Effects Of Enclosure Management On The Structure Of Standing Vegetation And Soil Seed Bank In Southwest Maowusu Sand Area

There are nearly 400 million hm~2 of meadows in China, among them 90% have already degraded or are degrading. And approx. 84.4% of the meadows are distributed in the western regions of China. The main reason why the western meadows degrade is overgrazing by livestock. This makes it very urgent to protect, harness and improve the meadows. Enclosure is one of effective measures to recover vegetation. Therefore this paper took the enclosed meadow and grazed meadow in southwest Maowusu sand area in the north west of China, as the research object. Ecological principles and methods are used to study the characteristics of the standing vegetation, the characteristics of the seed bank of soil, and the relationship between these two for enclosed and grazed meadows through field investigations and indoor tests. From this research, we obtain the following conclusions:(1) 20 species vegetables among 7 families of standing vegetation are founded in enclosed meadows. Whilst in grazed meadows, there are only 13 species among 5 families counted. Plant species in enclosed meadows are higher than that in grazed meadows by 54%. The average density of plants is 51.6 establish plants/m~2 in enclosed meadows, 34.23 establish plants/m~2 in grazed meadows. Since the differences in properties of plants and the habit of livestock, the 5 most frequent plants in enclosed meadows are: Setaria viridis, Leymus secalinus, Artemisia ordosica Krasch, Stipa breviflora and Chee reedgrass; the 5 most frequent plants in grazed meadows are: Artemisia ordosica Krasch, Leymus secalinus, Setaria viridis, Sophora alopecuroides and Cynanchum thesioides. Grazing reduces the uniformity of meadows, and then influences the richness and bio-diversity of community. This makes the bio-diversity in grazed meadows lower than that in enclosed meadows. Enclosed meadows have 0.46 time higher bio-mass than grazed meadows. All the characteristics addressed above indicate that there is a big difference existed between enclosed and grazed meadows and this difference exhibit a medium dissimilarity. And these differences prove that enclosure is one of the most effective methods to recover vegetation.(2) Through sprout experiment for soil seed bank, 6 species' seeds spout for enclosed meadows, while only 3 species' seeds spout for grazed meadows. The seed density of soil seed bank is 623 grains/m~2 in enclosed meadows, the seed density of. soil seed bank is 438 grains/m~2 in grazed meadows, The seed density of soil seed bank in enclosed meadows are higher than that of grazed meadows.The seeds of soil seed...