Understanding the trajectories and driving mechanisms behind land use/land cover(LULC)changes is essential for effective watershed planning and management.This study quantified the net change,exchange,total change,and...Understanding the trajectories and driving mechanisms behind land use/land cover(LULC)changes is essential for effective watershed planning and management.This study quantified the net change,exchange,total change,and transfer rate of LULC in the Jinghe River Basin(JRB),China using LULC data from 2000 to 2020.Through trajectory analysis,knowledge maps,chord diagrams,and standard deviation ellipse method,we examined the spatiotemporal characteristics of LULC changes.We further established an index system encompassing natural factors(digital elevation model(DEM),slope,aspect,and curvature),socio-economic factors(gross domestic product(GDP)and population),and accessibility factors(distance from railways,distance from highways,distance from water,and distance from residents)to investigate the driving mechanisms of LULC changes using factor detector and interaction detector in the geographical detector(Geodetector).The key findings indicate that from 2000 to 2020,the JRB experienced significant LULC changes,particularly for farmland,forest,and grassland.During the study period,LULC change trajectories were categorized into stable,early-stage,late-stage,repeated,and continuous change types.Besides the stable change type,the late-stage change type predominated the LULC change trajectories,comprising 83.31% of the total change area.The period 2010-2020 witnessed more active LULC changes compared to the period 2000-2010.The LULC changes exhibited a discrete spatial expansion trend during 2000-2020,predominantly extending from southeast to northwest of the JRB.Influential driving factors on LULC changes included slope,GDP,and distance from highways.The interaction detection results imply either bilinear or nonlinear enhancement for any two driving factors impacting the LULC changes from 2000 to 2020.This comprehensive understanding of the spatiotemporal characteristics and driving mechanisms of LULC changes offers valuable insights for the planning and sustainable management of LULC in the JRB.展开更多
The changes in utilization of agricultural land have gradually grown into one of the major factors impacting grain output in China. This study explores the various components of agricultural production in China from t...The changes in utilization of agricultural land have gradually grown into one of the major factors impacting grain output in China. This study explores the various components of agricultural production in China from the land utilization perspective, involving changes in grain production per unit area, multi-cropping index, and adjustment of agricultural structure. Compared with the record values, different research methodologies are used to analyze the po- tential of above three components. The results indicate that grain production potential of 65.68×109kg was unexploited in 2006, in which 45.8×109kg came from the restructuring in agriculture. So we can infer that the reduction of grain production in China could be primarily attributed to agricultural restructuring in recent years. So the productive poten- tial can be fully restored by increasing agricultural investment, or recovering agricultural structure in favorable condi- tions. So we can say that China’s current condition of food security is good.展开更多
Mu Us Sandy Land(MUSL) of China, as a typical eco-fragile and farming-pastoral transitional region, shows great vulnerability to disturbances from cultivation activity. In this region, the conflict between cultivation...Mu Us Sandy Land(MUSL) of China, as a typical eco-fragile and farming-pastoral transitional region, shows great vulnerability to disturbances from cultivation activity. In this region, the conflict between cultivation activity and environmental protection has not attracted great importance until the implementation of China's Grain-for-Green Policy(CGGP) since2000. Here, using Landsat5 TM/Landsat7 ETM+ images from 1990, 2000, and 2010, we monitor the cultivation activity and land-use/cover changes(LUCC) resulting from cultivation activity in the MUSL region. Based on the data from images, we developed a series of databases of cultivated activity-induced LUCC and use them to discuss comparatively the spatio-temporal evolution trends of cultivation activity before and after CGGP implementation. These results provide evidence for managers to evaluate the implementation effectiveness of governmental policy and the influence of cultivation activity on the ecological environment of the MUSL region.展开更多
