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    Transport Accessibility and Spatial Connections of Cities in the Guangdong-Hong Kong-Macao Greater Bay Area
    CAO Xiaoshu, OUYANG Shishu, YANG Wenyue, LUO Yi, LI Baochao, LIU Dan
    中国地理科学    2019, 20 (5): 820-833.   DOI: 10.1007/s11769-019-1034-2
    摘要162)      PDF (6142KB)(904)   

    Based on geographic information system (GIS) spatial analysis technology, the spatial pattern of raster grid transport accessibility for the Guangdong-Hong Kong-Macao Greater Bay area was studied and the states of spatial connectedness were simulated using highway passenger transport, railway passenger transport, port passenger transport and aviation passenger transport data. The result shows that transport accessibility within the Guangdong-Hong Kong-Macao Greater Bay area costs ‘one hour’ and the spatial distribution of accessibility in the area presents clear ‘core-periphery’ spatial characteristics, with Guangzhou, Foshan, Shenzhen constituting the core. The transport accessibility of Guangdong-Hong Kong-Macao is high. Average accessibility of urban nodes as measured by travel time is 0.99 h, and the areas accessible within 1.42 h occupy 79.14% of the total area. Most of the areas with the lowest accessibility are found in the peripheral area, with the worst accessibility being 4.73 h. Compared with the west-side cities, the economically developed east-side cities of the Guangdong-Hong Kong-Macao Greater Bay area have higher connectivity with roads, railways, ports, and aviation transport. Guangzhou, Foshan, Zhuhai, Shenzhen, Hong Kong and Macao are closely linked. The higher the accessibility, the closer the intercity connectedness.

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    A Synthesizing Land-cover Classification Method Based on Google Earth Engine: A Case Study in Nzhelele and Levhuvu Catchments, South Africa
    ZENG Hongwei, WU Bingfang, WANG Shuai, MUSAKWA Walter, TIAN Fuyou, MASHIMBYE Zama Eric, POONA Nitesh, SYNDEY Mavengahama
    中国地理科学    2020, 30 (3): 397-409.   DOI: 10.1007/s11769-020-1119-y
    摘要297)      PDF (3308KB)(795)   
    This study designed an approach to derive land-cover in the South Africa with insufficient ground samples, and made a case demonstration in Nzhelele and Levhuvu catchments, South Africa. The method was developed based on an integration of Landsat 8, Sentinel-1, and Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM), and the Google Earth Engine (GEE) platform. Random forest classifier with 300 trees is employed as land-cover classification model. In order to overcome the defect of insufficient ground data, the stratified sampling method was used to generate the training and validation samples from the existing land-cover product. Likewise, in order to recognize different land-cover categories, the percentile and monthly median composites were employed to expand input metrics of random forest classifier. Results showed that the overall accuracy of the land-cover of Nzhelele and Levhuvu catchments, South Africa in 2017-2018 reached to 76.43%. Three important results can be drawn from our research. 1) The participation of Sentinel-1 data can slightly improve overall accuracy of land-cover while its contribution on land-cover classification varied with land types. 2) Under-fitting problem was observed in the training of non-dominant land-cover categories using the random sampling, the stratified sampling method is recommended to make sure the classification accuracy of non-dominant classes. 3) When related reflectance bands participated in the training process, individual Normalized Difference Vegetation index (NDVI), Enhanced Vegetation Index (EVI), Soil Adjusted Vegetation Index (SAVI), Normalized Difference Built-up Index (NDBI) have little effect on final land-cover classification result.
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    Estimation and Spatio-temporal Patterns of Carbon Emissions from Grassland Fires in Inner Mongolia, China
    YU Shan, JIANG Li, DU Wala, ZHAO Jianjun, ZHANG Hongyan, ZHANG Qiaofeng, LIU Huijuan
    中国地理科学    2020, 30 (4): 572-587.   DOI: 10.1007/s11769-020-1134-z
    摘要120)      PDF (6122KB)(707)   
    Grassland fires results in carbon emissions, which directly affects the carbon cycle of ecosystems and the carbon balance. The grassland area of Inner Mongolia accounts for 22% of the total grassland area in China, and many fires occur in the area every year. However, there are few models for estimation of carbon emissions from grassland fires. Accurate estimation of direct carbon emissions from grassland fires is critical to quantifying the contribution of grassland fires to the regional balance of atmospheric carbon. In this study, the regression equations for aboveground biomass (AGB) of grassland in growing season and MODIS NDVI (Normalized Difference Vegetation Index) were established through field experiments, then AGB during Nov.-Apr. were retrieved based on that in Oct. and decline rate, finally surface fuel load was obtained for whole year. Based on controlled combustion experiments of different grassland types in Inner Mongolia, the carbon emission rate of grassland fires for each grassland type were determined, then carbon emission was estimated using proposed method and carbon emission rate. Results revealed that annual average surface fuel load of grasslands in Inner Mongolia during 2000-2016 was approximately 1.1978×1012 kg. The total area of grassland which was burned in the Inner Mongolia region over the 17-year period was 5298.75 km2, with the annual average area of 311.69 km2. The spatial distribution of grassland surface fuel loads is characterized by decreasing from northeast to southwest in Inner Mongolia. The total carbon emissions from grassland fires amounted to 2.24×107 kg with an annual average of 1.32×106 for the study area. The areas with most carbon emissions were mainly concentrated in Old Barag Banner and New Barag Right Banner and on the right side of the Oroqin Autonomous Banner. The spatial characteristics of carbon emission depend on the location of grassland fire, mainly in the northeast of Inner Mongolia include Hulunbuir City, Hinggan League, Xilin Gol League and Ulanqab City. The area and spatial location of grassland fires can directly affect the total amount and spatial distribution of carbon emissions. This study provides a reference for estimating carbon emissions from steppe fires. The model and framework for estimation of carbon emissions from grassland fires established can provide a reference value for estimation of carbon emissions from grassland fires in other regions.
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    Siting of Dark Sky Reserves in China Based on Multi-source Spatial Data and Multiple Criteria Evaluation Method
    WEI Ye, CHEN Zuoqi, XIU Chunliang, YU Bailang, LIU Hongxing
    中国地理科学    2019, 29 (6): 949-961.   DOI: 10.1007/s11769-019-1079-2
    摘要199)      PDF (6241KB)(685)   

