Table of Content

15 March 2022, Volume 39 Issue 2 Previous Issue    Next Issue

Weather and Climate

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The assessment on “warming-wetting” trend in Xinjiang at multi-scale during 1961-2019 YAO Junqiang,LI Moyan,Dilinuer Tuoliewubieke,CHEN Jing,MAO Weiyi 2022, 39 (2):  333-346.  doi: 10.13866/j.azr.2022.02.01 Abstract ( 2073 )   HTML ( 144 )   PDF (5656KB) ( 844 )   Based on the observed climatic and hydrological data in Xinjiang, China, and combined with the new results in recent years, the characteristics of “warming-wetting” trend in Xinjiang region from historical period to interdecadal scale were comprehensively analyzed and compared, and the evolution characteristics of “warming-wetting” trend in Xinjiang region were comprehensively evaluated at different spatial and temporal scales. The results show that: (1) according to the lake sediment and tree-ring reconstruction and wet climate change sequence, found the past climate in Xinjiang in one thousand and one hundred, scale is mainly a “dry-cold and warm-wet”, there is significant decadal variation characteristics, nearly a century of experience since 1980s the obvious “wet” process, but range is not beyond history the variability of each period. (2) the warming and wetting trend was occurred in the northern area, high latitudes in the northern hemisphere since 1961, the pattern is roughly the “T” type, Xinjiang is connected in high latitudes and link of the “wet” Qinghai-Tibet plateau region, the “warming-wetting” trend is not unique to Xinjiang, However, the climate humidification process in Xinjiang is unique in the middle latitude region. (3) The interannual temperature and humidity was dominated by “warm-wet-warm-dry” configuration in Xinjiang during 1961-2019. After the 1990s, the annual and seasonal temperature and humidity configurations were mostly warm and wet in Xinjiang. The rate of warming and humidification increases in each climate state period, but slows down in the current period, indicating that the warming and humidification trend has periodic characteristics and presents a nonlinear increase trend. Although there has been an obvious trend of “warming-wetting” trend in Xinjiang in the past 30 years, and the degree of warming has gradually increased, the absolute amount of precipitation increase is not large, and the current characteristics of humidification can not change the arid climate and arid area in Xinjiang. The research results provide an important scientific basis for the assessment of climate and “warming-wetting” trend in Xinjiang at different spatio-temporal scales. Figures and Tables | References | Related Articles | Metrics

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Chemical characteristics and their influencing factors of precipitation at the end of the Koxkar Glacier, Tianshan Mountains WANG Jian,HAN Haidong,XU Junli,YAN Wei 2022, 39 (2):  347-358.  doi: 10.13866/j.azr.2022.02.02 Abstract ( 603 )   HTML ( 40 )   PDF (4242KB) ( 328 )   Atmospheric precipitation was sampled in the summer at the end of the Koxkar Glacier, Tianshan Mountains, China. Based on analyses of the ion concentration, conductivity, and pH characteristics, we explored the solute sources and control factors for regional precipitation using factor analysis, enrichment factors, and backward trajectory tracking. Atmospheric precipitation was slightly alkaline, with a pH between 7.15 and 8.52, and their anions and cations were dominated by HCO3-and Ca2+, respectively, which belong to the typical HCO3-Ca type. The conductivity and total ion concentration of precipitation during the daytime were 11.56% and 9.40% higher, respectively, than those of the nighttime; this may be caused by the wet deposition of aerosol materials from the piedmont and plain areas with the near-surface wind under the action of valley wind or glacial wind during the daytime. Precipitation ions mainly originated from the supply of crustal source materials, accounting for 85.54% of the total ion content; among them, HCO3-, Ca2+, and Mg2+ were mainly supplied by carbonate rock weathering (CaxMg1-xCO3) in the Jurassic sedimentary layer and Quaternary loess sedimentary layer, whereas Cl-, SO42-, Na+, and K+ were mainly supplied by the evaporation of salt lakes caused by drought or the weathering of saline soil formed by alluvial/proluvial processes in Central Asia and the Tarim Basin. Only 41.52% of Na+ and 96.22% of Cl- in precipitation originated from ocean sources and salt lakes, and their concentration ratio was 2.13:1, indicating that ocean source air masses were affected by the precipitation reevaporation and wind erosion of surface materials during long-distance transportation; this resulted in ocean source recharge only accounting for 4.87% of the total precipitation ions. The solute supplied by human activities was approximately twice that of ocean sources, mainly NH4+,NO3-, and SO42-, which could provide the necessary nitrogen and sulfur for soil formation and alpine vegetation growth in the study area. Air mass backward trajectory tracking showed that westerly circulation had a significant impact on the precipitation and chemical composition in southern Xinjiang. The average proportion due to a water vapor source path and precipitation was 64.35% and 53.04% respectively. Although the total ion concentration in precipitation formed by westerly circulation accounted for only 69.91% of the local circulation, the average NO3-concentration was 1.42 times that of the local circulation precipitation, indicating that the air and water quality in the Tarim Basin may be affected by human activities in Central Asia. Figures and Tables | References | Related Articles | Metrics