Analysis of recent changes in the amount and nature of cultivated land and grain potential, and the impacts of these changes on grain security in China's Mainland provides vital information for revising and develo...Analysis of recent changes in the amount and nature of cultivated land and grain potential, and the impacts of these changes on grain security in China's Mainland provides vital information for revising and developing strategies regarding protection of cultivated land and national grain security. This study examined changes in the area of cultivated land and in grain potential in agro-ecological zones using the "change rate" method. Agro-ecological subzones were used as the basic units and agro-ecological zones as the research units. We then studied changes for all of China's Mainland using the "gravity centre model" and analyzed the structural change of cultivated lands in each agro-ecological zone to investigate the changes in detail. The results show that both cultivated land and grain potential in China's Mainland decreased from 1996 to 2007. The structural and quantitative changes in each zone have caused the shift of the gravity centres of cultivated land and grain potential in China's Mainland to the northeast. Unfortunately, it is unlikely that natural and economic resources can keep up with this change. Although a large gap remains between the grain potential and the actual grain yield, the rapid loss of grain potential and the direction of change pose great threats to grain security. To ensure comprehensive grain security in China, it is vital to rethink the regional patterns of grain production according to natural conditions without jeopardising cultivated land protection(quantitative and qualitative), and consider the direction of cultivated land use and reconstruction according to local natural conditions, water and soil resources, and the level of economic development, and then work steadily to improve the grain potential.展开更多
基于检索1950-2016年发表在中国知网、Google Scholar、Web of Science等数据库的文章,筛选出关于我国退耕还草工程与土壤有机碳的文献123篇(126个研究地点)。基于筛选文献,提取了农田和恢复草地的土壤有机碳含量、土壤有效养分含量、...基于检索1950-2016年发表在中国知网、Google Scholar、Web of Science等数据库的文章,筛选出关于我国退耕还草工程与土壤有机碳的文献123篇(126个研究地点)。基于筛选文献,提取了农田和恢复草地的土壤有机碳含量、土壤有效养分含量、恢复时间和气候等数据735条,旨在探究我国退耕还草工程对土壤有机碳含量的影响及其主导因素。结果表明:1)农田恢复为草地后,土壤有机碳含量呈先下降后上升趋势(时间拐点约为第6年),整体上退耕还草工程使土壤有机碳含量提高了19.8%。2)土壤有机碳的正响应随土壤深度增加而减弱,且深度超过1 m时其正响应不明显。3)土壤有效氮是影响土壤有机碳恢复的主要因素,而土壤有效磷和植物功能群对其影响不大。4)沿着增加的水分梯度,土壤有机碳的恢复效果由负变正,转变阈值为25.15 (干旱指数)。总体而言,我国退耕还草工程对土壤有机碳含量的影响为正效应,此效应受环境梯度和恢复时间的共同影响。本研究能够为我国土地利用变化背景下土壤碳库管理的相关决策提供科学依据。展开更多
科尔沁沙地生态环境脆弱,对气候变化反应敏感,明确沙地演化规律及其对气候变化的响应对于未来沙地保护和管理具有重要理论指导意义。以科尔沁沙地东北缘一处风沙古土壤剖面为研究对象,利用粒度、烧失量、植硅体指标系统重建了科尔沁沙...科尔沁沙地生态环境脆弱,对气候变化反应敏感,明确沙地演化规律及其对气候变化的响应对于未来沙地保护和管理具有重要理论指导意义。以科尔沁沙地东北缘一处风沙古土壤剖面为研究对象,利用粒度、烧失量、植硅体指标系统重建了科尔沁沙地中晚全新世以来的气候变化和沙地演化。结果表明:5700~2400 cal a BP期间,科尔沁沙地经历了2次固定期和2次扩张期。第一次固定期为5700~4800 cal a BP,东亚夏季风强烈,气候温暖湿润,沙地大部分为固定沙丘;第一次扩张期为4800~3900 cal a BP,此时夏季风不断衰退,气候开始变得冷干,导致沙地逐渐扩张;第二次固定期为3900~3300 cal a BP,气候转暖湿,土壤发育,沙地面积减少;第二次扩张期为3300~2400 cal a BP,气候转冷干,沙地再次扩张,古土壤层普遍被风沙覆盖。总之,东亚夏季风驱动的气候变化驱动了科尔沁沙地中晚全新世沙地演化,沙地管理政策的制定需要特别关注未来气候变化趋势。展开更多
We present an approach to regional environ- mental monitoring in the Northern Eurasian grain belt combining time series analysis of MODIS normalized difference vegetation index （NDVI） data over the period 2001-2008 ...We present an approach to regional environ- mental monitoring in the Northern Eurasian grain belt combining time series analysis of MODIS normalized difference vegetation index （NDVI） data over the period 2001-2008 and land cover change （LCC） analysis of the 2001 and 2008 MODIS Global Land Cover product （MCD 12Q 1）. NDVI trends were overwhelmingly negative across the grain belt with statistically significant （p ≤0.05） positive trends covering only 1% of the land surface. LCC was dominated by transitions between three classes; cropland, grassland, and a mixed cropland/natural vegeta- tion mosaic. Combining our analyses of NDVI trends and LCC, we found a pattern of agricultural abandonment （cropland to grassland） in the southern range of the grain belt coinciding with statistically significant （p≤0.05） negative NDVI trends and likely driven by regional drought. In the northern range of the grain belt we found an opposite tendency toward agricultural intensification; in this case, represented by LCC from cropland mosaic to pure cropland, and also associated with statistically significant （p≤0.05） negative NDVI trends. Relatively small clusters of statistically significant （p ≤ 0.05） positive NDVI trends corresponding with both localized land abandonment and localized agricultural intensification show that land use decision making is not uniform across the region. Land surface change in the Northern Eurasian grain belt is part of a larger pattern of land cover land use change （LCLUC） in Eastern Europe, Russia, and former territories of the Soviet Union following realignment of socialist land tenure and agricultural markets. Here, we show that a combined analysis of LCC and NDVI trends provides a more complete picture of the complex- ities of LCLUC in the Northern Eurasian grain belt,involving both broader climatic forcing, and narrower anthropogenic impacts, than might be obtained from either analysis alone.展开更多
