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16篇 您的检索式:作者名="Changzhen Yan"
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1Spatial patterns and driving forces of land use change in China during the early 21st century显示文摘Land use and land cover change as the core of coupled human-environment systems has become a potential field of land change science (LCS) in the study of global environmental change. Based on remotely sensed data of land use change with a spatial resolution of 1 km × 1 km on national scale among every 5 years, this paper designed a new dynamic regionalization according to the comprehensive characteristics of land use change including regional differentiation, physical, economic, and macro-policy factors as well. Spatial pattern of land use change and its driving forces were investigated in China in the early 21st century. To sum up, land use change pattern of this period was characterized by rapid changes in the whole country. Over the agricultural zones, e.g., Huang-Huai-Hai Plain, the southeast coastal areas and Sichuan Basin, a great proportion of fine arable land were engrossed owing to considerable expansion of the built-up and residential areas, resulting in decrease of paddy land area in southern China. The development of oasis agriculture in Northwest China and the reclamation in Northeast China led to a slight increase in arable land area in northern China. Due to the 'Grain for Green' policy, forest area was significantly increased in the middle and western developing regions, where the vegetation coverage was substantially enlarged, likewise. This paper argued the main driving forces as the implementation of the strategy on land use and regional development, such as policies of 'Western Development', 'Revitalization of Northeast', coupled with rapidly economic development during this period.LIU Jiyuan ZHANG Zengxiang XU Xinliang KUANG Wenhui ZHOU Wancun ZHANG Shuwen LI Rendong YAN Changzhen YU Dongsheng WU Shixin JIANG Nan 2010Journal of Geographical Sciences2010,20,4:154
2Cropland redistribution to marginal lands undermines environmental sustainability显示文摘Cropland redistribution to marginal land has been reported worldwide;however,the resulting impacts on environmental sustainability have not been investigated sufficiently.Here we investigated the environmental impacts of cropland redistribution in China.As a result of urbanization-induced loss of high-quality croplands in south China(~8.5 t ha^(-1)),croplands expanded to marginal lands in northeast(~4.5 t ha^(-1)) and northwest China(~2.9 t ha^(-1)) during 1990-2015 to pursue food security.However,the reclamation in these low-yield and ecologically vulnerable zones considerably undermined local environmental sustainability,for example increasing wind erosion(+3.47%),irrigation water consumption(+34.42%),fertilizer use(+20.02%) and decreasing natural habitats(-3.11%).Forecasts show that further reclamation in marginal lands per current policies would exacerbate environmental costs by 2050.The future cropland security risk will be remarkably intensified because of the conflict between food production and environmental sustainability.Our research suggests that globally emerging reclamation of marginal lands should be restricted and crop yield boost should be encouraged for both food security and environmental benefits.Wenhui Kuang Jiyuan Liu Hanqin Tian Hao Shi Jinwei Dong Changqing Song Xiaoyong Li Guoming Du Yali Hou Dengsheng Lu Wenfeng Chi Tao Pan Shuwen Zhang Rafiq Hamdi Zherui Yin Huimin Yan Changzhen Yan Shixin Wu Rendong Li Jiuchun Yang Yinyin Dou Wenbin Wu Liqiao Liang Bao Xiang Shiqi Yang 2022National Science Review2022,9,1:13
3Driving forces of land use and land cover change (LUCC) in the Zoige Wetland, Qinghai-Tibetan Plateau显示文摘The Zoige Wetland is located in the northeastern Qinghai-Tibetan Plateau, which is highly sensitive to global environment change and human disturbance because of its high elevation and cold environment, thus, it's a hotspot for land use and land cover change (LUCC) research. We used Landsat MSS images from 1975, Landsat ETM images from 2000, and Landsat TM images from 1990 and 2005 to assess the LUCC in the study area, using GIS techniques, as well as topographic, vegetation, and soil maps combined with field investigations. The monitoring result shows that the study area's environment degraded rapidly between 1975 and 2005, including wetland shrinkage from 5,308 km 2 to 4,980 km 2 , sandy land expansion from 112 km 2 to 137 km 2 , forest land decreasing from 5,686 km 2 to 5,443 km 2 , and grassland degradation from 12,309 km 2 to 10,672 km 2 . According to the analysis of meteorological data and social-economic statistical data, we concluded that the LUCC in the Zoige Wetland was caused by both natural and anthropogenic factors, but human activities were primarily responsible for the observed LUCC, thereby, we suggest human behaviors must be adjusted to control environmental degradation.GuangYin Hu ZhiBao Dong JunFeng Lu ChangZhen Yan 2012Research in Cold and Arid Regions2012,4,5:7
