Evaluation Of Land Ecological Risk In Karst Trough Area

In recent years,China’s rapid economic and social development,population explosion,urbanization expansion and rapid development of industry and agriculture have led to increasing pressure on land resources.The heavy use of chemical fertilizers and agro-membranes has caused soil pollution.In addition,due to the increasing population density and the continuous expansion of human economic activities,the habitat of animals and plants has been destroyed and the biodiversity has been reduced,which has aroused wide concern in the society.The identification of pressure factors of land ecological risk and the effective evaluation of land ecological risk are conducive to the smooth development of land management.Most focus on the study of land ecological risk assessment on the pesticide pollution and heavy metal pollution in soil level,has not yet formed a unified index system and method to recognized characterization and evaluation of land ecological risks.In this paper,based on the research of land ecological risk theory,ecological risk source analysis of land use,building ecological risk evaluation index system,and under the guidance of theory of natural disaster risk management from the IPCC related theories to build YinJiang county land ecological risk evaluation index system.The main research contents and research results are as follows:(1)the integrated natural disaster risk management(INDRM)from danger,exposure,vulnerability three aspects build YinJiang county land ecological risk evaluation model,establishes the land ecological risk evaluation index,using the analytic hierarchy process(ahp)to determine the weight of each index,threshold value method to standardize the indicators,natural breakpoint method to quantify the various index classification,will YinJiang county ecological risk level in the study area is divided into very low risk area,low risk area,medium risk area,high risk area,high risk during five levels.(2)land ecological risk assessment in multiple periods.Integrated use of ArcGIS techniques and related analysis methods,using the 2000,2005,2005 and 2015,four remote sensing data,ecological risk driving mechanism research YinJiang county,15 years,with lattice 30 m * 30 m as a research unit,ecological risk assessment of YinJiang county land.(3)analysis of spatial and temporal evolution characteristics of land ecological risk.As research YinJiang county ecological risk grade change types of spatial differentiation characteristics,in order to more intuitive understanding of the regional ecological risk dynamic change trend,this paper will be two different years ecological risk level diagram superimposed analysis of subtraction.Extremely low risk areas were assigned a value of 1,low risk areas were assigned a value of 2,medium risk areas were assigned a value of 3,high risk areas were assigned a value of 4,and high risk areas were assigned a value of 5.Received five types of change,respectively is: increase significantly(1-4,2-5,1-5),slow growth zone(1-3,2-4,3 to 5,1-2,3-2-3,4,4-5),did not change area(1-1,2,3-2-3,4,5-4-5),significantly reduce the area(4-1,2,5-5-1),slowly lower area(1,3-2-2,3,4,5-4-3-1,2,5-4-3).(4)analyze and evaluate the land ecological risk in yinjiang county from 2000 to 2015 according to the land use ecological risk grade map and existing data.The results showed that 15 years,YinJiang county overall good ecological environment,ecological risk index is low,the high risk area,high risk area and medium risk during the research period,area is declining,from 10.48% in 2000 down to 2.21% in 2015.Extremely low risk areas and low risk areas are expanding.Ecological risks tend to be good.According to the research results,policy Suggestions are proposed for the protection of land ecological risk in yinjiang county.(1)policies on risk:Areas with large cultivated land area also have large amount of cultivated and fertilized land,and in these areas,the ecological risk level is higher than the surrounding forest and grassland land.Due to the cultivation of economic crops such as tea and tobacco,the ecological risk in yongyi township is significantly higher than that in surrounding areas,indicating that there is a serious agricultural pollution problem in yongyi township.This requires that the policy of returning farmland to forests should be continued in yongyi township,and unscientific land development methods should be strictly prohibited.Scientific fertilization will be carried out in areas with degraded soil fertility to prevent land degradation and increase the yield per unit of crops such as tea and tobacco.At the same time,we will strictly control farmland pollution,avoid and ban the use of pollution of farmland irrigation water,using less or no high toxicity,high residual pesticides,herbicides and pesticides,etc.,to protect agricultural ecological environment(2)policies on exposure:YinJiang county is on behalf of the area of the development of guizhou karst fragile ecological environment,the ecological vulnerable area and ecological degradation area especially eling around town,the county seat,is using the related principle of restoration ecology and ecological engineering technology for returning farmland to forest and grass and restoration and reconstruction,expanding forest and green vegetation coverage.For central and eastern exposure risk factors for lower area,will continue to keep the original development model is not destroyed,rational use and development of land resources,achieve the harmonious development of the economic development and environmental protection.(3)policies on vulnerability:In YinJiang county in the eastern region should particularly pay attention to protect biodiversity,increase the natural protection forest construction and protection,strengthen protection against natural disasters such as floods,landslides and debris flows,strengthen ecological security maintenance and management.