不同放牧强度下短花针茅荒漠草原沙尘释放和土壤养分损失过程研究

Desert steppe is the important livestock husbandry base and “green ecological defense” of arid region, it frequently suffers from wind erosion and sandstorms influenced by natural conditions and grazing intensities. Especially, the dust emission and soil nutrient loss are the major reasons that led to grassland desertification and sandstorm, which are induced by over grazing. How does the grazing intensities affect the process of sand dust emission and the soil nutrient loss in desert steppe? It is not clear because the lack of profound research. The Stipa breviflora desert steppe of Siziwang Banner in Inner Mongolia as the research area, using combining method of field position measurement and indoor wind tunnel simulation, the study focuses on the changes in surface properties of vegetation and soil, and on the process of the sand-dust emission and the soil nutrients loss caused by the different grazing intensities to clarify their temporal and spatial variation rules. The research reveals the influence and driving function of the surface properties’ change caused by grazing intensity on the process of the sand-dust emission, and the study further clarify the coupling relationship among grazing intensity – surface properties – dust emission, and determine the key influencing factors of dust emission and set up model to quantitative calculate the amount of sand-dust emission and soil nutrient loss. It has important theory meanings in the effect of surface coverage and soil properties variation on the process of sand-dust emission and nutrients loss. Therefore it can provides scientific basis for the field of blown-sand activity and nutrient redistribution, and for wind erosion and dust suppression controlling and combating desertification.

荒漠草原是干旱区重要的畜牧业基地和生态屏障，受自然条件和人类活动（特别是过牧）的影响，土壤风蚀和沙尘暴频发。过度放牧诱发的沙尘释放和土壤养分损失是导致草原沙漠化和沙尘暴等环境问题的重要原因，但对荒漠草原沙尘释放与土壤养分损失过程及其影响机制的研究并未受到重视。.本研究以内蒙古四子王旗短花针茅荒漠草原为研究对象，采用野外定位观测与室内风洞模拟相结合的方法，观测不同放牧强度荒漠草原植被、土壤等地表属性的变化，研究沙尘释放及土壤养分损失过程，探究其时空变化规律；并揭示不同放牧强度导致的地表属性因子变化对沙尘释放过程的影响及驱动作用；阐明放牧强度－地表属性－沙尘释放的耦合关系，筛选沙尘释放量的关键影响因子并建模，定量估算沙尘释放量及土壤养分损失量。研究对揭示地表覆盖与土壤特性变化对沙尘释放与养分损失过程的影响具重要理论意义，为荒漠草原研究风沙活动与土壤养分再分配、控蚀抑尘及沙漠化防治提供科学依据。

过度放牧是造成荒漠草原沙尘释放与土壤养分损失过程的驱动因素之一，但其作用机制还不十分清楚。本研究以内蒙古四子王旗和苏尼特右旗短花针茅荒漠草原为研究对象，研究了不同放牧强度下地表属性、沙尘释放与土壤养分损失过程的时空变化、影响因素、驱动作用与模型构建。结果表明：（1）随放牧强度增加，植被高度、盖度、密度下降，多年生杂类草和一、二年生杂草数量增加，生物量与多样性指数呈先增大后降低趋势；植被盖度低值区空间上主要分布在饮水点、沙化明显地段、牧道与道路处。（2）不同放牧强度下土壤粒径组成以砂粒、粉粒为主，土壤理化性质、分形维数变化各异，具有中等强度空间自相关性，轻度放牧利于改善土壤理化性质。（3）放牧强度、土壤理化性质显著影响土壤可蚀性K值，K值基本上随放牧强度增大而增大，LG与CK的K值最低，K值与放牧强度（Gi）符合K=0.006Gi+0.021，与粉粒体积分数和有机碳含量符合K=0.012+0.001Vsilt+0.005C。（4）揭示了沙尘释放阈值、土壤风蚀强度、风蚀率随放牧强度、地表结皮扰动、植被盖度、土壤含水量的变化及其贡献率，明确了各因子驱动下的风速阈值范围为5.6-8.7m/s，构建了起动风速与影响因子的数量化方程。（5）不同放牧强度水平输沙通量、土壤蚀积表现为春季最强、秋季最小、随放牧强度增大而增强的时空变化特征，植被盖度、高度是影响春季地表蚀积的主要驱动因素，而植被高度、土壤含水量、放牧强度则是夏季地表蚀积空间变异的主要影响因子，放牧强度通过与植被、土壤等因子的交互作用影响沙尘释放。（6）不同放牧强度下风沙流沉积物粒径以粗砂、细砂、极细砂和粉砂为主，粒径组成随放牧强度和垂直高度增加由粗变细，风沙流输移损失的C、N含量随放牧强度与高度的增加而增大。研究对解析荒漠草原沙尘释放与养分损失过程及机制具有重要理论意义，可为荒漠草原放牧制度的制定、控蚀抑尘提供科学依据。