基金partly funded by the National Key Research and Development Program of China(NK2023190801)the National Foreign Experts Program of China(G2023041024L)the Key Scientific Research Program of Shaanxi Provincial Education Department,China(21JT028)。
文摘Understanding the trajectories and driving mechanisms behind land use/land cover(LULC)changes is essential for effective watershed planning and management.This study quantified the net change,exchange,total change,and transfer rate of LULC in the Jinghe River Basin(JRB),China using LULC data from 2000 to 2020.Through trajectory analysis,knowledge maps,chord diagrams,and standard deviation ellipse method,we examined the spatiotemporal characteristics of LULC changes.We further established an index system encompassing natural factors(digital elevation model(DEM),slope,aspect,and curvature),socio-economic factors(gross domestic product(GDP)and population),and accessibility factors(distance from railways,distance from highways,distance from water,and distance from residents)to investigate the driving mechanisms of LULC changes using factor detector and interaction detector in the geographical detector(Geodetector).The key findings indicate that from 2000 to 2020,the JRB experienced significant LULC changes,particularly for farmland,forest,and grassland.During the study period,LULC change trajectories were categorized into stable,early-stage,late-stage,repeated,and continuous change types.Besides the stable change type,the late-stage change type predominated the LULC change trajectories,comprising 83.31% of the total change area.The period 2010-2020 witnessed more active LULC changes compared to the period 2000-2010.The LULC changes exhibited a discrete spatial expansion trend during 2000-2020,predominantly extending from southeast to northwest of the JRB.Influential driving factors on LULC changes included slope,GDP,and distance from highways.The interaction detection results imply either bilinear or nonlinear enhancement for any two driving factors impacting the LULC changes from 2000 to 2020.This comprehensive understanding of the spatiotemporal characteristics and driving mechanisms of LULC changes offers valuable insights for the planning and sustainable management of LULC in the JRB.
基金Under the auspices of National Key Technologies R&D Program of China (No. 2006BAB15B02)National Natural Science Foundation of China (No. 40671009)
文摘The changes in utilization of agricultural land have gradually grown into one of the major factors impacting grain output in China. This study explores the various components of agricultural production in China from the land utilization perspective, involving changes in grain production per unit area, multi-cropping index, and adjustment of agricultural structure. Compared with the record values, different research methodologies are used to analyze the po- tential of above three components. The results indicate that grain production potential of 65.68×109kg was unexploited in 2006, in which 45.8×109kg came from the restructuring in agriculture. So we can infer that the reduction of grain production in China could be primarily attributed to agricultural restructuring in recent years. So the productive poten- tial can be fully restored by increasing agricultural investment, or recovering agricultural structure in favorable condi- tions. So we can say that China’s current condition of food security is good.
基金funded by the China National Key Basic Research Programme (2013CB429901)the National Natural Science Foundation of China (General Programme: 41171400)+1 种基金Youth Innovation Promotion Association, CAS (2016158)the National Key Research and Development Program of China (2016YFC0503706)
文摘Mu Us Sandy Land(MUSL) of China, as a typical eco-fragile and farming-pastoral transitional region, shows great vulnerability to disturbances from cultivation activity. In this region, the conflict between cultivation activity and environmental protection has not attracted great importance until the implementation of China's Grain-for-Green Policy(CGGP) since2000. Here, using Landsat5 TM/Landsat7 ETM+ images from 1990, 2000, and 2010, we monitor the cultivation activity and land-use/cover changes(LUCC) resulting from cultivation activity in the MUSL region. Based on the data from images, we developed a series of databases of cultivated activity-induced LUCC and use them to discuss comparatively the spatio-temporal evolution trends of cultivation activity before and after CGGP implementation. These results provide evidence for managers to evaluate the implementation effectiveness of governmental policy and the influence of cultivation activity on the ecological environment of the MUSL region.
