Study On The Vegetation Change Of Sandy Grassland And The Effect Of Fencing In Yanchi Of Ningxia

Yanchi County of Ningxia Hui autonomous region is located in the northern farming-pastoral region. Its ecological environment is fragile and its grassland is serious sandy. In order to understand the vegetation variation of Yanchi County in the recent ten years, and the influence of fencing on the vegetation, this study took six types of grassland as the object. Meanwhile, with the help of the theory of Restoration Ecology, more in-depth researches were done about the plant species composition,vegetation quantity characteristics,community structure characteristics and the effect of fencing after field investigation. The preliminary conclusions were as following:(1)The vegetation quantity characteristics (coverage,height,community density,biomass)reflected the vegetation growth condition and the grassland productivity. During the 2003—2010 period, the vegetation growth condition in 2003,2004 and 2009 were better and the grassland productivity were also higher. On the contrary, the vegetation growth condition in 2005,2008 were worse and the grassland productivity were also lower; The community structure meant overall community composition level and could be reflected by species diversity,evenness,species richness. The species richness and species diversity in 2007 were highest and the evenness in 2007 was relatively higher, which meant that the community structure of Yanchi County in 2007 was stable. On the contrary, the evenness and species diversity in 2006 were lowest, which meant the community structure was unreasonable.(2)The result of vegetation variation under different rehabilitation measures showed:the rehabilitated fields,abandoned land and nature grassland played important roles. Besides, fencing greatly influenced the species compositon,quantity characteristics,community structure and plant niche. By the analysis of 3 type of fencing sample plots, we can find that the measure of fencing could promote the vegetation restoration in beginning period. But the vegetation became degradation as the fencing time became longer. So, that is not to say that the longer the field is protected, the better the vegetation restores and grows. Much too long fencing time could lead the grassland and the vegetation to drought biochemical development tendency. Therefore, for fencing grassland, proper turning and plowing should be done at the appropriate time to break soil crust and promote infiltration of rainwater. In addition, the area and depth of turning and plowing should be suitable, which were good for the vegetation restoration and could make the soil avoid of being damaged by the wind.(3)Precipitation was the main nature factor that influenced the vegetation. The amount of precipitation strongly restricts the vegetation growth. In addition, unreasonable economic activities seriously destroyed the vegetation. But after the implementation of converting croplands to grasslands and forbidding pasturing, the vegetation coverage increased, the grassland desertification was effectively curbed, and the grassland construction was greatly promoted.