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Analysis of tempo-spatial characteristics and trends of precipitation in the Aral Sea Basin WANG Haoxuan,HUANG Feng,GUO Lidan,ZHONG Ruisen 2022, 39 (2):  359-367.  doi: 10.13866/j.azr.2022.02.03 Abstract ( 607 )   HTML ( 28 )   PDF (4761KB) ( 997 )   In this study, we extracted regional precipitation data of the general Aral Sea Basin in Central Asia from the Climate Research Unit (CRU) from 1945 to 2019. Simultaneously, we also calculated the spatial and temporal characteristics of annual precipitation change using the climate trend rate method. We first depicted the overall spatial distribution of the climate trend rate, then we used concentration period, concentration degree, and sharing entropy methods to describe the precipitation distribution, and separately depicted the spatial and temporal precipitation distribution. Additionally, we calculated the spatial and temporal change in precipitation complexity using the sample entropy and permutation entropy methods, and demonstrated these results graphically. Trends in the new series of concentration period, concentration degree, sharing entropy, sample entropy, and permutation entropy were tested using the Mann-Kendall method. Generally, the annual precipitation in the Aral Sea Basin in Central Asia remained largely unchanged, whereas precipitation showed a slight upward trend. From the perspective of spatial distribution, precipitation increased significantly in the northwest and central east of the Aral Sea Basin in Central Asia. Furthermore, precipitation was mainly concentrated in early and mid-February for each year. The general precipitation distribution showed a slightly homogenized trend, whereas the annual precipitation distribution was more uniform in the west, north, and east of the Aral Sea Basin, and more concentrated in the middle and south of the Aral Sea Basin. Moreover, the sample entropy and permutation entropy values were higher in the north, west, and east, but lower in the south and middle of the Aral Sea Basin. Altogether, the results demonstrate that the complexity of the precipitation series was relatively high in the north, west, and east, but relatively low in the south and middle of the Aral Sea Basin in Central Asia. The complexity of the precipitation series in the whole basin generally showed an upward trend. More specifically, the complexity of the precipitation series in the north and south of the basin showed a significant downward trend, whereas in the west, middle, and east of the basin, it showed a significant upward trend. Our results illustrate the variation in precipitation characteristics in this basin over the past 75 years, and provide a scientific basis for the development and utilization of water resources in the Aral Sea Basin in Central Asia. Figures and Tables | References | Related Articles | Metrics

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Assessment of TIGGE precipitation forecast models in arid and semi-arid regions of China HE Chaolu,LYU Haishen,ZHU Yonghua,LI Wentao,XIE Bingqi,XU Kaili,LIU Mingwen 2022, 39 (2):  368-378.  doi: 10.13866/j.azr.2022.02.04 Abstract ( 418 )   HTML ( 8 )   PDF (5178KB) ( 273 )   Short- and medium-term precipitation forecast products are important to improve the prediction period and accuracy of flood forecasts. With global climate change, the prediction of precipitation patterns becomes increasingly complex and important. To date, there have been no available reports on the applicability of TIGGE precipitation products (a significant aspect of the most authoritative data set for short-and medium-term ensemble forecasts) in the arid and semi-arid regions of China. On the basis of precipitation data measured from 2015-2017 in arid and semi-arid regions of China, the mean absolute deviation, root mean square error, TS score, and other indicators were used to analyze the precipitation forecast, precipitation classification forecast, precipitation detection ability, and spatial prediction accuracy. The prediction effects of the ECMWF, JMA, KMA, and UKMO models in the TIGGE data center were evaluated comprehensively in the study area. The results show that the four models effectively forecast light rain. The JMA model has the best forecast efficacy for light rain at different precipitation levels; for other precipitation levels, no significant difference was seen between the four models. The KMA model performs the worst for the daily precipitation forecast, whereas the ECMWF model is the most accurate. The evaluation results of precipitation detection capabilities under different precipitation thresholds show that ECMWF is more advantageous, especially when the threshold is 25 mm·d-1. The spatial accuracy test results show that each model performs better in the range of 80°-100°E and 35°-45°N, mainly in central Xinjiang and at the junction of Xinjiang, Gansu, and Qinghai provinces. Out of all the models, the ECMWF model demonstrated the best performance and the KMA model the worst. Figures and Tables | References | Related Articles | Metrics

