| Land is the site of various social and economic activities,and the breadth,depth,and changes of land-use will directly affect the evolution of the environmental system.A landscape pattern is a spatial configuration of different landscape elements and the laws of their changes over time;in other words,a landscape pattern results from the interaction of landscape structure and landscape ecological processes at different scales.As one of the five terrains,mountainous areas have absolute height and relative height difference whose typical natural geography and ecological characteristics have a profound impact on the way and degree of human land use there,and whose ecological location and typical landform types add to the complexity and heterogeneity of the landscape evolution.Located at the end of the upper reaches of the Yangtze River,the Three Gorges Reservoir Area(Chongqing section)with rich biodiversity but fragile ecological environment has special ecological function and is deemed as the throat of the ecological barrier of the Yangtze River basin,hence,the important ecological strategic significance.This paper uses Shizhu County,which has typical mountainous features in the hinterland of the Three Gorges Reservoir area,as the study area,to examine the realization path of coupling and optimization of land use landscape pattern and function in mountainous areas.This will have practical value for promoting the proper use of regional land resources and sustainable development of the environment.With the data mainly ranging from four years of land-use maps in the study area(2000,2005,2010,and 2015)to a topographical map(1:10,000),administrative maps and to Digital Elevation Model(DEM)of the study area,and the research methods such as the method of landscape ecology,GIS spatial analysis,spatial econometric model and other research methods,the thesis discusses the inner mechanism,drive mechanism and the characteristics of time and space of land-use landscape pattern and ecosystem services value changes,to examine the realization path of coupling and optimization of land use landscape pattern and function in mountainous areas.The main conclusions are as follows:(1)Landscape pattern based on the "pattern-function" coupling was constructed as an important perspective.Different natural conditions and differences in human needs will form different land use landscape patterns which lead to different ecosystem service functions,landscape pattern determines ecosystem service functions,and functional needs promote the evolution of landscape patterns.The landscape pattern and ecosystem service function are thus deemed in the paper as important perspectives and components of sustainable development of mountain land use.(2)Cropland and forestland were the dominant landscape types in the study area where landscape distribution and dynamics showed apparent spatial variation.(1)Cropland and forestland are the dominant landscape types in the study area,and their area ratios added up to more than 85%.Cropland and grassland exhibited an impressive decrease,mainly converted to forestland,but there was an apparent increase in forestland and built-up land,the increase in built-up land being mainly due to its invasion into cropland and that in forestland the conversion from cropland and grassland.Meanwhile water bodies continued to increase.The change in landscape was the most drastic from 2005–2010,mainly reflected by the rapid increase in built-up land and water bodies and the rapid decrease in grassland.(2)Landscape distribution and dynamics showed apparent spatial variation.Except that water bodies were mainly in the gentle slope area below 200 m elevation and 0–6° slope,other major landscapes were concentrated at an elevation higher than 500 m,along a slope of 15°–35°,on westerly and northwesterly aspects.These areas also had the most dramatic changes in landscape.(3)The landscape indices also showed apparent spatial variation.Both the type-level and the landscape-level landscape indices exhibited more distinct variation with elevation and slope than that with aspect.Different landscape types had very different variation characteristics in response to elevation,slope,and aspect.(3)There were significant differences in driving factors of the evolution of land use landscape types in the study area.The factors of landscape evolution in different land use types and different time periods were significantly different,and the driving effect of multi-factor combination on landscape type change was more obvious.Cropland and built-up land were mainly affected by social and economic factors,while forestland and water bodies were determined by both social and economic factors and natural factors.The driving factors of grassland were obviously different in different periods.(4)The total value of ecosystem services showed an overall increase in the study area.(1)The total value of ecosystem services increased by 39.46%(642 million yuan)from 2000 to 2015,the highest one being forestland,with a value of 6.324 billion yuan,accounting for 79.30% of the total value,and the lowest one unused land.(2)Soil conservation and water conservation had become the most important ecosystem protection functions in the study area.From the perspective of different ecosystems,the total value of ecosystem services provided by different land use types decreased from forestland to cropland to grassland to water bodies to built-up land and to unused land,with forestland at the top and unused land at the bottom.(3)The value of ecosystem services in the east was higher than that in the west,and gradually decreased from the east of the study area to the west.When it comes to towns and villages,Huangshui town had the highest value of ecosystem services,while the value of some towns and villages were quite low,affected by factors such as small area and land use types.(5)The GLP-BPNN-CA coupling model was constructed to simulate and optimize the landscape pattern of land use and ecosystem services.With 2015 as the base year for land use landscape in Shizhu County,the GLP-BPNN-CA model was used to optimize and simulate the land use landscape pattern-ecosystem services of Shizhu County in 2020,2025 and 2030.The simulation results show that the overall three-year transformation is generally consistent.In terms of space,the newly added land use extended from the boundary of the existing land use type,with the increased area of construction land mainly concentrated in Nanbin Street,Xialu Street,Sanhe Town,Xiqiao Town and Huangshui Town,and the increase in forestland and grassland primarily in the mountainous area of the northwestern part of Fangdou Mountain and Zhongshan District in the southeastern part of Laochangping.As for quantity,the area of the cropland is declining.And when it comes to transformation,the reduced cropland is transformed into forestland,built-up land and grassland in different degrees,the inter-transformation between the forestland and grassland and built-up land is not much,if any,and almost all the unused land turns into forestland and grassland with high value for ecosystem services,very little converted into built-up land.The total accuracy of the model simulation results was 91.65%,and the Kappa coefficient was 0.82,indicating that this model can better simulate the future land use landscape pattern and function. |
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