| The raw debris flow waste shoal land(DFWSL)is a natural ecosystem formed by debris flows.And with the intervention of human activities,it has gradually become a composite system,which is coupled with human society and the natural environment.In the ecologically fragile area where debris flow occurs frequently,DFWSL is prone to the human and natural factors.Therefoere,it is necessary and inevitable for the efficient DFWSL use to know how the land types transform,what factors and the resilience of the composite system of DFWSL are included,and how the land use and land cover will change in the future.Accordingly,this study takes the social-ecosystem as the main line,examines DFWSL and the relevant human and natural factors,combining the resilience indicators and system dynamic model,to mainly analyze the status,system service and future use trend of the social-ecological system of DFWSL(including forest land,cultivated land,grassland and construction land),clearly grasping the mutual feedback mechanism among the subsystems.And the layout and benefit of semi-composite system based on efficient and safe development and use mode of agriculture and forestry.Finally,through these analyses,we put forward the concept scheme and optimization layout of DFWSL use.Our study has achieved the following results:(1)Based on the present use situation of DFWSL in the typical watershed,the main characteristics and driving forces of DFWSL use change are preliminarily revealed.And the results show that the conversion trend of DFWSL in Wudu,Gansu province and Dongchuan,Yunnan province are both from cultivated land to construction land,which is mainly caused by the influence of national policies and strategies.At the same time,the area of water and unused land are transformed with each other,and the boundary is not obvious,which is mainly affected by natural driving forces(debris flow,landslide and earthquake).And by comparing the natural driving force with the human driving force,it is found that the natural driving force determines the initial development type,and the national policies or strategies in different periods only affect the guidance of land use change.(2)From the perspective of resilience,the interaction process and mechanism among social,economic and ecological factors of DFWSL are discussed,and the vulnerability and availability of typical DFWSL are evaluated.And the results show that the debris flow waste-shoal land system,which integrates nature,economy and society,is mainly characterized by natural ecosystem in the early period of DFWSL development and use.With the improvement of the social and economic system,the social and economic resilience occupy the main part of the resilience of the debris flow waste-shoal land's socio-ecological system.However,as the foundation of the social and economic system,we should pay more attention to the maintenance of the ecosystem stability by increasing the management and construction of the debris flow waste-shoal land's ecosystem.In addition,we found that the resilience is not increasing or decreasing linearly with the time,but in a fluctuation trend.And the disturbance is the instantaneous and direct result,by contrary,the coping capacity of the system is force-storing process,and will take a certain time to exert the effect.(3)Based on the risk zoning,we introduce the "regional risk coefficient" to modify the calculation method of ecosystem service proposed by Costanza,and finally form the suitable calculation formula to calculate the social-ecosystem service of the DFWSL.Meanwhile,we applied this modified formula to calculate the social-eco system service of DFWSL in AWang.And the results show that,in the debris flow area,the ecosystem service of water is relatively large,but because of the limited scale,the transformation between the adjacent land types can be easily generated by the influence from man-made or natural,and finally lead to the change.From 2012 to 2018,the social-ecosystem service of DFWSL in AWang shows a declining trend,and the main reason is due to the decrease in the area of water with greater social-ecosystem service and the increase in the area of construction land with consuming a great amount of social-ecosystem service value.(4)Combining the present development trend and influence factors,and integrating systemic dynamics and GIS,we preliminarily establish a social-ecosystem dynamic simulation model of DFWSL.And the predicted results in Awang,in 2025 and 2030,show that 2025 has little change compared with 2018,but the socio-system service decreases due to the increase of construction land in 2030 compared with 2018 and 2025.In the future construction and development,it will be necessary to coordinate the economic development with the environmental construction.(5)Based on the principle of safety and efficiency,we finally construct the guiding ideology,principle,conceptual framework and overall layout,and analyze the spatial optimization development mode of DFWSL in the typical small watershed.And the results show that land use with a comprehensive consideration of risk is much more considerable than other extensive land development,whether ecological effect,economic effect or social benefit.Although this model is a relatively simple,it provides a case for the optimal layout of DFWSL,and the specific problems need to be analyzed in the subsequent development and utilization. |
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