The thesis gives a brief account of the status of the labor economy in Three Gorges Reservoir area,which indicates that the labor economy in this area has made certain development and is characterized by fragile ecolo...The thesis gives a brief account of the status of the labor economy in Three Gorges Reservoir area,which indicates that the labor economy in this area has made certain development and is characterized by fragile ecology,backward economic development and weak capacity to absorb employment,the Three Gorges Reservoir area is densely populated and has lots of rural surplus labors which need to be transferred.Then the thesis analyzes the problems in the labor export of this region,which can be manifested in the following aspects:the exported labors are with low quality and single skill;they are narrow-minded and have strong intention for their employment regions;they have low income but high risk to get employed;the government does not provide strong supporting services for exported labors.In order to solve these problems,the thesis proposes the suggestions and measures to develop the labor economy in Three Gorges Reservoir area,say,to perfect and ameliorate the training mechanism and improve the quality and skills of labors;to build the platform of employment network and solve the problems of the asymmetric employment information;to actively develop the intermediary organizations and promote the a proper movement of labor forces;to fully exert the function of government in logistic services and resolve the difficulties of the exported workers.展开更多
Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultiv...Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultivated land in the head,central, and tail areas of the reservoir that took place between 1992 and 2015;we then studied the spatial distribution of the cultivated land in the three parts of the reservoir;finally, we studied the driving forces behind the changes in the cultivated land. The results derived are as follows.(1) During the construction of the Three Gorges Project(TGP, 1992–2015), the area of cultivated land around the reservoir decreased by30.23 million ha. This reduction occurred in phases:the most severe change in cultivated land occurred during the later stage of the project(2002–2010);only 0.62 million ha of cultivated land did not change between 1992 and 2015.(2) Spatial pattern analysis showed that the cultivated land in the three parts of the reservoir changed from a northern distribution to a southern distribution;thus, the area of cultivated land in the north decreased over the time period. The area of cultivated land in the head and tail areas decreased by varying degrees, while it increased in the central area over the 23 years, indicating that the change in cultivated land showed regional differences.(3) The TGP, the policy of reverting farmland to forest,and urbanization were the main driving factors for the change of cultivated land, but there were differences in their impacts at different stages.(4) According to the patch dynamics of the land cover change, the degree of change gradually intensified during the early and later stages of the project and then stabilized during the operational period. Our research provides scientific support for the protection of cultivated land resources and food security in the reservoir area and for the coordination of social and economic development, which is of great significance to sustainable development in the reservoir area.展开更多
In this study,taking the typical terracing land in Wushan County of Chongqing Municipality for example,we study the distribution of soil nutrients in the terracing land under different land use patterns in Three Gorge...In this study,taking the typical terracing land in Wushan County of Chongqing Municipality for example,we study the distribution of soil nutrients in the terracing land under different land use patterns in Three Gorges Reservoir Area. We conduct field survey and sampling on three different land use patterns( cash crop land,food crop land and abandoned land),and do the indoor experimental analysis of soil nutrient indicators. The results indicate that there is significant or very significant impact on soil nutrients under different land use patterns. The content of soil organic matter declines in sequence from abandoned land,food crop land to cash crop land; the content of soil N declines in sequence from cash crop land,abandoned land to food crop land; the content of soil P declines in sequence from cash crop land,food crop land to abandoned land; the content of soil K declines in sequence from abandoned land,cash crop land to food crop land. The result is in close relation to land use patterns,human cultivation activity,land disturbance and application of fertilizer.展开更多