    With the rapid development of population and urbanization and the progress of lighting technology, the influence of artificial light sources has increased. In this context, the problem of light pollution has attracted wide attention. Previous studies have revealed that light pollution can affect biological living environments, human physical and mental health, astronomical observations and many other aspects. Therefore, organizations internationally have begun to advocate for measures to prevent light pollution, many of which are recognized by the International Dark-Sky Association (IDA). In addition to improving public awareness, legal protections, technical treatments and other means, the construction of Dark Sky Reserves (DSR) has proven to be an effective preventive measure. So far, as a pioneer practice in this field, the IDA has identified 11 DSRs worldwide. Based on the DA requirements for DSRs, this paper utilizes NPP-VIIRS nighttime light data and other multi-source spatial data to analyze possible DSR sites in China. The land of China was divided into more than ten thousand 30 km×30 km fishnets, and constraint and suitable conditions were designated, respectively, as light and cloud conditions, and scale, traffic and attractiveness conditions. Using a multiple criteria evaluation, 1443 fishnets were finally selected as most suitable sites for the construction of DSRs. Results found that less than 25% of China is not subject to light pollution, and less than 13% is suitable for DSR construction, primarily in western and northern areas, including Tibet, Xinjiang, Qinghai, Gansu and Inner Mongolia.

