Table of Content

    25 November 2018, Volume 73 Issue 11 Previous Issue    Next Issue
    Climate Change and Earth Surface Processes
    Reconstruction of runoffs over Upper-Middle Reaches of Yellow River and its relationship between PDO since AD 1766
    PAN Wei, ZHENG Jingyun, MAN Zhimin
    2018, 73 (11):  2053-2063.  doi: 10.11821/dlxb201811001
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    This study, through establishing the regression model, inverts the annual runoff of 1766-1911 AD, builds up and improves the annual runoff series of 1766-2000 AD in flood season in Lanzhou, Qingtongxia and Sanmenxia by using the records of water level stake of three gauge stations in the Upper-Middle Yellow River (UMYR) in the Qing Dynasty. Combining the annual runoff of 1766-1911 AD at Tangnaihai Station in riverhead reach, the study builds the runoff series of four stations at the riverhead and UMYR, which is presently the clearest runoff curve of the Yellow River by historical records. According to the research, the heavy "river disaster" that appeared in the lower Yellow River in the mid-19th century was caused by sudden changes of the runoff at the Qingtongxia-Sanmenxia section. Drought period of the river in the 1920s existed from the riverhead to the middle reach, but it was not caused by sudden changes. Meanwhile, the study also reveals that PDO and the runoff of the UMYR had a periodic inverse phase relationship on the interdecadal scale. In the early and mid-20th century, the runoff of the four stations had an inverse phase relationship on the scale of 8-16 years. In the 1830-1850s, the inverse phase relationship between PDO and flow on the scale of 4-6 years was more obvious at Lanzhou-Sanmenxia section. According to the interactive wavelet analysis, there is a significant inverse correlation between PDO and the amount of water in the UMYR on a scale of 8-16 years, but only at the Sanmenxia-Lanzhou section, suggesting that the relationship between summer rainfall in the UMYR and PDO had obvious temporal and spatial differences. (1) During the study period, the change of runoff flow in the UMYR had obvious differences; On the natural state, there was no obvious consistency in the flow change of the UMYR. The occurrence of sudden change time point was not synchronous in history. In the long term, the runoff change of the UMYR had a unique phenomenon. The simultaneous reduction of flows of each reach since the 1970s is a special phenomenon, at least it is the only phenomenon discussed in this study within this time range. (2) It is concluded that the correlation between the PDO and runoff in the UMYR is periodic and there is no special obvious linear relationship, but regional differences are more obvious. The inverse correlation between PDO and runoff in the study reaches is mainly on a decadal scale. The Lanzhou-Sanmenxia section is relatively sensitive in the face of the change of the PDO on the decadal scale. When formulating the water resources strategy of the Yellow River, we should notice the differences in the response of different sections to the same environmental background. (3) In the mid-19th century, many large-scale floods in the lower reach resulted from the sudden increase of runoff in the middle reach. In the reign of Emperor Daoguang of the mid-19th century, the Qing Dynasty declined rapidly. During this period, large-scale flood disasters occurred in many parts of eastern China, especially in the populous North China Plain and Taihu Basin. The flood brought huge financial and social losses. Among them, eastern Henan of North China Plain suffered from the flood disaster in successive years by burst of the Yellow River in the 1840s, and the central government spent a huge amount of money to solve the problem of the river, which greatly aggravated the financial difficulties in that period. The large-scale flood in the lower Yellow River corresponds to the period of sudden change of runoff flow in Sanmenxia section revealed by this research, which indicates the sudden increase of rainfall in the Loess Plateau. Climate change was deeply involved in China's decline and depression during the reign of Daoguang. (4) Although some progress has been made in reconstruction of multi-site and long-time runoff series of the Yellow River based on different materials, further work is needed in data analysis so as to make clear the sequences of uncertainty, thus enabling the integration of data in the future to provide basic data for further research on long-time spatial and temporal change of runoff of the Yellow River.