To reveal the influencing factors of soil organic carbon( SOC) density in 0-30 cm soil layer of Lanlingxi watershed in Three Gorges Reservoir Area,build the regression equation for soil organic carbon density and adju...To reveal the influencing factors of soil organic carbon( SOC) density in 0-30 cm soil layer of Lanlingxi watershed in Three Gorges Reservoir Area,build the regression equation for soil organic carbon density and adjust carbon sink strategy in this region,soil samples of top soil profile( 0-30 cm) in five land use types were selected by the typical method. The SOC density of top soil profile( 0-30 cm) and other environmental factors,such as elevation,slope and aspect and soil properties in five land use types,including grassland,scrubland,woodland,land for tea plantation and farmland in the watershed was investigated. The relationship of SOC density with physical properties of soil was also examined. The SOC density of the above five land use types averaged 7. 55,3. 83,6. 04,10. 24,2. 83 kg·m^(-2),respectively. There was a significant difference in the SOC density( p < 0. 01); SOC density was significantly positively correlated with organic matter content( R= 0. 942,p < 0. 01),clay mass percentage( R = 0. 898,p < 0. 01),total nitrogen( R = 0. 863,p < 0. 01),elevation( R = 0. 599,p < 0. 01); SOC density was significantly negatively correlated with sand content( R =-0. 932,p < 0. 01) and slope( R =-0. 407,p < 0. 05); and the correlation between SOC density and soil p H,total phosphorus or total potassium was not obvious. Multiple correlation coefficient R = 0. 986( R > 0. 8,highly correlated) between SOC density and environmental factors was greater than the correlation coefficient between any one independent variable and dependent variable,which fully proved the combined effect of environmental factors on SOC density.展开更多
In the long-term symbiotic evolution process,the town areas along the Yangtze River and its natural and cultural landscapes have presented a sound "city-scene" landscape form. But with the implementation of ...In the long-term symbiotic evolution process,the town areas along the Yangtze River and its natural and cultural landscapes have presented a sound "city-scene" landscape form. But with the implementation of the Three Gorges project,the town relocation as well as the flooding in the natural and human landscape area,the original harmonious "city-scene" pattern started to collapse and fell into the situation of "fragmentation" and "islanding". The differentiation between city and landscape,uncoordinated scale and fractured urban context become pressing issues that affect the integral form optimization of the town areas. This paper aims at responding to the call of the government about proceeding the construction of the Yangtze River economic belt under the ecological and green strategy and seeking an attuned "cityscene" relationship of the town area. Based on the analysis of the dynamic evolution of the "city-scene" relationship,the paper also pointed out that the urban construction around the reservoir area in the postThree Gorges era was the key stage of "scene-city" integration and symbiosis while the maintenance of scenery pattern,the harmony of space scale and the protection of living culture should be applied as the vital strategies.展开更多
Numerous researches have been published on the application of landslide susceptibility assessment models;however,they were only applied in the same areas as the models were originated,the effect of applying the models...Numerous researches have been published on the application of landslide susceptibility assessment models;however,they were only applied in the same areas as the models were originated,the effect of applying the models to other areas than the origin of the models has not been explored.This study is purposed to develop an optimized random forest(RF)model with best ratios of positive-to-negative cells and 10-fold cross-validation for landslide susceptibility mapping(LSM),and then explore its generalization ability not only in the area where the model is originated but also in area other than the origin of the model.Two typical counties(Fengjie County and Wushan County)in the Three Gorges Reservoir area,China,which have the same terrain and geological conditions,were selected as an example.To begin with,landslide inventory was prepared based on field investigations,satellite images,and historical records,and 1522 landslides were then identified in Fengjie County.22 landslide-conditioning factors under the influence of topography,geology,environmental conditions,and human activities were prepared.Then,combined with 10-fold cross-validation,three typical ratios of positive-to-negative cells,i.e.,1:1,1:5,and 1:10,were adopted for comparative analyses.An optimized RF model(Fengjie-based model)with the best ratios of positive-to-negative cells and 10-fold cross-validation was constructed.Finally,the Fengjie-based model was applied to Fengjie County and Wushan County,and the confusion matrix and area under the receiver operating characteristic(ROC)curve value(AUC)were used to estimate the accuracy.The Fengjie-based model delivered high stability and predictive capability in Fengjie County,indicating a great generalization ability of the model to the area where the model is originated.The LSM in Wushan County generated by the Fengjie-based model had a reasonable reference value,indicating the Fengjiebased model had a great generalization ability in area other than the origin of the model.The Fengjiebased model in this study could be applied in other similar areas/countries with the same terrain and geological conditions,and a LSM may be generated without collecting landslide information for modeling,so as to reduce workload and improve efficiency in practice.展开更多
