Table of Content

15 July 2022, Volume 39 Issue 4 Previous Issue    Next Issue

Weather and Applied Climate

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Aerodynamic parameters of typical underlying surfaces in an aeolian region in the middle reaches of the Yarlung Zangbo River ZHANG Zhengcai,ZHANG Yan,MA Pengfei,PAN Kaijia,ZHA Duo,Yixi Lamu,Renqing Sangbu 2022, 39 (4):  997-1005.  doi: 10.13866/j.azr.2022.04.01 Abstract ( 279 )   HTML ( 19 )   PDF (6691KB) ( 514 )   Aerodynamic parameters are an important research focus in the study of aeolian areas. Some of the most severe aeolian damage occurs along the middle reaches of the Yarlung Zangbo River in Tibet. The floodplains and shifting sand dunes are the main surface types and source areas of wind-sand degradation in this region. The study of aerodynamic parameters is conducive to the assessment of aeolian damage and the forecasting of sandstorms. For this reason, we examined aeolian processes in three surface types: river floodplain vegetation area (vegetation coverage > 20%), disturbed river floodplain vegetation area (vegetation coverage < 20%), and sand dune area (without any vegetation). The wind speed profile method was used to calculate the frictional wind speed (u*) and aerodynamic roughness (z0). The results showed the following: (1) The wind speed reduction amplitude near the ground layer was in the following order: vegetation area > disturbed vegetation area > sand dune area, and the wind speed reduction near the ground layer in the vegetation area was nearly twice that of the sand dune. (2) Although the near-surface wind speed profiles of different underlying surfaces can be expressed as log-linear functions (uz = bln(z) + a), the fitting parameters are different. (3) The averaged values of u* in the vegetation area, disturbed vegetation area, and sand dunes are 0.73, 0.59, and 0.36 m·s-1, respectively, and the averaged values of z0 are 7.1 × 10-2, 3.7 × 10-2, and 4.7 × 10-4 m, respectively. The u* and z0 of the vegetation area are approximately 2 and 150 times those of the sand dunes, respectively. (4) The u* of the vegetation area, disturbed vegetation area, and sand dunes all increased with increasing averaged wind speed, and the increase in amplitude is in the following order: vegetation area > disturbed vegetation area > sand dunes. (5) The responses of z0 to the average wind speed in the vegetation zone and the sand dunes are clearly different. The z0 of the vegetation area increased slowly with the increase in wind speed. The value of z0 in the sand dunes area has a decreasing trend at low wind speeds but begins to increase when the wind speed increases to a threshold value of 6.5 m·s-1. Figures and Tables | References | Related Articles | Metrics

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Comparative study of the applicability of emission threshold determining method in the Taklimakan Desert YANG Xinghua,MA Mingjie,ZHOU Chenglong,HE Qing 2022, 39 (4):  1006-1016.  doi: 10.13866/j.azr.2022.04.02 Abstract ( 359 )   HTML ( 9 )   PDF (3836KB) ( 381 )   Aeolian sand movement is a crucial surface process in the study of regional and global changes. As a key parameter in determining wind-sand movement occurrence, the emission threshold (threshold velocity, threshold friction velocity) is a core issue in the study of wind-sand movement. Taking the Taklimakan Desert as the target area, using synchronously observed wind-sand movement and meteorological data in the field, combined with mathematical model calculations, the applicability of five emission threshold judgment schemes from Stout, Kurosaki and Mikami (KM), Li Xiaolan and Zhang Hongsheng (LZ), Marticorena and Bergametti (MB), and Shao and Lu (SL) was quantitatively assessed, and the optimal scheme was used to determine the new emission threshold of the Taklimakan Desert. The following results are presented. (1) Uncertainties exist in all five schemes. The emission threshold determined by the KM scheme overestimates the dust emission time and the dust level flux to a certain extent. The four other schemes are opposite, but the KM scheme is the best. (2) The 2 m threshold velocity in the hinterland of the Taklimakan Desert varies from 4.0 m·s-1 to 6.0 m·s-1, and the threshold friction velocity varies from 0.24 m·s-1 to 0.36 m·s-1. Moreover, the emission threshold has seasonal differences, which is consistent with summer > autumn > spring > winter. Figures and Tables | References | Related Articles | Metrics

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Different diurnal effects of floating dust on the structures in the atmospheric boundary layer over desert areas ZHU Congzhen,ZHAO Tianliang,MENG Lu,YANG Xinghua,HE Qing,Ali MAMTIMIN,YANG Jie,ZHU Yan,WU Zhaoye 2022, 39 (4):  1017-1026.  doi: 10.13866/j.azr.2022.04.03 Abstract ( 247 )   HTML ( 6 )   PDF (4180KB) ( 199 )   Based on data from four-times-daily intensive sounding and ground meteorological observations in the hinterland of the Taklamakan Desert in July 2016, this paper compares the structures in the atmospheric boundary layer and differences in surface radiation budget on sunny days and days with high amounts of floating dust (“floating dust days”) to reveal the diurnal change in the effect of floating dust aerosols on the structure of the atmospheric boundary layer and its underlying mechanism. The results show that the height of the stable boundary layer at night on a sunny day and a floating dust day is 270 m and 360 m, respectively. The stable boundary layer inversion intensity on a sunny day reaches 3.1 K·（100m）-1, which is stronger than 1.6 K·（100m）-1 on a floating dust day. The convective boundary layer height is close to 3600 m on a sunny day and only 2700 m on a floating dust day. The downward long-wave radiation of floating dust aerosols at night weakens the radiative cooling of the surface, raises the height of stable boundary layer, and weakens its stability. In the daytime, the strong solar short-wave net radiation heats the desert surface, and its strong sensible heat creates an ultrahigh convective atmospheric boundary layer. Floating dust aerosol significantly reduces the surface short-wave radiation and sensible heating and reduces the height of the convective boundary layer during the day. The unique radiation effect of floating dust aerosols in the Tarim Basin has opposite influences on the structure of the atmospheric boundary layer during the day and night. Figures and Tables | References | Related Articles | Metrics

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Last glacial millennium-scale climate event recorded by loess sediments in Linfen Basin TIAN Qingchun,SHI Xiaojing,HAO Xiaolong 2022, 39 (4):  1027-1035.  doi: 10.13866/j.azr.2022.04.04 Abstract ( 321 )   HTML ( 7 )   PDF (9031KB) ( 164 )   Global change is a hotspot of current geography research, among which the millennium-scale climate events during the last glacial stage are the focus of global change research. Optical luminescence dating was conducted on the Dingcun section of the Linfen Basin, and the grain age model was used to reconstruct the chronological sequence of the area. In addition, the climate proxy indicators such as grain size, frequency magnetic susceptibility, and chromaticity were compared and analyzed to investigate the change of millennium-scale climate abrupt events in the Linfen Basin. The performance and regional characteristics revealed the relationship between climate instability in the East Asian monsoon region since the last glacial period and that in the North Atlantic region. Results showed that the median particle size and frequency magnetic susceptibility curves of the Dingcun section clearly recorded five Heinrich events and 19 Dansgaard-Oeschger cycles between 80 and 20 ka BP. The change was evident, followed by the H5 event, and the H3 and H4 events were the smallest, indicating the local climate was not only controlled by large-scale climate changes, but also affected by regional climate changes. Moreover, climatic events recorded in the Dingcun section had a good correlation with the Greenland ice core δ18O, Lijiayuan section in the western Loess Plateau, and Zeketai and Tajikistan sections in the westerly region. Furthermore, the magnitude was affected by the westerly wind and East Asian summer monsoon. Figures and Tables | References | Related Articles | Metrics