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    A new method to attribute changes of pan evaporation: The experimental detrending approach
    WANG Tingting, SUN Fubao, ZHANG Jie, LIU Wenbin, WANG Hong
    2018, 73 (11):  2064-2074.  doi: 10.11821/dlxb201811002
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    Pan evaporation is the only long-term observation of potential evaporation around the world. In analyzing and predicting how droughts and hydrological cycles might change in a warming climate, change of pan evaporation is one crucial element to be understood. In this paper, we chose 416 sites with continuous monthly observations over 1960-2014 in China. We calibrated the wind function in the PenPan model to improve the estimation of pan evaporation. We developed a new approach, i.e., the experimental detrending (ED) approach, and made comparison with the traditional partial differential (PD) method in attributing changes of pan evaporation for the periods of 1960-2014, 1960-1993 (evaporation paradox) and 1993-2014 (evaporation paradox disappeared). The results first showed that improvement in estimating pan evaporation can be made when using the new calibrated wind function: fq(u2)=3.977×10-8(1+0.505u2). The comparison then showed that both methods can well attribute changes of pan evaporation, and the ED approach performs slightly better than the traditional PD method. In addition, the ED approach can help make effective adjustment for the PD method in attribution analysis so as to better understand the change of pan evaporation. Hence, the ED approach is recommended to assist a better understanding and prediction of water-energy cycles in a changing climate.

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    Proposition and certification of moving mean difference method for detecting abrupt change points
    BAO Weimin, SHEN Dandan, NI Peng, ZHOU Junwei, SUN Yiqun
    2018, 73 (11):  2075-2085.  doi: 10.11821/dlxb201811003
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    The abrupt change point detection is an important content in the research of current climate change problem. And many methods and achievements have already been proposed. The results of traditional methods are often considered to be unpersuasive due to the irrational structure of statistics, ideal assumptions and subjectivity. In this paper, a new method called moving mean difference method for abrupt change points detection is proposed. It is compared with four widely used methods via both hypothetic series and observed data. The results show that the moving mean difference method has three advantages: (1) The method has a simple structure and definite physical meaning; (2) It is more accurate to detect the mutation point; (3) It can simultaneously detect all the mutation points and calculate the corresponding intensity of the mutations. The sediment discharge abrupt changes in different reaches of the Yellow River are analyzed through the five methods, based on the annual data obtained from the main hydrological stations in the Yellow River Basin. The results indicate that the sediment discharge in the upper reaches the river mutated in 1986, while that in the middle reaches changed suddenly in 1979 and 1996. The mutations of sediment discharge at Huaxian and Tongguan stations occurred in 1979, 1996 and 2003. The main factors for the mutation are human activities, including hydraulic engineering construction and large-scale water and soil conservation measures.

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    Effects of urbanization on spatio-temporal distribution of precipitations in Beijing and its related causes
    ZHU Xiudi, ZHANG Qiang, SUN Peng
    2018, 73 (11):  2086-2104.  doi: 10.11821/dlxb201811004
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    Due to rapid urbanization and relevant impacts on precipitation in both space and time, effects of urbanization processes on precipitation changes have been widely discussed in recent years. Based on hourly precipitation dataset from 20 stations covering the period of 2011-2015 across Beijing city, statistical methods such as circular statistical method were applied to examine spatio-temporal characteristics of precipitation with respect to precipitation types, extreme precipitation events and so on. The results indicated that: (1) regions in the central Beijing city are dominated by higher rainstorm precipitation amount, duration and precipitation intensity. Compared with rainstorm events in suburbs, precipitation processes in the central city are characterized by long duration and larger precipitation amount. Urban Rain Island effects could contribute to the above-mentioned rainstorm changes in the central city. (2) Uneven daily distribution of precipitation can be found across Beijing with remarkable regional difference. Rainstorm events mostly occurred after noon, accounting for 47.53% of the total precipitation type. Rainstorms in mountainous regions, northern and southern Beijing occurred mostly after noon, at noon and even at night. However, due to valley wind circulation and heat island circulation, precipitation patterns in central Beijing are relatively complicated and storms in western-central part of the city occurred mainly at nighttime. (3) Peak value of precipitation intensity of rainstorms occurred mainly during 12:00-19:00 and delayed occurrence of peak rainstorm values was observed in central city when compared to that in suburbs. Meanwhile, altitude can further induce uncertainty in occurrence time of peak precipitation amount. (4) The extreme precipitation index and the continuous drought as well as moisture index showed the high value in the urban area. The high value of the frequency of extreme precipitation index was found in the downwind direction of the urban area. Urbanization may indirectly increase the risk of extreme precipitation by population growth and land-use change.