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Runoff simulation in an arid area using the Xin’anjiang model coupled with snowmelt ZHANG Meijie,LYU Haishen,LIU Di,ZHU Yonghua,SUN Mingyue 2022, 39 (2):  379-387.  doi: 10.13866/j.azr.2022.02.05 Abstract ( 349 )   HTML ( 5 )   PDF (4038KB) ( 247 )   Using datasets of the daily grid-based precipitation and temperature from 2011 to 2018 in the upstream research area of Jiutiaoling hydrological station in the Xiying River Basin, we simulated the daily runoff process in the study basin. We propose a new method for the identification and correction of abnormal grid precipitation, which is based on the relationship between precipitation and runoff. Moreover, we created a combination of the snowmelt module and the three water source model of the Xin’anjiang model, then analyzed the applicability of the Xin’anjiang model coupled with the snowmelt module in the Xiying River Basin. Two evaluation criteria, deterministic coefficient and relative error, were used to evaluate the simulation results. The simulation results, after precipitation correction and considering snowmelt, were compared with those without precipitation correction or snowmelt consideration. The correction of grid precipitation data, based on the relationship between precipitation and runoff, improved the accuracy of the runoff simulation, and produced an improved simulation certainty coefficient in 75% of the years. The Xin’anjiang model with a snowmelt module produced a better simulation of the Xiying River Basin than that without a snowmelt module in 75% of the years. Additionally, the simulated certainty coefficient was above 0.6 for more than 87% of the years. This study can act as a reference for the application of the model in the Xiying River Basin. Figures and Tables | References | Related Articles | Metrics

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Analysis of the spatial and temporal differences in surface temperature and the contribution of surface coverage in the urban agglomeration on the northern slope of the Tianshan Mountains LIANG Hongwu,Alimujiang Kasim,ZHAO Hemiao,ZHAO Yongyu 2022, 39 (2):  388-399.  doi: 10.13866/j.azr.2022.02.06 Abstract ( 481 )   HTML ( 23 )   PDF (9542KB) ( 200 )   The acceleration of urbanization has intensified land use changes, which in turn has led to increasingly prominent urban thermal environmental problems. Based on MYD21A2 surface temperature data from the summers of 2005 and 2018, the spatial and temporal distribution pattern of LST was analyzed using spatial statistics, combined with land use data, and the contribution index was used to determine the source of land cover types and administrative divisions of the urban agglomeration on the northern slope of the Tianshan Mountains. Between 2005 and 2018, construction land, cultivated land increased significantly, and natural resource types, such as glaciers and forest land, decreased significantly, indicating that urban development had a serious impact on the ecological environment and natural resources. The spatial distribution of surface temperature grades is negatively correlated with altitude; from 2005 to 2018, the spatial distribution of high temperature grades in the daytime has a discretization trend, while the opposite is true at night, and the overall spatial distribution of high temperature grades at night has a tendency to migrate to the southeast. Different cities and land cover types had different day/night source and sink roles due to different natural conditions, specific heat capacity, and other physical properties; these can be summarized as a day and night heat source type (CI > 0), a day and night sink type (day CI < 0, night CI > 0), and a day and night heat sink type (CI < 0). The unique climate and desert-oasis-mountain landforms of the urban agglomeration on the northern slope of the Tianshan Mountains led to a diurnal sink and night source land for construction land, with the role of source and sink being different from that of some inland urban agglomerations (Beijing-Tianjin-Hebei urban agglomeration). Figures and Tables | References | Related Articles | Metrics

Water Resources and Utilization

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Analyzing the water balance of Lake Balkhash and its influencing factors WANG Zheng,HUANG Yue,LIU Tie,ZHONG Ruisen,ZAN Chanjuan,WANG Xiaofei 2022, 39 (2):  400-409.  doi: 10.13866/j.azr.2022.02.07 Abstract ( 1137 )   HTML ( 64 )   PDF (8323KB) ( 394 )   Based on hydrological observations and remote-sensing monitoring data, time series and water level of Lake Balkhash in the past 60 years were extracted to reconstruct the Lake Balkhash water level-area-volume capacity curve. Additionally, we explored the characteristics of the Lake Precipitation volume changes, established a water balance model of Lake Balkhash based on water revenue (runoff, precipitation, and groundwater recharge) and expenditure (evaporation and infiltration), and quantitatively analyzed the changes in water balance elements in Lake Balkhash. The interaction between water revenue and expenditure and the influence mechanism was explored based on climate change and human activities over time. Results showed that (1) the water volume of Lake Balkhash decreased sharply at first and then fluctuated from 1961 to 2020. The change process of runoff into the lake was consistent with the water volume, and the average annual runoff was approximately 14.04 km3. Precipitation in the lake area fluctuated at a rate of 0.28 mm·a-1. Additionally, the average annual evaporation of the lake was about 17.95 km3, with a minimum of 16.10 km3 in 1987 and a maximum of 20.30 km3 in 2008. Moreover, (2) the groundwater and the lake supplemented each other, groundwater recharge was relatively high (about 1.91 km3) in the 1970s and 1980s. (3) At the lake scale, the change in runoff into the lake significantly correlated with the volume of Lake Balkhash and was the dominant factor of water volume change in Lake Balkhash. Furthermore, at the basin scale, the contribution of climate fluctuations to long-term changes in runoff to the lake was 71.67%, and the contribution of human activities was 28.33%. The contribution of Kapchagay reservoir establishment and the expansion of surrounding arable land from 1970 to 1985 to the sharp decline in water inflow to the lake was 47.47%. Finally, human activities have exacerbated the declining water levels in the lake during this period. Figures and Tables | References | Related Articles | Metrics

