The Researches Of Cutting Methods On Plant Community Succession Of Grassland

Cutting grass is one of the main uses of grassland resources. The research of mowing system has always been the main areas concerned with grassland resource management, some basic conclusions are reached. They are based on the continuous mowing experiment in the the Xilinhot for11years. Come to the following:1After Leymus chinensis steppe is treated by cutting grass, and under cutting two years and off-year for mowing, the community species composition has been reduced in the levels of families, genera and species. But under cutting a year and off-year, the community species composition has been less volatile. Basically, there are no significant differences with the original. So the processing mode of cutting a year and off-year affect meadows less.2Leymus chinensis community density have decline prodigiously under the mowing processing. Under cutting years off-year mowing system, from the viewpoint of density, the cardinal number of the grass family density is the biggest. Its variety dominates the trend of the total density directly. From the viewpoint of a different type of life and moisture ecotypes, perennial rhizomatous grass and the mesophytes play a leading role. Their total density change is the same as their changes. Under cutting a year off-year, the grass family density changes gently. First decreased and then tended to be stable, while the Liliaceae, Chenopodiaceae and the Compositae densities fluctuations. Different type of life and water ecological plant density change are affected by the constraints of perennial rhizomatous grasses and the mesophytes density change mainly.3The grassland plant communities biomass declines due to mowing treatments. In different cutting system, population biomass has different degrees varieties. But in general, we can be summarized in the following types:①Decreasing type. Leymus chinensis, Carex korshinskyi and Caragana microphylia belong to the category. In particular, the decreasing range of L. chinensis biomass is high. Because mowing can inhibit shrubs growth, it can result in decreasing the biomass of Caragana microphylla.②Increasing type. Some plants belong to this type, for example, Koeleria glauca and Agropyron cristatum, and so on. Koeleria glauca biomass increases obviously.③Volatile type. There is Artemisia scoparia Waldst.EtKit、Artemisia commutate and Salsola collina Pall. to belong to this type. Annual and biennial plants like those have large fluctuations. They are very unstable in the community.④Relatively stable. Some plants belong to this type, for instance. Stipa grandis, Cleitogenes squarrosa and so on. These plants are affected small by mowing. Their biomass has little change.4On the important value, especially, the important value of Leymus chinensis that is the main of grassland has the volatility decline under cutting years of-year deal. But the important value of that is relatively gentle decline under cutting a year off-year treatment. The Carex important value is was maintained at a certain stable level. But due to off-cut for two years in the1999-2000, there is upward trend. Koeleria glauca important value increases obviously. Stipa grandis value is first increased and then decreased, and then decreased to the original level, but the declining range is small under the two treatments.5In short, the grassland community density and biomass are more substantial decline after mowing the grass. The proportion of good herbage reduce and the proportion of weeds increased. In particular, there is a greater impact on mowing system by cut two years and taken a year.