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    Comparison of Carbon, Nitrogen, and Sulfur in Coastal Wetlands Dominated by Native and Invasive Plants in the Yancheng National Nature Reserve, China
    WAN Siang, LIU Xingtu, MOU Xiaojie, ZHAO Yongqiang
    中国地理科学    2020, 30 (2): 202-216.   DOI: 10.1007/s11769-020-1108-1
    摘要146)      PDF (1109KB)(657)   
    The rapid invasion of the plant Spartina alterniflora in coastal wetland areas can threaten the capacity of their soils to store carbon (C), nitrogen (N), and sulfur (S). In this study, we investigated the spatial and temporal distribution patterns of C, N and S of both soil and (native and invasive) plants in four typical coastal wetlands in the core area of the Yancheng National Nature Reserve, China. The results show that the invasive S. alterniflora greatly influenced soil properties and increased soil C, N and S storage capacity:the stock (mean ±standard error) of soil organic carbon (SOC, (3.56 ±0.36) kg/m3), total nitrogen (TN, (0.43 ±0.02) kg/m3), and total sulfur (TS, (0.69 ±0.11) kg/m3) in the S. alterniflora marsh exceeded those in the adjacent bare mudflat, Suaeda salsa marsh, and Phragmites australis marsh. Because of its greater biomass, plant C ((1193.7 ±133.6) g/m2), N ((18.8 ±2.4) g/m2), and S ((9.4 ±1.5) g/m2) storage of S. alterniflora was also larger than those of co-occurring native plants. More biogenic elements circulated in the soil-plant system of the S. alterniflora marsh, and their spatial and temporal distribution patterns were also changed by the S. alterniflora invasion. Soil properties changed by S. alterniflora's invasion thereby indirectly affected the accumulation of soil C, N and S in this wetland ecosystem. The SOC, TN, and TS contents were positively correlated with soil electrical conductivity and moisture, but negatively correlated with the pH and bulk density of soil. Together, these results indicate that S. alterniflora invasion altered ecosystem processes, resulted in changes in net primary production and litter decomposition, and increased the soil C, N and S storage capacity in the invaded ecosystems in comparison to those with native tallgrass communities in the coastal wetlands of East China.
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    Spatial Patterns of LULC and Driving Forces in the Transnational Area of Tumen River: A Comparative Analysis of the Sub-regions of China, the DPRK, and Russia
    NAN Ying, WANG Bingbing, ZHANG Da, LIU Zhifeng, QI Dekang, ZHOU Haohao
    中国地理科学    2020, 30 (4): 588-599.   DOI: 10.1007/s11769-020-1136-x
    摘要134)      PDF (3033KB)(615)   
    Understanding the spatial patterns of land-use and land-cover (LULC) and their driving forces in transnational areas is important for the sustainable development of these regions. However, the spatial patterns of LULC and their driving forces across multiple scales are poorly understood in transnational areas. In this study, we analyzed the spatial patterns of LULC and driving forces in the transnational area of Tumen River (TATR) in 2016 across two scales: the entire region and the sub-regions of China, the Democratic People’s Republic of Korea (DPRK), and Russia. Results showed that the LULC was dominated by broadleaf forest and dry farmland in the TATR in 2016, which accounted for 66.86% and 13.60% of the entire region, respectively. Meanwhile, the LULC in the three sub-regions exhibited noticeable differences. In the Chinese and the DPRK’s sub-regions, the area of broadleaf forest was greater than those for the other LULC types, while the Russian sub-region was dominated by broadleaf forest and grassland. The spatial patterns of LULC were mainly influenced by topography, climate, soil properties, and human activities. In addition, the driving forces of the spatial patterns of LULC in the TATR had an obvious scaling effect. Therefore, we suggest that effective policies and regulations with cooperation among China, the DPRK, and Russia are needed to plan the spatial patterns of LULC and improve the sustainable development of the TATR.
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    Responses of Alpine Wetlands to Climate Changes on the Qinghai-Tibetan Plateau Based on Remote Sensing
    WANG Rui, HE Min, NIU Zhenguo
    中国地理科学    2020, 30 (2): 189-201.   DOI: 10.1007/s11769-020-1107-2
    摘要304)      PDF (1759KB)(509)   
    The alpine wetlands in QTP (Qinghai-Tibetan Plateau) have been profoundly impacted along with global climate changes. We employ satellite datasets and climate data to explore the relationships between alpine wetlands and climate changes based on remote sensing data. Results show that:1) the wetland NDVI (Normalized Difference Vegetation Index) and GPP (Gross Primary Production) were more sensitive to air temperature than to precipitation rate. The wetland ET (evapotranspiration) across alpine wetlands was greatly correlated with precipitation rate. 2) Alpine wetlands responses to climate changes varied spatially and temporally due to different geographic environments, variety of wetland formation and human disturbances. 3) The vegetation responses of the Zoige wetland was the most noticeable and related to the temperature, while the GPP and NDVI of the Qiangtang Plateau and Gyaring-Ngoring Lake were significantly correlated with both temperature and precipitation. 4) ET in the Zoige wetland showed a significantly positive trend, while ET in Maidika wetland and the Qiangtang plateau showed a negative trend, implying wetland degradation in those two wetland regions. The complexities of the impacts of climate changes on alpine wetlands indicate the necessity of further study to understand and conserve alpine wetland ecosystems.
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    Spatial-temporal Dynamics and Driving Forces of Land Development Intensity in the Western China from 2000 to 2015
    HUANG Xin, HUANG Xiaojun, LIU Mengmeng, WANG Bo, ZHAO Yonghua
    中国地理科学    2020, 30 (1): 16-29.   DOI: 10.1007/s11769-020-1095-2
    摘要402)      PDF (5745KB)(486)   
    The change in land development intensity is an important perspective to reflect the variation in regional social and economic development and spatial differentiation. In this paper, spatial statistical analysis, Ordinary Least Squares (OLS), and Geographically weighted regression (GWR) methods are used to systematically analyse the spatial-temporal characteristics and driving forces of land development intensity for 131 spatial units in the western China from 2000 to 2015. The findings of the study are as follows:1) The land development intensity in the western China has been increasing rapidly. From 2000 to 2015, land development intensity increased by 3.4 times on average. 2) The hotspot areas have shifted from central Inner Mongolia, northern Shaanxi and the Beibu Gulf of Guangxi to the Guanzhong Plain and the Chengdu-Chongqing urban agglomeration. The areas of cold spots were mainly concentrated in the Qinghai-Tibet Plateau, Yunnan, and Xinjiang. 3) Investment intensity and the natural environment have always been the main drivers of land development intensity in the western China. Investment played a powerful role in promoting land development intensity, while the natural and ecological environment distinctly constrained such development. The effect of the economic factors on land development intensity in the western China has changed, which is reflected in the driving factor of construction land development shifting from economic growth in 2000 to economic structure, especially industrial structure, in 2015.
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    Optimization of Rural Settlement Distributions Based On the Ecological Security Pattern: A Case Study of Da'an City in Jilin Province of China
    YIN Jingbo, LI Hong, WANG Dongyan, LIU Shuhan
    中国地理科学    2020, 30 (5): 824-838.   DOI: 10.1007/s11769-020-1128-x
    录用日期: 2020-04-28

