The Study On Vegetation Characteristics Of Artificial Cultivating Arear In Yanchi Of Ningxia

The of Yanchi Cpunty, Ningxia, is located in the semi-arid desertifaction region, the vegetation of grassland is easy to be damaged, because of the fragile ecological environment. In order to analyze the structure and variation of plant communities in the research area, samples of the plant population were recorded according to species, abundance, coverage, height, and biomass. They were analyzed in respect to diversity indices, principal component analysis and polar ordination, and we analyzed the surface crust by infiltration experiments.The results showed that:(1) The number of species of sample area E2 was the lowest, and the dominant position of species in the genera (leguminosae and compositae) in all kinds of sample areas were gradually weakened. The diversity index, and evenness index of E2 was the lowest, and the advantage of concentration index was the highest. In all sample areas, the diversity index was significantly correlated with the evenness index and the richness index. In the applying binary of β diversity, Cody index(βC), as well as βCJ and βcs derived from Jaccard and Sorenson similarity indexes(Cj and Cs), were able to reflect the community changes as the time gradient. In the numerical data measure, with the relative coverage and importance value as an index to measure, the result was more reasonable.(2) The results of principal component analysis showed that the main environmental factors affecting the plant communities in the artificial cultivating area was soil moisture content at the depths of 20～30cm. The figures of polar ordination showed that the quadrats forming sample E were the most similar, for the time of cultivating was so long and there was no human disturbance.(3) The stability ratio of each sample plots were 37.82/62.18,36.46/63.54,35.75/64.25 and 38.12/61.88, which indicated that the vegetation of artificial cultivating area in Yanchi was not stable, but the method of cultivating can availably improve the stability of vegetation community.(4) In the artifaical cultibating area of Liuyangbu, the coverage of soil crust has a significant negative correlation with vegetation coverage and infiltration depth. The crust hindered the recovery of vegetation, so the time of cultivating should not be too long. From the rate of change in biodiversity of the sample plot which was loughing again, the best time of cultivating in Yanchi was 3 to 5 years. Closed after 3-5 years should be allowed appropriate grazing and human disturbance.