Effect Of Different Enclosure On Vegetation And Soil In Xilamuren Desert Steppe

To investigate the effects of fenced enclosure on grassland health situation in Xilamuren desert grassland.We divided different plots of treatments into three types:year-round exclusion,seasonal exclusion and non-exclusion,which has the same soil type,topography and hydrothermal conditions.The changes of vegetation characteristics and soil properties under different sealing measures were studied by combining field investigation sampling and laboratory experiments,and the principal component analysis were used.The comprehensive evaluation method was applied to analyze and evaluate the 10 grass indexes and 18 soil indexes of 0-30 cm soil layer.Our results showed that:(1)By investigating three kinds of plots,there were 33 species of plants in 19 families,including 7 Gramineae,4 Leguminosae,3 Quinoa and 2 Compositae,accounting for 48.49% of the total plants.The succession sequence of the dominant species was Artemisia frigida + Heteropappus altaicus + Stipa grandis + Leymus chinensis ? Leymus chinensis + Stipa grandis + Convolvulus ammannii ? Stipa grandis+ Leymus chinensis + Agropyron cristarum + Cleistogenes squarrosa.The perennial herb accounts for 78.79% of the plots.Compared with unenclosed grassland,the important value of forage grass in the enclosure area increased significantly.(2)The year-round exclusion increased vegetation height,coverage,density,aboveground biomass,litter biomass and Margalef species richness.The Shannon-Wiener index,Simpson index and Pielou index all showed unenclosed grassland,seasonal pasture and fully enclosed grassland.The similarity coefficient between different communities was distributed within the range of 0.4-0.6,indicating that the similarity of communities was low.The Euclidean distance from three plots to stable points is 19-30,indicating that the community structure of desert steppe is not stable.(3)After the implementation of enclosure measures,it is conducive to the accumulation of fine particles.The fractal dimension of soil particles ranged from large to small,followed by year-round exclusion grassland(2.36),seasonal exclusion grassland(2.33),and non-exclusion grassland(2.16),and the soil gradually coarsened.The frequency distribution curve shows that the average distance between the three plots is the highest at 200 um.The average soil moisture content of 0-30 cm soil is: seasonal exclusion > year-round exclusion > non-exclusion,different sealing measures havesignificant influence on soil bulk density of each soil layer of 0-30cm(P<0.05).The size of soil porosity in 0-30 cm was in order of complete pasture,seasonal pasture and unsealed grassland,and the total soil porosity of each soil layer showed a different trend and significant difference(P<0.05).(4)The content of soil organic matter,total nitrogen,alkali hydrolysable nitrogen and available phosphorus were the highest in the complete pasture,while the content of total phosphorus,total potassium and available potassium were in seasonal exclusion >year-round exclusion > non-exclusion,and the main source of phosphorus and potassium and livestock excrement,and moderate grazing.A large amount of phosphorus and potassium is returned to the grassland.On the soil profile,all kinds of nutrient contents decreased with the increase of soil depth.(5)The scoring sequence of different meadows was year-round exclusion > seasonal exclusion > non-exclusion.