According to groundwater level monitoring data of Shuping landslide in the Three Gorges Reservoir area, based on the response relationship between influential factors such as rainfall and reservoir level and the chang...According to groundwater level monitoring data of Shuping landslide in the Three Gorges Reservoir area, based on the response relationship between influential factors such as rainfall and reservoir level and the change of groundwater level, the influential factors of groundwater level were selected. Then the classification and regression tree(CART) model was constructed by the subset and used to predict the groundwater level. Through the verification, the predictive results of the test sample were consistent with the actually measured values, and the mean absolute error and relative error is 0.28 m and 1.15%respectively. To compare the support vector machine(SVM) model constructed using the same set of factors, the mean absolute error and relative error of predicted results is 1.53 m and 6.11% respectively. It is indicated that CART model has not only better fitting and generalization ability, but also strong advantages in the analysis of landslide groundwater dynamic characteristics and the screening of important variables. It is an effective method for prediction of ground water level in landslides.展开更多
The application of ensemble learning models has been continuously improved in recent landslide susceptibility research,but most studies have no unified ensemble framework.Moreover,few papers have discussed the applica...The application of ensemble learning models has been continuously improved in recent landslide susceptibility research,but most studies have no unified ensemble framework.Moreover,few papers have discussed the applicability of the ensemble learning model in landslide susceptibility mapping at the township level.This study aims at defining a robust ensemble framework that can become the benchmark method for future research dealing with the comparison of different ensemble models.For this purpose,the present work focuses on three different basic classifiers:decision tree(DT),support vector machine(SVM),and multi-layer perceptron neural network model(MLPNN)and two homogeneous ensemble models such as random forest(RF)and extreme gradient boosting(XGBoost).The hierarchical construction of deep ensemble relied on two leading ensemble technologies(i.e.,homogeneous/heterogeneous model ensemble and bagging,boosting,stacking ensemble strategy)to provide a more accurate and effective spatial probability of landslide occurrence.The selected study area is Dazhou town,located in the Jurassic red-strata area in the Three Gorges Reservoir Area of China,which is a strategic economic area currently characterized by widespread landslide risk.Based on a long-term field investigation,the inventory counting thirty-three slow-moving landslide polygons was drawn.The results show that the ensemble models do not necessarily perform better;for instance,the Bagging based DT-SVM-MLPNNXGBoost model performed worse than the single XGBoost model.Amongst the eleven tested models,the Stacking based RF-XGBoost model,which is a homogeneous model based on bagging,boosting,and stacking ensemble,showed the highest capability of predicting the landslide-affected areas.Besides,the factor behaviors of DT,SVM,MLPNN,RF and XGBoost models reflected the characteristics of slow-moving landslides in the Three Gorges reservoir area,wherein unfavorable lithological conditions and intense human engineering activities(i.e.,reservoir water level fluctuation,residential area construction,and farmland development)are proven to be the key triggers.The presented approach could be used for landslide spatial occurrence prediction in similar regions and other fields.展开更多
The effects of risk perception and sense of place on disaster preparedness have been widely reported.However, most studies have only demonstrated weak relationships and it is unknown whether these are applicable to Ch...The effects of risk perception and sense of place on disaster preparedness have been widely reported.However, most studies have only demonstrated weak relationships and it is unknown whether these are applicable to China. This study investigated such relationships in hazard-threatened areas of the Three Gorges Reservoir area in southwestern China. Data were collected from 348 farming households in landslide-prone areas. Binary logistic and Tobit regression models were constructed to determine whether risk perception and sense of place influence landslide preparedness. The results show that:(1)Farming households' awareness of the need to prepare for disasters was relatively low, and disaster preparedness behaviors were mainly based on self-learning. Among the348 sampled households, 67% exhibited no disaster preparedness behavior, and only 2% adopted four of the five types of disaster preparedness behaviors. About a quarter of farming households consciously learned disaster-related knowledge.(2) Risk perception and sense of place had important influences on disaster preparedness. Respondentswho received higher scores on the perception of the probability of a landslide, the threat of a landslide, and the place dependence variables were more likely to adopt a greater number of disaster preparedness behaviors.Respondents with higher scores on the perception of controllability in the case of a landslide were less likely to adopt a greater number of disaster preparedness behaviors.Additionally, individual and household socioeconomic characteristics—education, loss, distance from hazard site,information acquisition channel, and housing material—were all related to household disaster preparedness behavior. This study contributes to the current literature by improving the understanding of the relationships of risk perception and sense of place to disaster preparedness in farming households threatened by geological disasters in southwestern China.展开更多