4Observations of several characteristics of aeolian sand movement in the Taklimakan Desert显示文摘With both sides of the Taklimakan Desert highway line as the study area, three typical aeolian sand landforms, i.e. complex dune ridge, barchan dune and flat sand land, were selected as sand beds for the observation, analysis and research of the characteristics of aeolian sand movement such as aeolian sand stream structure, sand transport intensity, etc. in the Taklimakan Desert. The results show that there is a linear relation between the height and the log of sand transport rate over transverse dune chain, longitudinal dune ridge and flat sand land, i.e. the sand transport percentage decreases exponentially with increasing height. Sand transport rate within the 10 cm height above the bed surface accounts for 80%-95% of the total sand transport rate of the observed height (40 cm), while the sand transport rate in 20 cm occupies 98% of the total amount. Sand transport rate (g·cm-1·min-1) differs greatly with respect to different landform types and different topographic positions. Based on the investigation and analysis on aeolian sand landform origin, morphological type and distribution feature, the two typical landform assemblages, complex transverse dune chain-alluvial plain and huge longitudinal dune ridge-interridge lowland in the Taklimakan Desert were divided into several characteristic zones of aeolian sand movement states. From this one can qualitatively judge the types and severities of sand disasters at various topographic positions in the engineering installation region and further put forward concrete schemes and measures to control sand damages.HAN Zhiwen DONG Zhibao WANG Tao CHEN Guangting YAN Changzhen YAO Zhengyi 2004Science China Earth Sciences2004,47,1:7
5Change of lake area in the southeastern part of China's Badain Jaran Sand Sea and its implications for recharge sources显示文摘Understanding the relationship between the changes in lake water volume and climate change can provide valuable information to the recharge sources of lake water. This is particularly true in arid areas such as the Badain Jaran Sand Sea, an ecologically sensitive area, where the recharge sources of lakes are heatedly debated. In this study, we determined the areas of 50 lakes(representing 70% of the total permanent lakes in this sand sea) in 1967, 1975, 1990, 2000 and 2010 by analyzing remote-sensing images using image processing and Ar GIS software. In general, the total lake area decreased from 1967 to 1990, remained almost unchanged from 1990 to 2000, and increased from 2000 to 2010. Analysis of the relationship between these changes and the contemporaneous changes in annual mean temperature and annual precipitation in the surrounding areas suggests that temperature has significantly affected the lake area, but that the influence of precipitation was minor. These results tend to support the palaeo-water recharge hypothesis for lakes of the Badain Jaran Sand Sea, considering the fact that the distribution and area of lakes are closely related to precipitation and the size of mega-dunes, but the contemporaneous precipitation can hardly balance the lake water.Zhi ZHANG ZhiBao DONG ChangZhen YAN GuangYin HU 2015Journal of Arid Land2015,7,1:4
6Driving Force and Ecosystem Service Values Estimation in the Extreme Arid Region from 1975 to 2015:A Case Study of Alxa League,China显示文摘The research on ecosystem service values(ESVs)estimation in arid region is weak.We took the Alxa League of China’s Inner Mongolia Autonomous Region,an extreme arid region,as an example and constructed an equivalent coefficient method to assess its ESVs from 1975 to 2015,by determining the standard unit of ESVs and the basic equivalent of the value of different ecosystem services per unit area based on the regional characteristics,literature research,expert knowledge and land use data.The results show that the ESVs first decreased from 83170.4 million yuan(RMB)in 1975 to 82337.8 million yuan(RMB)in 2000 and then increased to84033.6 million yuan(RMB)in 2015,and the ESV of sparse grassland and desert account for about 33%and 29%of the total ESVs,respectively.Among the four service types,the regulating services,support services,supply services and cultural services account for66.5%,22.8%,6.0%and 4.7%,respectively.The changes of ESVs in Alxa League are determined by the socio-economic development and ecological changes.This study provides a new method to estimate the ESVs in arid region by integrating existing methods and regional characteristics,such as the cost of water for arid ecosystems.XIE Jiali LU Zhixiang XIAO Shengchun YAN Changzhen 2021Chinese Geographical Science2021,31,6:3