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Spatiotemporal characteristics of climate change in Afghanistan from 1951 to 2020 Dilinuer TUOLIEWUBIEKE,YAO Junqiang,MAO Weiyi,LI Shujuan,CHEN Jing,MA Liyun 2022, 39 (4):  1036-1046.  doi: 10.13866/j.azr.2022.04.05 Abstract ( 748 )   HTML ( 42 )   PDF (6187KB) ( 401 )   The fragile ecosystems of Afghanistan, in the southern arid region of Central Asia, are greatly affected by climate change. In this study, we systematically analyzed the change in the average climate of Afghanistan from 1951 to 2020, in terms of both temporal and spatial patterns, using updated CRU TS V4.05 high-resolution gridded data. Results indicate that the extremely arid, arid, semihumid, and humid climate zones of Afghanistan are distributed from the southwest to the northeast. The annual average air temperature and potential evapotranspiration decreased from the Sistan Basin in the southwest to the Wakhan Corridor in the northeast. By contrast, the annual average precipitation increased. The annual and seasonal average temperature increased consistently, with the most substantial warming over the past 70 years occurring in the western part of Afghanistan; the greatest increase in the seasonal average temperature was in the spring. The data indicated strong spatial heterogeneity in precipitation as well as large seasonal differences. There was a slight decrease in the annual precipitation [-0.43 mm·(10a)-1] over the study period and a “decrease-increase-decrease” trend in the spatial distribution changes, from the southwest to the northeast. The precipitation was concentrated in winter and spring. From 1951 to 2020, the trend in the potential evapotranspiration in Afghanistan was a significantly upward trend, with a rate of 5.59 mm·(10a)-1. Annual potential evapotranspiration was found to have decreased over the central region of Afghanistan. Although there were seasonal differences, potential evapotranspiration tended to increase in the spring, summer, and autumn and decrease in the winter. Analysis of the aridity index (AI) revealed interannual variations in the climate of Afghanistan. Drought had intensified in the extremely arid Sistan Basin in the southwest, whereas warmer and wetter weather occurred in the central Hindu Kush region, and the Wahan Corridor area was generally warmer and dryer. The average AI decreased substantially in the spring, leading to the risk of staged drought. Generally, since the beginning of the 21st century, Afghanistan has experienced a slight increase in temperature, a sharp increase in precipitation, and a significant decrease in annual potential evapotranspiration. The region experienced warming and wetting stages, most notably in the spring. In conclusion, all of these changes pose risks and challenges to agricultural production, the cryosphere, and water management. Figures and Tables | References | Related Articles | Metrics

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Movement paths and characteristics of hail clouds in Bayannur, Inner Mongolia YU Shuiyan,BI Lige,SU Lijuan,LIU Jidong,SHI Jinli,YI Na’na,FAN Ruxia,XU Zhili 2022, 39 (4):  1047-1055.  doi: 10.13866/j.azr.2022.04.06 Abstract ( 259 )   HTML ( 7 )   PDF (9351KB) ( 251 )   Bayannur is an important agricultural and animal husbandry production area. The ecological environment in this area is highly sensitive. In addition, hail frequently occurs in this area. This paper used the manual records of 67 ground anti-hail operation sites in Bayannur, western Inner Mongolia, from 2009 to 2019 and the weather radar data of Linhe Station to statistically analyze the movement paths and characteristics of hail clouds in this area. Results showed that the moving paths of hail clouds in Bayannur in the past 11 years were primarily northwest, southwest, and west. The occurrence frequency of hail cloud in the northwest route was the highest (46.70%), and its moving distance during the heavy hailstorm phase was the longest (23.86 km). Moreover, the duration of the heavy hailstorm was longer (40.25 min). In summer (June-August), the impact of hail disasters should be paid attention to. The hail cloud in July and August can develop in a short time (14.09 and 17.00 min) and a short moving distance (5.49 km and 8.48 km). In the mature stage, the movement slowly and continuously affected the cloud coverage. In this region, hail clouds are devastating during these months. The time period with the highest initial frequency of hail cloud source points was concentrated between 13:00 and 15:00, whereas hail primarily occurred between 14:00 and 17:00. The hail cloud and hail in Bayannur are primarily due to water vapor and dynamic hail, which can reach 79.44%. Under dynamic conditions, hail is primarily due to the northwest paths (68.57%), and under water vapor conditions, hail is primarily due to the northwest paths, southwest paths, and west paths (96.00%). The characteristics of the movement paths of the hail clouds in Bayannur in the past 11 years showed that the hail clouds along the northwest paths in summer were the most disastrous. Figures and Tables | References | Related Articles | Metrics

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Optimal time period for PM2.5 control based on decision tree model: A case study of Guanzhong, China JIA Ce,CHEN Zhen,HAN Mei 2022, 39 (4):  1056-1065.  doi: 10.13866/j.azr.2022.04.07 Abstract ( 259 )   HTML ( 5 )   PDF (3844KB) ( 283 )   A simple spatiotemporal identification method for PM2.5 pollution control based on a machine learning model is proposed. A spatiotemporal clustering algorithm was used to cluster PM2.5 in the winter prevention period, and different PM2.5 polluted areas were identified. Furthermore, a decision tree model was constructed using the meteorological data of different areas to identify the most unfavorable influences on PM2.5 concentration in different areas. The changes in PM2.5 under the most unfavorable meteorological conditions were analyzed, and the optimal time period for PM2.5 pollution control in the different study areas was determined. Using the Guanzhong area as an example, the correlation analysis of the spatial clustering of mean daily PM2.5 in winter showed that the Guanzhong area is mainly divided into a low-altitude plain area (the Guanzhong Plain) and a relatively high mountain range. The classification tree model was then constructed, using the meteorological data of the plain and mountain areas. The analysis showed that the mountain elevations have a higher PM2.5 concentrations under Ⅰ-10 (1.57 h ≤ sunshine hours < 7.88 h; maximum wind speed < 3.72 m·s-1) and Ⅰ-11 (sunshine hours < 1.57 h; maximum wind speed < 3.72 m·s-1) meteorological conditions; low-altitude areas have a higher PM2.5 concentrations under Ⅱ-10 (small-scale evaporation ≥ 0.96 mm; average relative humidity ≥ 45.38%; sunshine hours < 8.55 h; average wind speed ≥ 2.43 m·s-1) and Ⅱ-11 (small evaporation < 0.96 mm) meteorological conditions. Lastly, the regression analysis results showed that in the mountain elevations area in the Ⅰ-10, Ⅰ-11 category and the plain altitude area under the most unfavorable meteorological conditions (Ⅱ-10 and Ⅱ-11 category), the PM2.5 concentration will continue to increase for 4.76 days on average, before reaching a maximum concentration. Figures and Tables | References | Related Articles | Metrics

Water Resources and Utilization

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Sustainable utilization of water resources in Yulin City based on an emergy ecological footprint model LI Xiaoge,ZHANG Ying,SHAN Yongjuan 2022, 39 (4):  1066-1075.  doi: 10.13866/j.azr.2022.04.08 Abstract ( 220 )   HTML ( 15 )   PDF (3956KB) ( 226 )   Yulin City was selected as the research area to study the development and utilization of water resources in a semi-arid climate area based on water resource statistics. This paper aimed to comprehensively evaluate the water ecological footprint and water ecological carrying capacity of Yulin City from 2000 to 2019 by using the emergy ecological footprint model, to obtain the change characteristics of water resource development and utilization in Yulin City, and to compare such characteristics with those of the traditional water ecological footprint model. Results show that (1) From 2000 to 2019, the annual average value of water resource emergy ecological footprint is 1.17 hm2·cap-1; the annual average value of water resource emergy ecological carrying capacity is 0.49 hm2·cap-1, and the ecological deficit of water resources in Yulin is evident and increasing. (2) In addition, the annual average value of Yulin’s water resource ecological pressure is 2.43, and it is in a semi-safe state all year round. (3) The annual average value of the water resource economic coordination index is 1.31, and the socio-economic coordination of the water resource ecosystem is relatively stable. In the traditional ecological footprint of water resources, the annual average of water footprint per 10000 yuan GDP decreased from 0.97 hm2 per 10000 yuan to 0.04 hm2 per 10000 yuan, indicating that the utilization efficiency of water resources is gradually improving. The state of water resource ecological security in Yulin City is relatively severe. Therefore, strengthening water conservation in agriculture and industry, innovating sewage treatment technology, advocating domestic water saving, and comprehensively improving the utilization efficiency of water resources are necessary to promote the sustainable development of water resources in Yulin City Figures and Tables | References | Related Articles | Metrics

