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15 July 2020, Volume 37 Issue 4 Previous Issue    Next Issue

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Analysis of water resources and their utilization in countries targeted by the “Belt and Road”initiative LIU Zhen-wei, CHEN Shao-hui 2020, 37 (4):  809-818.  doi: 10.13866/j.azr.2020.04.01 Abstract ( 927 )   PDF (13742KB) ( 202 )   Using ArcGIS mapping and a chart analysis method to analyze data on per capita water resources, cross-border water resources, and water resource utilization from the Food and Agriculture Organization of the United Nations and the World Bank, the development and utilization status of water resources in countries targeted by the Belt and Road initiative in recent years were investigated. The results show that the area with the highest amount of water resources per capita is Southeast Asia, while the areas with the lowest are West Asia and North Africa, with obvious regional differences. In most countries, the amount of water resources per capita is shrinking, most prominently in West Asia; meanwhile, in Central and Eastern Europe, there is a slight growth trend. The development and utilization of water resources is clearest in Southeast Asia and West Asia. The rate of utilization of water resources is highest in West Asia and lowest in Southeast Asia. Cross-border water exists in most countries, although the proportion of cross-border water in Central and Eastern Europe is higher than that elsewhere. In some countries, the amount of imported water resources is zero. The proportion of water used for agriculture is generally higher in Asia, while the proportion of water used in industrial and urban domestic settings is greater in Central and Eastern Europe. References | Related Articles | Metrics

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Analysis of drought evolution in the Xilin River Basin based on Standardized Precipitation Evapotranspiration Index 2020, 37 (4):  819-829.  doi: 10.13866/j.azr.2020.04.02 Abstract ( 490 )   PDF (19043KB) ( 159 )   To analyze the evolution trend of droughts for many years and predict future droughts, we used the Standardized Precipitation Evapotranspiration Index（SPEI）, Mann-Kendall test, Mann Whitney Pettitt mutation test, nonparametric statistical test, and rescaled range R/S analysis method based on daily meteorological observation data from 13 national meteorological stations around the Xilin River Basin. The results indicated that sudden changes in the drought pattern began in the 1990s. In the past 60 years, SPEI has shown a significant decrease trend, and the decreasing trend in the upstream is smaller than that in the middle and lower reaches. The middle and lower reaches are drought-prone, and the northwest end of the downstream is a dangerous area where drought exists. Although droughts are mitigated in the future, they may continue to increase in winters. Therefore, drought monitoring needs to be strengthened. References | Related Articles | Metrics

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Effects of film-mulched drip irrigation on the physical, chemical, and biological characteristics of tomato soil in a greenhouse WANG Jing-wei, WANG Lei-yuan, LI Yuan, NIU Wen-quan 2020, 37 (4):  870-880.  doi: 10.13866/j.azr.2020.04.07 Abstract ( 624 )   PDF (7211KB) ( 192 )   To investigate the laws of soil water and salt transport in a crop root zone as well as their effects on soil-microorganism and enzyme-root interactions under film-mulched drip irrigation（FDI）, and to further enhance the efficiency of water and fertilizer utilization and improve the precision of the irrigation system, a field experiment in a greenhouse was carried out. Tomatoes were taken as the research object and a method of dynamic monitoring in continuous irrigation cycles was used. The effects of conventional drip irrigation（CDI）and FDI on dynamic changes in soil moisture and salt in the tomato root zone, as well as on tomato root growth, soil microorganisms, and enzymes were studied. Further, the interactions among soil environmental factors, soil microorganisms, enzymes, and root growth were analyzed. The results showed that:（1）Compared with CDI, the soil water transfer rate under FDI was significantly lower, the soil water distribution was relatively uniform, and the soil area in which the lower limit of soil moisture content（22%）was maintained within the determination range was five times that under CDI（P < 0.05）.（2）The local salt accumulation rate decreased by 50% and the degree of local salt accumulation decreased under FDI compared with CDI.（3）The root zone soil temperature and pH were significantly increased and decreased by FDI, respectively.（4）The root length density in the surface soil under FDI was 12.8-28.5 times that under CDI. These changes created by FDI further strengthened soil-microorganism and enzyme-root interactions and improved soil urease activity by 20.83%-30.61% and soil phosphatase activity by 76.92%-84.61% compared with CDI. Therefore, compared with CDI, FDI has greater potential to improve the utilization efficiency of water and soil resources. However, relevant agronomic measures of FDI need to be further refined and improved to provide references for further improving water and soil utilization efficiency References | Related Articles | Metrics