    摘要161)      PDF (935KB)(483)   
    Following the trends of Chinese rural transformation development, and the sustainable development goals for resources and environment, reasonable arranging the potential development space and the ecological space, so as to optimize the distributions of rural settlement would be the key challenge for rural areas in ecologically fragile regions. From the perspective of maintaining regional ecological security, this paper takes Da'an City, a typical ecological fragile region in Jilin Province, as the case area, constructing the comprehensive ecological security pattern (ESP) on basis of landscape ecology, and applying the landscape pattern indexes to quantitative analysis the spatial distribution characteristics of rural settlements. Then, different optimization directions and management strategies are put forward for rural settlements in each secure zone under the comprehensive ESP. The experimental results showed that 1) the area of the low security zone, the general security zone, the moderate security zone and the extreme security zone was 1570.18 km2, 1463.36 km2, 1215.80 km2 and 629.77 km2, representing 32.18%, 29.99%, 24.92% and 12.91% of the total area of the target area, respectively. 2) The rural settlements in Da'an City were characterized by a high degree of fragmentation with a large number of small-scale patches. 3) The area of rural settlements in the ecological relocation zone, the in situ remediation zone, the limited development zone and the key development zone was 22.80 km2, 42.31 km2, 36.28 km2 and 19.40 km2, accounting for 18.88%, 35.03%, 30.04% and 16.06% of the total area of rural settlements, respectively. Then, different measures were proposed for settlements in different optimization zones in order to scientifically plan important ecological space, production space and living space in rural areas. This paper aims to provide fundamental support for rural settlements based on redistribution from the perspective of landscape ecology and provide insights for rural planning and rural habitat environmental improvement.
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    Spatiotemporal Variations and Regional Transport of Air Pollutants in Two Urban Agglomerations in Northeast China Plain
    LI Xiaolan, HU Xiaoming, SHI Shuaiyi, SHEN Lidu, LUAN Lan, MA Yanjun
    中国地理科学    2019, 29 (6): 917-933.   DOI: 10.1007/s11769-019-1081-8
    摘要241)      PDF (2401KB)(482)   

    Characteristics of air pollution in Northeast China (NEC) received less research attention in the past comparing to other heavily polluted regions in China. Spatiotemporal variations of six criteria air pollutants (PM10, PM2.5, SO2, NO2, O3 and CO) in Central Liaoning Urban Agglomeration (CLUA) and Harbin-Changchun Urban Agglomeration (HCUA) in NEC Plain were analyzed in this study based on three-year hourly observations of air pollutants and meteorological variables from 2015 to 2017. The results indicated that the annual mean concentrations of air pollutants are generally higher in the middle and southern regions in NEC Plain and lower in the northern region. Megacities such as Shenyang, Harbin and Changchun experience severe air pollution, with a three-year averaged air quality index (AQI) larger than 80, far exceeding the daily AQI standard at the first-level of 50 in China. The annual mean PM and SO2 concentrations decrease most significantly in NEC urban agglomerations from 2015 to 2017, followed by CO and NO2, while O3 shows a slight increasing trend. All the six pollutants exhibit obvious seasonal and diurnal variations, and these variations are dictated by local emission and meteorological conditions. PM2.5 and O3 concentrations in NEC urban agglomerations strongly depend on wind conditions. High O3 concentrations at different cities usually occur in presence of strong winds but are independent on wind direction (WD), while high PM2.5 is usually accompanied by weak winds and poor dispersion condition, and sometimes also occur when the northerly or southerly winds are strong. Regional transport of air pollutants between NEC urban agglomerations is common. A severe haze event on November 1-4, 2017 is examined to demonstrate the role of regional transport on pollution.

