Effects Of Fenced Grazing Prohibition Project On The Health Status Of Stipa Glareosa Steppe Ecosystem

In order to study the impact of the fenced grazing prohibition project on the health status of Stipa glareosa steppe,the Stipa glareosa steppe fence enclosure area and free grazing area were used as experimental areas to analyze the changes of grassland vegetation characteristics and soil physical and chemical properties under enclosure.The changes were screened for grassland health evaluation indicators.The CVOR comprehensive index evaluation method and principal component analysis method were used to evaluate the health status of Stipa glareosa steppe in the fenced enclosure.The results are as follows:1.The fenced grazing prohibition project has a certain recovery effect on the families,genera and species in the community.The number of species is increased,which is the largest increase.Short-term enclosured(1 to 3 years)can promote the increase of perennial herbs,and the enclosing time is too long(4 to 9 years),which is not conducive to the continued recovery of perennial herbs.Enclosure has increased the number of bud plants on the ground in shrubs for many years,which has increased the shrubization of grassland.The density of the community showed a phenomenon of increasing first and then decreasing,and increasing at the later stage(5-8 years),reaching the peak in the 8th year(2017).The annual plants and shrubs and shrubs were the main functional groups that affected the changes of plant community density.And leguminous is the main family that affects the change of plant community density.2.The fenced grazing prohibition project significantly increased the above-ground biomass of the community,and three peaks appeared in the enclosure for 9 years.Annual plants and perennial grasses are the main functional groups that affect plant biomass changes.Chenopodiaceae and Compositae are the main families affecting the biomass change of the total land.The long-term enclosure is conducive to the increase in the biomass of Chenopodiaceae(biennial plants)and Leguminosae(shrubs).The enclosure of a certain number of years(1 to 5 years)is conducive to the increase and maintenance of the cluster grass dominated by Stipa glareosa,but a long envelope is not conducive to the increase of the cluster grass.3.The important values of the main population have different responses to the grazing prohibition: short-term enclosure has a certain promoting effect on scallions and asparagus.Long-term enclosure is not conducive to its increase and maintenance;enclosure is conducive to the absence of awns Increased;sand burial caused by years of enclosure will affect the germination and emergence of Stipa glareosa,causing a serious decline in Stipa glareosa.4.The enclosure is conducive to the increase of the community uniformity index;the enclosure of a certain number of years is conducive to the increase of the diversity index and the richness index,and the long enclosure period is not conducive to the increase of the diversity index and the richness index.5.Fence enclosure reduced the bulk density of 0~10 cm surface soil and the soil water content of 0~30 cm soil layer.The soil bulk density and soil water content in the enclosed area increased with the deepening of the soil layer.6.Enclosure reduced the soil organic matter and total nitrogen content.The soil organic matter and total nitrogen in the 0~30 cm soil layer showed an increasing trend with the deepening of the soil layer;in the soil layer of 10~30 cm depth,the soil total nitrogen content in the enclosed area significantly lower than the grazing area.In different enclosure years,soil organic matter and total nitrogen content showed a trend of 4 years of enclosure>1 year of enclosure>not enclosed>6 years of enclosure>9 years of enclosure.The 1-4 years of closure is more conducive to its recovery.7.Enclosure increased the content of total phosphorus,available nitrogen,available phosphorus and available potassium in soil,and significantly increased the available phosphorus in 10~30cm soil and available potassium in 20~30cm soil.The soil available phosphorus and available potassium increased with soil depth decreasing,showing the phenomenon of surface aggregation.The soil available nitrogen and total phosphorus content are both increasing with the deepening of the soil layer.In different enclosure years,the total phosphorus content of the soil showed a trend of 4 years of enclosure >1 year of enclosure >6 years of enclosure >9 years of enclosure >unenclosed.The 1-4 years of closure is more conducive to its recovery.8.The amount of sand accumulated in the fence increased by 1.75 cm per year on the 5th to 9th year of enclosing.The annual increase in the amount of sediment in the fence affects the germination of ground bud plants such as Stipa glareosa,which results in a significant reduction in Stipa glareosa in the enclosure.At the same time,the increase in sand accumulation changes the soil compaction,resulting in a significantly higher rat hole density in the fence than outside the fence.For many years,with the increase of sand thickness and rat hole density,it has a certain negative impact on ecosystem health.9.Using CVOR comprehensive index model and principal component analysis method to evaluate the health of Stipa glareosa grassland under fenced enclosure,the results showed that the comprehensive health index of each enclosure was higher than free grazing,surrounded by 6 years> enclosure 9 years> Free grazing.It is indicated that the enclosing of 6 years is conducive to the healthy restoration of grassland.The long enclosure period is not conducive to the health of the grassland ecosystem.The long-term enclosure will have a negative impact on the restoration of degraded grassland.The occurrence of protective deterioration occurs.