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    The sediment sources and quantitative evaluation of tidal flat at Qidong foreland, the Yangtze Estuary in recent 100 years
    ZHANG Yunfeng, ZHANG Zhenke, REN Hang, GAO Lei, DING Haiyan
    2018, 73 (11):  2105-2116.  doi: 10.11821/dlxb201811005
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    The transport of sediment by rivers to the oceans plays an important role in coastal stabilization. The Qidong foreland is located on the junction between Yangtze Estuary and Jiangsu coast, where strong land-ocean interactions are highly sensitive to environmental changes. In order to examine sediment sources and change, QDZ-1 core sediments were collected at Qidong foreland tidal flat. And the content of micro-elements was analyzed by ICP-MS, further, the source-indicating significance of micro-elements was discussed based on distribution and enrichment coefficient. The result showed that sediment sources derive from the Yangtze River and the south Yellow Sea. In addition, sediment sources were quantitatively evaluated by estimation of sedimentary end-members. The result showed that sediment sources could be divided into three stages. The sediment flew mainly from the sediment transport of the Yangtze River into the sea, with the contribution rate being 68.1%. Then, the contribution rate gradually decreased with the decline of the North Branch, down to 38.5% during the period of 1930-1972, and to 17.5% after 1972. Meanwhile, the suspended sediments from southern Yellow Sea moved mainly to the south by strong tide and Subei coastal current, and the contribution rate was 27.1% before 1930. Subsequently, the contribution rate gradually increased, up to 55.6% during the period of 1930-1972, and to 75.9% after 1972. The sediment sources of Qidong foreland tide flat mainly transformed from the Yangtze sediment to the south Yellow Sea sediment. The changes in stages of sediment source were consistent with the decline of the North Branch.

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    Spatio-temporal characteristics of evapotranspiration and its relationship with climate factors in the source region of the Yellow River from 2000 to 2014
    YE Hong,ZHANG Tingbin,YI Guihua,LI Jingji,BIE Xiaojuan,LIU Dong,LUO Linling
    2018, 73 (11):  2117-2134.  doi: 10.11821/dlxb201811006
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    Located at the eastern margin of the Tibetan Plateau, the source region of the Yellow River is an important ecological security shelter for economic development in Southwest China, with its unique natural habitats and abundant natural resources. Based on the data of 18 meteorological stations within and around the source region, map of China vegetation types (1:1000,000) and DEM data, and using the methods of trend analysis, relative inter-annual variation and correlation analysis, we selected MODIS evapotranspiration (ET) as the main data source to research the spatio-temporal characteristics of ET and its variation under different land use types as well as its relationship with climate factors in the study area from 2000 to 2014. The results indicate that: (1) the regional differentiation of mean ET over years is obvious, the northern ET is significantly weaker than that of the central and southeastern parts, and the strongest ET is observed in the southeastern part. The multi-year mean value of ET is 538.61 mm/a, and the anomaly relative variation is obvious. In addition, the trend of inter-annual variation of ET decreases firstly and then increases, and the trend variation rate is 0.44 mm/a. (2) During the study period, the ET shows a periodic unimodal trend and peaks in July. Moreover, seasonal differences of ET are apparent in the source region of the Yellow River, and the highest value of ET reaches 188.14 mm/a in summer, followed by spring and autumn, yet the lowest is only 97.15 mm/a in winter. (3) From 2000 to 2014, the value of ET in different types of land use has a similar regular pattern, namely: wetland > forest > grassland > other types > bare land. On the whole, the value of ET in each type of land use increases gradually. (4) According to the correlation analysis results, there are positive correlations between ET and air temperature, as well as between ET and precipitation, while ET has a negative correlation with relative humidity. The effect of precipitation on ET is stronger than that of air temperature. Furthermore, the result of ET driven by different factors demonstrates that the climate-driven region of ET is predominantly precipitation-driven in the source region of the Yellow River.