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    Regional Sustainable Assessment at City Level Based on CSDIS (China Sustainable Development Indicator System) Concept in the New Era, China
    WEI Jianfei, DING Zhiwei, MENG Yiwei, LI Qiang
    中国地理科学    2020, 30 (6): 976-992.   DOI: 10.1007/s11769-020-1158-4
    录用日期: 2020-08-27
    预出版日期: 2020-08-27

    摘要112)      PDF (13098KB)(479)   
    The core issue of sustainable development refers to the coordinated development of economic-social-environmental issues. In the present study, by complying with the China Sustainable Development Indicator System (CSDIS) concept, a comprehensive index system was built; besides, Natural Breaks (Jenks) Classification Method, Exploratory Spatial Data Analysis and Geographic Detector Analysis were conducted to delve into the sustainability and coordinated degree at city level in China from 2007 to 2017. The achieved results are presented as follows. First, for spatial differentiation, the overall spatial distribution pattern was characterized by the high-value units in eastern China and the low-value units in western China from 2007 to 2017. To be specific, the high-value units were radiated along the Beijing-Guangdong Axis (Jing-Guang Axis) centered on the core of Beijing-Tianjin-Hebei Region, the middle-value units were distributed in strips along the coast, and the low-value units were vastly gathered in western China and gradually break via the Hu Huanyong line (Hu Line) in south China from 2007 to 2017. More specifically, based on the five subsystems, the pattern of each system was consistent with the whole, whereas the degree of concentration was different. Second, for spatial correlation, the significant High-High (HH) areas were primarily distributed in the core of Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta Regions. The significant Low-Low (LL) areas were continuously distributed in the southwest China and broke through the Hu Line from 2007 to 2017. There were insufficient number of significant High-Low (HL) and significant Low-High (LH) areas, whereas the spatial agglomeration of them was less obvious. Third, for internal coupling coordination, the spatial differentiation between the coupling degree and the coupling coordinated degree was significantly consistent in 2007 and 2017. The Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta Regions have demonstrated a high level of coordinated evolution, and the pattern of western mountainous areas exhibited a low degree of coordinated growth. Lastly, based on the combination of quantitative and qualitative, its factors were underpinned by robust economic strength, the vitality support of the information level and the basic support function of the topography, active guidance of national policies and path dependence and industrial transfer.
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    Spatial and Temporal Changes of Arable Land Driven by Urbanization and Ecological Restoration in China
    WANG Liyan, ANNA Herzberger, ZHANG Liyun, XIAO Yi, WANG Yaqing, XIAO Yang, LIU Jianguo, OUYANG Zhiyun
    中国地理科学    2019, 20 (5): 809-819.   DOI: 10.1007/s11769-018-0983-1
    摘要256)      PDF (781KB)(433)   

    Since the industrial revolution, human activities have both expanded and intensified across the globe resulting in accelerated land use change. Land use change driven by China's development has put pressure on the limited arable land resources, which has affected grain production. Competing land use interests are a potential threat to food security in China. Therefore, studying arable land use changes is critical for ensuring future food security and maintaining the sustainable development of arable land. Based on data from several major sources, we analyzed the spatio-temporal differences of arable land among different agricultural regions in China from 2000 to 2010 and identified the drivers of arable land expansion and loss. The results revealed that arable land decreased by 5.92 million ha or 3.31%. Arable land increased in the north and decreased in the south of China. Urbanization and ecological restoration programs were the main drivers of arable land loss, while the reclamation of other land cover types (e.g., forest, grassland, and wetland) was the primary source of the increased arable land. The majority of arable land expansion occurred in the Northwest, but the centroid for grain production moved to northeast, which indicated that new arable land was of poor quality and did not significantly contribute to the grain production capacity. When combined with the current ‘Red Line of Arable Land Policy’ (RAL) and ‘Ecological Redline Policy’ (EPR), this study can provide effective information for arable land policymaking and help guide the sustainable development of arable land.