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Optimization of reservoir operation for multi-object protection and ecosystem restoration LIU Zhejie,BAI Tao,GAO Fan,YANG Pengnian,WANG Guangyan 2022, 39 (2):  410-418.  doi: 10.13866/j.azr.2022.02.08 Abstract ( 308 )   HTML ( 12 )   PDF (4039KB) ( 366 )   Over the past 20 years, the implementation of a comprehensive plan for water resources of the Tarim River basin has resulted in ecological water delivery to Taitema Lake and Daxihaizi Reservoir of an average 350 million m3. However, two areas between the Wenkuer River and Old Tarim River, in the lower reaches of the Tarim River, have sparse vegetation and fragile ecological environments. Ecological restoration efforts over many years have not had a significant effect. In view of this, the study attempted to establish the medium-and long-term ecological optimization of the reservoir. A model was developed based on the Daxihaizi Reservoir as the main water body for regulation, the ecological water discharged from Daxihaizi, the ecological base flow in the river, the ecological water delivery of Taitema Lake, and the ecological water supply outside the river as ecological protection objects. The scheduling model was solved using particle swarm optimization. (1) Under optimal operation conditions, the Daxihaizi Reservoir had an average annual discharge volume of 523 million m3, which meets the 350 million m3 water requirement of the first phase of the Tarim River, and the downstream river channel had a significantly longer constant flow time. (2) With optimized discharge, the average volume of water entering Taitema Lake was 18 million m3, which is an increase of 20.0% compared with the measured data. The process for water entering the lake was more stable, which is conducive to consolidating the initially formed lake ecosystem. (3) With optimized discharge, the guaranteed rate of ecological base flow in the lower reaches of the Tarim River was 50.0%, and the guaranteed rate of continuous flow reached 64.6%. The improved ecological flows had an important positive effect on the ecosystem of the lower reaches of the Tarim River, which is greatly affected by human activities. (4) After the optimized operation, the average ecological water supply outside the lower reaches of the Tarim River was 167 million m3, laying a foundation for ecological restoration of the forests on the banks of the lower two rivers. These results have important application value for the restoration and protection of desert riparian vegetation in the lower reaches of the Tarim River. Such efforts could help to maintain the ecological health of river courses and tail lakes, and develop ecological groundwater banks. Figures and Tables | References | Related Articles | Metrics

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Hydrochemical characteristics and quality of groundwater in the plains of the Turpan Basin BAI Fan,ZHOU Jinlong,ZENG Yanyan 2022, 39 (2):  419-428.  doi: 10.13866/j.azr.2022.02.09 Abstract ( 515 )   HTML ( 6 )   PDF (3569KB) ( 310 )   In order to study the hydrochemical characteristics and quality of groundwater in the plains of Turpan Basin, 44 groundwater samples (33 phreatic water and 11 confined water) were analyzed. The latest comprehensive groundwater pollution survey data in Turpan Basin in 2015 was used. Mathematical statistics, Piper trilinear diagram, Gibbs diagram, and the ion ratio method were used to analyze the hydrochemical characteristics of groundwater. The Nemerow index method, improved Nemerow index method, and fuzzy comprehensive evaluation method were used to evaluate groundwater quality. The results showed that groundwater was weakly alkaline, with low salinity. The main groundwater hydrochemical types were SO4·Cl-Na·Ca and HCO3·SO4-Na·Ca, followed by HCO3·SO4·Cl-Na·Ca. Groundwater chemical composition was mainly affected by evaporation concentration and rock weathering. Ca2+ and Mg2+ in groundwater are mainly derived from the dissolution of evaporite; Na+, K+ and Cl- are derived from the dissolution of rock salt, and a small amount of Na+ and K+ in partial phreatic water comes from the dissolution of silicate. γ(Na+-Cl-)/γ[(Ca2++Mg2+)-γ(SO42-+HCO3-= -1 showed a significant negative correlation, indicating that the formation of groundwater chemical components was affected by cation exchange. In the three evaluation methods, the proportion of grade Ⅲ and higher water quality was >55%, and the groundwater quality was good on the whole; the proportion of grade Ⅳ and Ⅴ water in the fuzzy comprehensive evaluation method was the lowest (27.3%), and grades Ⅳ and Ⅴ water were mainly distributed in the Bostan township of Toksun County and Railway station town and Qiketai town to the east of Shanshan County. Figures and Tables | References | Related Articles | Metrics