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Analysis of Qinghai Lake expansion and lakeside sandy land change characteristics based on GF-1 satellite ZHU Cunxiong,SHI Feifei,QIAO Bin,ZHANG Juan,CHEN Guoqian 2022, 39 (4):  1076-1089.  doi: 10.13866/j.azr.2022.04.09 Abstract ( 317 )   HTML ( 13 )   PDF (6644KB) ( 242 )   In the context of climate change, the ecological environment of the Qinghai-Tibet Plateau has undergone a series of changes, including the increase in the lake area. As the largest inland plateau saltwater lake in China, Qinghai Lake is located in the Northeast of the Qinghai-Tibet Plateau and is an important part of the “Asian water tower.” Since 2005, Qinghai Lake has demonstrated area expansion. Therefore, understanding the causes of changes in Qinghai Lake and the impact of such changes on the surrounding environment (such as lakeside sandy) is crucial. Based on multisource satellite and meteorological station data, combined with the snow cover, glacier, permafrost, and meteorological data in the basin, this paper analyzed the dynamic change characteristics of the lake area, lakeside sand area, and sand vegetation coverage in Qinghai from 2013 to 2020. The following results are presented. (1) Qinghai Lake continued to expand in recent years, especially after 2017. The expansion affected the areas of Buha River entering the lake, Shaliu River entering the lake, Sand Island, Bird Island, and Spring Bay. The interannual fluctuation and expansion trend of the Gahai sublake affiliated to Qinghai Lake is consistent with that of the main lake, and its expansion rate is lower than that of the main lake. (2) The expansion of the lake led to the extensive inundation of the zigzagging low-lying areas, and the shoreline length showed a trend of fluctuating reduction, especially after 2017. The shoreline significantly decreased mainly due to the inundation of the lake in the lakeside sandy land and sand dike, leading to a fluctuating reduction trend in the area of the lakeside sand area; among which, the Bird Island sand area was completely submerged. (3) The vegetation in the sand region is characterized by low coverage, uneven distribution, spatial aggregation, obvious interannual fluctuation, and insufficient stability. (4) The Qinghai Lake basin presents a trend of warm and humid climate, increasing snow cover area and snow cover days, glacier retreat, and shallow maximum frozen soil depth. (5) The precipitation in the basin increased, and the snow cover area increased in winter. The increase in snow cover days affected lakes and rivers, which was significantly correlated with the change in lake area (P < 0.01). Temperature rise, seasonally frozen ground degradation, and glacier retreat indirectly affect water resource allocation in the basin and have an impact on the inflow of Qinghai Lake. The method and extent of the impact of frozen soil on the lake need further study. (6) The regional warm and humid climate background has created a good opportunity for ecological restoration projects in arid sand areas. Meanwhile, the expansion of Qinghai Lake has had a certain impact on bird habitats and surrounding infrastructure. However, focusing on the prevention of regional potential ecological risks is still necessary. Figures and Tables | References | Related Articles | Metrics

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Applicability of CMADS in runoff simulation of Yulong Kashi River LUO Chengyan,CHEN Fulong,HE Chaofei,LONG Aihua,QIAO Changlu 2022, 39 (4):  1090-1101.  doi: 10.13866/j.azr.2022.04.10 Abstract ( 280 )   HTML ( 4 )   PDF (9396KB) ( 134 )   In this paper, the Yulong Kashi River Basin was selected as the research area, and the runoff simulation of SWAT hydrological model driven by The China Meteorological Assimilation Driving Datasets (CMADS) for the SWAT model was carried out to assess the accuracy of CMADS in the watershed and its applicability to the SWAT model. The results showed that (1) the correlation coefficients of precipitation, maximum temperature, and minimum temperature of CMADS with the measured hydrological stations were 0.650, 0.998, and 0.995, respectively, and their simulation of temperature was significantly better than that of precipitation. The spatial-temporal distribution characteristics of CMADS to precipitation and maximum and minimum temperatures were studied by using collaborative Kriging interpolation, which shows that the data set can well capture the topographic characteristics of the underlying surface in the study area, and its meteorological data has high quality. (2) With regard to runoff simulation of the SWAT model, except for poor simulation, the Nash-Sutcliffe efficiency coefficient of the periodic rate and validation period reached 0.845 and 0.836, respectively, and satisfactory simulation results were obtained. This paper showed that the CMADS+SWAT model had good applicability for hydrological simulation in the study area and provided an alternative to construct a hydrological model in areas with scarce ground stations, which plays a certain role in promoting hydrological simulation in cold and dry areas. Figures and Tables | References | Related Articles | Metrics

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Dynamic simulation and carrying capacity analysis of a water resource system in Kubuqi Desert LU Fangyuan,JIA Debin,GAO Ruizhong,SU Wenxu,ZHAO Hang,YANG Li’na 2022, 39 (4):  1102-1111.  doi: 10.13866/j.azr.2022.04.11 Abstract ( 228 )   HTML ( 6 )   PDF (7340KB) ( 193 )   Based on the integration of water resources and socio-economic data in the Kubuqi Desert from 1999 to 2019, this paper used the system dynamic model to simulate the water resource-society-ecological system of the Kubuqi Desert. In addition, a multi-scenario parameter control model was established to comprehensively simulate the changes in the total water demand of water resources in the region under the influence of different parameters. Results show that if no other measures are taken (conventional development mode), then the total water demand in 2035 will reach 11.90 per one hundred million cubic meters, which is greater than the total water supply in the region, showing an overload state. After adjustment for different parameter schemes, the planting area and current irrigation method remain unchanged, and the water demand is 9.76 per one hundred million cubic meters. In addition, the penetration rate of drip irrigation exceeds 50% (S3), showing a loadable state, and the water demand will drop to 7.80 per one hundred million cubic meters, which alleviates the contradiction between the supply and demand of desert water resources. Therefore, during ecological restoration of the Kubuqi Desert, emphasis should be placed on the promotion of drip irrigation to save water, rational use of local water resources, and sustainable ecological development. Figures and Tables | References | Related Articles | Metrics

Plant Ecology

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Effects of artificial vegetation construction on soil physical properties in the northeastern edge of Tengger Desert ZHAO Chenguang,LI Huiying,YU Tengfei,CHEN Weiyu,XIE Zongcai,ZHANG Binwu,ZHANG Jun 2022, 39 (4):  1112-1121.  doi: 10.13866/j.azr.2022.04.12 Abstract ( 273 )   HTML ( 10 )   PDF (8083KB) ( 226 )   Dryland covering 41% of the Earth’s terrestrial land surface involves regions where land degradation and desertification are the most prominent global environmental problems. For restoring the degraded ecosystem, artificial afforestation of native or exotic species has been widely implemented, of which aerial-seeding afforestation was one of the effective measures owing to its penetration capability in inaccessible areas and labor- and cost-saving characteristics. Thus, this measure is crucial for understanding the change in soil physicochemical property with the aerial-seeding community succession in arid regions. To identify the effect of aerial-seeding afforestation on soil physical properties, the study selected one migratory dune (CK) and six aerial-seeding communities of successional sequence from 1984 to 2018 in the Alxa Desert to analyze the change in soil physical properties and their relationship. Compared with CK, the results show that slit and very fine sand increased by 2.6% and 7.6%, respectively, fine sand decreased by 27.1%, and sand and very coarse sand increased by 15.0% and 0.5% after 37 a, respectively. Compared with the other areas and afforesting means, the aerial-seeding afforestation has minimal effect on soil texture improvement, suggesting that the transition of soil texture from sand to loam is difficult in the short term. Otherwise, the saturated moisture content decreased while dry bulk density increased, which may induce an increase in sand and very coarse sand. The mass moisture content was significantly positive with very fine sand content, that is, the former increased with aerial-seeding ages; however, this content demonstrated differentiation patterns among soil layers, as indicated by a 0.7% reduction in deep layers and a 0.6% increase in shallow layers. Soil mass and saturated water contents were significantly negatively correlated with dry bulk density and uncorrelated with saturated infiltration rate, while the latter two were negatively relevant. Except for the mass water content, the other aforementioned contents were correlated with soil particle size content. Overall, the aerial-seeding afforestation also has positive but limited effects on the improvement of soil texture in the short term and enhanced the soil water-holding capacity and soil water availability. The differentiation of mass moisture content among soil top and deep layers induced community succession from shrub to grass. Figures and Tables | References | Related Articles | Metrics

