内蒙古中部荒漠草原微斑块发育与土壤优先流响应机制

Grassland of central Inner Mongolia is considered as temperate desert steppe, which is a special type of transition from typical steppe to desert. It also in the transition zone of the agricultural area to the pastoral area. The land is seriously desertified, and the biological crust, bare ground and vegetation patches are arranged in the landscape, During the wind season, the weather of floating happens frequently while the soil is eroded and the sediment is transported during the rainy days. The research area is located in the transition zone between agricultural and pasture areas in the north foot region of Yinshan Mountain. The species, area and diversity character of vegetation in desert steppe are studied from the site and slope scale by field observation. The study reveals the formation mechanism of micro plaque under three conditions (grazing, tourism activity and enclosure) and the relationship between micro patch and grassland degradation and desertification. The infiltration experiment in different water gradient combined with the heterogeneity of soil mechanical composition, bulk density and porosity in different habitat patches is set out to study the chestnut soil infiltration process and its main factors. The runoff processes of different patches are measured, and the coupling mechanism of the occurrence and distribution of soil preferential flow is explored. The study clarifies the interaction mechanism between degradation degree of micro plaque and soil preferential flow on the composite forces under the drive of wind and water, reveals the water process of grassland desertification and enriches the theory of soil erosion in desert steppe.

内蒙古中部草原为温性荒漠草原，是典型草原向荒漠过渡的一种特殊类型，处于农区向牧区的过渡地带，土地沙化严重，景观上呈现生物结皮、裸地斑块、植被斑块镶嵌分布，形成风季起沙扬尘，雨期侵蚀产沙的恶化局面。项目选择内蒙古中部阴山北麓农牧交错带的荒漠草原地区，通过野外原位监测试验、从样地、坡面尺度上研究荒漠草原植被微斑块种类、面积、多样性格局，揭示放牧、旅游活动和围封三种条件下微斑块形成机制，研究微斑块与草原退化、沙化的关系；设计不同水分梯度的入渗试验结合不同斑块生境的土壤机械组成、容重、孔隙度等异质性，研究薄层栗钙土入渗过程及主要因素；测定不同斑块坡面径流过程，结合土柱模拟实验，探索土壤优先流发生、分布耦合机制。阐明风水复合外营力驱动下，内蒙古中部荒漠草原不同退化程度微斑块与土壤优先流相互作用机制，揭示“草原荒漠化”的水分过程，丰富和完善荒漠草原土壤侵蚀理论。

为阐明风水复合外营力驱动下，内蒙古中部荒漠草原不同退化程度微斑块与土壤优先流相互作用机制，揭示“草原荒漠化”的水分过程，丰富和完善荒漠草原土壤侵蚀理论。 本研究选取内蒙古中部希拉穆仁荒漠草原为研究对象，通过野外原位监测试验、从样地、坡面尺度上研究荒漠草原植被微斑块种类、面积、多样性格局，揭示放牧、季节放牧和围封三种条件下微斑块形成机制，研究微斑块与草原退化、 沙化的关系；设计不同水分梯度的入渗试验结合不同斑块生境的土壤机械组成、容重、孔隙度等异质性，研究薄层栗钙土入渗过程及主要因素；探索土壤优先流发生、分布耦合机制。研究结果表明：围封区到自由放牧区的各类草地微斑块最大斑块占比逐渐下降，本底斑块特征逐渐减弱，根据景观指数分析，围封区各类斑块相互交错性最高，其次是自由放牧区，半围封区最弱。在各类草地微斑块中，以冷蒿为优势种的草地微斑块邻近斑块类型最多，表明在斑块边缘交错影响最大的地方，草场出现明显退化。土壤理化性质和植物根系特征均与土壤入渗速率存在明显的相关性，其中土壤容重和植物根系体积与土壤入渗速率相关性最强。土壤容重是影响土壤入渗速率的最直接的因素，其它影响因子均通过改变土壤容重间接影响土壤入渗速率，霍顿模型最适合描述研究区土壤入渗速率随时间变化情况。相比于自由放牧和冬季放牧草地，禁牧草地中更发达的土壤孔隙系统能有效地增加水分和养分的优先输送，这对干旱半干旱地区深层土壤水分的补充和植被的维持具有重要意义。