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Spatial and temporal variability of soil moisture content during vegetation succession in sand-binding areas WANG Bo, DUAN Yu-xi, WANG Wei-feng, LI Xiao-jing, LIU Yuan, LIU Zong-qi 2020, 37 (4):  881-889.  doi: 10.13866/j.azr.2020.04.08 Abstract ( 564 )   PDF (4705KB) ( 370 )   Experiments were conducted by taking sandy soil at different stages of vegetation succession（primary stage, middle stage, later stage, and maturation stage of succession）in the eastern Hobq Desert, China, as a sand-binding area. Soil volumetric moisture content from 0 to 180 cm of the top, middle, and bottom of the windward slope of sandy land was measured from during the growing season between 2017 and 2018. This study aimed to investigate the spatiotemporal dynamic characteristics of soil moisture content and reveal the response of desert soil moisture content to environmental factors. The results showed that precipitation differences caused annual fluctuation of average soil moisture content in the study area; 2018（8.8%）> 2017（4.8%）. Affected by precipitation and plant growth, the soil moisture content in the four sample plots showed obvious seasonal variations. Moisture content decreased slowly in the early growing season, increased rapidly after replenishment with precipitation during the intense growing season, and remained constant at the end of the growing season. Soil moisture content at different vegetation succession stages is generally shown as primary stage（7.3%）>maturation stage（7.2%）>later stage（6.7%）>middle stage（5.9%）. Soil moisture content in the middle of the windward slope was the lowest in all four sample plots. Soil moisture content in the top and bottom layers varied in different succession stages. The soil moisture content of four sample plots showed clear vertical changes, decreasing first and then increasing with soil depth. The moisture content of the surface layer（0-20 cm）was significantly higher than that of the other layers. There was an inflection point in the moisture content of the deep soil in each sample plot, which was the dry sand layer with the lowest moisture content. The depth of the dry sand layer changed at different succession stages or precipitation conditions. At the end of the growing season, the precipitation supply and vegetation consumption of soil moisture in the study area reached a positive balance. Besides, the soil moisture storage was able to sustain the normal growth of artificial vegetation in the sand-binding area. References | Related Articles | Metrics

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Large eddy simulation of the effect of the intensity of capping inversion on a super-thick convective boundary layer in an arid area WANG Rong , HUANG Qian , ZHANG Qiang 2020, 37 (4):  925-935.  doi: 10.13866/j.azr.2020.04.13 Abstract ( 510 )   PDF (7068KB) ( 462 )   The impacts of the intensity of capping inversion on the development of a super-thick convection boundary layer and the entrainment process in an arid area were simulated by large eddy simulation using intensive field observation data from Dunhuang, China. The results show that:（1）Before the capping inversion was broken, the weaker inversion was, the more unstable the mixed layer; the more favorable the turbulent vertical upward development; the thicker the convective boundary layer, mixed layer, and entrainment layer; and the greater the entrainment speed. Additionally, the entrainment effect was strong at the top of the boundary layer when the inversion was weaker. When the capping inversion layer was completely convective through the fully developed boundary layer, the boundary layer convection, which was originally confined to the strong overlying inversion layer with low thickness and high energy, the convection mixing was more intense, the entrainment was stronger, and the more likely it was that the mixed layer and the neutral layer above the inversion layer would mix to form a super-thick boundary layer.（2）Before the capping inversion was broken, the turbulent kinetic energy of the boundary layer was mainly provided by thermal buoyancy. After the capping inversion layer was broken, the shear production term in the mixing layer contributed the most to the turbulent kinetic energy of the boundary layer. References | Related Articles | Metrics

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Diagnostic analysis and numerical simulation of a Central Asian vortex rainstorm based on CloudSat satellite data DING Ming-yue, WANG Li-li, XIN Yu, LIU Qiong, CHEN Yong-hang, ZHANG Guang-xin, YANG Lian-mei, LIANG Qian, HUANG Guan, LIU Tong-qiang 2020, 37 (4):  936-946.  doi: 10.13866/j.azr.2020.04.14 Abstract ( 531 )   PDF (23909KB) ( 95 )   A Central Asian vortex rainstorm episode was simulated using the Weather Research and Forecasting model based on reanalysis data from the European Centre for Medium-Range Weather Forecasts. Hourly precipitation data from regional automatic weather stations, CloudSat satellite 2B-CWC-RO data, and FY-2D/E satellite TBB（Black Body Temperature）data were used to evaluate the applicability of the Lin, WSM 6, Thompson, and WDM 6 schemes in forecasting precipitation in Xinjiang. The results were as follows: the Thompson scheme was superior in the simulation of light rain（0.1-5.0 mm）and moderate rain（5.1-10.0 mm）. The distribution of the cloud top bright temperature simulated using the four schemes was similar to, though slightly lower than, that measured by FY-2E satellite observation. According to the vertical distribution of the average ice content measured by CloudSat observation, the Thompson scheme was also superior in the numerical simulation of ice content and height in the high-value region; the Lin scheme performed worst in these areas. According to the vertical distribution of average ice content in a 3 km area, the cloud ice content simulated with the Thompson scheme was the highest, followed by the WSM 6 and WDM 6 schemes, and finally the Lin scheme. The ice content-height profile of the WSM 6 and WDM 6 schemes were almost coincident. References | Related Articles | Metrics