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Study on the hydraulic connection between the Sugan Lake Wetland and the Kuitunnuoer Wetland LI Pingping,WANG Xiaodan,CHEN Hailong 2022, 39 (2):  429-435.  doi: 10.13866/j.azr.2022.02.10 Abstract ( 292 )   HTML ( 11 )   PDF (6202KB) ( 246 )   The Sugan Lake Wetland and Kuitunnuoer Wetland selected as the research objects are located in the Sugan Lake Basin in the Northwest of the Qaidam Basin. Technologies and methods of hydrogen and oxygen isotope, groundwater dynamics, geophysical exploration and remote sensing interpretation were used to study the hydraulic connection between the Sugan Lake Wetland and the Kuitunnuoer Wetland. The results showed that the groundwater of the Sugan Lake Wetland was mainly supplied by atmospheric precipitation and lateral runoff. In contrast, the meltwater from the Altun Mountains glacier supplied that of the Kuitunnuoer Wetland through underground runoff. Furthermore, the alluvial fans of Qingshigou between the Sugan Lake Wetland and the Kuitunnuoer Wetland have faults that behave as aquicludes, which is a different hydrogeological unit and has no underground hydraulic interaction. Therefore, the research results provide a theoretical basis and scientific support for the sustainable development and usage of water resources in the basin. Figures and Tables | References | Related Articles | Metrics

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Spatial-temporal assessment of water resource security based on the agricultural water footprint: A case in the Hotan Prefecture of Xinjiang ZHANG Lili,DENG Xiaoya,LONG Aihua,GAO Haifeng,REN Cai,LI Zhiyun 2022, 39 (2):  436-447.  doi: 10.13866/j.azr.2022.02.11 Abstract ( 442 )   HTML ( 37 )   PDF (4050KB) ( 400 )   The Hotan Prefecture is a typical inland arid area. Regional water resource security assessment is of great significance for guiding the development and utilization of water resources and promoting the sustainable development of social economy and water resources. Based on the water footprint theory, this paper studied the composition and spatial-temporal changes of the water footprint of agricultural production in the Hotan Prefecture from 1989 to 2018, then analyzed and evaluated the temporal and spatial pattern changes of water resource security status through water footprint intensity and water resource pressure indicators. The water footprint for agricultural production in Hotan has experienced three stages: rapid growth, slow growth, and obvious decline. It is composed of an approximately 8:2 ratio in terms of the water footprint of crop production and that of animal products. Changes in each stage were dominated by the increase and decrease in the blue water footprint of crop production, which were spatially high in the west and low in the east. The intensity of the water footprint decreased according to a logarithmic trend; by 2018, it had shrunk to 1/19 of the original size. The pressure value for water resources in the Hotan Prefecture has not reached 1 for many years; the water resource have remained in a safe state, and the pressure on water resource has been relatively high in the past 10 years. Overall, the water footprint of agricultural production in Hotan has fluctuated and increased over time, the efficiency of water use has increased significantly, and the pressure on water resources has also increased simultaneously, constantly threatening the security of regional water resource. Figures and Tables | References | Related Articles | Metrics

Soil Resources

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Variation in soil salinity and ions in a shallow groundwater area under freeze-thaw LIU Lei,CHEN Junfeng,LYU Pengpeng,ZHAO Dexing,DU Qi 2022, 39 (2):  448-455.  doi: 10.13866/j.azr.2022.02.12 Abstract ( 494 )   HTML ( 8 )   PDF (6305KB) ( 504 )   In shallow groundwater areas, freeze-thaw is one of the most important factors affecting the soil salinization process. Determining the variation in soil salinity and different soil salinity ions during the freeze-thaw process is of great significance for the prevention and control of soil salinization in seasonal freeze-thaw areas. A ground lysimeter system located on Taigu Water Balance Experimental Field was used to examine soil salinity and soil salinity ions. The ground lysimeter system had six different groundwater depths (0.5, 1.0, 1.5, 2.0, 2.5 m, and 3.0 m) and the soil water content, soluble soil salinity content, and content of soluble soil salinity irons were analyzed during the freeze-thaw period from 2020 to 2021. Correlations between the soil salt content and five salinity ions were analyzed using the Gray correlation method. The results showed that the soluble salinity ions in the soil mainly consisted of Na+, Ca2+, HCO3-, SO42-, and Cl-. The correlation analysis revealed that the soil salt content of soil was highly significantly correlated with Na+ and HCO3-, and significantly correlated with Ca2+ and SO42-. The position of the frozen layer had a strong influence on changes in Na+, HCO3-, SO42-, and soil salt content throughout the freeze-thaw process; however, Ca2+ and Cl- were less affected by the frozen layer. When the entire frozen layer was within the maximum capillary water rise height, salt accumulation in the frozen layer was obvious. However, the frozen layer acted as an obstruction when it was not within the maximum capillary water rise height. There was an inverse relationship between the groundwater depth and soil salt content. When the depth of groundwater was 3.0 m, the change in soil salt content was much lower than that at groundwater depths of 0.5-2.5 m. These results provide a theoretical basis for the prevention and control of soil salinization in shallow groundwater areas. Figures and Tables | References | Related Articles | Metrics

