内蒙古典型草原土壤及其水文过程对灌丛化的响应

基于野外观测和室内试验相结合的方法,研究了内蒙古典型草原小叶锦鸡儿灌丛化过程对土壤和土壤水文过程的影响,旨在为干旱半干旱区环境保护和恢复提供理论基础。结果表明,斑块尺度上,灌丛斑块土壤有机质和全氮含量分别是草地斑块的1.54倍和1.16倍;灌丛斑块平均沙粒、粉粒和粘粒含量是草地斑块的0.87倍、1.34倍和1.35倍;灌丛斑块土壤容重是草地斑块的0.97倍;灌丛斑块钙积层上表面出现深度是草地斑块的1.27倍。地形等自然条件也是形成土壤异质性的重要因子,坡面尺度上,灌丛和草地斑块土壤有机质、全氮、土壤容重、土壤钙积层上表面出现深度呈自坡顶向坡下方向增加的趋势。染色示踪实验表明,灌丛斑块土壤剖面湿润锋和土壤水分入渗速率分别是草地斑块的1.36倍和5.16倍,草地斑块0~10cm土层对水分的响应较敏感,而灌丛斑块25 cm以下土层对水分的响应较敏感。研究认为,灌丛化过程增强了土壤空间异质性,灌丛斑块能将土壤水分快速输送并存储于深层土壤中,灌丛斑块是土壤养分和水分富集区,灌木植物的定居和发展过程与土壤形态之间形成了正反馈。

Effects of Thicketization of Rangeland on Soil and Soil Hydrological Processes in Inner Mongolia

Research of shrub encroachment is becoming an important field in the researches of the global change of terrestrial ecosystem, because grasslands have undergone a period of change in community structure and composition in the arid and semiarid regions on the earth. This study investigated effects of encroachment of Caragana microphylla Lam. on soil and soil hydrological processes in grassland of Inner Mongolia, with field observation and laboratory experiment, wishing to provide theoretical foundation for environment protection and restoration in arid and semiarid regions. Results showed that, soil organic matter, total nitrogen, sand content, silt content, clay content, soil bulk density and the position of upper surface of caliches in soil layers under canopies of shrub patches were 1.54, 1.16, 0.87, 1.34, 1.35, 0.97 and 1.27 times of those under canopies of grass patches, respectively. In addition, topography was one of the important natural factors which formed soil spatial heterogeneity. Soil organic matter, total nitrogen, soil bulk density and the position of caliches in soil layers under canopies of shrub and grass patches all had increasing trend from the top position to the lower position at slope scale. Results of dye tracing experiment showed that wetting front on soil profiles and velocity of soil water infiltration in soil layers under canopies of shrub patches were 1.36 and 5.16 times of those under canopies of grass patches, respectively. Soil water was more sensitive at the upper 0-10 cm soil layers under canopies of grass patches, but it was more sensitive at the soil layers below 25 cm under shrub patches. This study suggested that shrub encroachment strengthened soil heterogeneity, soil water under canopies of shrub patches can be rapidly transported to the deeper soil layers, and soil layers under canopies of shrub could capture more soil nutrients and water. There were positive feedbacks between the development and settlement of C. microphylla and soil morphology in the typical steppe in Inner Mongolia.