黄土区坡改梯后土壤团聚体微结构的演变特征及其稳定机制研究

Soil structure is central to fulfil the functions of soil. The recovery of good soil structure, especially aggregate structure plays a key role in improving soil quality. by terracing slope cropland.Until now, there are less researches on the effect of terracing slope cropland on the pore network of aggregates; evolvement characteristics and stability mechanism of soil aggregate microstructure after slope cropland changed into terraces, however, are not well understood. Considering the deficiencies in the research of soil aggregate microstructure and the need of improving soil quality on the Loess Plateau, We will use synchrotron-based high-resolution X-ray micro-computed tomography and image analysis to quantify and systematically analysis the microstructure of soil aggregates under the terraces of different ages and different fertilization practices on the plateau. From the perspective of visualization and quantification of aggregate microstructure, the evolution mechanism of the internal structures of the aggregates will be revealed.The relationships between the aggregate pore parameters and aggregate stability will be obtained, and the stability mechanism of soil aggregate microstructure will be is explored by quantitative analysis.The results will provide a scientific basis for improving our understanding of the importance of improving soil quality.

土壤结构是维持土壤功能的基础，而坡耕地改造为梯田后土壤质量提升的核心就是土壤结构，尤其是团聚体结构的改善。目前有关坡改梯后土壤团聚体微结构研究开展较少，团聚体微结构的演变特征及其稳定机制尚不清楚。本课题针对土壤微结构研究的薄弱环节和黄土高原土壤质量培育需求，选取黄土丘陵区不同年限和不同施肥管理梯田为研究对象，利用同步辐射显微CT技术和图像分析技术量化表征团聚体微结构特征，系统分析坡改梯后土壤结构的演变过程，从团聚体微结构可视化和定量化角度，揭示团聚体内部结构的演变机理，建立团聚体稳定性与团聚体孔隙参数的定量关系，探索影响团聚体稳定性的作用机制，为黄土高原土壤质量培育提供理论依据。

土壤团聚体稳定性作为重要的土壤质量指标，影响着土壤水热运移、气体交换及微生物活动，进而影响着土壤抗侵蚀能力、水肥水平。土壤团聚体稳定性受内部几何构造的直接影响，若忽略了团聚体内孔隙特征的差异，则难以区分和判别各类土壤团聚体性状与特征，不利于准确地评价土壤结构的质量水平。因此，本项目利用同步辐射显微CT开展了土壤团聚体三维结构研究，分析了团聚体稳定性与团聚体孔隙参数的关系。研究不同年限梯田对土壤团聚体稳定性、水分特征的影响，发现坡改梯后团聚体稳定性显著增大，且土壤入渗和蓄水能力得到增强。分析了不同年限梯田土壤团聚体孔隙结构特征，发现坡改梯田后，总孔隙度、>100 μm孔隙度、瘦长型孔隙度以及分形维数不断增大，尤其是以>100 μm孔隙为主，而孔隙总数量、<75 μm孔隙度显著减少，土壤孔隙结构变得更加疏松和复杂。通过构建团聚体稳定性和团聚体孔隙参数定量关系，发现孔隙总数量、分形维数、大于100 μm孔隙度、长孔隙度、75-100 μm孔隙度、孔隙总数量对团聚体稳定性起着重要作用。本研究结果可为黄土丘陵区土壤结构演变机制及土壤质量的精准评价提供理论依据。