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Soil bacterial characteristics of six plant communities in the desert areas to the North of Yinshan Mountains JIANG Xingchi,LI Junyao,CHEN Feng,LI Shenglin,Wensuyaletu ,WANG Guolin,WANG Shaokun 2022, 39 (4):  1122-1132.  doi: 10.13866/j.azr.2022.04.13 Abstract ( 265 )   HTML ( 11 )   PDF (6960KB) ( 159 )   Shrubs are the main plant forms in arid desert areas and play an important role in maintaining biodiversity and ecological functions in these areas. We utilized high-throughput sequencing technology to analyze the soil bacterial diversity of six typical desert plant communities in the desert areas to the north of the Yinshan Mountains: Reaumuria songarica, Nitraria tangutorum, Ammopiptanthus mongolicus, Brachanthemum mongolicum, Kalidium foliatum, and Haloxylon ammodendron. The results showed the following: (1) The dominant phyla of soil bacteria in the six vegetation communities were Actinobacteria and Proteobacteria. (2) The Shannon diversity index of bacteria is sensitive to environmental changes. The higher the Shannon index, the better the soil nutrient status. (3) Soil moisture content, mechanical composition, pH value, electrical conductivity, and vegetation type are all factors that significantly drive the composition of the bacterial community structure. Figures and Tables | References | Related Articles | Metrics

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Characteristics of Populus euphratica root under various irrigation modes WANG Zikang,JIAO Ayong,LING Hongbo,SHAN Qianjuan,ZHANG Guangpeng,WANG Wenqi 2022, 39 (4):  1133-1142.  doi: 10.13866/j.azr.2022.04.14 Abstract ( 432 )   HTML ( 12 )   PDF (5356KB) ( 133 )   With the improvement of water resource management in Tarim River basin, the ecological environment in the lower reaches of Tarim River has been improved after ecological water diversion. Adopting appropriate irrigation methods combined with ecological restoration technology such as root cutting and sprouting is necessary to consolidate the effect of downstream water transfer, thereby promoting the regeneration and rejuvenation of Populus euphratica forest and the ecological protection and restoration of downstream. However, few studies have combined different irrigation patterns with ecological restoration effects of root cutting and sprouting. In this regard, this study was divided into A1, A2, and A3 in accordance with the terrain characteristics of the study area. Irrigation modes of different treatments were adopted after ditching and root cutting in the study area. Four irrigation modes were set in accordance with the water quantity of irrigation interval, and the specific control group was referred to as F1. The irrigation interval was 11 days; the irrigation water amount was 6 m3 every 10 m, and the irrigation duration was 2 days (F2). The irrigation interval was 23 days; the irrigation water amount was 7 m3 every 10 m, and the irrigation duration was 3 days (F3). In investigating the sprout renewal situation of Populus euphratica under different irrigation treatments, the irrigation interval was 33 days; the irrigation water amount was 8 m3 every 10 m, and the irrigation duration was 4 days (F4). Results showed that the germination ability of distal roots was better than that of proximal roots, and the germination rate of distal roots in A1, A2, and A3 zones was 70.7%, 77.1%, and 64.1%, respectively. The distance between the sprout point and sprout root section of Populus euphratica was concentrated in 1-16 cm. In addition, the distance between the root sprout seedling and parent tree was 5.5-7 m. The distribution depth of the sprout root was concentrated in 30-50 cm. The diameter of the sprout root was concentrated in 0.4-0.7 cm. Based on the germination number of the root and tillering seedlings of Populus euphratica, the optimum soil temperature and water content were determined to be 26.5-28.1 ℃ and 10.6%-13.1%, respectively. The suitable irrigation mode for Populus euphratica root cutting ditch was 23-day interval, and the irrigation water amount was 7 m3 per 10 m root ditch. Moreover, the irrigation duration was 3 days (F3). The results can provide reference for the regeneration and rejuvenation of Populus euphratica in Tarim river basin. Figures and Tables | References | Related Articles | Metrics

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Characteristics of stem sap flow of Haloxylon ammodendron and its response to environmental factors in Qingtu Lake, Minqin QIANG Yuquan,XU Xianying,ZHANG Jinchun,LIU Hujun,GUO Shujiang,DUAN Xiaofeng 2022, 39 (4):  1143-1154.  doi: 10.13866/j.azr.2022.04.15 Abstract ( 249 )   HTML ( 8 )   PDF (9456KB) ( 213 )   The daily and seasonal variation characteristics of stem sap flow of Haloxylon ammodendron with different diameters from May to October in Qingtu Lake were monitored by a TDP plug-in plant stem flow meter. Combined with meteorological data, the water consumption characteristics of Haloxylon ammodendron and its response characteristics to environmental factors were investigated. The following results are presented. (1) The diurnal variation curve of stem sap flow from June to August was mainly a single peak, and occasional multipeaks were observed in July. The peak appeared early, that is, the night sap flow was weak, and the difference between day and night was significant. From September to October, the stem fluid flow (SV) decreased significantly, and the peak time in the daily variation was delayed. On rainy days, Haloxylon ammodendron SV decreased with the increase in rainfall. (2) The stem sap flow of Haloxylon ammodendron was the largest in May, with a peak value of 291.04 cm3·cm-2·h-1. The SV of Haloxylon ammodendron increased first and then decreased from June to October and decreased sharply after reaching 225.73 cm3·cm-2·h-1 in September. (3) A large base diameter of Haloxylon ammodendron induced increased water consumption. The total water consumption of four Haloxylon ammodendron is 1988.41 kg, and the daily average water consumption is 2.76 kg, which is close to the daily average water consumption of native Haloxylon ammodendron in Gurbantunggut Desert from May to September. (4) The response of stem fluid flow of Haloxylon ammodendron to environmental factors showed substantial differences each month. The correlation degree between SV and meteorological factors on a daily scale is as follows: air temperature > net radiation > saturated water air pressure difference > relative humidity > wind speed. (3) Soil moisture has a considerable influence on Haloxylon ammodendron SV. A significant correlation was observed between soil moisture and Haloxylon ammodendron SV on sunny days, and the main area affecting Haloxylon ammodendron SV was below 100 cm of the soil layer. Figures and Tables | References | Related Articles | Metrics

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Spatio-temporal heterogeneity evaluation of grassland TI-NDVI and NDVImax in northern Xinjiang JIAO Ayong,CHEN Fulong,YAN Junjie,LING Hongbo,SHEN Ruihua 2022, 39 (4):  1155-1165.  doi: 10.13866/j.azr.2022.04.16 Abstract ( 266 )   HTML ( 8 )   PDF (5443KB) ( 895 )   Grassland change is an important component of global change, which has attracted considerable attention. The temporal and spatial heterogeneity of grassland dynamics is the main concern in evaluating grassland dynamics. Northern Xinjiang, which is characterized with diverse grassland types, was selected as the research area. In this study, we calculated the time-integrated normalized vegetation index (TI-NDVI) and annual maximum NDVI (NDVImax) on the basis of the MODIS NDVI data. Using spatial analysis technology of GIS, mathematical statistical methods of coefficient of variation (CV), and Mann-Kendall non-parametric statistics, the dynamic changes of grassland in northern Xinjiang were analyzed from 2000 to 2019, and the comparative advantages of TI-NDVI and NDVImax in expressing the temporal and spatial heterogeneity of grassland were explored. Results indicated that (1) the grasslands in northern Xinjiang, characterized by NDVImax and TI-NDVI, showed evident altitudinal differentiation. In general, the TI-NDVI increased with the increase of NDVImax. However, the areas with the same NDVImax or TI-NDVI showed great differences in TI-NDVI or NDVImax. (2) From 2000 to 2019, the grassland TI-NDVI and NDVImax in the northern Xinjiang showed a significant increasing trend (P<0.01), but the spatial differentiation of the changing trends of TI-NDVI was different from that of NDVImax. 17.55% of the grassland in northern Xinjiang showed opposite changing trends in TI-NDVI and NDVImax. For Altai Mountains and the mountains around Ili Valley, which are characterized with grassland of high coverage, the NDVImax and TI-NDVI showed opposite changing trends. (3) The CV of TI-NDVI was higher than NDVImax in temporal and spatial dimensions in grassland with high coverage in northern Xinjiang. Furthermore, TI-NDVI was more sensitive to the temporal and spatial heterogeneity of high-coverage grassland, which can weaken the influence of saturation defect of NDVI in grassland dynamic evaluation to a certain extent. Figures and Tables | References | Related Articles | Metrics