7Oasis Functional Stability Evaluation Based on Multiple Indicators, Northwest China显示文摘We produced and analyzed oasis structure information, and evaluated oasis functional stability using the multiple indicators based on Remote Sensing(RS) and Geographical Information System(GIS) in the arid region of China in 2015. The results showed that the oases area was 193,734 km^2, accounting for 8.17% of the arid region of China. The spatial difference in the functional stability of oases was obvious. The Beijiang zone had the highest functional stability and was relatively stable state, and the Hexi Corridor-Alashan Plateau zone had the lowest functional stability and was relatively unstable. The functional stability is dominated by production and ecological functions, which have regional differences. Increasing oasis agricultural output, strengthening highway infrastructure construction and paying attention to education will become important ways to improve oasis functional stability. Water resources determine the ecological function, thus affecting the oasis functional stability. The results provide references for the formulation of related policies according to local conditions.LI Sen ZHANG Zhishan WANG Tao YAN Changzhen DU Heqiang 2020Acta Geologica Sinica(English Edition)2020,94,3:3
8Assessment of sandy desertification trends in the Shule River Basin from 1978 to 2010显示文摘Sandy desertification in the Shule River Basin has expanded dramatically during the past 30 years.We evaluated the status,evolution,and main causes of sandy desertification by interpreting Landsat images which were acquired in 1978,1990,2000,2005,and 2010,and analyzing the relevant meteorological data.The results show there was 3,477.95 km2,3,733.32 km2,3,620.29 km2,3,565.65 km2,and 3,557.88 km2of sandy desertified land in 1978,1990,2000,2005,and 2010,respectively.From 1978 to 1990,not only the area of sandy desertified land(SDL)but also the degree of SDL levels increased.From 1990 to 2010 there was widespread restoration of SDL but the recovery trend of SDL gradually slowed.Although climate change contributes to expanding sandy desertification,human activities can either accelerate or reverse trends of natural sandy desertification.Some detrimental human activities can accelerate sandy desertification,but,conversely,desertification control measures such as the Three-North Shelter Forest Project and watershed rehabilitation programs in areas including the Shule River Basin resulted in many SDL being turned into grasslands or forest lands when shrubs and trees were planted to fix mobile sands at the edges of oases and cities.With population growth,much SDL has been reclaimed as farm land using water-saving agricultural methods or has been turned into built-up land as a result of urbanization.Xiang Song ChangZhen Yan Sen Li JiaLi Xie 2014Research in Cold and Arid Regions2014,6,1:1
9Spatial patterns and driving forces of land use change in China during the early 21st century显示文摘Jiyuan Liu Zengxiang Zhang Xinliang Xu Wenhui Kuang Wancun Zhou Shuwen Zhang Rendong Li Changzhen Yan Dongsheng Yu Shixin Wu Nan Jiang 0,2010,:1
10Mechanism Research of Electroacupuncture Stimulation at Baihui and Zusanli in Cerebral Ischemia-reperfusion Injury Using RNA-Sequencing显示文摘Background:Electroacupuncture(EA)therapy,as a combination of electric stimulation and traditional acupunc-ture technology,is currently an important mean for treatment of ischemic stroke and post-stroke rehabilitation in China.Because of its remarkable therapeutic effect,it has been widely used in hospitals and clinic,however,the detailed mechanism remains unclear.Objective:This research aims to comprehensively and systematically elucidate the mechanisms of EA treatment at the acupoints of Zusanli(ST36)and Baihui(GV20)on ischemic stroke.Methods:In this study,EA was performed twice at onset of reperfusion and 20 h after reperfusion following cerebral ischemia-reperfusion(I/R)in middle cerebral artery occlusion(MCAO)rats,and transcriptomic changes of various molecules in ischemic hippocampal neurons of rats in Sham,I/R and EA groups were detected by RNA-Sequencing(RNA-Seq).Results:Thus,we detected 18 significantly different genes related to atherosclerosis(AS),with their functions associated with lipid metabolism,thrombosis,monocytes and vascular smooth muscle cells.And,we detected 10 significantly different genes related to oxidative stress and apoptosis and 10 significantly different genes related to calcium overload and excitatory amino acids release.Also,we detected 19 significantly different genes related to blood-brain barrier(BBB)and 22 significantly different genes related to inflammatory response.Conclusion:In conclusion,EA can play a role in treating ischemic stroke through a variety of mechanisms,affecting atherosclerosis,oxidative stress,apoptosis,calcium overload,excitatory amino acids release,blood-brain barrier(BBB)and inflammatory response.Huanyuan Wang Xifa Xu Zekun Wang Gonglei Yue Bin Tang Qingchen Zhou Changzhen Gong Kaili Wang Guangzhong Du Yan Li 2023Clinical Complementary Medicine and Pharmacology2023,3,2:0