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    Assessment of soil erosion in karst critical zone based on soil loss tolerance and source-sink theory of positive and negative terrains
    QIAN Qinghuan,WANG Shijie,BAI Xiaoyong,ZHOU Dequan,TIAN Yichao,LI Qin,WU Luhua,XIAO Jianyong,ZENG Cheng,CHEN Fei
    2018, 73 (11):  2135-2149.  doi: 10.11821/dlxb201811007
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    Traditional classic soil erosion models are not applicable in karst areas. In this study, the effective rainfall erosion threshold was obtained and the rainfall erosivity was re-estimated, according to the lithologic difference of the karst critical zone. The soil formation rate was calculated and used as the soil loss tolerance, based on the chemical composition variation of carbonate rocks. The spatial distribution information of karst depression was extracted by geomorphologic-hydrologic analysis, and the soil erosion algorithm in the karst critical zone was modified and improved. The results showed that: (1) The traditional algorithm ignored the specificity of the underlying surface of the karst critical zone. The average rainfall erosivity was estimated to be 47.35%, and the average rainfall erosivity in the karst area is only 59.91% of the non-karst area. (2) The soilless or less soil areas could be miscalculated as the high erosion region by using the conventional algorithm. However, the soil loss tolerance by continuous carbonate, carbonate clastic, carbonate and clastic interbeds were about 0.21, 1.2 and 2.89 t ha-1 yr-1, respectively. (3) Sloping lands and croplands in the depressions are generally regarded as the high incidence area of soil erosion, but the depression of the karst should be the sediment area of surface erosion. The spatial distribution of karst depression was basically coincided with that of carbonate rocks. (4) The traditional algorithm overestimated the soil erosion area at about 27.79%, while the soil erosion amount at approximately 47.72%. Generally, the traditional classic model could greatly overestimate the soil erosion amount in the karst area, therefore, an accurate and applicable model should be established. In addition, due to the slow soil formation rate, the thin soil layer and the less total amount of soil in karst area, the soil loss tolerance was far lower than the erosion standard of non-karst area. The classifying and grading standard and risk assessment method of soil erosion applicable to karst area should be set and established.

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    Ecosystem and Carrying Capacity
    Changes of soil organic carbon storage in Chinese terrestrial ecosystems from the 1980s to the 2010s
    XU Li, YU Guirui, HE Nianpeng
    2018, 73 (11):  2150-2167.  doi: 10.11821/dlxb201811008
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    Soils store a large amount of the terrestrial ecosystem carbon (C) and play an important role in maintaining global C balance. However, very few studies have addressed the regional patterns of soil organic carbon (SOC) storage and the main factors influencing its changes in Chinese terrestrial ecosystems, especially using field measured data. In this study, we collected information on SOC storage in the main types of ecosystems (forest, grassland, cropland, and wetland) across 18 regions of China during the 1980s (from the Second National Soil Survey of China, SNSSC) and the 2010s (from studies published between 2004 and 2014), and evaluated whether trends changed over the 30-year period. The SOC storage (0-100 cm) in China was 83.46±11.89 Pg C in the 1980s and 86.50±8.71 Pg C in the 2010s, and the net increase over 30 years was 3.04±1.65 Pg C, with a rate of 0.101±0.055 Pg C yr-1. This increase was mainly observed in the topsoil (0-20 cm). Forest, grassland, and cropland SOC storage increased by 2.52±0.77, 0.40±0.78, and 0.07±0.31 Pg C, respectively, which can be attributed to the several ecological restoration projects and agricultural practices implemented. On the other hand, SOC storage in wetlands declined by 0.76±0.29 Pg C, most likely due to the decrease in wetland area and SOC density. These results, combined with those of vegetation C sink (0.100 Pg C yr-1), show that the net C sink in Chinese terrestrial ecosystems was about 0.201±0.061 Pg C yr-1, which offsets 14.85%-27.79% of the C emissions from fossil fuels from the 1980s to the 2010s. These estimates of soil C sink based on field measured data supported the premise that China's terrestrial ecosystems have a large C sequestration potential, and further emphasized the importance of forest protection and reforestation to increase SOC storage capacity.