The Three Gorges Reservoir Area(TGRA)is typical of an ecologically vulnerable area,comprised of rural and mountainous areas,and with high immigration.Because of its economic and ecologic importance,studying the tradit...The Three Gorges Reservoir Area(TGRA)is typical of an ecologically vulnerable area,comprised of rural and mountainous areas,and with high immigration.Because of its economic and ecologic importance,studying the traditional agroecosystem changes in the TGRA is key to rural development and revitalization.In this study,we apply a framework of theoretical analysis,empirical study,and trend prediction to the Caotangxi River watershed within the TGRA.Using QuickBird high-resolution remote sensing images from 2012 to 2017 to evaluate natural resources and farmers’behavior,we analyze the transition and trends in the traditional agroecosystem in mountainous areas of the TGRA at spatial scale of the man-land relationship.We find that the agroecosystem in the TGRA can be divided into four modes using 100 m interval buffer rings:high-low-low,high-low-high,low-high-low and low-low-high mode where the different modes represent the agricultural development stages in the TGRA.Furthermore,the traditional agroecosystem in TGRA,represented by system elements such as farmers and sloping farmland,is transforming to accommodate the diversification of farmer livelihoods.For example,sloping farmland,which was dominated by a production function,now has equal emphasis on ecological and economic functions.Spatially,the range of the agroecosystem transition has migrated beyond high mountain areas to flat valley areas.Generally,this study provides an overview of land use in rural areas,controls on soil and water loss in mountainous areas,and better rural living environments in the TGRA.展开更多
Analyzing the agricultural landscape patterns in mountainous areas is critical to clarify the dynamic changes and development direction of agricultural landscapes.This also plays a significant role in the rational pla...Analyzing the agricultural landscape patterns in mountainous areas is critical to clarify the dynamic changes and development direction of agricultural landscapes.This also plays a significant role in the rational planning and management of agricultural land.A theoretical framework for agricultural landscape pattern transitions in mountainous areas is proposed to fill the gap of current research with an empirical study in the Caotangxi Watershed,Three Gorges Reservoir Area(TGRA),China.The transition characteristics of agricultural landscape patterns from 2000 to 2018 as represented by sloping farmland,abandoned land,and orchards are analyzed from a holistic-local perspective.The results indicate that the orchards expanded along river valleys,and abandoned land expanded at high elevations,which led to reduced sloping farmland.This phenomenon gives regional landscape differences at the holistic and local levels.Namely,it enhances the region’s holistic landscape diversity but causes fragmentation and aggregation of landscape patches in local areas.The agricultural landscape pattern transitions within the farming range in the study area are manifested primarily in four modes:sloping farmland-orchard conversion type(FOCT),comprehensive conversion type(CCT),partially abandoned type(PAT),and wholly abandoned type(WAT).Each transition mode reveals different development stages of the mountainous agricultural landscape patterns.In general,the agricultural landscape pattern transition is driven by socioeconomic factors in mountainous areas of the TGRA and is bidirectional.This attribute is expressed as the transition from the traditional grain-planting landscape with an even distribution to the eco-economic win-win orchard in valleys and transitions from sloping farmland to abandoned land in high-elevation areas.Overall,the results of this study reveal the uniqueness of agricultural landscape pattern evolutions in China’s mountainous areas in recent decades,which has enlightened the in-depth understandings of rural land use and agricultural ecosystems in mountainous areas of the TGRA,as well as improvements in rural developments and ecological environments.展开更多
文摘The thesis gives a brief account of the status of the labor economy in Three Gorges Reservoir area,which indicates that the labor economy in this area has made certain development and is characterized by fragile ecology,backward economic development and weak capacity to absorb employment,the Three Gorges Reservoir area is densely populated and has lots of rural surplus labors which need to be transferred.Then the thesis analyzes the problems in the labor export of this region,which can be manifested in the following aspects:the exported labors are with low quality and single skill;they are narrow-minded and have strong intention for their employment regions;they have low income but high risk to get employed;the government does not provide strong supporting services for exported labors.In order to solve these problems,the thesis proposes the suggestions and measures to develop the labor economy in Three Gorges Reservoir area,say,to perfect and ameliorate the training mechanism and improve the quality and skills of labors;to build the platform of employment network and solve the problems of the asymmetric employment information;to actively develop the intermediary organizations and promote the a proper movement of labor forces;to fully exert the function of government in logistic services and resolve the difficulties of the exported workers.