Soil Ecology

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Runoff and sediment yield and relationship between water and sediment of sand covered slope of loess hilly region SU Yuanyi,FENG Zhaohong,ZHANG Yang,LEI Na,ZHANG Tingyu 2022, 39 (4):  1166-1173.  doi: 10.13866/j.azr.2022.04.17 Abstract ( 341 )   HTML ( 15 )   PDF (3636KB) ( 595 )   The characteristics of runoff and sediment and runoff-sediment relationship under four overlying sand conditions and three runoff slope length conditions were studied by indoor water discharge scoring tests. Results showed that the initial runoff time of the sand-covered slope was significantly longer than that of the loess slope, and the initial runoff time increased with the increase of sand-covered thickness. In addition, the unsynchronized time of peak runoff and sediment was found. The runoff rate of different slopes was small at the beginning of the test, and it gradually increased and stabilized with the extension of the runoff time. The sediment rate of the loess slope had a stable trend with the extension of runoff time, whereas the sediment rate of the sand-covered slope had a larger fluctuation range. The accumulated sediment on different slopes increased gradually with the increase of accumulated runoff, and a power function relationship was observed between them. The sand layer had a certain water storage function; thus, the erosion process of the sand-covered slope was evidently different from that of the loess slope. The thickness of the sand cover is an important factor affecting the erosion characteristics of the slope, which provides a scientific basis for further study of the erosion characteristics of the composite slope. Figures and Tables | References | Related Articles | Metrics

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Effects of initial bulk density on soil water characteristic curve ZHANG Pengfei,JIA Xiaoxu,ZHAO Chunlei,SHAO Ming’an 2022, 39 (4):  1174-1180.  doi: 10.13866/j.azr.2022.04.18 Abstract ( 323 )   HTML ( 6 )   PDF (3430KB) ( 233 )   Soil water characteristic curve is one of the important soil water movement parameters affected by soil texture, bulk density, structure, and temperature. Three types of soil were selected in this study and five initial bulk density treatments were set to explore the effect of initial bulk density on soil water characteristic curve and its corresponding water movement parameters. The soil water characteristic curve and its water movement parameters were obtained by van Genuchten model fitting, and the effect of initial bulk density on soil water characteristic curve and corresponding water movement parameters of different types was analyzed. The results showed that in the near-saturation stage (S < 100 kPa), the water characteristic curves of the three soils under the same soil water suction all showed a gradual increase in soil volumetric water content with the initial bulk density. In the high soil water suction section (S > 100 kPa), the water characteristic surface of black soil gradually increased with the initial bulk density, and the water characteristic surface of red soil decreased with the increase in initial bulk density from 1.3 cm3·cm-3 to 1.4 cm3·cm-3. The difference lies in a remarkably steep increase in the water characteristic surface of loess soil from 1.3 cm3·cm-3 to 1.4 cm3·cm-3. The van Genuchten model had a good fitting effect on the soil water characteristic curve (R2 > 0.99), which was suitable for fitting the water characteristic curve of the three types of soil under different bulk densities. The water movement parameters α and θs of the three soils were significantly negatively correlated with the initial bulk density (P < 0.01), and the water movement parameters α were significantly different from the initial bulk density of the black soil (P < 0.05). The water movement parameter θr of red soil was also significantly negatively correlated with the initial bulk density (P < 0.01), demonstrating a 10% reduction. A significant positive correlation was also found between the initial bulk density of black soil and soil water movement parameter n (P < 0.01). The initial bulk density of red and loess soil was negatively correlated with soil water movement parameter n, but the relationship was insignificant (P > 0.01). The variation range of water movement parameter n of the three soils under different initial bulk density treatments is small, and the variation range remains at approximately 0.1. The results can provide a reference for the acquisition of soil water movement parameters and hydrological process simulation under different types of soil and initial bulk densities. Figures and Tables | References | Related Articles | Metrics

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Desert shrub soil enzyme activity of UV-B radiation and litter decomposition response WEI Changlin,LI Yi,SHAN Lishan,XIE Tingting 2022, 39 (4):  1181-1190.  doi: 10.13866/j.azr.2022.04.19 Abstract ( 226 )   HTML ( 8 )   PDF (2763KB) ( 206 )   Exploring the response of soil enzyme activity to UV-B radiation and decomposition of different litters is crucial for revealing litter turnover and soil nutrient dynamics. The effects of UV-B radiation on soil enzyme activities of litters of Reaumuria soongarica and Salsola passerina and their mixture were studied by using simulated UV-B radiation filtration (mylar film method) and decomposition bag method. The following results are presented. (1) Radiation filtration increased the soil urease and alkaline phosphatase activities of different litters and promoted the soil enzyme activities of S. passerina shrub significantly, which increased by 45.45%, 58.28% and 39.04%, 117.65% in different soil layers (0-5 cm and 5-15 cm), respectively. The radiation filter minimizes the different litter reductions. However, soil polyphenol oxidase and peroxidase activities of lignin, which are the same soil enzyme activity of S. passerina thickets of inhibition effect, are observed in different soil reductions by 36.69%, 39.52% and 59.78%, 43.63%, respectively. Radiation filtration did not affect on soil cellulase activity. (2) Under radiation filtration and natural light conditions, the activity of polyphenol oxidase in the soil of mixed litters was lower than that of single litters, indicating that the degree of organic matter humification in the soil of mixed litters was larger than that of organic matter accumulation, and the degree of soil humification was high. (3) The effects of different litters on the enzyme activities of surface soil (0-5 cm) were observed. Soil urease and phosphatase activities decreased and polyphenol oxidase activities increased with the deepening of the soil layer. Figures and Tables | References | Related Articles | Metrics

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Effects of rainfall frequency change on soil nitrogen components in Gahai wet meadow QIN Haode,LI Guang,WU Jiangqi,WEI Xingxing,WANG Haiyan,XU Guorong 2022, 39 (4):  1191-1199.  doi: 10.13866/j.azr.2022.04.20 Abstract ( 226 )   HTML ( 6 )   PDF (9345KB) ( 54 )   In the context of global climate change, precipitation patterns have changed significantly, both in terms of rainfall frequency and amount of precipitation. Changes in precipitation patterns will significantly affect the ecosystem functions of wetlands, especially the process of soil nitrogen cycle transformation. To explore the effects of different rainfall frequencies on the soil ammonium nitrogen ( $\mathrm{NH}_{4}^{+}-\mathrm{N}$), nitrate nitrogen ($\mathrm{NO}_{3}^{-}-\mathrm{N}$), and total nitrogen (TN) of the Gahai wet meadow in Gannan (located in Gansu Province, China), we set five different rainfall frequencies by simulating extreme rainfall (25 mm irrigation) in the 2019 plant growth season, May-October: CK, natural rainfall only; DF1, watered once a week (19 times×25 mm); DF2, watered once every 2 weeks (9 times × 25 mm); DF3, watered once every 3 weeks (6 times×25 mm); and DF4, watered once every 4 weeks (4 times × 25 mm). All treatments were exposed to natural rainfall. The results showed that different rainfall frequencies have significant effects on the soil nitrogen components of the wet meadow (P < 0.05). The increase of rainfall frequency increased the soil $\mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ content in the growing season, from May to October; the peak of $\mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ increased significantly. Compared with CK, the increase in rainfall frequency increased the soil $\mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ content and reduced the TN content. Among different rainfall frequencies, with the gradient of rainfall frequency increasing, the 0-40 cm layer $ \mathrm{NH}_{4}^{+}-\mathrm{N}$ and $\mathrm{NO}_{3}^{-}-\mathrm{N}$ showed a trend of first increasing and then decreasing and $\mathrm{TN}$ showed a trend of first decreasing and then increasing. Under different rainfall frequency treatments, the proportion of TN of $\mathrm{NH}_{4}^{+}-\mathrm{N}$ in each soil layer was higher than that of $\mathrm{NO}_{3}^{-}-\mathrm{N}$, and soil$\mathrm{NH}_{4}^{+}-\mathrm{N}$, $\mathrm{NO}_{3}^{-}-\mathrm{N}$, and $\mathrm{TN}$ content decreased with the increase in soil depth. Figures and Tables | References | Related Articles | Metrics

