| Chengdu Plain has attracted widespread research attention due to its unique geological background.Much geoscientific research has been conducted on the Chengdu Plain,resulting in great contributions to the fields of Quaternary geology,tectonics,ecological geology,and physical geography.The Chengdu Plain region has the highest population density and the greatest economic development in Sichuan Province.It has a long history and plays an important role in sustainable human-land development.Linpan is the traditional rural settlement in Chengdu Plain with its own unique geological background.Due to its extremely distinctive spatial distribution and compositional characteristics,Linpan possesses important ecological functions and ecological service value,contributing to local ecological safety and peasant household production and development.Chengdu City attaches great significance to the protection and utilization of Linpan.The geological background of the region is related to the regional land use patterns and land use changes,including spatial settlement and composition structural characteristics of settlement.Hence,the mechanisms underlying the relationship between the geological background and settlement,and the impact of geological environmental factors on the formation and development of the settlement have become research hotspots.However,at present,there is an inadequate understanding of the characteristics and functions of Linpan and few studies have discussed the relationship between Linpan and the geological environment.As a result,no perfect plan for sustainable human-land development in Chengdu Plain has been developed yet and the current plans fail to consider the geological background in the protection and utilization of Linpan.Further work must be done to protect Linpan.Guided by theories of ecological geology and Quaternary geology,zoning of Linpan was performed in this study.The zoning process was performed based on the geological background in combination with relevant theories and methods of geology,ecology and geostatistics through literature review,field surveys,remote sensing interpretation,geographical information spatial analysis,geoscience model evaluation,and mathematical statistics.A quantitative study of the characteristics and ecological functions of Linpan was performed.The different characteristics and ecological functions of the different zones of Linpan were identified.Further,the influence of the geological background on the characteristics and ecological functions of Linpan were interpreted.On this basis,a quality evaluation model of Linpan was constructed.Constraint and degrees of impact of geological background factors and social environmental factors on the quality of Linpan were studied by a geodetector.Moreover,suggestions for the protection and use of Linpan were proposed for the different zones.Several major conclusions were drawn:(1)According to relevant theories and geological background system methods,a geological background system framework of Linpan was proposed by combining a driving force-state-response(DSR)model.A total of seven indices of geological information(fault density,strata,and Quaternary contour thickness)and geological information(degree of topographic relief,soil type,soil thickness,and dominant tree species)were selected.A spatial clustering comprehensive analysis method was used.Linpan in the Chengdu Plain was divided into three types of zones: the Jurassic-Cretaceous-Pleistocene platform-low mountain-hilly masson pine-camphor-eucalyptus type area in the east(Zone I),the Holocene fan-shaped plain sinocalamus affinis-Eucalyptus-Maple Poplar type area in the middle(Zone II),and the Holocene floodplain and first-class platform oak-alder-other soft extensive type area in the west(Zone III).The areas of these three zones accounted for 46.95%,33.40%,and 19.65% of the total area of Chengdu Plain,respectively.(2)According to studies of the spatial distribution and compositional structural characteristics of Linpan in the different zones of the Chengdu Plain,the Linpan density,mean area,landscape shape index,diversity index,and landscape evenness index of Zone I were low.The mean area and density of Linpan in Zone II were relatively high,while the landscape shape index,diversity index,and landscape evenness index were moderate.Linpan density was high,while the landscape shape index,diversity index,and landscape evenness index were relatively high in Zone III.Differences in the compositional and structural characteristics among the different zones were mainly reflected in the scale,shape,and dominant tree species of Linpan.The correlation analysis between the geological background factors and Linpan density revealed that Quaternary contour thickness,degree of topographic relief,soil type,and soil thickness were significantly correlated with Linpan density(p<0.05).(3)According to the ecological functional assessment results of the different zones of Chengdu City,the water conservation capacity per unit area of Linpan in Zone III was the highest,followed by those of Zone II and Zone I,successively.The soil conservation capacity per unit area of Linpan in Zone I was the highest,followed by those of Zone III and Zone II,successively.The carbon storage capacity per unit area of Linpan in Zone I was relatively high,but the carbon storage capacities in Zone II and Zone III were similar.The biological diversity index of Zone III was slightly higher than that of Zone II,while the biological diversity index of Zone I was the lowest.Several geological background factors were significantly correlated with the ecological functions of Linpan.Specifically,fault density,strata,Quaternary contour thickness,and degree of topographic relief were significantly correlated with water conservation capacity(p<0.05).Quaternary contour thickness,degree of topographic relief,soil type,and soil thickness were significantly correlated with the soil conservation capacity of Linpan(p<0.05).Fault density,degree of topographic relief,and soil type were significantly correlated with the carbon reserves of Linpan(p<0.05).(4)A quality evaluation index system of Linpan was constructed based on the landscape stability,ecological functions,and social-cultural functions of Linpan.The quality of Linpan was evaluated by an analytic hierarchy process(AHP).The results demonstrated that the quality index of Linpan in Zone II was the highest,followed by those of Zone III and Zone I,successively.According to the single-factor model analysis based on a geodetector,the degree of topographic relief,fault density,and land use development were significantly correlated with the quality of Linpan(p<0.05),accounting for 23.80%,16.03%,and 15.43% of the variance,respectively.In other words,geological background factors had important impacts on the quality of Linpan.According to the multi-factor interaction analysis,the interactions between geological background factors and social environmental factors could better explain constraints on the quality of Linpan.Specifically,the interaction between the degree of topographic relief and land use development,between the degree of topographic relief and rural population density,between fault density and land use development,between Quaternary contour thickness and fault density,between fault density and rural per capita net income,and between the degree of topographic relief and Quaternary contour thickness had strong explanatory powers.(5)The characteristics and ecological functions of Linpan were affected by both the geological background and human activities.Therefore,protection and use of Linpan should give full consideration to the geological environment and social environmental factors.Based on studies of the relationship between Linpan and the geological background,this study proposed a conceptual model and path framework for the protection and use of Linpan and identified protection zones of Linpan.Moreover,strategies for the protection and use of Linpan in the three zones were proposed. |
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