基金funded by the 135 Strategic Program of the Institute of Mountain Hazards and Environment, CAS (Grant No. SDS135-1703)Coupled relationship and regulation mechanism between rural livelihoods and ecosystem services in the Three Gorges Reservoir Area (No.41371539)
文摘Changes of cultivated land patterns caused by major water conservation projects are rarely reported. We selected the Three Gorges Reservoir area in China to study the change in area and landscape pattern of the cultivated land in the head,central, and tail areas of the reservoir that took place between 1992 and 2015;we then studied the spatial distribution of the cultivated land in the three parts of the reservoir;finally, we studied the driving forces behind the changes in the cultivated land. The results derived are as follows.(1) During the construction of the Three Gorges Project(TGP, 1992–2015), the area of cultivated land around the reservoir decreased by30.23 million ha. This reduction occurred in phases:the most severe change in cultivated land occurred during the later stage of the project(2002–2010);only 0.62 million ha of cultivated land did not change between 1992 and 2015.(2) Spatial pattern analysis showed that the cultivated land in the three parts of the reservoir changed from a northern distribution to a southern distribution;thus, the area of cultivated land in the north decreased over the time period. The area of cultivated land in the head and tail areas decreased by varying degrees, while it increased in the central area over the 23 years, indicating that the change in cultivated land showed regional differences.(3) The TGP, the policy of reverting farmland to forest,and urbanization were the main driving factors for the change of cultivated land, but there were differences in their impacts at different stages.(4) According to the patch dynamics of the land cover change, the degree of change gradually intensified during the early and later stages of the project and then stabilized during the operational period. Our research provides scientific support for the protection of cultivated land resources and food security in the reservoir area and for the coordination of social and economic development, which is of great significance to sustainable development in the reservoir area.
基金Supported by National Natural Science Foundation of China(41471234)Chongqing Basic and Cutting-edge Research Project(cstc2015jcyjB X0141)+2 种基金Natural Science Foundation of Chongqing(CSTC,2010BB0326)Social Sciences Project of Chongqing Municipal Education Commission(08JWSK043)Ph.D.Fund Project of Chongqing Normal University(05XLB)
文摘In this study,taking the typical terracing land in Wushan County of Chongqing Municipality for example,we study the distribution of soil nutrients in the terracing land under different land use patterns in Three Gorges Reservoir Area. We conduct field survey and sampling on three different land use patterns( cash crop land,food crop land and abandoned land),and do the indoor experimental analysis of soil nutrient indicators. The results indicate that there is significant or very significant impact on soil nutrients under different land use patterns. The content of soil organic matter declines in sequence from abandoned land,food crop land to cash crop land; the content of soil N declines in sequence from cash crop land,abandoned land to food crop land; the content of soil P declines in sequence from cash crop land,food crop land to abandoned land; the content of soil K declines in sequence from abandoned land,cash crop land to food crop land. The result is in close relation to land use patterns,human cultivation activity,land disturbance and application of fertilizer.