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    Investment Environment Assessment and Strategic Policy for Subjects of Federation in Russia
    LI Fujia, LIU Qian, DONG Suocheng, CHENG Hao, LI Yu, YANG Yang, TSYDYPOV Bair, BILGAEV Alexey, AYURZHANAEV Alexander, BU Xiaoyan, XIA Bing
    中国地理科学    2019, 20 (5): 887-904.   DOI: 10.1007/s11769-019-1051-1
    摘要134)      PDF (2151KB)(408)   

    Russia is the largest neighboring country of China. Between the two countries, the resources and industry are complemented, the political mutual trust is at a high level, and trade cooperation has a broad prospect. Choosing the best regions and the best industries to strengthen investment in Russia has a major strategic significance in promoting ‘the Belt and Road Initiative’ and China-Mongolia-Russia Economic Corridor Construction. However, the related researches are extremely limited. The investment environment is unclear, and the investment risk is unknown, which seriously restrict the investment in Russia and the trade cooperation with Russia. Our research team carried out scientific expedition, government visits and scientific research cooperation in Russia for several years, and obtained a great number of first-hand valuable data. According to the analysis on the data and Russian regional policies, this study constructed an investment environment evaluation model (ESI-PRA model), scientific assessed the investment environment for 83 subjects of federation in Russia, in terms of economic, social, infrastructure, policy, resource and accessibility, classified 4 types of investment regions, chose 3 investment priority regions, revealed the investment priority industries, demonstrated the main investment risks, and proposed the strategic policies. The research results provide direct scientific and technological support for strategic decisions, such as investment in Russia, bilateral economic and trade cooperation, and overseas layout of Chinese-funded enterprises. Moreover, it has an important practical and strategic significance for improving overseas geo-strategic interests of China and ensuring the construction of China-Mongolia-Russia Economic Corridor.

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    The 2012 Flash Drought Threatened US Midwest Agroecosystems
    JIN Cui, LUO Xue, XIAO Xiangming, DONG Jinwei, LI Xueming, YANG Jun, ZHAO Deyu
    中国地理科学    2019, 20 (5): 768-783.   DOI: 10.1007/s11769-019-1066-7
    摘要181)      PDF (35692KB)(405)   

    In the summer of 2012, the US Midwest, the most productive agricultural region in the world, experienced the most intense and widespread drought on record for the past hundred years. The 2012 drought, characterized as ‘flash drought’, developed in May with a rapid intensification afterwards, and peaked in mid-July.~76% of crop region and 60% of grassland and pasture regions have been under moderate to severe dry conditions. This study used multiple lines of evidences, i.e., in-situ AmeriFlux measurements, spatial satellite observations, and scaled ecosystem modeling, to provide independent and complementary analysis on the impact of 2012 flash drought on the US Midwest vegetation greenness and photosynthesis carbon uptake. Three datasets consistently showed that 1) phenological activities of all biomes advanced 1-2 weeks earlier in 2012 compared to the other years of 2010-2014; 2) the drought had a more severe impact on agroecosystems (crop and grassland) than on forests; 3) the growth of crop and grassland was suppressed from June with significant reduction of vegetation index, sun-induced fluorescence (SIF) and gross primary production (GPP), and did not recover until the end of growing season. The modeling results showed that regional total GPP in 2012 was the lowest (1.76 Pg C/yr) during 2010-2014, and decreased by 63 Tg C compared with the other-year mean. Agroecosystems, accounting for 84% of regional GPP assimilation, were the most impacted by 2012 drought with total GPP reduction of 9%, 7%, 6%, and 29% for maize, soybean, cropland, and grassland, respectively. The frequency and severity of droughts have been predicted to increase in future. The results imply the importance to investigate the influences of flash droughts on vegetation productivity and terrestrial carbon cycling.