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Soil wind erosion characteristics and main influencing factors in Mongolia in recent 20 years GUO Yin,LEI Jiaqiang,FAN Jinglong,WANG Haifeng,LYU Zhentao 2022, 39 (4):  1200-1211.  doi: 10.13866/j.azr.2022.04.21 Abstract ( 848 )   HTML ( 44 )   PDF (6309KB) ( 415 )   The accurate evaluation of wind erosion dynamics is important to reduce the damage caused by wind erosion in Mongolia. In this study, we used GLDAS, OLM, MOD13Q1, NASA-SRTM, and other meteorological and remote sensing data and the revised wind erosion equation model on the Google Earth Engine cloud computing platform to explore the spatio-temporal dynamics of soil wind erosion in Mongolia from 2001 to 2020. Results showed that wind erosion modulus had a significantly increased trend during the study period. In general, soil wind erosion tended to increase significantly over the last 20 years with the modulus of wind erosion increasing at a rate of 0.06 t·hm-2·a-1. Spatially, wind erosion was strong in the southern regions and weak in the northern regions. Meanwhile, wind erosion in spring accounted for 45% of the whole year. Changes in soil wind erosion in Mongolia were by and large identified with climatic factors and changes in vegetation cover, but they were also firmly identified with expanded anthropogenic exercises, for example, overgrazing and development of arable land. This study will provide a comprehensive understanding of the development trend of wind erosion desertification in Mongolia and a reference value to study dust storm in East Asia. Figures and Tables | References | Related Articles | Metrics

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Soil wind erosion rule of two types of rodent mounds in a degraded grassland area of the Yellow River source zone ZHAI Hui,LI Guorong,LI Jinfang,ZHU Haili,ZHAO Jianyun,LIU Yabin,CHEN Wenting,HU Xiasong 2022, 39 (4):  1212-1221.  doi: 10.13866/j.azr.2022.04.22 Abstract ( 261 )   HTML ( 8 )   PDF (4452KB) ( 377 )   To clarify the characteristics and rules of soil wind erosion of rodent mounds in alpine grassland, studies were conducted on the Ochotona curzoniae and Eospalax baileyi mounds of He’nan County in Qinghai Province. The characteristics and rules of soil wind erosion and nutrient loss of the two types of rodent mounds were analyzed through a field-simulated wind erosion test, and the differences in soil wind erosion between the two types of rodent mounds were also compared and analyzed. The results of this analysis provide a theoretical basis for elucidating the characteristics of soil loss in rodent-infested degraded areas and reveal the degradation mechanism as well as the possible ways to protect the grassland ecological environment in the Yellow River Source Zone. The key results are as follows: (1) Under the action of 9 m·s-1 constant wind speed erosion, the loss of soil particles was concentrated in the first 15 min, and the soil loss of the Ochotona curzoniae mound was significantly higher than that of the Eospalax baileyi mound, which was approximately 1.5 times that of the Ochotona curzoniae mound. (2) With respect to the form of soil erosion, the amount of soil lost from the mounds was in the following order: surface creep > saltation > suspension, and the amount of soil lost in each of these forms in the Ochotona curzoniae mound was 1.45, 1.58, and 1.50 times the corresponding values in the Eospalax baileyi mound. (3) The nutrient content of the rodent mound soil was significantly lower than that of the original meadow soil; the order of nutrient content was original meadow soil > Ochotona curzoniae mound soil > Eospalax baileyi mound soil. (4) The soil nutrient loss law was similar to that of the rodent mounds, and the nutrient loss mainly depended on the degree of soil loss. The soil nutrient loss of the Ochotona curzoniae mound was 1.42-3.53 times higher than that of the Eospalax baileyi mound. Figures and Tables | References | Related Articles | Metrics

Ecology and Environment

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Relationship between trade-off intensity of ecosystem services and matching degree of supply and demand: A case study in Shanxi Province FENG Qiang,ZHAO Wenwu,DUAN Baoling 2022, 39 (4):  1222-1233.  doi: 10.13866/j.azr.2022.04.23 Abstract ( 316 )   HTML ( 23 )   PDF (8749KB) ( 70 )   Revealing the relationship characteristics between the intensity of ecosystem service (ES) tradeoffs and the matching degree of ES supply and demand can provide possible ways to alleviate the ES conflict and supply-demand contradiction simultaneously. The districts and counties of Shanxi Province are selected in this study. Considering the tradeoff between supply and support service, tradeoff type 1 is when the supply service is relatively enhanced but support service is decreased, whereas tradeoff type 2 is the opposite condition. The influencing factors of ES tradeoffs and supply-demand and their related characteristics are revealed by redundancy analysis and piecewise linear regression. The following results are presented. (1) The high-value regions of tradeoff type 1 and the low-value regions of supply-demand ratio are mainly located in the basins, and the high-value regions of tradeoff type 2 and supply-demand ratio are mainly located in the mountainous area. (2) Tradeoff type 1 is mainly affected by cropland, forestland, grassland, air temperature, and other factors. Meanwhile, tradeoff type 2 is primarily influenced by cropland, forestland, NDVI, and soil organic matter, but the direction of effects is opposite to that of tradeoff type 1. (3) The forestland, grassland, and slope gradient have significant positive effects on the supply-demand ratio of type 1, while the cropland and construction land have significant negative effects. The factors have minimal effects on the supply-demand ratio of type 2. (4) The effects of factor direction on tradeoff type 1 and the supply-demand ratio are opposite, which mainly contributes to the negative correlation between them. The response of the ES supply-demand ratio to tradeoffs is relatively strong when the contradiction between ES supply and demand is small. However, this response weakens with the deepening of the supply-demand contradiction. The relationship characteristics indicate the ecological dilemma: the human demand increases-development intensity increases-tradeoff type 1 enhances-the contradiction between supply and demand intensifies. A weak positive correlation is observed between tradeoff type 2 and supply-demand ratio, indicating the situation of ecological surplus. Overall, a correlation is observed between ES tradeoff and supply-demand. The results generally present the correlation characteristics and its formation mechanism, which can provide a scientific basis for land ecological restoration and management. Figures and Tables | References | Related Articles | Metrics

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Temporal and spatial evolution characteristics of the coupling between county high-quality development and ecosystem services in Shanxi Province LIU Hailong,TANG Fei,DING Ya’nan,ZHANG Yu,GUO Xiaojia,TAN Jingbai,CHENG Yue 2022, 39 (4):  1234-1245.  doi: 10.13866/j.azr.2022.04.24 Abstract ( 275 )   HTML ( 13 )   PDF (7976KB) ( 339 )   Based on the data of 107 counties and regions in Shanxi Province in 2000, 2005, 2010, and 2018, this paper constructs the evaluation index system of high-quality development in Shanxi Province, uses the InVEST model to calculate the ecosystem services of counties and regions in Shanxi Province, and analyzes the spatiotemporal coupling characteristics of the high-quality development system and ecosystem services of counties in Shanxi Province by using the coupling coordination model and elasticity coefficient method. The following results are presented. (1) The grade effect of cities has a significant impact on the level of high-quality development. The spatial differentiation law of high-quality development is strong, which roughly forms the north-south-middle three-level cores, and the polarization effect in the central region is prominent. (2) Ecosystem services in the study area have locking effects in time scale and spatial pattern. The temporal and spatial evolution characteristics are consistent with the topographic distribution of the study area, showing a stable “mirror L-shaped” spatial distribution pattern. (3) Ecosystem services in the study area generally lag behind high-quality development. From the perspective of the time change, the coupling level shows an upward trend. From the perspective of spatial pattern characteristics, ecosystem services and the high-quality development show the coordination main axis of “northeast-southwest.” (4) The coupling type of high-quality development and ecosystem services in the study area mainly changes in different directions, generally showing a retrogressive development trend. A “polarization” pattern, in which recession and lag types compete, is also observed, forming a convergent “S” type attenuation area. As an ideal model of coupling type, growth type is remarkably few in the study area. Figures and Tables | References | Related Articles | Metrics