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    Spatial-temporal evolution and trend prediction of agricultural eco-efficiency in China: 1978-2016
    HOU Mengyang, YAO Shunbo
    2018, 73 (11):  2168-2183.  doi: 10.11821/dlxb201811009
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    Based on the panel data of 30 provinces in China from 1978 to 2016, the super efficiency SBM model was used to measure the inter-provincial agricultural eco-efficiency in our study. On the basis of time series analysis and spatial correlation analysis, traditional and spatial Markov probability transfer matrices were constructed to explore the spatial and temporal evolution of agricultural eco-efficiency of China, and the long-term trends were also predicted. The result shows that: (1) The agricultural eco-efficiency in China presents a "double-peak" distribution with stable rise in fluctuation, and the gap between peak heights is narrowing, but the overall level is still relatively low. Therefore, there is still room for improvement in agricultural eco-efficiency. Besides, the agricultural eco-efficiency improvement in the eastern region is more significant than that in the central and western regions. (2) The trend of China's agricultural eco-efficiency shifting to a higher level is significant, but the evolution of agricultural eco-efficiency has maintained the stability of the original state, and it is difficult to achieve a leap-forward shift. The geospatial structure plays an important role in the spatial-temporal evolution of agricultural eco-efficiency and the spatial agglomeration is significant. The provinces with higher agricultural eco-efficiency have positive spillover effects, while those with lower agricultural eco-efficiency have negative spillover effects. As a result, the "club convergence" phenomenon of "high agglomeration, low concentration, high radiates low, and low inhibits high" has been gradually formed in the spatial pattern. (3) From the long-term trend prediction, the agricultural eco-efficiency in most provinces gradually shifts upward to a relatively high level, and gradually evolves from a low-to-high incremental pattern. In the context of the low agricultural eco-efficiency, its long-term stable evolution is manifested as a "partial unimodal" distribution; while under the geographical background of higher agricultural eco-efficiency, it has evolved into a "double-peak" distribution of higher-level agglomeration for a long time. Finally, we analyze the shortcomings and what needs to be improved for current research. What's more, we propose that controlling agricultural pollution emissions, inter-regional agro-ecological policy linkages, and strengthening inter-regional agro-ecological cooperation, exchange, and learning can effectively improve China's agricultural eco-efficiency and narrow the gap between provinces.

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    Modelling potential productivity of Chinese super hybrid rice in Bangladesh, India and Myanmar
    WANG Xiaobo, WANG Shaoqiang, CHEN Jinghua, CUI Huijuan, WU Yijin, N H RAVINDRANATH, A RAHMAN
    2018, 73 (11):  2184-2197.  doi: 10.11821/dlxb201811010
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    In this study, information is collected from statistics on the weather, soils, field management and agriculture in the Bangladesh, India and Myanmar (BIM) region. Crop growth parameters within the EPIC (Environmental Policy Integrated Climate) model are calibrated using cultivar data and regional experimental records of indica hybrid rice Fyou498 and Fengliangyou4 in China. Potential yields of rice are then simulated in the BIM region from 1996 to 2005. The effects of local irrigation and fertilization levels on super hybrid rice yield are examined. The potential yields of Chinese hybrid rice at local irrigation and fertilization levels in 2000 and at full irrigation and rational fertilization levels are found to be 10.22 t/ha and 11.33 t/ha, respectively. The potential for increasing monsoon rice production in the study area is 227.71 million tonnes. The eastern Indo-Gangetic Plain in India, the southeast coast of India Peninsula and the Ayeyarwady Delta in Myanmar have the largest potentials for monsoon rice production. It is necessary for the northeastern and southwestern parts of the Deccan Plateau and the northwestern part of the Indo-Gangetic Plain to improve irrigation equipment to meet the water-use requirements of high-yield rice. The central and southern plains in Myanmar and northeastern India should have greater access to nitrogen fertilization for high-yield rice.

