Study On The Change Of Landscape Pattern And Driving Forces In Lower Reaches Of Heihe River

The lower reaches of Heihe River is located in an important arid region of northwest China.Its rise and decline plays an extremely important role in safeguarding the ecological security of the Alxa region,the Hexi Corridor,and the security and protection of neighboring scientific research bases of national defense.With the economic development in the lower reaches of the Heihe River and the implementation of the Water Diversion Project in Heihe,the downstream landscape has undergone significant changes.Therefore,in this paper,the author chooses the lower reaches of Heihe river as the research object and selects the Landsat TM/ETM+ remote sensing images from 2000,2008,and 2015 as the classification maps of land use by using the RS and GIS technology,and through the way of transfer matrices of land use and landscape index to analyze the spatial and temporal characteristics of landscape types and the main types of landscape shifts.In addition,the way of principal component analysis and the model of SD was also used to study the human-driven factors that affected the landscape pattern changes.Finally,relevant suggestions are put forward.The main conclusion are as following:(1)Judging from the changes of number in types of the lower reaches of the whole Heihe River,the author finds that,from 2000 to 2015,the area of construction land have increased significantly,and grassland and water area have also increased in varying degrees and the ecological environment has generally improved;through the calculation and analysis of the use of land-use transfer matrices,the results show that from 2000 to 2015,retrograde succession occurred in the forest land and its area continued to decline.During the entire study period,the main types of landscape transfer is that unutilized land was transformed to the construction land and grassland;from the viewpoint of the conservation of landscape components,in 2000-2015,the land types closely related to human activities such as construction land and cultivated land were large in number and relatively stable,while the retention rate of landscape component in forest lands was relatively low,varied and unstable under the influence of the external disturbances.(2)Through the analysis of the change of landscape index of different grain sizes,the 120 m grain size is taken as the best analysis scale on the landscape level.the analysis of landscape pattern shows that from 2000 to 2015,the degree of aggregation of grassland and woodland in the study area continued to decline,and the patches were continuously divided and broken.Due to human's disturbance,landscape fragmentation was severe,and the shape of patch became more regular and the degree of aggregation also decreased.(3)The established system dynamics model starts from the causal relationship that influences the landscape pattern change in the study area.By establishing a system dynamic equation,the driving mechanism of the influencing factors such as the population quantity and the total production value is analyzed.The model error is controlled within 8%.It shows that the constructed model system is basically consistent with the facts and is feasible and effective.It also shows that the human factors that affect the landscape pattern change are mainly concentrated in the two aspects related to economy and population.Through the study of the driving forces of changes in the landscape pattern,the author also finds that the driving forces affecting the changes of landscape in the lower reaches of the Heihe River mainly include 12 kinds of human factors such as the primary industry,tertiary industry,gross domestic product,industrial output value,and public budget expenditures and so on.Then,the author also makes analysis to these factors from four aspects: economy,policy,technology,and culture.Finally,on the basis of the above analysis,the author proposes the corresponding suggestion to problems such as the occurrence of retrograde succession,severe fragmentation of landscapes,and reduced connectivity in the lower reaches of the Heihe River.from the landscape pattern change driving force of the research shows that the first industry,per capita net income of farmers and herdsmen,gross domestic product,at the end of the livestock population Numbers,public budget spending 12 as the main influence factors.(4)the corresponding Suggestions about of management and supervision are put forward for the problems of reverse succession,serious landscape fragmentation and reduced connectivity in the lower reaches of heihe river basin.