11Endoscopically controlled surgery with open hemilaminectomy for the treatment of intradural extramedullary tumors:an operative technique and short-term outcomes of 20 consecutive cases显示文摘Background:To present a surgical technique for the treatment of intradural extramedullary(IDEM)tumors by using endoscopically controlled surgery with open hemilaminectomy technique.Methods:In this study,20 patients with 22 IDEM tumors were enrolled.An endoscopically controlled surgery with open hemilaminectomy was employed to remove the tumors.Data related to clinical symptoms and medical images before and after surgery were collected for perioperative evaluation and follow-up analysis.Results:All the tumors in 20 patients were well removed.The clinical symptoms were significantly reduced in all the patients as well.The short-term follow-up data showed that there was no tumor recurrence or spinal deformity.Conclusion:The endoscopically controlled surgery with open hemilaminectomy technique provided favorable exposure and satisfactory resection to the IDEM tumors.It may be an effective surgical method for treating IDEM tumors.Larger samples and longer follow-up data are needed to verify its long-term effectiveness.Xiaorong Yan Huiqing Wang Cai Li Yuanxiang Lin Lin Lin Shinong Zhu Chenyang Wang Zhangya Lin Changzhen Jiang Dezhi Kang 2021Chinese Neurosurgical Journal2021,7,2:0
12Cultivated-land change in Mu Us Sandy Land of China before and after the first-stage grain-for-green policy显示文摘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.Na Li ChangZhen Yan JiaLi Xie JianXia Ma 2018Research in Cold and Arid Regions2018,10,4:0
13Ecosystem changes revealed by land cover in the three-river headwaters region of Qinghai,China(1990–2015)显示文摘The Three-River Headwaters Region(TRHR) of Qinghai Province, in the Tibetan Plateau of China, is the main source of the Yangtze, Yellow, and Lancang rivers, and is very significant to the security of freshwater resources for China and southeastern Asia. It is a critical ecological region of China for its ecological functions, and has been changed or even degraded in recent decades owing to climate change and human pressure. To effectively protect and restore the degraded ecosystems, the Chinese government initiated a series of ecological conservation projects in TRHR. It is essential to quantitatively assess ecosystem changes and their relationship to driving factors for indepth understanding of long-term changes of ecosystems and effects of ecological restoration policies and offer practical insights for ecological restoration. Here, land cover data has been interpreted with the series data of Landsat during 1990–2015. The patterns of different ecosystems and their developing process have been derived from land cover change. The results show that ecosystem types in TRHR include forest, grassland, cropland,wetland, artificial surface and barren land, accounting for 4.51%, 70.80%, 0.15%, 9.47%, 0.16% and 14.90%,respectively. Barren land converted to wetland was the significant ecosystem change from 1990 to 2015. Increases in temperature and precipitation and implementation of ecological rehabilitation helped maintain relatively stable ecosystem patterns. It is necessary to continue ecological projects to improve and/or maintain the ecosystems in TRHR because there is still a risk of land degradation under increasing climate change and human activity.XuWei Sun Sen Li XiaoHui Zhai XiaoXu Wei ChangZhen Yan 2023Research in Cold and Arid Regions2023,15,2:0
14Quantitative retrieval of soil salt content based on measured spectral data显示文摘Choosing the Minqin Oasis, located downstream of the Shiyang River in Northwest China, as the study area, we used field-measured hyperspectral data and laboratory-measured soil salt content data to analyze the characteristics of saline soil spectral reflectance and its transformation in the area, and elucidated the relations between the soil spectral reflectance, reflectance transformation, and soil salt content. In addition, we screened sensitive wavebands. Then, a multiple linear regression model was established to predict the soil salt content based on the measured spectral data, and the accuracy of the model was verified using field-measured salinity data. The results showed that the overall shapes of the spectral curves of soils with different degrees of salinity were consistent, and the reflectance in visible and near-infrared bands for salinized soil was higher than that for non-salinized soil. After differential transformation, the correlation coefficient between the spectral reflectance and soil salt content was obviously improved. The first-order differential transformation model based on the logarithm of the reciprocal of saline soil spectral reflectance produced the highest accuracy and stability in the bands at 462 and 636 nm; the determination coefficient was 0.603, and the root mean square error was 5.407. Thus, the proposed model provides a good reference for the quantitative extraction and monitoring of regional soil salinization.HanChen Duan Tao Wang Xian Xue CuiHua Huang ChangZhen Yan 2016Research in Cold and Arid Regions2016,8,6:0