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Vegetation changes during the 2013-2018 period and its response to ecological water transport in the lower reaches of the Tarim River LI Jun-li, XIAO Hao, SHEN Zhan-Feng, BAI Jie 2020, 37 (4):  985-992.  doi: 10.13866/j.azr.2020.04.19 Abstract ( 520 )   PDF (17601KB) ( 320 )   Desert riparian vegetation plays a significant role in maintaining ecological stability in extremely arid regions. Understanding the response of desert riparian vegetation to ecological water transport in the arid areas and its changing process is crucial for the formulation of ecological conservation and restoration and water transport policy development. The desert riparian vegetation in the lower reaches of the Tarim River was selected as the research objective. We used multi-source data, including Landsat8 OLI and Sentinel-2A, to construct the vegetation cover data and typical monitoring section vegetation index time-series data. Besides, the temporal and spatial variation characteristics of vegetation in the desert riparian zone from 2013 to 2018 were analyzed. Combined with groundwater level data, we analyzed the response of desert riparian vegetation and ecological water transfer projects. The results showed that the different types of vegetation presented different spatial and temporal changing characteristics after the ecological water transport. The area and spatial distribution of new shrubs were significantly higher than those of other vegetation types. The new Populus euphratica is mainly distributed within 0-1 km and 4.5-6 km of the river channel, and the new shrubs are mainly distributed within 1-4 km of the river channel. The new herbal plants are mainly distributed within 2.5 km of the river channel. Different types of vegetation are affected by ecological water transport modes and monitoring section spaces. The influence of location shows different responses to ecological water transport. At the same time, groundwater levels downstream of the Tarim River is generally uplifted, and vegetation growth is generally improved with the development of ecological water transfer projects. References | Related Articles | Metrics

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Analysis of patterns in the variation and stability of oases in the Heihe River basin DONG Jing-ru, XIE Yao-wen, DUAN Han-ming, WANG Xiao-yun, LI Ru-yan 2020, 37 (4):  1048-1056.  doi: 10.13866/j.azr.2020.04.26 Abstract ( 510 )   PDF (9179KB) ( 378 )   This article aims to explore spatiotemporal patterns in the variation and stability of oases in the Heihe River basin in the last 55 years. This study involved multi-source remote sensing images in 16 periods from 1963 to 2017. Information on the distribution of oases in the Heihe River basin was extracted from the images. Then, the temporal and spatial characteristics of the variation and stability of oases in the basin were analyzed using overlay analysis and a grid-transformed model. According to the transformation from oasis to desert and changes in oasis boundaries, the oases were divided into four categories: stable, expanding, shrinking, and fluctuating. In order to make up for the shortcomings of previous research methods such as single dynamic degree, we established a grid-transformed model of spatial dynamic degree and cumulative dynamic degree considering total change to analyze the spatial distribution of the stability of oases. The results show the following: In the past 55 years, the oases in the Heihe River Basin were predominantly fluctuating. Oasis fluctuations mainly occurred in areas with poor water source reliability and saline-alkaline soil. Expansions of the oasis mainly occurred in the gap between the existing oasis patches in the early years, and occurred on the outer edge of the existing oasis in the middle and later years. Shrinkages of the oasis mainly occurred in the ecologically fragile zone on the edge of the oasis. The expansions of oases in the early years were mainly due to population growth and immigration policies, while the expansion of oases after the year 2000 was mainly caused by the innovation of agricultural production technologies such as drip irrigation and sprinkling irrigation. Oases in the Heihe River basin gradually became stable. The stability of oasis in the lower reaches of the Heihe River was lower than that of oases in the middle of the river. Fluctuations in oases in the middle and lower reaches in Jinta County and Dingxin County mainly occurred in the early stage, while oases in Ejina County fluctuated in the middle stage. Land salinization and broad-shallow and shifting channels of the Heihe River are the important factors influencing oasis stability. This paper constructed a time series of oasis dynamics on the basis of a grid-transformed method. It simultaneously detects the temporal and spatial characteristics of changes in oases and reduces the analysis unit to the grid scale so that changes in oases can be identified and analyzed more effectively. References | Related Articles | Metrics