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    Assessing the Dynamics of Grassland Net Primary Productivity in Re-sponse to Climate Change at the Global Scale
    LIU Yangyang, YANG Yue, WANG Qian, KHALIFA Muhammad, ZHANG Zhaoying, TONG Linjing, LI Jianlong, SHI Aiping
    中国地理科学    2019, 20 (5): 725-740.   DOI: 10.1007/s11769-019-1063-x
    摘要188)      PDF (9146KB)(395)   

    Understanding the net primary productivity (NPP) of grassland is crucial to evaluate the terrestrial carbon cycle. In this study, we investigated the spatial distribution and the area of global grassland across the globe. Then, we used the Carnegie-Ames-Stanford Approach (CASA) model to estimate global grassland NPP and explore the spatio-temporal variations of grassland NPP in response to climate change from 1982 to 2008. Results showed that the largest area of grassland distribution during the study period was in Asia (1737.23×104 km2), while the grassland area in Europe was relatively small (202.83×104 km2). Temporally, the total NPP increased with fluctuations from 1982 to 2008, with an annual increase rate of 0.03 Pg C/yr. The total NPP experienced a significant increasing trend from 1982 to 1995, while a decreasing trend was observed from 1996 to 2008. Spatially, the grassland NPP in South America and Africa were higher than the other regions, largely as a result of these regions are under warm and wet climatic conditions. The highest mean NPP was recorded for savannas (560.10 g C/(m2·yr)), whereas the lowest was observed in open shrublands with an average NPP of 162.53 g C/(m2·yr). The relationship between grassland NPP and annual mean temperature and annual precipitation (AMT, AP, respectively) varies with changes in AP, which indicates that, grassland NPP is more sensitive to precipitation than temperature.

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    Monitoring Intra-annual Spatiotemporal Changes in Urban Heat Islands in 1449 Cities in China Based on Remote Sensing
    LI Yuanzheng, WANG Lan, ZHANG Liping, LIU Min, ZHAO Guosong
    中国地理科学    2019, 29 (6): 905-916.   DOI: 10.1007/s11769-019-1080-9
    摘要245)      PDF (1642KB)(366)   

    This study aimed to accurately study the intra-annual spatiotemporal variation in the surface urban heat island intensities (SUHIIs) in 1449 cities in China. First, China was divided into five environmental regions. Then, the SUHIIs were accurately calculated based on the modified definitions of the city extents and their corresponding nearby rural areas. Finally, we explored the spatiotemporal variation of the mean, maximum, and minimum values, and ranges of SUHIIs from several aspects. The results showed that larger annual mean daytime SUHIIs occurred in hot-humid South China and cold-humid northeastern China, and the smallest occurred in arid and semiarid west China. The seasonal order of the SUHIIs was summer > spring > autumn > winter in all the temperate regions except west China. The SUHIIs were obviously larger during the rainy season than the dry season in the tropical region. Nevertheless, significant differences were not observed between the two seasons within the rainy or dry periods. During the daytime, the maximum SUHIIs mostly occurred in summer in each region, while the minimum occurred in winter. A few cold island phenomena existed during the nighttime. The maximum SUHIIs were generally significantly positively correlated with the minimum SUHIIs during the daytime, nighttime and all-day in all environmental regions throughout the year and the four seasons. Moreover, significant correlation scarcely existed between the daytime and nighttime ranges of the SUHIIs. In addition, the daytime SUHIIs were also insignificantly correlated with the nighttime SUHIIs in half of the cases.

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    Quantitative Analysis of the Coupling Coordination Degree Between Urbanization and Eco-environment in Mongolia
    DONG Suocheng, ZHENG Ji, LI Yu, LI Zehong, LI Fujia, JIN Liang, YANG Yang, BILGAEV Alexey
    中国地理科学    2019, 20 (5): 861-871.   DOI: 10.1007/s11769-019-1074-7
    摘要144)      PDF (253KB)(361)   

    Mongolia is an important country in the Economic Corridor of China-Mongolia-Russia, a deep understanding of the coupling relationship between urbanization and the eco-environment in Mongolia is meaningful to achieve green development of the Belt and Road. The entropy method and coupling coordination degree model were integrated to evaluate the coupling coordination degree between urbanization and the eco-environment in Mongolia during 2000-2016. The results showed that the coupling coordination degree between urbanization and the eco-environment in Mongolia was generally at the stage of seriously unbalanced development, and that the main contributor of the urbanization and the eco-environment subsystem were demographic urbanization and eco-environment endowment, respectively. The southern part of Mongolia central zone should be paid more attention due to the lower degree of coupling coordination between urbanization and the eco-environment. To promote the healthy urbanization development in Mongolia, six-layer eco-city establishing green development pattern is proposed to provide scientific support for Mongolia.

