Effects Of Enclosing Spring-autumn Grassland On Features Of Vegetation And Soil At Zhaosu Horse Ranch

Natural grassland is seriously degraded in XinJiang and enclosure of grassland is widely used for protection and restoration as it is an effective method. Using the approach of spatial sequence replacing temporal sequence, we studied the characteristics of plant communities, populations, physical characteristics and chemical properties of soil and soil seed bank in Zhaosu horse ranch through field investigations and laboratory analysis. The results showed:1,Vegetation coverage increase gradually with the restoration of the enclosed natural grassland, biomass of the 5a enclosing is 770.24 g/m2, it's 1.03,1.35,and 4.36 times than enclosed 6a,1a and unenclosed grassland respectively. Species richness and diversity index show an upward trend, but species evenness index shows reveres variation. Enclosing impel the growth of grass, inhibit forbs and chenopodiaceae plants. Aboveground biomass changes as the "S" curve of growth with the season change in 6a,5a,1a enclosed grasslands, peak of aboveground biomass appear in mid-July, biomass accumulation of unenclosed grassland changes as bimodal curve, two peak values appear in Early-June and mid-August. The percentage of grass is the largest, and the proportion of leguminosae forages is the least in all enclosing grasslands. The forbs are dominant in unenclosed grassland. AGR and RGR of Community aboveground biomass appear the similar trend with seasonal changes. Belowground biomass increase gradually with prolongation of enclosing, and distribution of belowground biomass gradually extend to the deep soil.2,Distribution of population patterns is stable relatively, only Phlomis pratensis and Medicago falcata present random distribution with the restoration of the enclosed natural grassland, other species appear clusters distribution, Most of the population's aggregation intensity shows decreased first and then increased, unenclosed grassland has largest population's aggregation intensity .3,Overall interspecific association is faint in community of 6a,5a enclosed grassland, interspecific association is relative loosely. slightly negative correlation exist in 1a enclosed and unenclosed grassland community. There is neutral association between dominant species and other species, association between forbs and all species association is significant.4,Soil bulk density decreased, soil porosity is gradually increasing with prolongation of enclosure, soil organic matter increased and change significantly, soil available nutrients reduced gradually, total nutrient increasing slowly with the restoration of grassland. Activity of urease gradually increased, and catalase activity is the highest in unenclosed grassland. 5,Species density of soil seed bank increases gradually with prolongation of enclosing, especially the increased density of grass and legumes forages seed weeds are significant, but the proportion of forbs gradually declining. Seed of sedges and grass only exist on soil surface. Soil seed bank and aboveground vegetation has similarity of species composition, and changes trend of similarity follows"increase- decrease-increase"trend.