基金Supported by National Natural Science Foundation(31670616)
文摘To reveal the influencing factors of soil organic carbon( SOC) density in 0-30 cm soil layer of Lanlingxi watershed in Three Gorges Reservoir Area,build the regression equation for soil organic carbon density and adjust carbon sink strategy in this region,soil samples of top soil profile( 0-30 cm) in five land use types were selected by the typical method. The SOC density of top soil profile( 0-30 cm) and other environmental factors,such as elevation,slope and aspect and soil properties in five land use types,including grassland,scrubland,woodland,land for tea plantation and farmland in the watershed was investigated. The relationship of SOC density with physical properties of soil was also examined. The SOC density of the above five land use types averaged 7. 55,3. 83,6. 04,10. 24,2. 83 kg·m^(-2),respectively. There was a significant difference in the SOC density( p < 0. 01); SOC density was significantly positively correlated with organic matter content( R= 0. 942,p < 0. 01),clay mass percentage( R = 0. 898,p < 0. 01),total nitrogen( R = 0. 863,p < 0. 01),elevation( R = 0. 599,p < 0. 01); SOC density was significantly negatively correlated with sand content( R =-0. 932,p < 0. 01) and slope( R =-0. 407,p < 0. 05); and the correlation between SOC density and soil p H,total phosphorus or total potassium was not obvious. Multiple correlation coefficient R = 0. 986( R > 0. 8,highly correlated) between SOC density and environmental factors was greater than the correlation coefficient between any one independent variable and dependent variable,which fully proved the combined effect of environmental factors on SOC density.
基金Sponsored by:National Key Technology of China(2012BAJ15B00)Efficiency Optimization of Key Technology Research on High Urban Population Density Space(2012BAJ15B03)
文摘In the long-term symbiotic evolution process,the town areas along the Yangtze River and its natural and cultural landscapes have presented a sound "city-scene" landscape form. But with the implementation of the Three Gorges project,the town relocation as well as the flooding in the natural and human landscape area,the original harmonious "city-scene" pattern started to collapse and fell into the situation of "fragmentation" and "islanding". The differentiation between city and landscape,uncoordinated scale and fractured urban context become pressing issues that affect the integral form optimization of the town areas. This paper aims at responding to the call of the government about proceeding the construction of the Yangtze River economic belt under the ecological and green strategy and seeking an attuned "cityscene" relationship of the town area. Based on the analysis of the dynamic evolution of the "city-scene" relationship,the paper also pointed out that the urban construction around the reservoir area in the postThree Gorges era was the key stage of "scene-city" integration and symbiosis while the maintenance of scenery pattern,the harmony of space scale and the protection of living culture should be applied as the vital strategies.
基金the National Natural Science Foundation of China(No.41807498)the National Key Research and Development Program of China(No.2018YFC1505501)the Humanities and Social Sciences Foundation of the Ministry of Education of China(No.20XJAZH002)。
文摘Numerous researches have been published on the application of landslide susceptibility assessment models;however,they were only applied in the same areas as the models were originated,the effect of applying the models to other areas than the origin of the models has not been explored.This study is purposed to develop an optimized random forest(RF)model with best ratios of positive-to-negative cells and 10-fold cross-validation for landslide susceptibility mapping(LSM),and then explore its generalization ability not only in the area where the model is originated but also in area other than the origin of the model.Two typical counties(Fengjie County and Wushan County)in the Three Gorges Reservoir area,China,which have the same terrain and geological conditions,were selected as an example.To begin with,landslide inventory was prepared based on field investigations,satellite images,and historical records,and 1522 landslides were then identified in Fengjie County.22 landslide-conditioning factors under the influence of topography,geology,environmental conditions,and human activities were prepared.Then,combined with 10-fold cross-validation,three typical ratios of positive-to-negative cells,i.e.,1:1,1:5,and 1:10,were adopted for comparative analyses.An optimized RF model(Fengjie-based model)with the best ratios of positive-to-negative cells and 10-fold cross-validation was constructed.Finally,the Fengjie-based model was applied to Fengjie County and Wushan County,and the confusion matrix and area under the receiver operating characteristic(ROC)curve value(AUC)were used to estimate the accuracy.The Fengjie-based model delivered high stability and predictive capability in Fengjie County,indicating a great generalization ability of the model to the area where the model is originated.The LSM in Wushan County generated by the Fengjie-based model had a reasonable reference value,indicating the Fengjiebased model had a great generalization ability in area other than the origin of the model.The Fengjiebased model in this study could be applied in other similar areas/countries with the same terrain and geological conditions,and a LSM may be generated without collecting landslide information for modeling,so as to reduce workload and improve efficiency in practice.