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Land use in the Gan-Lin-Gao region of middle reaches of Heihe River Basin based on a PLUS-SD coupling model JIANG Xiaofang,DUAN Hanchen,LIAO Jie,SONG Xiang,XUE Xian 2022, 39 (4):  1246-1258.  doi: 10.13866/j.azr.2022.04.25 Abstract ( 595 )   HTML ( 29 )   PDF (5305KB) ( 300 )   A quantity-space coupling model can effectively simulate the number of land-use patches and their rapid spatial changes. Thus, this model has become the main method of land use research in recent years. This research first compared the simulated land-use structure of the patch-generating land-use simulation model (PLUS), future land-use simulation model (FLUS), and conversion of land use and its effects at small regional extent (CLUE-S) in the Gan-Lin-Gao region (Ganzhou District, Linze County and Gaotai County of Zhangye City) of the middle reaches of the Heihe River Basin in 2015. In addition, this research selected the suitable spatial simulation model for the study area; then, it was coupled with the system dynamics model (SD) to form a quantitative-spatial coupling model. Finally, the coupling model was used to predict the land-use structure of the economic development (ED), ecological protection (EP), and harmonious development (HD) scenarios, and comparative evaluation was conducted. The research results showed that (1) at the same pixel scale, the figure of merit of the PLUS model was higher than that of the FLUS and CLUE-S models, and the Kno and Klocation of the three models were PLUS, CLUE-S, and FLUS from high to low, indicating that the PLUS model had the best spatial fitting effect in this study area. (2) Moreover, the different scenarios predicted by the PLUS-SD coupling model showed that the construction land and arable land in the ED scenario expanded rapidly, but the forest coverage rate was low. Furthermore, the forest coverage rate in the EP scenario increased significantly, but the level of ED was low, and the urbanization in the HD scenario improved when the ecological environment was gradually developing. This research determined the significant advantages of the PLUS-SD coupling model and highlighted the effective land-use spatial simulation capabilities of the PLUS model and powerful data processing capabilities of the SD model. The results can provide reference for the formulation of land planning policies. Figures and Tables | References | Related Articles | Metrics

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Landscape pattern vulnerability and its influencing factors on a semi-arid lake basin: A case study of Liangcheng County ZHANG Yunxia,ZHANG Jinxi,GONG Jie 2022, 39 (4):  1259-1269.  doi: 10.13866/j.azr.2022.04.26 Abstract ( 304 )   HTML ( 12 )   PDF (4791KB) ( 150 )   Research on landscape spatiotemporal variation and its pattern vulnerability can provide a scientific basis for regional landscape optimization and ecological protection. Based on six periods of landscape type data from 1980 to 2020, this paper analyzes the lake basin landscape and its variation process in Liangcheng County. Moreover, a comprehensive evaluation index of landscape vulnerability is constructed by using landscape sensitivity and adaptability indexes to analyze the spatiotemporal differentiation characteristics and influencing factors of landscape pattern vulnerability in the entire county. The main findings are listed below. (1) The landscape types of Liangcheng County have significantly changed over the past 40 years. Except for the unused land, the dynamic degree of cultivated land, forestland, and grassland from 1980 to 1995, that of each landscape type from 1995 to 2010, and that of waters and construction land from 2010 to 2020 are the largest, which indirectly reflects the life and production modes of the study area in different periods. (2) The landscape pattern vulnerability was mainly medium and high-grade with an area of more than 70% in Liangcheng Country from 1980 to 2020. The areas of high landscape pattern vulnerability were mainly concentrated in the central and southeast of Liangcheng, and the low-value areas were located in the Daihai and its northern parts. The landscape vulnerability integrated index generally decreased first; this index then increased and finally decreased. Moreover, the spatial aggregation increased, indicating that the ecological environment began to improve. (3) The vulnerability of ecological environments is significantly different in various landscape types and topographies in the study area. Forestland and grassland have more higher vulnerability and water has the lowest vulnerability among all landscape types. The landscape pattern vulnerability is the lowest in the area with an altitude of <1300 m and a slope of <5° and the highest with an altitude of 1700-1900 m and a slope of 25°-40° on different altitudes and slopes. (4) The gray correlation analysis revealed that the population, water area, and farmland area are the leading factors that affected the landscape pattern vulnerability, indicating that human activities significantly impacted the ecological environment more than climatic factors in the study area. Optimizing landscape structure, reducing excessive disturbance, and protecting water resources and their environment are the primary ways to reduce the vulnerability of landscape patterns and ecological protection in Liangcheng Country. Figures and Tables | References | Related Articles | Metrics

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Distribution characteristics of heavy metals in river sediments and their relationship with land use types in Xi’an City HU Changtong,YANG Tao,WAN Xuhao,SUN Laikang,ZHENG Yiwen,YAN Xuerong 2022, 39 (4):  1270-1281.  doi: 10.13866/j.azr.2022.04.27 Abstract ( 205 )   HTML ( 4 )   PDF (4716KB) ( 123 )   Typical urban rivers in Xi’an (Ba River, Chan River, Feng River, and Hei River) were selected as the research object to understand the impact of different land-use types on the distribution of heavy metals in river sediments. The spatial distribution, environmental risks, and sources of heavy metals (Cr, Mn, Ni, Cu, Zn, Cd, and As) in river sediments were analyzed and evaluated using potential ecological risk (RI), pollution load index (PLI), correlation analysis, and principal component analysis. Results showed that the content of heavy metals in the sediments of the four rivers was presented in the following order: Chan River > Ba River > Hei River > Feng River. The RI results showed that Cd remarkably contributed to the pollution, and the four rivers were all at moderate potential ecological risk. The PLI results showed that the H1 sample site in Hei River was moderately polluted, which was the highest. The RI and PLI results showed that the sample sites in the Chan River were the most polluted, and they were concentrated in the middle and lower reaches where the proportion of artificial ground and intensity of human activities were high. In addition, the results of correlation analysis and principal component analysis showed that most heavy metals came from human activities such as emissions from industrial and agricultural production and traffic pollution. Therefore, attention should be paid to the prevention and control of Cd pollution, particularly in the middle reaches of Feng River and Hei River, to prevent further pollution. Figures and Tables | References | Related Articles | Metrics

Agricultural Ecology

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Grain size characteristics and spatial heterogeneity of farmland soils in the Syr Darya River Basin of Kazakhstan HE Jing,Jilili ABUDUWAILI,MA Long,Galymzhan SAPAROV,Gulnura ISSANOVA 2022, 39 (4):  1282-1292.  doi: 10.13866/j.azr.2022.04.28 Abstract ( 246 )   HTML ( 9 )   PDF (6247KB) ( 290 )   This article takes the farmland soils in the Syr Darya River Basin of Kazakhstan as the research object, combining classical statistics and geostatistics methods, and investigates the characteristics of soil grain size and spatial heterogeneity in the 0-20 cm soil layer. Results showed that the distribution characteristics of soil particles with different particle sizes in each study area were similar, and the average content of particles with particle sizes of 0.25-0.05 mm and 0.05-0.01 mm is the highest. Except for subzone 3, the content of soil particles with a particle size of 1.0-0.25 mm has strong variability, while that of other sizes has a moderate degree of variability; Except for soil particles with a particle size of 1.0-0.05 mm in subzone 1, the nugget coefficient of soil particle content of other particle sizes is all < 40%, and that of each particle size in subzone 2 is all < 50%, in subzone 3, except for soil particles with a particle size of < 0.001 mm, the nugget coefficient of soil particle content of other particle sizes is < 40%. These findings revealed that the composition of soil particles in each study area has been affected by varying degrees of random factors; The Kriging interpolation method was used to interpolate the content of soil particles of different sizes in the study area. The interpolation results showed that the content of soil particles of different sizes in the study area demonstrated different distribution characteristics in the spatial distribution. The research results can provide a scientific basis for the rational use of farmland soil and the improvement of degraded soil. Figures and Tables | References | Related Articles | Metrics