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Variation in soil extracellular enzyme activities stoichiometry during biological soil crust formation in the Loess Plateau YAO Hongjia,WANG Baorong,AN Shaoshan,YANG E’nv,HUANG Yimei 2022, 39 (2):  456-468.  doi: 10.13866/j.azr.2022.02.13 Abstract ( 647 )   HTML ( 15 )   PDF (8514KB) ( 131 )   Biological soil crusts (BSCs) play an important role in enhancing soil resistance to water and wind erosion, and improving soil nutrients. Soil extracellular enzyme activity can be used as a microbial indicator of the intensity of soil biochemical reactions, which is important for understanding the nutrient cycling processes involving microorganisms in desert ecosystems. However, there is a lack of understanding of the variation in soil extracellular enzymes and their stoichiometry during the formation of BSCs on the Loess Plateau. Soils from five biological crust formation stages (CK, A, AM, MA, and M) in Liudaogou watershed, Shenmu County, on the Loess Plateau were selected for the study. Soil extracellular enzyme activities [β-1,4-glucosidase (BG), β-1,4-N-acetylaminoglucosidase (NAG), leucine aminopeptidase (LAP), and alkaline phosphatase (AP)] and their stoichiometric changes during the formation of biocrusts were characterized. The activities of soil BG, NAG, LAP, and AP increased significantly with the sequence of biological crust development, and activity was significantly greater in Mo soil than that in Al soil (P<0.05). Extracellular enzyme activities were significantly higher in the BSCs layer than those in the lower soil layer, and decreased continuously with the depth of the soil. Soil C, N, P, C:P, and N:P all showed highly significant positive correlations with soil extracellular enzyme activities (P<0.05). The nutrient content and soil extracellular enzyme activity of soil with crust cover were significantly higher than those of bare land, and those of Mo soil were significantly higher than those of Al soil. Standardized major axis estimates indicated that soil extracellular enzyme activities were significantly enhanced and showed homeostasis with formation of biological crusts, and the slopes between N- and P-acquiring enzymes relative to C-acquiring enzymes showed isotropic relationships. Soil microorganisms play an important role in nutrient cycling in arid and semi-arid ecosystems through homeostatic regulation of extracellular enzyme stoichiometry. Figures and Tables | References | Related Articles | Metrics

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Soil nutrients and stoichiometric characteristics of the Elaeagnus angustifolia shelterbelt in the Hobq Desert SHI Shiling,REN Xiaomeng,ZHANG Xiaowei,MENG Zhongju,WANG Tao 2022, 39 (2):  469-476.  doi: 10.13866/j.azr.2022.02.14 Abstract ( 358 )   HTML ( 10 )   PDF (5473KB) ( 300 )   To investigate the soil nutrients and stoichiometric characteristics of the Elaeagnus angustifolia shelterbelt in the northeastern margin of the Hobq Desert, and to offer a theoretical basis for the development of desert shelterbelt, we studied the E. angustifolia shelterbelt with different forest ages (3 a, 9 a, 15 a ) using 30 m×30 m representative sample plots. The soil nutrient content of these plots were measured by stratified sampling of the 0-50 cm soil layer. The pH of different soil layers in the different forest ages had little fluctuation; however, the nutrient elements were significantly affected by forest age and soil depth. Nutrient content increased significantly with forest age, and decreased vertically along the soil profile, illustrating a surface accumulation phenomenon. Among nutrients, forest age had a great influence on available K, total P, and total K; at a forest age of 15 a, these nutrients increased by 152.2%, 58.0%, and 69.5%, respectively, compared with bare sandy land. The C:N, C:P, and N:P of the 0-50 cm soil layer across the different forest ages was 9.25-18.99, 4.78-5.96, and 0.31-0.63, respectively, and was affected by forest age and soil depth. The comprehensive stoichiometric analysis showed a remarkable improvement effect of the E. angustifolia shelterbelt on aeolian sandy soil in the northeastern margin of Hobq Desert, with the soil nutrient status mainly affected by the C and N. The mineralization ability of soil N was weak and nitrogen was poor. As such, nitrogen fertilizer should be appropriately applied in later management. Figures and Tables | References | Related Articles | Metrics