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    Spatial equilibrium and pattern evolution of ecological civilization construction efficiency in China
    WANG Geng,LI Sujuan,MA Qifei
    2018, 73 (11):  2198-2209.  doi: 10.11821/dlxb201811011
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    To study the spatial distribution and its evolving patterns of ecological civilization construction efficiency in China is of great help to clarify the spatial difference mechanism of ecological civilization construction efficiency, and of an important guiding significance and reference value for narrowing down regional differences and probing into the driving factors. Ecological civilization construction is a complex process, and its core lies in the coordinated development of each component of the compound natural-economic-society (N-E-S) ecosystem. Therefore, based on the compond N-E-S (nature-economy-society) ecosystem theory and the perspectives on the ecological civilization construction efficiency connotation, this paper establishes an input-output indicators system for ecological civilization construction efficiency and applies the undesirable output SBM model to calculate China's ecological civilization construction efficiency between 2003 and 2015. Further, we use the kernel density estimation, Gini coefficient, Theil index, logarithmic deviation and gravity standard ellipse to explore the spacial evolving characteristics and distribution patterns of ecological civilization construction efficiency connotation in China. The results show that: (1)There is obvious spatial disequilibrium in the efficiency of ecological civilization construction in China. During the study period (2003-2015), the spatial disequilibrium decreases gradually and then increases gradually. According to the mean Theil indexes in the three regions of China, the western region has the biggest spatial disequilibrium degree (0.1174), followed by the eastern (0.0365) and central China (0.0223). (2) Judged by the moving track of gravity center, the gravity center of China's ecological civilization construction efficiency, located in Henan province, has moved to the southeast and then to the northeast. The moving direction of gravity center shows the increase of ecological civilization construction efficiency in space. (3) Judged by the gravity standard ellipse, the spatial distribution of China's ecological civilization construction efficiency shows a pattern inclined northeast to southwest, and has the trend of a shift to right north and south.

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    Ecosystem and Carrying Capacity
    Tracking embodied carbon flows in the Belt and Road regions
    YAO Qiuhui, HAN Mengyao, LIU Weidong
    2018, 73 (11):  2210-2222.  doi: 10.11821/dlxb201811012
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    Due to the high levels of connectivity among countries, carbon flows and leakage play increasingly significant roles in global carbon reduction. In concert with global industrial shifts, high-carbon activities in developed countries have gradually transitioned to developing ones, alongside high imports from the latter for the other countries' final consumption. This work aims to illustrate the transfer flows of embodied carbon emissions among countries and regions whilst quantifying the spatial distribution of production- and consumption-based intensities and the related responsibilities of the Belt and Road regions based on multi-regional input-output modeling. The results of this work reveal that production-based carbon intensities of Belt and Road regions are significantly higher than those of their consumption-based ones, and that differences between these two intensities are much larger than in developed countries. Up to 95% of the net embodied carbon exports are derived from the Belt and Road regions, and about 30% of the consumption-based emissions are from developed countries including the United States and Europe outside the Belt and Road area. In consideration of the cross-border international trade, the Belt and Road regions bear high-level pressure of consumption-based carbon emissions. To provide effective approaches for the mitigation of global climate change, it is necessary to evaluate the environmental responsibilities of the Belt and Road regions from the perspective of consumption and build an inclusive global climate governance system towards regional cooperation and development.

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    Land Use and Geographic Information
    Data fusion and accuracy evaluation of multi-source global land cover datasets
    BAI Yan, FENG Min
    2018, 73 (11):  2223-2235.  doi: 10.11821/dlxb201811013
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    Accurate global and regional land cover classification datasets based on remote sensing are of fundamental importance in research on global changes, land surface process modeling, ecological progress, and regional sustainable development and so on. The overall objective of this study is to present a decision-fuse method that integrates existing multi-source land cover information into a 'best-estimate' dataset using fuzzy logic. Combined with another three global datasets, i.e., MODIS VCF (Vegetation Continuous Field), MODIS Cropland Probability, and AVHRR CFTC (Continuous Fields of Tree Cover), this method is applied to five global land cover datasets (GLCC, UMD, GLC2000, MODIS LC, and GlobCover) to generate a new 1-km global land cover product SYNLCover with desired legends, which are properly defined in terms of plant functional types. Pixel-based comparisons among these six global land cover datasets are performed, and results reveal that compared with five original global land cover datasets: (1) In terms of map-specific consistency, overall consistencies of both eight life forms and twelve objective legends of SYNLCover are the highest, accounting for about 65.6% and 59.4%, respectively; followed by the accuracy of MODIS LC, GLC2000, GLCC, and GlobCover in a descending order, and the lowest map-specific consistencies of life forms and objective legends are separately 48.9% and 42.6% in UMD. Besides, among all dataset pairs, SYNLCover agrees best with each original land cover dataset regarding the occurrences of life forms and leaf attributes. (2) In terms of class-specific consistency, it is suggested that SYNLCover gets the highest average class consistencies for all the five leaf attributes, as well as major life forms except Shrubland, among which the consistency for Others in SYNLCover is up to 67.73%. (3) For Trees, Grassland, Cropland, Water, Urban and built-up and Others, SYNLCover shows particular improved average class-consistencies by about 10% to 15% over the maximum consistency of original datasets, and the consistencies of five leaf attributes in SYNLCover also increases by about 10%. This study indicates a successful integration of multi-source land cover information into a new refined dataset with improved characteristics scientifically.

