放牧强度季节调控对荒漠草原土壤风蚀的影响

由超载过牧导致的草地退化是土壤沙化的重要来源,放牧导致的草地风蚀加剧和草地沙化现象已经引起人们的普遍关注。以短花针茅荒漠草原为研究对象,采用完全随机区组设计设置6个放牧处理,对不同放牧处理下草地枯落物生物量、冬春季集沙量及土壤表层粒径等进行研究。结果表明:1)冬春季草地保存枯落物生物量越多,草地的固沙能力越强,适度放牧草地流沙量比重度放牧降低了45.16%;2)随着放牧强度的增大,草地不同粒径流沙量绝对值明显增加,>0.25 mm和<0.05 mm粒径沙粒的比例在重度放牧下较不放牧和轻度放牧高,0.25~0.10 mm粒径沙粒在重度放牧下最低;3)秋季重度放牧能增加草地流沙量,因此荒漠草原放牧利用在秋季应降低载畜率。所以,草地不合理的放牧利用降低了草地防风固沙能力,导致地表粗粒化,荒漠草原冬春季保持不少于32.93 g·m^-2的枯落物,能显著降低草地风蚀,起到很好的固沙作用。

Effects of seasonal regulation of grazing intensity on soil erosion in desert steppe grassland

Overgrazing is an important cause of grassland degradation and desertification affecting large land areas. The aim of this project was to investigate the effects on soil erosion of seasonal regulation of grazing intensity. Litter biomass, sand collection in winter and spring and the particle size of the soil surface layer were evaluated under six grazing intensity treatments in Stipa breviflora desert steppe in a randomized complete block design. It was found that: 1) The more that litter biomass was preserved in winter and spring, the stronger the sand-fixation ability of the grassland, and the proportion of ‘flow sand' under moderate grazing intensity (45.16%), which was lower than that of heavy grazing. 2) With increase in grazing intensity, the amount of loose sand of various particle sizes increased significantly. Severe grazing increased the proportion of particles of size >0.25 mm and <0.05 mm, compared to that of ungrazed or lightly grazed treatments, while the proportion of particles sized 0.25-0.10 mm was lowest under severe grazing. 3) Heavy grazing in autumn increased the amount of loose sand in grassland. Therefore grazing practice in desert grassland should be to reduce stocking rate in autumn. Based on these results, it was concluded that unreasonable grazing utilization of grassland reduces the windbreak and sand fixation capacity of the vegetation, resulting in surface roughening. In the desert steppe, maintenance of no less than 32.93 g·m^-2 litter in winter and spring was conducive to reducing wind erosion.