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Relationship between 137Cs and soil particles in the main soil types in the eastern Jungar Basin YANG Jianjun,WANG Heping,WANG Mingli,GUAN Tianze 2022, 39 (2):  477-484.  doi: 10.13866/j.azr.2022.02.15 Abstract ( 373 )   HTML ( 3 )   PDF (1792KB) ( 368 )   We selected three main soil types in the the eastern Jungar Basin, and explored the relationship between 137Cs and soil particles and natural geographic environment conditions to further understand the influence of soil particles on the distribution of 137Cs. The three soil types were dominated by soil particles > 50 μm, accounting for 51.35%-90.22% of the three soil types. The median particle size (D50) of aeolian sandy soil was greater than that of gray-brown desert soil, which was greater than that of gray desert soil. The range of 137Cs mass activity in gray-brown desert soil was 0.32-15.70 Bq·kg-1, The distribution of 137Cs specific activity in aeolian sandy soil is consistent with the particle content of soil >50 μm and the distribution of D50 profile, but the specific activity of 137Cs in gray desert soil followed a different trend from that of soil particles of various sizes. Among aeolian sand and gray desert soils, those with the greatest impact on the 137Cs mass activity were 2-5 μm soil particles, whereas 137Cs in the gray-brown desert soil were most affected by 10-50 μm soil particles. The content of soil particles in different grain fractions of the soil profile has certain reference value for predicting the mass activity of 137Cs in different profiles. Figures and Tables | References | Related Articles | Metrics

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Soil salt accumulation characteristics of long-term drip irrigation in cotton fields during non-irrigation seasons TAN Mingdong,WANG Zhenhua,WANG Yue,LI Wenhao,ZONG Rui,ZOU Jie 2022, 39 (2):  485-492.  doi: 10.13866/j.azr.2022.02.16 Abstract ( 295 )   HTML ( 22 )   PDF (3924KB) ( 268 )   To explore the changing characteristics of soil water and salt movement in cotton fields with different drip irrigation years during the freezing and thawing process, this study conducted field sampling and monitoring on five plots with different drip irrigation years and a wasteland (CK) in the Xinjiang oasis irrigation area. The soil salt content of the 0-120 cm soil layer decreased significantly as the drip irrigation years increased, and the salt distribution characteristics changed from a surface accumulation type to a uniform type. During the freezing and thawing process, the characteristics of soil salt movement in cotton fields had obvious plot differences, wherein the soil salt in each layer of the wasteland and the cotton field with 17, 19, and 23 drip irrigation years increased, with average salt fluxes of 43.61, 172.57, 38.18, and 10.53 g·m-2·d-1, respectively. 0-60 cm range was the sensitive layer of soil water storage in the drip irrigation cotton field. More specifically, the ablation period was the most active period of water and salt movement in each plot. After freezing and thawing, the soil water storage in this area of the wasteland and the cotton field with 13, 15, 17, 19, and 23 drip irrigation years increased by 23.43 mm, 81.26 mm, 31.68 mm, 62.39 mm, 96.98 mm, and 69.64 mm, respectively. This study reveals trends in soil water and salt transport during the freeze-thaw process and the characteristics of salt accumulation in cotton fields with different drip irrigation years. Results provide scientific guidance for soil management under freeze-thaw conditions in non-irrigation seasons and long-term drip irrigation in Xinjiang. Figures and Tables | References | Related Articles | Metrics

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Effects of protective measures on N2O emission from farmland soil in a semi-arid area of the Loess Plateau DU Mengyin,YUAN Jianyu,LI Guang,YAN Lijuan,LIU Xingyu,QI Xiaoping,PANG Ye 2022, 39 (2):  493-501.  doi: 10.13866/j.azr.2022.02.17 Abstract ( 317 )   HTML ( 18 )   PDF (8004KB) ( 438 )   Nitrous oxide (N2O) is an important greenhouse gas. It has attracted much attention as a factor in climate change, and farmland soil is the main source of emissions. Among many variables affecting N2O emission from farmland, tillage is a key factor but exactly how it regulates N2O emission from dryland farmland soil is unclear. In this study, traditional tillage (T) was used as a control, and three kinds of conservation tillage were used: no tillage (NT), traditional tillage + straw mulch (TS), and no tillage + straw mulch (NTS). The soil N2O emission flux of a spring wheat field was measured by static box gas chromatography, and factors affecting N2O emission and spring wheat yield were measured concurrently. Soil N2O cumulative emissions under different tillage measures in the spring wheat field decreased in the order T > NT > TS > NTS. Emissions under treatment T were significantly higher than those under other treatments (by 15.87%, 28.08%, and 39.58%, respectively, compared with NT, TS, and NTS). In addition, compared with treatment T, conservation tillage helped to increase the surface soil content of NH4+-N and the yield of spring wheat, and reduce the accumulation of NO3--N. Correlation analysis showed that soil temperature, soil water content, and NH4+-N content were associated with soil N2O emission. Of these, soil water content and NH4+-N content showed significant negative correlations with soil N2O emission, and soil temperature showed a highly significant positive correlation with N2O emission. Based on economic and environmental benefits and considering N2O emission and crop yield, we suggest that NTS is the best tillage strategy in semi-arid areas of the Loess Plateau. Figures and Tables | References | Related Articles | Metrics

