内蒙古科尔沁沙地放牧草地的沙漠化机理研究

Study on Desertification Mechanism of Grazing Grassland in Kerqin Sandy Land in Inner Mongolia, China.

研究结果表明：在半干旱地区，过牧是沙质草地沙漠化（沙质荒漠化）的主要原因之一。（１）由于过牧，植物大部分光合器官被啃食，生长受到抑制，使高度和盖度下降，生产力降低；同时根层变浅，根量减少，生长期缩短，最终导致部分植株死亡，种群数量下降，甚至消亡。（２）过牧情况下，群落植物组成趋于简单，种群密度下降，但均匀度和多样性增加，群落由“持续型”向“恢复型”转变，稳定性低。（３）伴随着地面裸地率的增大和土壤根系结持力的下降，在风力作用下土壤发生风蚀。最初出现风蚀沟，随之形成风蚀斑，严重时形成浅洼地或风蚀坑，并在下风向出现薄层积沙，牲畜的过度践踏使这一过程加速。（４）过牧造成植被的恶化，导致草地承载力和次级生产力下降，如果不及时降低草地的放牧强度。

The results show that heavy grazing is one of improtant factors resulting in sandy grassland desertification (Sandy Desertification) in the semi-arid region. 1) Under the heavy grazing conditions most of the photosynthetic organs are eaten, plant growth is restrained, declining in height, coverage and productivity. Meanwhile the root layer tends to become thinner, root weight decreases and its growth period is shortened. Finally some plants are dead, the population number drops or disappears. 2) Under heavy grazing conditions composition of the plant species in the community tends to get simple and density drops, but even degree and diversity are increased. The communities transforms from “continued type” into “resmued type” and become less stable. 3) The soil erosion happens with both the surface exposed to wind and the decrease of the ability holding soil of the root system: at first small ditch of wind erosion appears. Then it becomes wind erosion spot, and finally shallow lowlying land and blow-off, while sands begin to accumulate in the leeward slope. This process is speeded up by the heavy tread of the stocks. 4) The heavy grazing results in vegetation deterioration so that the bearing capacity of grassland and the second productivity decrease. If the grazing intensity is not reasonable, the soil-grass-animal one another will get into vicious circle.