文摘Analysis of recent changes in the amount and nature of cultivated land and grain potential, and the impacts of these changes on grain security in China's Mainland provides vital information for revising and developing strategies regarding protection of cultivated land and national grain security. This study examined changes in the area of cultivated land and in grain potential in agro-ecological zones using the "change rate" method. Agro-ecological subzones were used as the basic units and agro-ecological zones as the research units. We then studied changes for all of China's Mainland using the "gravity centre model" and analyzed the structural change of cultivated lands in each agro-ecological zone to investigate the changes in detail. The results show that both cultivated land and grain potential in China's Mainland decreased from 1996 to 2007. The structural and quantitative changes in each zone have caused the shift of the gravity centres of cultivated land and grain potential in China's Mainland to the northeast. Unfortunately, it is unlikely that natural and economic resources can keep up with this change. Although a large gap remains between the grain potential and the actual grain yield, the rapid loss of grain potential and the direction of change pose great threats to grain security. To ensure comprehensive grain security in China, it is vital to rethink the regional patterns of grain production according to natural conditions without jeopardising cultivated land protection(quantitative and qualitative), and consider the direction of cultivated land use and reconstruction according to local natural conditions, water and soil resources, and the level of economic development, and then work steadily to improve the grain potential.
文摘科尔沁沙地生态环境脆弱,对气候变化反应敏感,明确沙地演化规律及其对气候变化的响应对于未来沙地保护和管理具有重要理论指导意义。以科尔沁沙地东北缘一处风沙古土壤剖面为研究对象,利用粒度、烧失量、植硅体指标系统重建了科尔沁沙地中晚全新世以来的气候变化和沙地演化。结果表明:5700~2400 cal a BP期间,科尔沁沙地经历了2次固定期和2次扩张期。第一次固定期为5700~4800 cal a BP,东亚夏季风强烈,气候温暖湿润,沙地大部分为固定沙丘;第一次扩张期为4800~3900 cal a BP,此时夏季风不断衰退,气候开始变得冷干,导致沙地逐渐扩张;第二次固定期为3900~3300 cal a BP,气候转暖湿,土壤发育,沙地面积减少;第二次扩张期为3300~2400 cal a BP,气候转冷干,沙地再次扩张,古土壤层普遍被风沙覆盖。总之,东亚夏季风驱动的气候变化驱动了科尔沁沙地中晚全新世沙地演化,沙地管理政策的制定需要特别关注未来气候变化趋势。
文摘We present an approach to regional environ- mental monitoring in the Northern Eurasian grain belt combining time series analysis of MODIS normalized difference vegetation index （NDVI） data over the period 2001-2008 and land cover change （LCC） analysis of the 2001 and 2008 MODIS Global Land Cover product （MCD 12Q 1）. NDVI trends were overwhelmingly negative across the grain belt with statistically significant （p ≤0.05） positive trends covering only 1% of the land surface. LCC was dominated by transitions between three classes; cropland, grassland, and a mixed cropland/natural vegeta- tion mosaic. Combining our analyses of NDVI trends and LCC, we found a pattern of agricultural abandonment （cropland to grassland） in the southern range of the grain belt coinciding with statistically significant （p≤0.05） negative NDVI trends and likely driven by regional drought. In the northern range of the grain belt we found an opposite tendency toward agricultural intensification; in this case, represented by LCC from cropland mosaic to pure cropland, and also associated with statistically significant （p≤0.05） negative NDVI trends. Relatively small clusters of statistically significant （p ≤ 0.05） positive NDVI trends corresponding with both localized land abandonment and localized agricultural intensification show that land use decision making is not uniform across the region. Land surface change in the Northern Eurasian grain belt is part of a larger pattern of land cover land use change （LCLUC） in Eastern Europe, Russia, and former territories of the Soviet Union following realignment of socialist land tenure and agricultural markets. Here, we show that a combined analysis of LCC and NDVI trends provides a more complete picture of the complex- ities of LCLUC in the Northern Eurasian grain belt,involving both broader climatic forcing, and narrower anthropogenic impacts, than might be obtained from either analysis alone.
