| The deterioration of the ecological environment worldwide continues to threaten the existence and development of human beings.Thus,studying and guaranteeing ecological safety has become a consensus across all populations.The Hubei segment of the Han River involves the upper,middle,and lower reaches of the Han River,accounting for 55.25%of the total length.Moreover,the river is the water corridor connecting the northwest Hubei and the Jianghan Plain,thus "linking the north and south and connecting the east and west." The watershed area accounts for 33.89%of total area of Hubei Province.The watershed area,which is rich in natural resources and features a solid economy,is an important economic area of Hubei Province and serves as a major base of marketable grains in China.As an important ecological barrier for Hubei Province and even the economic zone at the middle reaches of the Yangtze River,the Han River watershed features an ecological safety that relates to the existence and development of people in the middle and lower reaches of the Yangtze River and adjacent areas.However,the decreased flow at the upper reaches,the rapid growth of the population,the increasing industrial and agricultural activities at the middle and lower reaches,the increasing demands for natural resources in the watershed,and the changes in the modes of land use within the watershed as a result of human activities all affect the ecosystem service function and ecological safety of the watershed.Thus,establish a comprehensive understanding of the changes in the land use and the ecosystem of the Han River watershed and evaluate and maintain its ecological safety,which is an important measure to maintain the sustainable development of river basin.Specifically,this work,using remote sensing images and land use data in 1980?2010,explores the changes in land use of the watershed and evaluates the changes in land use in the Han River watershed by employing quantitative methods based on land use structure,land use dynamic index,land use intensity,Markov model,and landscape patter index.With the application of ecological equivalence method,the study has a calculation and a comparative analysis of ecological service economic effect caused by changes in land use.Subsequently,the study performs a spatial-temporal evaluation of the ecological service economic effect by gravity model and exploratory spatial data analysis.With the application of the principle of water balance,Universal Soil Loss Equation,soil carbon balance principle and regional total calories of food,the study analyzes the spatial-temporal variation tendency of four key functions,namely,water supply,soil conservation,carbon sequestration,and product supply within the watershed.On the basis of the modified pressure-state-response(PSR)model,this study builds a comprehensive index system of Watershed ecological security assessment in terms of the changes in ecosystem services.Subsequently,the study estimates the ecological security limit factors,the ecological safety state and variation tendency over the past 20 years based on the extension theory and entropy weight theory.Finally,this study probed into the variation trend and law of the ecosystem service and ecological safety within the watershed,and proposed countermeasures for the management of ecological safety in the watershed.The major studies are as follows.(1)This work revealed the spatial-temporal evolution law of land use in 1980?2010 within the watershed.The land use intensity structure within the watershed has undergone obvious changes.Specifically,land is being developed into construction lands that feature a high degree of artificial interference.During the studied period,cultivated land and forest land are the main types of land use,and the largest decline was found in the area of cultivated land.The cropland areas were converted to construction land and water areas.Frequent land use changes were concentrated in both sides of the watershed,the plain hinterland,and hilly areas.Therefore,these areas should be treated as key areas with land use that requires close monitoring.The total area of cropland patch was the largest among all types of land and accounted for the largest proportion in the total landscape area.The connecting degree of dominant patch types within the watershed decreased,the landscape fragmentation increased,and the patch shape tended to be complex.(2)This work evaluated the ecosystem service value based on the land use change and explored the spatial-temporal evolution trend of ecosystem service value in 1980?2010.The total ecosystem service value formed by the changes in land use of the watershed was significant and showed a dynamic growth trend of increasing,decreasing,increasing,and decreasing.The total ecosystem service value increased by RMB 10.525 billion yuan.However,the ecosystem service value in gas conditioning and climate conditioning decreased obviously.Spatially,the largest proportion in area of ecosystem service value is medium level within the watershed.The center of the ecosystem service value within the watershed shifted 9.89 km from the south to the northwest.The ESV per unit area showed an aggregated distribution spatially,including the high-high autocorrelation type and the low-low autocorrelation type.The high-high autocorrelation type was mainly distributed in the mountainous area of Northwest Hubei and Dahong Mountain area,and showed a first-increase-and-then-decrease "?"-shaped trend.The low-low autocorrelation type was distributed mainly along the Han River,increased gradually with time,and tended to form a cluster within Nanzhang,Tianmen and Wuhan.The area of Western Hubei and Northwest Hubei are the key maintenance areas and protected zones of the ecosystem service value in the future,whereas the both sides of watershed are the key development zone.(3)This work evaluated the four important ecosystem service function based on the land use change and explored the spatial-temporal evolution trend in 1980?2010.The state and spatial features of the four ecosystem service function,i.e.,ecological water supply,soil conservation,carbon sequestration,and product supply,differed from one another within the watershed during the changes in land use.In the watershed,the slightly low-grade and low-grade ecological water supply,the high-grade soil conservation,the slightly high-grade and high-grade carbon sequestration,and the slightly high-grade and high-grade product supply took the dominant position.The slightly low and low value areas of the ecological water supply were mainly located at the humpy ground of north and northwest Hubei,the low mountains and hills,and the mountainous area at the middle reaches of the Han River.The slightly low or low value area of soil conservation was mainly located at the bare cultivated area on low mountains and hills.The slightly low-grade area of carbon sequestration was located along both sides of the river and the lower reaches of the watershed.The low-grade and slightly low-grade areas of product supply were located at Wuhan City and Shenlongjia forest area,respectively.The humpy ground of north and northwest Hubei,the low mountains and hills,the mountainous area,and the both side of the Han Riveris are the fragile area of ecological service function to be protected.Meanwhile,the low mountains and hills,the mountainous area in the west of Hubei Province are the key areas of watershed soil erosion management.(4)This work improved the PSR mode,established the comprehensive evaluation index system and evaluation model of ecological security from the viewpoint of ecosystem service,and revealed the spatial-temporal evolution law of ecological security.The ecological security level of 60%counties within the basin was lower than the critical security level.During the studied period,the ecological security level within the watershed showed a gradual increase followed by a gradual decrease and"?"-shaped development.The raw material production,gas regulation and water conservancy and Hydropower investment were the most important factors in the evaluation system,the main limit factors of ecological security in most counties were raw material production,climate regulation and afforestation area.The ecological security level of Laohekou,Shayang,Hanchuan,Tianmen,Qianjiang,Wuhan city and Caidian district were low.These cities should be listed as the area of urgent improve and enhance the region.(5)This work proposed an ecological management strategy from five viewpoint of land policy,fiscal policy,investment policy,industrial policy and population policy based on the changes trend of watershed ecosystem service value,ecosystem service function. |
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