factors, including the soil basic properties, soil microorganism and the soil carbon mineralization enzymes, to the SOC stock under the drought condition, and the relationship between the growth and development of winter wheat and the SOC stock and its affected soil factors will be further observed to reveal the mechanism of SOC sequestration under the drought condition and the response of growth and development of winter wheat on the SOC sequestration. Moreover, the chemometrics method will be applied on extracting the sensitive spectral information and constructing the monitor model of SOC stock and its affected soil factors to determine the quantitative relationship between the hyperspectrum and the SOC stock and its affected soil factors. The project will finally provide some theoretic reference to illuminate the mechanism of SOC sequestration in the field of winter wheat on arid of Loess Plateau, China, and also supply some technical method and practical guidance on hyperspectral monitor of the SOC sequestration and adjusting the farmland management of the SOC sequestration responding to the drought disaster.

干旱将持续成为影响黄土高原地区冬小麦生产的主要自然灾害，并诱发土壤有机碳排放而使土壤碳“汇”成为碳“源”，开展干旱条件下冬小麦田土壤有机碳固定机制及高光谱定量监测研究具有重要现实意义。本项目拟结合水分池小区试验和区域大田试验，分析干旱处理条件下土壤基础属性、土壤微生物和土壤碳矿化酶等有机碳固定因子对土壤有机碳库的定量贡献，研究土壤有机碳库及有机碳固定因子与冬小麦生产力关系，揭示干旱条件下土壤有机碳固定机制和冬小麦生长对土壤有机碳固定的响应关系；利用化学计量学方法，提取土壤有机碳库及有机碳固定因子的高光谱特征，并构建其光谱监测模型，以探清土壤有机碳库与高光谱的定量关系和实现其高光谱定量监测。研究结果将探明黄土高原冬小麦田土壤有机碳固定机制及其与干旱的响应机制，实践上可为黄土高原冬小麦田土壤有机碳固定的高光谱定量监测及为应对干旱而制定土壤有机碳固定的麦田管理措施提供技术方法和实践指导。

未来全球气候变暖将会引发干旱灾害的持续频繁发生，而干旱是影响黄土高原地区冬小麦生产的主要自然灾害，土壤有机碳会因为干旱而使碳“汇”变为碳“源”，土壤有机碳的固定被认为是减缓全球气候变化的重要农业途径，开展干旱条件下冬小麦田高光谱定量监测研究具有重要现实意义。因此，本项目以冬小麦田为研究对象，结合水分池，保护性耕作和区域大田试验开展了黄土高原干旱区冬小麦田土壤有机碳固定机制研究，得到以下重要结论：（1）探究土壤有机碳库形成机制发现，秸秆腐解速率严重影响土壤固定秸秆碳的速率，免耕能较好地维护耕层土壤的团粒结构。同时，秸秆还田能够增加耕层土壤大团聚体含量，弱化不同耕作方法对耕层团聚体含量的差异化影响，有利于增加土壤团聚结构的稳定性。土壤有机碳含量与团聚体稳定性具有协同作用，长期免耕与秸秆还田可有效提高农田土壤固碳潜力。（2）从土壤物理属性，生理属性及生化特性解析土壤有机碳固定的高光谱响应机理，发现碳库影响因子与光谱反射率均存在一定数量关系，近红外长波（1100-2500 nm）对其贡献率均最高，且广义土壤结构指数（R2=0.93）、分形维数（R2 = 0.714）、黏粒（R2 = 0.714）、全氮（R2=0.7686）和土壤脲酶活性（R2 = 0.8564）光谱预测结果均较好。该研究可为定量化研究土壤结构、功能与质量提供参考。（3）研究土壤有机碳固定的高光谱定量监测发现，土壤有机碳与光谱反射率成反比，有机碳重要波长区域为400~610、690~720、870~900、1010~1060和2150~2350 nm，预处理有利于提高土壤有机碳与土壤光谱的相关性，且所构建的模型可以实现对土壤有机碳的准确估算。该项目明确了土壤有机碳库及有机碳固定影响因子与土壤高光谱的定量关系，形成土壤有机碳库及其有机碳固定影响因子的高光谱定量监测方法体系，可为制定土壤有机碳固定的麦田管理措施提供技术方法和实践指导。