基金supported by the China Earthquake Administration, Institute of Seismology Foundation (IS201526246)
文摘According to groundwater level monitoring data of Shuping landslide in the Three Gorges Reservoir area, based on the response relationship between influential factors such as rainfall and reservoir level and the change of groundwater level, the influential factors of groundwater level were selected. Then the classification and regression tree(CART) model was constructed by the subset and used to predict the groundwater level. Through the verification, the predictive results of the test sample were consistent with the actually measured values, and the mean absolute error and relative error is 0.28 m and 1.15%respectively. To compare the support vector machine(SVM) model constructed using the same set of factors, the mean absolute error and relative error of predicted results is 1.53 m and 6.11% respectively. It is indicated that CART model has not only better fitting and generalization ability, but also strong advantages in the analysis of landslide groundwater dynamic characteristics and the screening of important variables. It is an effective method for prediction of ground water level in landslides.
基金This research was funded by the National Natural Science Foundation of China(Grant No.41877525)the National Natural Science Foundation of China(Grant No.41601563)。
文摘The application of ensemble learning models has been continuously improved in recent landslide susceptibility research,but most studies have no unified ensemble framework.Moreover,few papers have discussed the applicability of the ensemble learning model in landslide susceptibility mapping at the township level.This study aims at defining a robust ensemble framework that can become the benchmark method for future research dealing with the comparison of different ensemble models.For this purpose,the present work focuses on three different basic classifiers:decision tree(DT),support vector machine(SVM),and multi-layer perceptron neural network model(MLPNN)and two homogeneous ensemble models such as random forest(RF)and extreme gradient boosting(XGBoost).The hierarchical construction of deep ensemble relied on two leading ensemble technologies(i.e.,homogeneous/heterogeneous model ensemble and bagging,boosting,stacking ensemble strategy)to provide a more accurate and effective spatial probability of landslide occurrence.The selected study area is Dazhou town,located in the Jurassic red-strata area in the Three Gorges Reservoir Area of China,which is a strategic economic area currently characterized by widespread landslide risk.Based on a long-term field investigation,the inventory counting thirty-three slow-moving landslide polygons was drawn.The results show that the ensemble models do not necessarily perform better;for instance,the Bagging based DT-SVM-MLPNNXGBoost model performed worse than the single XGBoost model.Amongst the eleven tested models,the Stacking based RF-XGBoost model,which is a homogeneous model based on bagging,boosting,and stacking ensemble,showed the highest capability of predicting the landslide-affected areas.Besides,the factor behaviors of DT,SVM,MLPNN,RF and XGBoost models reflected the characteristics of slow-moving landslides in the Three Gorges reservoir area,wherein unfavorable lithological conditions and intense human engineering activities(i.e.,reservoir water level fluctuation,residential area construction,and farmland development)are proven to be the key triggers.The presented approach could be used for landslide spatial occurrence prediction in similar regions and other fields.
基金the financial support from the National Natural Science Foundation of China(Grant No.41771194)the West Light Foundation of the Chinese Academyof Sciences(Y5R2080080)+2 种基金the 135 Strategic Program of the Institute of Mountain Hazards and Environment,Chinese Academy of Science(sds-135-1703)the Youth Talent Team Program of the Institute of Mountain Hazards and Environment,Chinese Academy of Sciences(SDSQB-2015-01)the Youth Innovation Promotion Association,Chinese Academy of Sciences(2016332)
文摘The effects of risk perception and sense of place on disaster preparedness have been widely reported.However, most studies have only demonstrated weak relationships and it is unknown whether these are applicable to China. This study investigated such relationships in hazard-threatened areas of the Three Gorges Reservoir area in southwestern China. Data were collected from 348 farming households in landslide-prone areas. Binary logistic and Tobit regression models were constructed to determine whether risk perception and sense of place influence landslide preparedness. The results show that:(1)Farming households' awareness of the need to prepare for disasters was relatively low, and disaster preparedness behaviors were mainly based on self-learning. Among the348 sampled households, 67% exhibited no disaster preparedness behavior, and only 2% adopted four of the five types of disaster preparedness behaviors. About a quarter of farming households consciously learned disaster-related knowledge.(2) Risk perception and sense of place had important influences on disaster preparedness. Respondentswho received higher scores on the perception of the probability of a landslide, the threat of a landslide, and the place dependence variables were more likely to adopt a greater number of disaster preparedness behaviors.Respondents with higher scores on the perception of controllability in the case of a landslide were less likely to adopt a greater number of disaster preparedness behaviors.Additionally, individual and household socioeconomic characteristics—education, loss, distance from hazard site,information acquisition channel, and housing material—were all related to household disaster preparedness behavior. This study contributes to the current literature by improving the understanding of the relationships of risk perception and sense of place to disaster preparedness in farming households threatened by geological disasters in southwestern China.
