| Affected by global climate change and population growth,the ecological and environmental systems have been severely damaged.The research on ecological environmental vulnerability has also been increasingly strengthened,especially with regard to the research on human and land has become one of the core issues in the changes of ecological environmental vulnerability.Wetlands are known as"the kidney of the earth"due to their numerous ecological functions,in recent years,because of the impacts of climate change and man-made factors,in addition,wetland ecosystems have a high sensitivity to disturbance with human activities,leading to the deterioration of wetland ecosystem structure,the obvious trend of declining diversity,the frequent loss of freshwater deposits and the loss of flood control and storage functions.In order to protect the unique ecological functions of karst wetlands and reduce the degradation of wetland ecosystems,in this paper,the Puzhehei karst wetland basin as the research area,to evaluate the ecological vulnerability of the karst wetland basin.This research is based on remote sensing image data,using GIS,mathematical statistics and other technical means.The image was interpreted by wetland of the Karst Lake in Puzhehei from 1995 to 2015,the characteristics and regularity of land use change in the study area were analyzed from the aspects of land use dynamic degree and Landscape pattern index during the past 25 years(1990 to 2015).On this basis,using the analytic hierarchy process and the entropy mutation theory model,Was evaluated of the spatial-temporal evolution of ecological vulnerability in 10 years(2006 to 2015).The main results are as follows:(1)From 1990 to 2015,the area of construction land and agricultural land was increased continuously in Puzhehei basin,while the area of wetland and unused land continued to decrease,the forest land and the orchard area fluctuated;From the views of the land use dynamic degree,the dynamic changes of unused land changes fastestly,following is the construction land,wetlands and agricultural land,whereas the dynamic changes of the forest land changes slowly most.Additionally,from the point of land use types of mutual transformation,The area of agricultural land,wetland,and unused land was most intensely transformed,while the area of forest land and garden land was significantly transformed,and the conversion area of land for construction land was not significant.the decreasing area is mainly the agricultural land and forest land but the agricultural land,forest land and wetland dominated plays the important rules in the increasing area;There are different ways of transferring land use types under different scenario simulation predictions,Under scenario I,wetlands and agricultural land are the main sources of land circulation,and they mainly flow to township residents'land use;under scenario II,the increased occupancy of construction land and unused land In some of the agricultural lands and woodlands,under scenario III,conversion of agricultural land to building land,forest land,and wetland is the main land use method in the Puzhehei karst wetland basin.(2)During the year 1990 to 2015,the landscape pattern in Puzhehei lake basin has changed obviously.The disturbance degree of agricultural land and woodland is higher,the interference degree of building land,garden and wetland comes second,and the interference degree with the index 0.2087~0.2180 of unused land is less.In addition,the variation range of land disturbance is 0.3758~0.3796,While the interference index of construction land fluctuates greatly with the change rate of-14.10%;The landscape loss degree of different land use in Puzheihei Basin was changed significantly,and the loss degree of farmland and unused land were 0.5422 and 0.5514,respectively.The landscape loss degree of wetlands,construction land and forest land came second and the landscape loss degree of garden land with the damage degree index of 0.1197 is smallest among all the landscape pattern.What's more,the loss degree of construction land loss degree has obvious changed(P<0.05);From 1990 to 2015,the spatial distribution of ecological risk in the study area was different,and the proportion of the lower ecological risk was the highest between 1990 and 2005,and the ecological risk was mainly in the period of 2005 to 2015.Meanwhile,ecological risk in this period mainly performed as the middle ecological risk level and the ecological risk increased slowly.(3)From 2006 to 2015,the comprehensive index of ecological vulnerability was decreased gradually from 5.34 to 4.37 of Puzhehei karst wetland basin,and the comprehensive grade of ecological vulnerability was moderately fragile.The spatial and temporal distribution of ecological vulnerability of Puzhehei basin in the period of2006-2015 was more scattered,the area of extreme vulnerability shifted from the lower reaches to the upper reaches of the Puzhehei basin,and the area of extremely vulnerable areas decreased from 5 617.09 hm~2 to 3 015.27 hm~2,the trend of deterioration of ecological vulnerability has eased;The entropy of the eco-environment has undergone many mutations during this decade in the Puzhehei basin from 2006 to 2015,Compare the characteristics of mutations of the three stages in a decade:The second stage mutation characteristic value(2009~2012)>first stage mutation characteristic value(2006~2008)>stage 3 mutation characteristic value(2012~2015);The superposition factors of natural factors and human factors is the reason for the change of ecological vulnerability in the study area,however pollution evolution,land use,economic development and population pressure are the main driving forces.The spatial and temporal distribution of ecological fragility is closely related to the intensity of land use and human activities.Therefore,the regional sustainable development can be realized by strengthening the integrated management of land and human activities,promoting the synergistic effect among the social,economic and ecological protection. |
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