Land Cover Change And Its Ecological Environment Response Based On"3S" Technique In Dongting Lake Region

The Dongting Lake area includes 25 counties of the 3 cities Yueyang,Yiyang and Changde.The total area of the study area is about 45338 km~2 and the landform is dominated by the plain.The natural resources are abundant in the area,but the pressure on land resources such as soil erosion,soil degradation,water pollution,flood disasters and the loss of biodiversity and other environmental problems have been increased in the past 20 years due to the rapid development of economy and society.Human activities and natural resource changes have direct impact on land use/land cover change,and then change the regional ecological environment.Study on the spatio-temporal process of land use and the driving force of changes as well as analysis of the regional ecological environment caused by land use change of Dongting Lake area in the recent 20 years have important theoretical value and practical significance for promotion of sustainable development and sustainable utilization of land resources and regional economy.Based on field investigation and literature review as well as the temporal and spatial change process of land use/cover in Dongting Lake area,the following main findings are obtained by means of 3S technology,relevant ecological model simulation and mathematical statistics analysis.(1)The spatio-temporal change process of land use in the last 20 years in the Dongting Lake area was revealed.(1)The comprehensive degree of land use:The land use of Dongting Lake is in a era of development and the degree of land use has been improved.The comprehensive index of land use degree increased generally in this period,but in 1995 and 2010,the comprehensive index of land use showed a smaller downward trend.(2)The change of area of each land type:The size of land types in the Dongting Lake area sorted successively from large to small by forest land,cultivated land,water area,construction land,grassland and unused land.The most significant changes of the land types in the recent 20 years were cultivated land,Construction land,woodland and cultivated land have obvious characteristic of periods.(3)The transformation of land use types:The trend of farmland,woodland,grassland and water area decreased while the construction land and unused land increased.The conversion between farmland and woodland,farmland and water area were more frequent.The increase of construction land mainly comes from the transfer of cultivated land and woodland,and the increase of unused land area is mainly from the diversion of water area.(4)The spatial variation:The net gravity move distance of 6 types of land uses during1990-2013 sorted successively from large to small by unused land construction land,water area,construction land,grassland,cultivated land and woodland.The total movement distance of the center of gravity sequenced by grassland>unused land>construction land>water area>cultivated land>forest land area.The spatial distribution of cultivated land and forestland in the study area are more stable whereas the spatial distribution of grassland,water,construction land and unused land are more complicated.(2)The ecological environment effect caused by land use change in Dongting Lake area is analyzed.(1)Carbon effect:The vegetation density and soil carbon density in the terrestrial ecosystem of Dongting Lake area are sorted by woodland>grassland>cultivated land>construction land>unused land,and their overall carbon sink capacity is weakened.In the three cities of Yueyang,Changde and Yiyang,the spatial variation of carbon sequestration capacity in Yueyang and Changde were more obvious than that of Yiyang.The spatial variation of carbon sink capacity in Yueyang and Changde showed a strong difference during the 1990~2000.After 2000,it became flat.During 2010~2013,the spatial difference index of carbon sink capacity in Yiyang exceeded that of Yueyang and Changde which is directly related to the population density of the region,the economic and social development,and the imbalance of regional administrative policies.(2)The value of the ecosystem service function:During 1990~2013 the ESV in the Dongting Lake area is slightly promoted.The most prominent value of ecosystem services was water conservation,followed by waste treatment,climate regulation and biological diversity conservation which accounted about 62%of the total service value.The lowest ecosystem service value was food production which is insufficient 3%of total service value.The edge between high value zone and low value zone of ESV dissolved and permeated each other in the area,and the secondary high value zone is surrounded by high value and low value area.The high value area of ESV is mainly distributed in the waters of Dongting Lake and its surrounding wetlands.The eastern and western regions are mostly sub forests of ESV,and the low value areas of ESV are mainly distributed in the urban area of the three cities and their surrounding areas.ESV and its dynamic evolution in the Dongting Lake area also showed obvious spatial autocorrelation and low value aggregation.Although the total ESV increased,the degree of autocorrelation and aggregation tends to weaken.The spatial distribution of the degree of fragmentation is on the rise.The concentration area of high value ESV also decreased.The center of gravity of ESV moves from westward to the north.Its trajectory migration is very slow,but it has obvious stages.In general,it has a"S"trend and has undergone a"violent slow and intense"change stage.(3)The changes of biodiversity hot spots:The distribution of avian biodiversity hotspots was conducted by the usage of 14 endangered species of birds as indicative species.The results showed that the distribution of avian biodiversity hotspots had a characteristic of cluster during 1990-2013 and the hot area decreased.The landscape pattern of avian habitat tends to become fragmentation.The shape of habitat tend to be simple and flat while the pattern of habitat became complex.The factors of economic and social development had significant effect on the avian biodiversity hotspots but the influence of natural factors is more less.In addition,the biological protection work carried out in the Dongting Lake nature reserve and the extensive land use management mode in the area have an important impact on the fluctuation of the avian biodiversity hotspot.(3)The Countermeasures of sustainable utilization of land resources in Dongting Lake area are put forwardThe main function of the regional land use regulation was suggested by land use zoning including reasonable distribution of agriculture,forest,urban and rural construction and mining and natural protection area.The methods such as Scientific development of regional scientific development plan,construction and improvement of ecological compensation mechanism,establishment of land information management system and other measures were put forward to control the comprehensive ecological environment and implement ecological restoration of Wetland.Implementing differentiated land supply,and taking the green development and beautiful countryside construction as an opportunity to focus on the development of eco-tourism industry in order to ensure the sustainable development of social economy and the quality of regional ecological environment.Compared with previous studies,this thesis focuses on the cartographic expression of the final analysis results of environmental and ecological responses and the relevance between ecological effects and environment(including natural environmental factors and socio economic environmental factors).The cartographic expression of eco-environmental response plays an important role in the decision-making process of ecological protection,and the environmental relevance analysis of ecological effects can reveal the mechanism of targeted factors that cause some environmental response.