基金Key Basic Science and Cutting Edge Technology Research Plan of Chongqing,No.cstc2015jcyjB0439Chongqing University Innovation Team for 2016,No.CXTDX201601017+1 种基金National Natural Science Foundation of China,No.41661020Chongqing Research Program of Basic Research and Frontier Technology,No.cstc2018jcyjAX0539。
文摘The Three Gorges Reservoir Area(TGRA)is typical of an ecologically vulnerable area,comprised of rural and mountainous areas,and with high immigration.Because of its economic and ecologic importance,studying the traditional agroecosystem changes in the TGRA is key to rural development and revitalization.In this study,we apply a framework of theoretical analysis,empirical study,and trend prediction to the Caotangxi River watershed within the TGRA.Using QuickBird high-resolution remote sensing images from 2012 to 2017 to evaluate natural resources and farmers’behavior,we analyze the transition and trends in the traditional agroecosystem in mountainous areas of the TGRA at spatial scale of the man-land relationship.We find that the agroecosystem in the TGRA can be divided into four modes using 100 m interval buffer rings:high-low-low,high-low-high,low-high-low and low-low-high mode where the different modes represent the agricultural development stages in the TGRA.Furthermore,the traditional agroecosystem in TGRA,represented by system elements such as farmers and sloping farmland,is transforming to accommodate the diversification of farmer livelihoods.For example,sloping farmland,which was dominated by a production function,now has equal emphasis on ecological and economic functions.Spatially,the range of the agroecosystem transition has migrated beyond high mountain areas to flat valley areas.Generally,this study provides an overview of land use in rural areas,controls on soil and water loss in mountainous areas,and better rural living environments in the TGRA.
基金National Natural Science Foundation of China,No.41661020Chongqing Basic and Frontier Research Innovation Project,No.cstc2018jcyjAX0539,No.cstc2017jcyjB0317+1 种基金Chongqing Normal University Graduate Student Research Innovation Project,No.YKC20049,No.YKC20030Academician Expert Workstation Academician Guided Science and Technology Innovation Special Project,No.CXTDX201601017。
文摘Analyzing the agricultural landscape patterns in mountainous areas is critical to clarify the dynamic changes and development direction of agricultural landscapes.This also plays a significant role in the rational planning and management of agricultural land.A theoretical framework for agricultural landscape pattern transitions in mountainous areas is proposed to fill the gap of current research with an empirical study in the Caotangxi Watershed,Three Gorges Reservoir Area(TGRA),China.The transition characteristics of agricultural landscape patterns from 2000 to 2018 as represented by sloping farmland,abandoned land,and orchards are analyzed from a holistic-local perspective.The results indicate that the orchards expanded along river valleys,and abandoned land expanded at high elevations,which led to reduced sloping farmland.This phenomenon gives regional landscape differences at the holistic and local levels.Namely,it enhances the region’s holistic landscape diversity but causes fragmentation and aggregation of landscape patches in local areas.The agricultural landscape pattern transitions within the farming range in the study area are manifested primarily in four modes:sloping farmland-orchard conversion type(FOCT),comprehensive conversion type(CCT),partially abandoned type(PAT),and wholly abandoned type(WAT).Each transition mode reveals different development stages of the mountainous agricultural landscape patterns.In general,the agricultural landscape pattern transition is driven by socioeconomic factors in mountainous areas of the TGRA and is bidirectional.This attribute is expressed as the transition from the traditional grain-planting landscape with an even distribution to the eco-economic win-win orchard in valleys and transitions from sloping farmland to abandoned land in high-elevation areas.Overall,the results of this study reveal the uniqueness of agricultural landscape pattern evolutions in China’s mountainous areas in recent decades,which has enlightened the in-depth understandings of rural land use and agricultural ecosystems in mountainous areas of the TGRA,as well as improvements in rural developments and ecological environments.
