| Social ecological system Science(SES)conceptualizes the environment as an open system,which is composed of ecological and social processes and components.These processes are integrated through the interaction of multiple scales and cycles.In the current study of social ecological system evolution,it is common to identify the evolution stage and analyze the driving force according to the change point of a single social or ecological component.The disadvantage is that their interaction is often ignored.Tianzhu Tibetan Autonomous County is located in the eastern part of Qilian Mountains,in the middle and upper reaches of the Yellow River Basin,and also the source of Shiyang River.The forest in the territory is mainly Qilian water conservation forest,which plays a very important strategic role in maintaining national ecological security.At the same time,Tianzhu is also the only Plateau Tibetan Autonomous County in Hexi corridor.The county economy has distinctive characteristics.The economy is dominated by agriculture and animal husbandry,and the contradiction between agriculture,forestry and animal husbandry is more prominent.The research analyzes the evolution process and evolution driving force from the perspective of the interaction process between the constituent elements of Tianzhu social ecological system,and highlights the necessity of integration and system perspective in social ecological system management.Through the statistical analysis of social economy and the application of GIS methods,this paper analyzes the social and ecological subsystem and related climate change.Based on the above analysis data,the dynamic evolution of social ecological system in the study area is quantitatively analyzed by using entropy weight catastrophe theory method and adaptive cycle theory.Finally,the driving factors of social ecological system evolution are further quantitatively analyzed by using PLS model.The study draws the following preliminary conclusions:(1)In terms of social system,Tianzhu takes agriculture and industry as the main economic sectors,and the per capita income has increased steadily,but the gap between the income of urban residents and the farmers and herdsmen has gradually widened.The population shows a trend of steady growth and then slow decline.The strength and intensity of policies in the study area are increasing,the policies and systems of water resources,forest and grass resources management are constantly improving.During the study period,the resilience of social system gradually increased from low resilience to high resilience,and its evolution is the result of the interaction of policy,economy,production and population indicators.(2)In terms of ecosystem evolution,grassland is the main land use / cover type in Tianzhu County,followed by forest land and cultivated land.During the study period,the area of cultivated land and forest land is increasing,and the area of grassland is shrinking and degraded seriously.The high value area of carbon storage distribution is concentrated in the woodland area of the study area,and the total carbon storage fluctuated and increased during the study period;There are significant differences in the spatial distribution of habitat quality,the habitat quality of the southwest and Northern outer edges of the study area is the best.During the study period,the habitat quality showed an overall trend of improvement.Ecosystem service value and its function value show a fluctuating growth trend.Grassland and forest land are the main components of ecosystem service value,the contribution rate of forest land to ecosystem service value is increasing.The overall change of water conservation showed an increasing trend and reached the maximum value in 2007.The high value areas of water conservation are concentrated in the high-altitude forest land distribution area.Grassland is the main contributor to water conservation in this area,but its contribution is fluctuating and decreasing,the contribution of forest land is increasing.The annual average NPP value shows a fluctuating growth trend.The study of landscape index shows that the diversity of the overall landscape,the richness of landscape types and the uniformity of landscape distribution in the study area are increased.With the continuous adjustment,the resilience of the ecosystem has gradually improved,from the level 1 in 1990 to the current level 5.Its evolution is the result of the interaction of resources,habitat and services,climate change.(3)In terms of climate change,according to historical meteorological data and climate temporal-spatial model,the change characteristics of climate system are analyzed.The study found that 1997 was the turning year of average temperature in Tianzhu County,and the temperature anomaly showed a consistent positive anomaly from that year.The climate temporal-spatial model shows that the climate in Tianzhu county developed in the direction of increasing temperature and humidity from 1986 to 2020.(4)Based on resilience theory and methodology,combined with catastrophe theory and adaptive cycle theory,this paper quantitatively analyzes the evolution process and adaptive cycle process of social subsystem,ecological subsystem and social ecological system in the study area from 1990 to 2020.The results show that the coordinated development of society ecosystem in the study area has made great progress in the past few decades.The study area has a high degree of coupling and strong connection between social and ecological coordinated development.This shows the great role and success of ecological protection policies and ecological protection projects in the study area in the past few decades.The improvement of social system resilience will become the key to the improvement of social ecological system resilience in the study area.Using PLS model,this paper makes a quantitative analysis on the evolution driving forces of social ecological system in the study area.The results show that policy,production,population and climate change are the key driving forces of social ecological system evolution in the study area.The social ecological system is affected by the interaction of social subsystem and ecological subsystem,so that the composite system seeks a balance in solving the internal and external contradictions of each subsystem respectively,so as to complete the adaptive cycle evolution of each stage and finally develop in a sustainable direction.How to improve the resilience of social system,develop green ecological industry and convert the value of ecological products will become one of the important topics for the further development of the study area. |
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