An Assessment on Basin Ecological Security and Its Variation Characteristics in Factors Based on GIS Technique and Geometric Mean Model——A Case in Nebula Lake Basin

LI Yimin;ZHU Jun;YU Yanhong;Department of Environment and Resources,Yunnan Institute of Geography,Yunnan University;Key Laboratory of Pollution Process and Management of Lake Basin in Yunnan Province;

geometric mean model;;GIS technique;;ecological security pattern;;spatial differentiation;;Xingyun Lake Basin

The 10 factors includes elevation,slope,soil erosion intensity,prone to geological disasters,land use types,vegetation coverage,distance from the natural ecological protection zone,the distance of construction land,population density and the distance from the water were selected to evaluate the ecological security of Nebula Lake Basin.The spatial distribution and formation mechanism of regional ecological security was analyzed by using the geometric mean model and 3Stechnology tentatively.The study showed that the average ecological security index was 2.33 in Nebula Lake basin.From the aspect of area proportion of all security levels,the area of moderate security zone accounted for 42.34%,high security for 22.84%,the low security for 26.43%,the unsafe for 8.39% of the total basin area,which illustrated that ecological security was mainly moderate security in the basin;from spatial distribution aspect,the zone of higher ecological security mainly distributed in the northern,eastern and southern and built-up zones in Nebula Lake basin where the slope gradients of land are great,terrain was undulated,the forest landscape was fragemental,land use wasnot reasonable,soil erosion was severe,and geological disasters has happened except that the city building intensive area was disturbed by the human,these regiions are the key areas of ecological protection and construction;there is a big difference between the two results that the regional ecological security is affected by multiple factors,single factor evaluation is difficult to accurately reflect the characteristics and mechanism of spatial differentiation of the regional ecological security through the comparison and analysis between the results of comprehensive evaluation and single factor evaluation.There is the relationship of mutual promotion and inhibition among each factor.The factors such as slope,water resource environment,soil and water loss and disturbance factors of human activities such as land use pattern,distance from construction land are the main factors to form the ecological security pattern of the basin.