The Research Of Spatio-temporal Evolution Of Landscape Ecological Security Level In Lanzhou

Lanzhou is a typical city in the northwest semiarid area,the ecological environment is fragile.With the further development of regional urbanization and industrialization,the intensity of human activities on the ecological environment is increasing,which is more sensitive to the fragile ecological environment.The Communist Party of China’s 18 th Central Committee pointed out that promoting the construction of beautiful China and making contributions to global ecological security.Therefore it is very important to maintain the ecological security of fragile areas.With support of RS and GIS,the thesis analyzed the landscape pattern characteristics and land use dynamic change of Lanzhou from 1995 to 2015,which was based on the statistical data,remote sensing data,land use interpretation data,DEM data and MODIS data of Lanzhou in 1995,2005 and 2015 as data sources.In addition,in order to explore the ecological safety level and spatio-temporal variation of regional landscape,this thesis profited theory from the landscape ecology,and constructed landscape ecological security evaluation model based on landscape structure-function-stress with grid scale.This thesis analyzed the factors that affect the level of regional landscape ecological security,and puts forward the strategies to improve the level of landscape ecological security which based on the research results.The conclusions were as following:(1)From 1995 to 2015,The landscape type of Lanzhou was mainly grassland,which has the characteristics of landscape matrix,the proportion of 40%;The conversion of different landscape types were obvious,the same type of landscape in different periods of transfer direction was generally consistent,cultivated land、forest land、grassland、water and unused land were mainly transferred to construction land;The average annual growth rate of woodland、grassland and construction land were 0.06%,0.05% and 9.45%,respectively,cultivated land、water and unused land were reduced in varying degrees.(2)The degree of landscape fragmentation、shape index、diversity and evenness index increased,while the degree of spread and cohesion index decreased,the number of patches increased first and then decreased,the fractal dimension was more than 1.The results showed the overall landscape of the region was fragmented,diversified and irregular.Based on the calculation of seven kinds of landscape types can find that the plaque aggregation of grassland was better,but the degree of fragmentation has intensified;The spatial distribution of patches in the water was relatively dispersed,the connectivity was low and the stability was gradually deteriorated;The spatial distribution of unused land and construction land tended to be concentrated,and the degree of agglomeration was high while the shape of patches was regular;The degree of fragmentation of cultivated land increased,the independence of plots increased,and the spatial distribution was scattered;The degree of agglomeration of forest was high,the patch connectivity was reduced and the fragmentation trend was obvious.(3)During the study period,the landscape structure and landscape function index of Lanzhou increased year by year while the landscape stress index decreased first and then increased.The level of landscape structure was mainly high stability,the landscape function was in the medium level,and the landscape stress was mainly high sensitivity.The structural stability of 6 landscape types had little difference,but the stability of the artificial landscape is higher than that of natural landscape;The functional safety level of the different landscape types was significant,the forest safety level was the highest,the water area was higher,the grassland was medium and the cultivated land was lower,the safety level of unused land and construction land was the lowest;The stress degree of different landscape types was significant,the stress of artificial landscape construction land was the highest,the stress level of water,forest land and cultivated land was the lowest,and the degree of coercion to unused land was low,and the stress of grassland was higher.(4)The spatial distribution of landscape structure,function,stress and landscape ecological security in Lanzhou showed a high correlation with landscape types.From 1995 to 2015,the landscape security index were 0.1336,0.1344 and 0.1352 in Lanzhou,the trend was increasing year by year,the results showed that the ecological security status of the landscape was improved;The ecological status of the landscape was dominated by moderate safety level and had a controlling effect on the whole area;The safety level of the six landscape types was obviously different,the forest land was the highest in safety,the lowest unused land,the lower cultivated land,the middle of grassland and construction land,the safety level of the waters was higher.Through the natural,man-made and policy factors influencing the ecological security level,according to the actual situation and the evaluation results of landscape ecological security of Lanzhou,this thesis put forward different strategies for five landscape ecology levels.