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    On the neighborhood patterns of urban land use using vector grids
    LI Ye, GONG Yongxi, ZHANG Zhaodong, FENG Changchun
    2018, 73 (11):  2236-2249.  doi: 10.11821/dlxb201811014
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    The spatial distribution of urban land use is an important issue in urban geography and urban planning, and the research on the spatial patterns of urban land use could help us to understand the status of urban systems. We reviewed the research progress on urban spatial structure and urban land use patterns, and we improved the existing methods of enrichment factors from two aspects to analyze the neighborhood patterns of urban land use. The first was to adopt vector grids instead of raster grids to decrease errors, and the second was to use fastigiated grids and Manhattan distance to measure the neighborhood. We used the proposed method to analyze six types of urban land uses in Shenzhen in 2015 and identified three neighborhood patterns that revealed the variation of enrichment degrees between different types of urban land uses with respect to distance. Pattern I showed that the enrichment degree between the same urban land use type was high over short distances and became low over increasing distances, indicating the attraction of the same type of urban land use within short distances and the decrease of attraction over long distances. The value of the enrichment degree between different types of land uses was negative over short distances in both Pattern II and Pattern III. In Pattern II the enrichment degree gradually increased to 0 when the distance increased, demonstrating the repulsion between different types of land uses over short distances and the decrease of repulsion over long distances. In Pattern III the enrichment degree increased quickly to a positive value, then decreased gradually to 0, which revealed repulsion between different types of land uses over short distances, and the interaction became attraction over long distance. Compared with the method based on raster grids, the proposed method based on fastigiated vector grids can reduce the error of neighborhood patterns of urban land uses.

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    Spatial allocation of fallow land in karst rocky desertification areas: A case study in Qinglong County, Guizhou Province
    YANG Qingyuan,BI Guohua,CHEN Zhantu,ZENG Li,YANG Renhao
    2018, 73 (11):  2250-2266.  doi: 10.11821/dlxb201811015
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    Fallow is important to promote the recuperation of cultivated land and enhance the sustainable development of agriculture and society. To examine the direction of fallow, this paper developed a conceptual framework and logical process to select fallow regions. First, the fallow regions were selected by diagnosing the cultivated land vulnerability using the VSD model, grey GM(1, 1) model and GIS spatial analysis methods. Second, the fallow scales were revised based on the restriction of cultivated land quantity. Third, the fallow regions were determined in ecological vulnerable karst areas. The results indicate that: (1) The farmland ecosystem in Qinglong County is in quite a dire state, with more than 70% of arable land in the county classified as very vulnerable or extremely vulnerable. Improvement of the land use pattern through fallowing is urgently needed to promote restoration of the ecosystem. (2) Under the constraints of food security, the fallow areas reach 13540.05 ha in the period of 2015-2020, or 37.18% of cultivated land in the county. (3) According to the fallow area, quality, landforms, and location of cultivated land and socioeconomic development levels, the fallow regions in Qinglong can be divided into three "grades" and five "types", which can be converted to the fallow land in the future. The implementation of fallow policies should consider the local conditions, so as to formulate different fallow modes and organizational form. (4) The fallow region-selecting is an optimizing process of fallow based on the two constraints of "object" and "scale". In the process, identification is the base, scale prediction is the constraint and implementation of fallow project is the final product.

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