The Effect Of Different Original State On Community Restoration Succession Of Typical Steppe

The steppe of xilinggol is one of four biggest grasslands in China, and it is the typical representative of the Semi-arid grasslands in Asia. Aiming to answer whether the previous bottom of degradation of grassland communities has effect on the recovery of grassland communities, and in which kind it casts its effect, the research is done on vegetation which experience six years non-grazing recovery after different degree degradation under different grazing rates. The experimental research point locates in the middle reaches of Xilin River in Inner Mongolia, grassland ecosystem research station of Chinese Academy of Sciences in Inner Mongolia, which is500meters to the west of the grassland ecosystem research station of Chinese Academy of Sciences in Inner Mongolia. The geographic coordinates is43°37’-43°38’N,116°40’-116°41’E.Here is the general situation of the sample land:The grazing experiment on the research point started in the summer of1989. Before the experiment, the sample plot is the degradation grassland which is Artemisia frigida and small grasses dominated, and the experimental animal is sheep. There are six processing, including five different stocking rate(1.33、2.67、4.00、5.33、6.67sheep/hm2) and non-grazing rate(control). Having grazed for16years under different grazing rates by2005, the structure and function of the ecological system (Plant community, soil physical and chemical properties) have experienced significant changes. Grassland ecological systems are in different degree of degradation. In order to discuss the recovery process of grassland ecological system in different degree of degradation after "suspending grazing", the grazing experiment has stopped since2005. The grassland ecological systems have recovered for6years in the natural state by2011. The investigation and sampling on the field are conducted in August,2011.In recent years, influenced by the high strength utilization and adverse natural factors, most majority of Inner Mongolia Steppe is in the state of degradation. In order to fulfill the recovery of the degraded grassland, the research is done on typical steppe of Baiyinxile ranch in xilinggol. The author has analyzed a series of indicators about the grassland of different communities state (each after six years natural recovery), which include plant community composition, aboveground biomass, plant height, internode length, main species leaf length and width, soil compactness, soil bulk density, soil nutrient and soil micro-morphological features. The findings suggest that:1) After six years non-grazed recovery, the communities of different stocking rate have changed in their community type and the dominant species of communities tended to be consistent. But there are a group of differences in association level—the dominant species are different in mild advantage synusia.2) The start states of succession have no significant effect on above biomass recovery when the stocking rate is less than5.33sheep/hm2, however, if the stocking rate is more than5.33sheep/hm2, the start states of succession lead to the current biomass decreased. In other words, it delays the recovery of grassland.3) Plant individual characteristics of different grazing rates community tend to be consistent after six years natural recovery,"Individual miniaturization" phenomenon has disappeared. At the same time, it also shows that even though the starting point of the community recovery succession is different, the time of normalization is almost the same. But compare with the similar grassland which growing in chestnut soil, the normalization rate increase, the reason perhaps is that the stability of compactness layer in sand soil inferior to compactness layer in chestnut soil.4) After six years recovery, the soil compactness and bulk density of different grazing rates community did not fully recovered, but tend to be consistent.5) Soil organic matter and rapid available phosphorus of different stocking rate have no obvious differences in each soil layer, especially in the surface layer, It shows that after six years recovery, soil organic matter and rapid available phosphorus of different grazing rates community tend to be consistent. In another word, different original state of grassland community has no effect on the two nutrient index (soil organic matter and rapid available phosphorus).6) After six years recovery, to see from soil porosity and soil aggregate structure, different plots of grazing rates tend to be consistent. Compare with the plot of nature grazing, the plots of different grazing rates show the effect of recovery. Soil aggregate structure and physical clay content increased; Compare with the non-grazing plot, however, soil aggregate structure and physical clay content is less, it shows that soil had been restored, but did not fully recovered, this is consistent with the study of soil compactness and bulk density.