Analysis Of Landscape Pattern Change And Ecological Security Evaluation In Urumqi City

The rapid development of the economy has created sufficient material wealth for mankind,and as the world entering the "urban age",the surface environment and landscape pattern of the city have changed greatly and brought many ecological problems.Urumqi belongs to the arid continental climate with fragile and poor ecological environment,so it leads to this consequence,which is difficult to recover once destroyed.Therefore,it is of great significance to carry out reasonable ecological security evaluation research.This paper chooses Urumqi city as the study area,and based on the 4periods of Landsat TM/ETM+,OLI images taken at the same month in 1990,2002,2014 and2018,along with the related statistical data,the extraction of Urumqi city landscape space segment information classification,based on the theory of landscape ecology in the study area in 3 periods of landscape pattern was analyzed and the level of type based on the landscape level.Then using the moving window method,the internal level difference of Urumqi landscape pattern between the 4 periods is analyzed in detail.From the factors of landscape pattern change and the social and economic impact of the pressure state response(PSR)of this model,the construction of 3 levels and 17 indexes of Urumqi city ecological security evaluation index system,evaluation carried out in 1990?2018 years on the time scale of the city environmental ecological safety.The following conclusions are drawn:(1)In this paper,Urumqi city landscape is divided into grassland,forest land,construction land,cultivated land,waters and six types of land use,during the 1990-2018 years,obvious changes have occurred in the unused land and construction land,the overall land of unused land has showed declining trend;therefore,the overall construction land has showed increasing trend.The area with the smallest change is water,and the total area of water remains unchanged.The two landscape types of unused land and construction land in Urumqi city have the fastest changing rate,and their area changes are the most significant.(2)In 1990,the degree of fragmentation and heterogeneity in the city were low,and the city was at the stage of development,and the level of urbanization was low.In this period of 2002,the speed of urban expansion in Urumqi showed a significant increasing trend,and the urbanization level was further improved.In the 2014 period,the speed of Urumqi's outward expansion continued to increase,and the level of urbanization was higher than before.The city is in a period of rapid development.Therefore,during 2018 continuesly showed outer expansion tend,patch density showed decreasing trend,the fragmentation level kept increasing.In the 1990-2018 landscape types of Urumqi,all kinds of landscape showed fragmentation trend.The fragmentation of construction land is serious and the dominance is increasing.At the same time,the heterogeneity of the unused ground increased and the dominance decreased.The heterogeneity of grassland also has obvious enhancement,while woodland is the most fragmented and heterogeneous landscape type in the region.The spatial distribution of cultivated land tends to be dispersed.The landscape pattern of Urumqi from 1990 to 2018 has been viewed as a whole,and its landscape spatial patterns tend to be complex and irregular.The landscape segmentation index showed a continuous rising trend,and the fragmentation of the landscape also increased.Landscape diversity increased and heterogeneity increased.The patch types tended to be evenly distributed in the landscape,and the difference of landscape components in the proportion of the area decreased.(3)Using the three aspects of "pressure","state" and "response",in terms of pressure,the year with better ecological security level is 2018,mainly because per capita GDP showed high value and the natural population increase showed negative value,which is contributed to the whole value to show the highest level;The minimum value of ecosystem safety is 2002,mostly because,during 2002,the population growth was too fast.In terms of state,the state safety value of 1990 is the highest,because in 1990,the impact of human activity is minor,and the rate of forest is relatively high,and the rate of water area is the same;during 2018,the impact of human is strong,fragmentation level was the highest,that's why 2018 shows the lowest level.And the state safety value of 2002 is similar to the 2014.In terms of state,from 1990 to2018,all of the values almost the same,however,among all the indexes,the capital put in to the health and science have big differences between the standard value,which means the investment to the environment management should be increased.(4)The analysis of Urumqi city ecological security evaluation results on the comprehensive ecological security index of 1990,2002,2014 and 2018 were 0.5797,0.5186,0.5290 and0.5738 respectively,which belongs to the second,third,third and second security level,which is in good condition,general condition,general condition and good condition,all of the ecological security condition is good.The value of ecological safety reached the highest in 1990,and the minimum ecological safety value was in 2002.During 1990 to 2018,human factors have great influence on the improvement of the ecological environment.However,Urumqi city still needs to invest more in environmental protection and management so as to promote regional ecological security.