Analysis On Spatial Characteristics Of Vegetation Coverage And Its Environmental Factors In Keriya Oasis

Water resources has high strength throughout all contradictions in arid area,water and salt imbalance under the high intensity of water and land resources development has become a key factor caused by the change of landscape pattern of oasis in arid area,which caused soil secondary salinization of the oasis,Land desertification and the reduction of biodiversity and other issues,these problems make oasis ecological environment more fragile,more serious contradictory between human and water,oasis ecological security threatened.Water and salt as the most basic ecological environment factor,which have shown a certain heterogeneity in time and space,this habitat heterogeneity comprehensively influence vegetation from quantitative to qualitative change,so that oasis vegetation showing a certain spatial characteristics.It is the key scientific problem to solve the stable development of oasis to analyze the relationship between the spatial characteristics of oasis vegetation and its environmental factors under the influence of existing water and salt.Therefore this paper selects the indicative factor-vegetation coverage,which is the most sensitive to the change of terrestrial ecosystem,and explores the spatial distribution pattern,spatial fractal structure,spatial autocorrelation and spatiotemporal variation of vegetation coverage under the existing water and salt conditions by means of remote sensing and GIS from1996 to 2016,and the selection of water,soil,topography,climate and land from the natural and human two subsystems A total of 11 environmental variables were used to analyze the spatial coupling relationship between its spatial characteristics and the environmental factors.Finally,principal component analysis and geo-weighted regression were used to analyze the dominant environmental factors and the Spatial Heterogeneity of dominant Environmental Factors.The conclusions are as follows:I The vegetation coverage generally showed that the core area of oasis was higher than that of oasis in Keriya Oasis,and the spatial difference was obvious.The Moran I index of vegetation coverage was above 0.5 in five periods,which was positively correlated with space.The spatial clustering effect was the highest in 2000,followed by 2006 and 1996,followed by 2016,Compared to the weakest in 2011.II From 1996 to 2016,the spatial form of the whole vegetation cover is from a complex to simple to complex in Keriya Oasis,and the spatial structure is from unstable to steady to unstable,Which is a dynamic process.the vegetation coverage increased wholely in the past 20 years,and the local area was slightly reduced.The increase was mainly agricultural region,Vegetation coverage reduced significantly is mainly Surrounding land of buildings.The change of the area ratio of vegetation cover types in the grid shows that the area change of the conjunctive sites of each vegetation cover is vigorous,and the "edge effect" is obvious,and present the "medium to high,low to medium,very low to low,Non-polar to very low " trend.III In the environmental factors that affect the spatial differentiation of vegetation cover in Keriya Oasis,the groundwater depth,groundwater salinity,surface water distance,surface temperature,soil salinity and vegetation coverage were negatively correlated,soil water content was positively correlated,The results show that almost all vegetation cover types show the east and west slope> slope> north slope> south slope.The range of influence of distance from road distance on vegetation coverage is limited,and the density of irrigation channel mainly affects the vegetation coverage of agricultural area.IV The results of Spearman rank correlation analysis showed that the vegetation coverage was not positively correlated with the soil water content,and the correlation was not significant.The correlation between the coverage and the other salt groups except HCO3-ion And negatively correlated with Cl-,SO42-,K+ in 20-40 cm soil layer,and negatively correlated with conductivity and Na+ ions in 40-60 cm soil layer,and in 60-80 cm soil layer And negatively correlated with Cl-and Na+ ions,and negatively correlated with Cl-ions in 80-100 cm soil layer.There was a significant positive correlation with HCO3-in soil surface and 20-40 cm soil layer.But the correlation was not significant.The effects of soil physical and chemical properties on vegetation are mainly salt stress,especially the sulfate,carbonate and sodium chloride of 20-60 cm soil layer are more harmful to vegetation.V The results of principal component analysis show that the temperature,aspect,distance from the highway,distance from surface water and salinity of groundwater are the most important ecological factors that affect the spatial differentiation of vegetation cover.The results of geo-weighted regression show that the temperature,irrigation-soil water and temperature-groundwater salinity are most affected by vegetation coverage in all explanatory variables,and the distance from the road,the distance from the surface water,and the slope and vegetation coverage The correlation is relatively low.