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    Population Shrinkage in Resource-dependent Cities in China: Processes, Patterns and Drivers
    LI He, Kevin LO, ZHANG Pingyu
    中国地理科学    2020, 30 (1): 1-15.   DOI: 10.1007/s11769-019-1077-4
    摘要225)      PDF (1603KB)(360)   
    Resource-dependent cities (RCs) are a vulnerable group of urban settlements that often face population shrinkage; however, population changes in RCs in China are not well understood. This study offers new insight into this matter through a robust analysis that features a longer time scale, a larger sample of RCs, and a finer unit of analysis. It finds new evidence that problems of population shrinkage in RCs are more serious than previous literature has suggested. Approximately 30% of the studied units have experienced either long-term or short-term population shrinkage, and many more are experiencing a slowing down of population growth. Problems are especially common among three types of RCs:the resource-depleted RCs, the forestry-based RCs, and RCs in Northeast China. These results underscore transition policy inadequacies in addressing population loss, and call for a more comprehensive and diversified population policy that tackles the multifaceted factors that contribute to population shrinkage, including lack of industrial support, maladjustment to market oriented reformation, poor urban environment and natural population decline.
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    Trade-offs and Synergies of Ecosystem Services in Karst Area of China Driven by Grain-for-Green Program
    WANG Xiaofeng, ZHANG Xinrong, FENG Xiaoming, LIU Shirong, YIN Lichang, CHEN Yongzhe
    中国地理科学    2020, 30 (1): 101-114.   DOI: 10.1007/s11769-020-1098-z
    摘要148)      PDF (2537KB)(352)   
    As an important means regulating the relationship between human and natural ecosystem, ecological restoration program plays a key role in restoring ecosystem functions. The Grain-for-Green Program (GFGP, One of the world's most ambitious ecosystem conservation set-aside programs aims to transfer farmland on steep slopes to forestland or grassland to increase vegetation coverage) has been widely implemented from 1999 to 2015 and exerted significant influence on land use and ecosystem services (ESs). In this study, three ecological models (InVEST, RUSLE, and CASA) were used to accurately calculate the three key types of ESs, water yield (WY), soil conservation (SC), and net primary production (NPP) in Karst area of southwestern China from 1982 to 2015. The impact of GFGP on ESs and trade-offs was analyzed. It provides practical guidance in carrying out ecological regulation in Karst area of China under global climate change. Results showed that ESs and trade-offs had changed dramatically driven by GFGP. In detail, temporally, SC and NPP exhibited an increasing trend, while WY exhibited a decreasing trend. Spatially, SC basically decreased from west to east; NPP basically increased from north to south; WY basically increased from west to east; NPP and SC, SC and WY developed in the direction of trade-offs driven by the GFGP, while NPP and WY developed in the direction of synergy. Therefore, future ecosystem management and restoration poli-cy-making should consider trade-offs of ESs so as to achieve sustainable provision of ESs.
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    Effect of Hydrological Connectivity on Soil Carbon Storage in the Yellow River Delta Wetlands of China
    FENG Jiuge, LIANG Jinfeng, LI Qianwei, ZHANG Xiaoya, YUE Yi, GAO Junqin
    中国地理科学    2021, 31 (2): 197-208.   DOI: 10.1007/s11769-021-1185-9
    录用日期: 2021-01-05

    摘要154)      PDF (2816KB)(350)   
    Hydrological connectivity has significant effects on the functions of estuarine wetland ecosystem. This study aimed to examine the dynamics of hydrological connectivity and its impact on soil carbon pool in the Yellow River Delta, China. We calculated the hydrological connectivity based on the hydraulic resistance and graph theory, and measured soil total carbon and organic carbon under four different hydrological connectivity gradients (Ⅰ 0?0.03, Ⅱ 0.03?0.06, Ⅲ 0.06?0.12, Ⅳ 0.12?0.39). The results showed that hydrological connectivity increased in the north shore of the Yellow River and the south tidal flat from 2007 to 2018, which concentrated in the mainstream of the Yellow River and the tidal creek. High hydrological connectivity was maintained in the wetland restoration area. The soil total carbon storage and organic carbon storage significantly increased with increasing hydrological connectivity from Ⅰ to Ⅲ gradient and decreased in Ⅳ gradient. The highest soil total carbon storage of 0?30 cm depth was 5172.34 g/m2, and organic carbon storage 2764.31 g/m2 in Ⅲ gradient. The hydrological connectivity changed with temporal and spatial change during 2007?2018 and had a noticeable impact on soil carbon storage in the Yellow River Delta. The results indicated that appropriate hydrological connectivity, i.e. 0.08, could effectively promote soil carbon storage.
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