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Soil pH inversion based on electromagnetic induction data in cotton field of southern Xinjiang WANG Jiawen,PENG Jie,JI Wenjun,BAI Jianduo,FENG Chunhui,LI Hongyi 2022, 39 (4):  1293-1302.  doi: 10.13866/j.azr.2022.04.29 Abstract ( 224 )   HTML ( 6 )   PDF (5148KB) ( 138 )   Soil salinity aggregation will change soil acidity or alkalinity. As an important land resource reserve area in China, soil salinization and secondary salinization problems are frequent in Xinjiang, Therefore, accurately obtaining soil salinity information and effectively improving soil salinity is beneficial to regulating the contradiction between agricultural irrigation and freshwater resources. Such regulation is of considerable important to the sustainable development of agricultural production and ecological environment. In this study, the soil pH value of cotton fields in Alar Reclamation Area, southern Xinjiang, was taken as the research object, and the EM38-MK2 geodetic conductivity meter was used on the basis of electromagnetic induction technology to obtain soil apparent conductivity data of nine cotton fields in the Reclamation Area. In each cotton field, soil apparent conductivity thresholds were collected in accordance with cotton fields of 0-0.375, 0.375-0.75, 0.75-1.00 m depth, 54 profile samples were collected from three soil layers, and 486 soil profile samples were collected from nine cotton fields. The linear regression model between soil pH and soil apparent conductivity was constructed using two ideas of the global and different regions and combined with geostatistical software to quantify in cotton fields in the Reclamation Area. The two-tailed test results revealed that the correlation coefficients between apparent conductivity and soil pH were 0.60-0.95 for the idea of different regions under the condition of P < 0.01; while those for the global regions were 0.28-0.46. Both findings were highly significant negative correlations, indicating that EM38-MK2 could be used for the determination of soil pH. Linear regression models between apparent conductivity data and soil pH were constructed using the global region and different regions. The zonal models 0.74 ≤ R2 ≤ 0.93 and 2.00 ≤ RPD ≤ 3.50, which have smaller RMSE, showed high accuracy, indicating that the accuracy of the different region model is better than that of the global region models. Meanwhile, the accuracy of the soil pH inversion model is also higher in areas with higher salinity. The Kriging interpolation results showed that the soil pH in the deep layer of cotton fields in the Reclamation Area was higher than that in the surface layer due to the influence of winter irrigation, cotton root system and cotton dead leaves. This study aims to provide ideas for the rapid determination of soil pH. Therefore, soil acid-base risk prediction can be accurate, and effective risk countermeasures can be formulated rationally. Figures and Tables | References | Related Articles | Metrics

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Spatial and temporal variation of net carbon sink function of farmland in Aksu oasis in the past 17 years LI Yuanhang,HAO Xingming,ZHANG Jingjing,FAN Xue,ZHAO Zhuoyi 2022, 39 (4):  1303-1311.  doi: 10.13866/j.azr.2022.04.30 Abstract ( 275 )   HTML ( 17 )   PDF (5187KB) ( 264 )   Studying the spatial and temporal variations of the net carbon sink function of oasis farmland is important for its management and sustainable development. The net carbon sink of Aksu oasis farmland was estimated on the basis of remote sensing, meteorological data and agricultural inputs, and other related statistics from 2001 to 2017. The following results are presented. (1) In the past 17 years, the net ecosystem productivity (NEP) of oasis farmland in Aksu showed an increasing trend yearly, with an average annual growth rate of 7.43%. Among which, the area of oasis farmland with a significant increasing trend of NEP was 1.44 × 104 km2, accounting for 97.7% of its total area, which is mainly distributed in various counties and cities. The area with a significant decreasing trend was 339 km2, accounting for 2.3% of the total area, mainly in the oasis areas of Wensu, Awati, Aksu, and Kuche counties. (2) Carbon emissions from agricultural production inputs increased from 39.94 × 104 t in 2001 to 106.73 × 104 t in 2017, with an average annual growth rate of 25.14% and high and low distribution patterns in the Southeast and Northwest, respectively, considering spatial distribution. The largest proportions of agricultural production input pathways are fertilizer and agricultural machinery at 28% and 26%, respectively. (3) From 2001 to 2017, the net carbon sink of Aksu oasis farmland showed a fluctuating upward trend, spatially demonstrating a gradual increase from Northwest to Southeast, with high values mainly distributed in the southwestern part of Wensu county, the western part of Aksu City, the entire territory of Alar City, and the eastern part of Xinhe County. Overall, Aksu oasis farmland has a high net carbon sink capacity. However, regional differences are found in the net carbon sinks of oasis farmland among counties and cities. Thus, the net carbon sink capacity of oasis farmland should be improved by optimizing the agricultural industry structure and enhancing farming measures. Figures and Tables | References | Related Articles | Metrics

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Effects of water treatment on stoichiometric ratio and homeostasis of silage corn soil in Hexi XIE Mingjun,LI Guang,MA Weiwei,LIU Shuainan,CHANG Haigang,DU Jia’nan,DING Ning 2022, 39 (4):  1312-1321.  doi: 10.13866/j.azr.2022.04.31 Abstract ( 211 )   HTML ( 8 )   PDF (2095KB) ( 447 )   A study was conducted using irrigation treatments and changes in soil and plant carbon (OC), nitrogen (TN), and phosphorus (TP) stoichiometry and homeostasis were investigated to explore the soil nutrient limitation in farmland ecosystems in the Hexi irrigation area. The following results are presented. (1) The OC, TN, and TP concentrations of silage maize soils under different irrigation treatments reached the highest values in 0-10 cm. (2) Among four irrigation treatments, the nutrient content of plant organs was the highest under W0 irrigation. However, at 0-30 cm soil layers, the values of soil OC, TN, and TP concentrations were the highest under W1 irrigation treatment (i.e., traditional irrigation), soil TN and TP contents were more than those under other irrigation treatments (6.66%-26.17% and 4.67%-19.21%, respectively), and the decrease in soil and plant nutrients was more significant than that in irrigation water amount. (3) The ranges of C:N, C:P, and N:P ratios in soil and plants were at 3.60-61.2, 4.39-53.9, and 1.01-1.24, respectively. Soil C:N ratios were relatively stable among three soil layers and different irrigation treatments. The N:P ratios of leaves (11.9) and roots (7.58) were less than the threshold of plant N limitation (14), indicating that plant growth was limited by N. (4) Among four irrigation treatments, corn OC and TP and their ratios remained stable. However, the leaf N:P homeostasis was more sensitive to W2 treatment (20% water-saving irrigation) than to W0 treatment. Thus, 10% water-saving treatment in the Hexi irrigation area might be beneficial to the retention of soil nutrients in silage corn and maintains the stable adaptability of crop growth, realizing the purpose of water-saving and alleviating the current water scarcity situation. Figures and Tables | References | Related Articles | Metrics

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Distribution characteristics of soil particle size in farming-pastoral ecotone: A case study of Wuchuan County in Inner Mongolia FU Dongsheng,REN Xiaomeng,WANG Yanling,ZHANG Cuiying,MENG Zhongju 2022, 39 (4):  1322-1332.  doi: 10.13866/j.azr.2022.04.32 Abstract ( 298 )   HTML ( 12 )   PDF (3658KB) ( 218 )   This paper takes different farmland and natural grassland in Wuchuan County, Hohhot, as the research object and adopts the method of combining in-situ field monitoring and indoor test to study the following four types of farmland soils: typical wheat stubble land, sunflower stubble land, plowed land, and abandoned farmland. The wind erosion resistance capability of land under different utilization modes is discussed by analyzing the average particle size, standard deviation, skewness, and kurtosis. Research results show the following: (1) The soil in the study area is dominated by fine sand, very fine sand, and silt, accounting for 80% to 85%. (2) The soil particle size composition from fine to coarse is as follows: tillage 1 a > natural grassland > tillage slope > wheat stubble > tillage 15 a > abandoned 5 a > sunflower stubble. Meanwhile, the average particle size of sand is 2.12-2.61. (3) The soil sorting capability of each layer is poor, the skewness is positive and nearly symmetrical, and the kurtosis belongs to the broad flat. The particle size range of soil that is prone to wind erosion is between 200 and 400 μm. (4) Compared with natural grassland, farmland reclamation and utilization lead to the expansion of soil particle size distribution, and the overall particle size is coarse. Figures and Tables | References | Related Articles | Metrics