Analysis Of Temporal And Spatial Differences In Ecological Effects Of Land Change In Yan'an City

The research of land use is the basic of the land ecosystem research.It is not only the most closely related to human relations in the global change,but also the focus of the study of the ecological environment.Since the twenty-first Century,with the increasingly prominent contradiction between the social and economic development and the ecological environment,the problem of land has been paid more and more attention.And a reasonable way of land use is a very important part of sustainable development.It connects the rationalization development of the land and the human social activities and it is also a great significance to the assessment of ecological value.Ecological effect is the key expression mode of ecological research.In recent years,the development of urbanization and industrialization has caused the irrational changes in the ecological environment.Environmental pollution,severe haze and the occupation of farmland erode our environment.Therefore,it is very important to study the ecological environment changes.The study of ecosystem service effect has become an important index for the study of ecosystem changes.Yanan located in the north of Shaanxi Province.It is an important energy development zone in Shaanxi Province and it contains rich coal,oil and natural gas.It has led to the development of energy economy in Shaanxi Province.However,as the rapid development of the city chemical industry,the ecological environment of the land has also been strongly impacted.Because of the semi arid region and the Loess Plateau,the soil erosion in this area is serious.The ecological environment has been destroyed.Therefore,it is very important to strengthen the detection of land use change and the study on the change of land ecosystem servicesin Northern Shaanxi.This article takes Yanan as the research object and based on grid scale and remote sensing data,DEM data,statistics,survey data and other related data.Using GIS and RS technology to analyse the spatial and temporal difference of ecological benefits of land change in Yanan.It analyses the current land use and changes in the type of land use.This article reveals the dynamic evolution process of ecosystem service functions in Yanan and the effects of Grain-for-Green Programme(GFGP)on ecosystem services and their changes in Yanan.It also discuss the trade-off and synergy between the net initial productivity of vegetation(NPP),grain production,soil conservation,and water conservation service function of the ecosystem and find the spatial and temporal differences between trade-offs and synergies.Finally,the influence factors are analyzed through the study of GFGP and the impact of terrain slope on the dynamic changes of trade-off and synergy.The conclusions are as follows:(1)During 1993-2013,the area of forest land and construction land in Yanan is increasing.Among the types of land use,the area of grassland is the largest,followed by forest land and cultivated field.From the point of view of the dynamic degree of land use change,the change rate of construction land is the most obvious.During 2003-2013,the change rate of forest land was remarkable.(2)During 1993-2003,the area of grassland reduced obviously,which was mainly converted into forest land and cultivated field.During 2003-2013,the area of cultivated field reduced obviously,which was mainly converted into forest land.From the point of view of the degree of land use,it mainly presents the low distribution characteristics in the North of YanAn.The land use degree of the cultivated field is high,and the forest land is the opposite.The trend of land use in Yanan in the past 20 years is increasing first and then decreasing.The area of GFGP is mainly distributed in the northern part of Yanan.It is mainly converted from cultivated field to forest land and grassland.(3)In the past 20 years,all kinds of ecosystem services have shown a trend of overall increase.The low value of NPP mainly distributed in the north of YanAn.The trend is the most significant in the southwest.The low value of soil conservation mainly distributed in the north of YanAn.The trend is the most significant in the northwest.The low value of water conservation mainly distributed in the north of YanAn.The trend is the most significant in the middle part.The low value of food providing mainly distributed in the south of YanAn.Welch's t-test is applied to compare the quantity of ecosystem services of different land-use types.The value of all kinds of ecosystem services in GFGP is significantly higher than that in the non-GFGP.It shows that the measures of GFGP have positive significance on the ecosystem.(4)Various kinds of ecosystem services in Yanan have different correlations.There is a trade-off relationship between food providing and soil conservation,water conservation and NPP.NPP has a synergistic relationship with soil conservation and water conservation.There is a synergistic relationship between soil conservation and water conservation.The results show that there is a trade-off between supply services and support services,regulatory services.There is a synergistic relationship between the regulatory services and the support services.And there is also a synergistic relationship within the regulatory services.(5)The overall synergy degree of all kinds of ecosystem services in Yanan is declining.But the overall trade-off is increasing.In a word,the trade-off of ecosystem service in Yanan has shown a trend of increasing and the synergy of ecosystem service has shown a trend of decreasing in the past 20 years.This is a violation of the goal of reducing conflict and increasing synergy in ecological management.It has a negative impact on the ecological environment.(6)Various ecosystem services in GFGP show a synergistic relationship.But they show a conflicting relationship in non-GFGP.From the trend of dynamic change,the trade-off strengthened and the synergy waekened in GFGP.This is in accordance with the goal of ecological management.It shows that the measures of GFGP are beneficial to the sustainable development of ecology.Under different terrain slopes,the dynamic changes of correlation of three types of ecosystem services are different.The conflict between ecosystem services in the area of 15 degree-25 degrees is obvious.The synergy between ecological service in the area of more than 25 degrees is obvious.It is shown that the slope of terrain is also an important factor affecting the dynamic change of correlation of ecosystem services.(7)Through the method of partial correlation analysis of pixel by pixel,we can obtain the spatial distribution map of tradeoff and synergy between NPP,water conservation and food providing.The low correlation between NPP and water conservation mainly distributed in the south of YanAn.The low correlation between NPP and food providing mainly distributed in the middle of YanAn.The low correlation between water conservation and food providing mainly distributed in the north of YanAn.(8)The characteristics and innovation of this paper are as follows:?Welch's t-test is applied to compare the quantity of ecosystem services of different land-use types.From the perspective of regional ecological management policy to explore the influence factors of ecosystem services.? It revealed the dynamic change characteristics of tradeoffs and synergies within a specific region under different policy management.It further reflects the development direction of trade-off and synergy between ecosystem services.?It analyse the forming factors of the dynamic change characteristics of the trade-off and synergy between ecosystem services.?Through the method of partial correlation analysis of pixel by pixel,we can obtain the spatial distribution map of tradeoff and synergy between NPP,water conservation and food providing.