Study On The Effects Of Artificial Enclosure On The Sandy Grassland Vegetation

Artificial fencing pasture of Yanchi County in Ningxia is located in semi-arid desertification area, grassland vegetation can easily be damaged due to the fragile ecological environment. In this paper, based on vegetation field survey data of artificial fencing area in four kinds of processing methods, and use the theory and methods of ecology, the paper has analyzed the plant community structure, vegetation diversity and the variation of the niche during2008to2012, for grassland restoration have a more in-depth study under artificial enclosure measures, draw the following main conclusions:(1)The result of plant community structure characteristics under four processing methods showed: a large number of plant species and the perennial herbaceous plants in the core area and edge area, the turning area and outside area had less plant species, reflected that taken enclosure for grassland promote the number of plant species on a certain extent; plant relative important value was more balanced distribution in the edge area, it was more favorable for the grassland vegetation restoration; combined with the clustering analysis, the main constructive species of the outside area and edge area were Artemisia ordosica for Krasch and Salsola ruthenica Hjin, Heteropappus altaicus(Willd.) Novopokr. was the constructive species in the core area and new turning area.(2) Vegetation biodiversity index under different processing methods results showed that:it was not a proportional relationship between the grassland vegetation diversity index and fencing time, in the early stages of the investigation (2008), the richness index (Ma) and diversity index (SP, SW) in the core area and new turning area were significantly higher than that of outside area (P<0.05); With the fencing time prolonged, advantage species for expanding and the grass surface crust was thickening in fencing area, plant community was showing signs of deterioration phenomena, In the medium (2010), the richness index and diversity index of new turning area was the highest in the whole, the diversity index (SW) of outside area was significantly higher than that of the core area (P<0.05), in the late(2012), the diversity index was the biggest in the outside area that not to take fencing measures, followed by new turning area, it was small in the core area and edge area, there was no significant difference between each index (P>0.05), showed that long-term fencing could not improve the productivity of grassland vegetation, it should be appropriate grazing or plowing.(3)Vegetation niche breadth and overlap of four kinds of processing methods showed:in the early stages of the investigation, niche breadth of Artemisia ordosica Krasch was larger in the outside area, in the edge area and new turning area was Sophora alopecuroides L., the core area was Heteropappus altaicus (Willd.) Novopokr., Respectively was the dominant specie in these area, the vegetation niche width of the edge area was more even distribution, and higher in ues resources, with time, the species of larger niche breadth become Heteropappus altaicus (Willd.) Novopokr. which was stronger xerophytes in the edge area and turning area, showed that the grassland had a trend that to dry biochemical development; The results of niche overlap showed that the niche breadth didn’t have directly liner relation with niche overlap.