15Remote sensing monitoring of the recent rapid increase in cultivation activities and its effects on desertification in the Mu Us Desert, China显示文摘The recent ecological improvement in the Mu Us Desert of China, largely attributed to large-scale afforestation projects, has created new opportunities for cultivation activities. However, the subsequent rapid increase in reclamation on desertification land and its impact on desertification have raised concerns. In this study, we first extracted data on cultivated land and desertification land in 1975,1990, 2000, 2005, 2010, 2015, and 2020 through the human-computer interaction visual interpretation method. By overlaying the cultivated land dynamics and desertification land, we subsequently explored the effect of cultivation activities on desertification in the Mu Us Desert during the six periods from 1975 to 2020(1975–1990, 1990–2000, 2000–2005, 2005–2010, 2010–2015, and 2015–2020). The results showed that cultivated land in the Mu Us Desert showed a fluctuating and increasing trend from 3769.26 km~2 in 1975 to 4865.73 km~2 in 2020, with 2010 as the turning point for the recent rapid increase. The main contributors included the large and regular patches distributed in Yuyang District and Shenmu of Shaanxi Province, and relatively smaller patches concentrated in Inner Mongolia Autonomous Region. The increased cultivated land from the reclamation on desertification land was dominated by moderate and severe desertification lands, and the decreased cultivated land that was transferred into desertification land as abandoned cultivated land was dominated by slight and moderate desertification lands. The effect of cultivation activities on desertification reversal(average area proportion of 10.61% for reversed desertification land) was greater than that of the development of desertification(average area proportion of 5.82% for developed desertification land). Nevertheless, compared to reversed desertification land,both the significant increase of developed desertification land during the periods of 2000–2005 and 2005–2010 and the insignificant decrease during the periods of 2005–2010, 2010–2015, and 2015–2020 implied a potential remobilization risk. Therefore, this study provides a significant theoretical reference for the formulation of ecological restoration projects and regional macroeconomic development policies by considering the influence of cultivation activities, to ensure the overall environmental stability and sustainability in desertification land where reclamation and abandonment activities have taken place.ZHAO Hongyan YAN Changzhen LI Sen WANG Yahui 2023Journal of Arid Land2023,15,7:0
16Remote-sensing data reveals the response of soil erosion intensity to land use change in Loess Plateau, China显示文摘Developing an effective approach to rapidly assess the effects of restoration projects on soil erosion intensity and their extensive spatial and temporal dynamics is important for regional ecosystem management and the development of soil conservation strategies in the future. This study applied a model that was developed at the pixel scale using water soil erosion indicators(land use, vegetation coverage and slope) to assess the soil erosion intensity in the Loess Plateau, China. Landsat TM/ETM+ images in 2000, 2005 and 2010 were used to produce land use maps based on the object-oriented classification method. The MODIS product MOD13Q1 was adopted to derive the vegetation coverage maps. The slope gradient maps were calculated based on data from the digital elevation model. The area of water soil-eroded land was classified into six grades by integrating slope gradients, land use and vegetation coverage. Results show that the Grain-To-Green Project in the Loess Plateau worked based on the land use changes from 2000 to 2010 and enhanced vegetation restoration and ecological conservation. These projects effectively prevented soil erosion. During this period, lands with moderate, severe, more severe and extremely severe soil erosion intensities significantly decreased and changed into less severe levels, respectively. Lands with slight and light soil erosion intensities increased. However, the total soil-eroded area in the Loess Plateau was reduced. The contributions of the seven provinces to the total soil-eroded area in the Loess Plateau and the composition of the soil erosion intensity level in each province are different. Lands with severe, more severe and extremely severe soil erosion intensities are mainly distributed in Qinghai, Ningxia, Gansu and Inner Mongolia. These areas, although relatively small, must be prioritised and preferentially treated.JiaLi Xie ChangZhen Yan ZhiXiang Lu Sen Li 2016Research in Cold and Arid Regions2016,8,4:0
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