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Effects of different short-term straw returning methods on soil structure and water content ZHOU Yanli,WU Haimei,ZHOU Yandong,SHANG Xumin,PANG Lei 2022, 39 (2):  502-509.  doi: 10.13866/j.azr.2022.02.18 Abstract ( 448 )   HTML ( 8 )   PDF (3752KB) ( 188 )   Soil structure and water content are key factors influencing crop production. The effects of different short-term straw returning measures on soil structure and water evaporation were analyzed via field experiment and using evaporation bucket simulation tests. Four treatments were used: control (CK), broken stalks returned to the field (T1), broken stalks returned to the field plus whole stalk cover (T2), and whole stalk cover (T3). The study found the following results: (1) for the 0-20 cm soil layer, T1, T2, and T3 decreased soil bulk density and increased soil capillary porosity but had significant effects on aggregates. The contents of large aggregates in T1 and T2 significantly increased by 36.90% and 63.06%, respectively, compared with CK (P<0.05). Moreover, large aggregate content in T3 decreased by 9.89% compared with that in CK. (2) T1, T2, and T3 may increase the average soil water content in the 0-60 cm soil layer and decrease the cumulative evaporation of soil water. The smallest cumulative evaporation was seen in T3, and no significant difference was observed between T2 and T3. Compared with CK, the transpiration inhibition rate of T2 and T3 was 3.65% and 4.13%, respectively. (3) Broken stalks returned to the field plus whole stalk cover had the best effect on improving soil structure and inhibiting soil water evaporation. Figures and Tables | References | Related Articles | Metrics

Plant and Plant Physiology

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Dynamic changes and driving factors of vegetation cover in the oasis-desert ecotone: A case study of Cele, Xinjiang CAO Yongxiang,MAO Donglei,Xue Jie,SU Songling,Kaimaierguli Abulaiti,CAI Fuyan 2022, 39 (2):  510-521.  doi: 10.13866/j.azr.2022.02.19 Abstract ( 604 )   HTML ( 21 )   PDF (5699KB) ( 416 )   The oasis-desert ecotone is an ecological buffer zone between the oasis and desert ecosystems,playing an important ecological role in maintaining oasis stability, preventing wind, and fixing sand. Based on Landsat remote sensing image data taken from 1993 to 2017, and meteorological and socioeconomic data, we used the normalized vegetation index (NDVI), the pixel dichotomy model, and the principal component analysis method to investigate long-term vegetation changes and their driving factors in small-scale regions. The results show that (1) the average annual NDVI of the Cele oasis-desert ecotone has been increasing yearly in the last 25 years. The high-value area of the NDVI is mainly distributed in the southeast, whereas the low-value area is mainly distributed in the west and northwest of study area; (2) the annual mean fractional vegetation coverage (FVC) was 0.23, and the FVC in 1993, 1998, 2008, 2011, 2014, and 2017 were 0.20, 0.18, 0.19, 0.23, 0.27, and 0.28, respectively, indicating that vegetation coverage has continuously improved; (3) regional vegetation coverage was mainly medium and low, accounting for 30.73% and 21.47% of the total area of the study area, respectively. Low, high, higher, and very low vegetation coverage accounted for 21.48%, 20.39%, 20.12%, and 7.26% of the total study area, respectively. The areas with improved vegetation coverage were relatively small and mainly concentrated in the middle and southeast of the Cele River basin, whereas the distribution of other vegetation cover types was scattered; and (4) on the interannual timescale, human activities are the dominant factor affecting vegetation change in the oasis-desert ecotone, and vegetation is more sensitive to precipitation than to air temperature. Artificially forested land, cultivated land, populated areas, and shelter belt areas accounted for 0.850, 0.810, 0.853, and 0.779 of the first principal component, respectively. Atmospheric relative humidity, precipitation, and livestock inventory accounted for 0.845, 0.753, and -0.608 of the second principal component, respectively, but air temperature accounted for 0.883 of the third principal component. This study provides a theoretical basis to further understand vegetation change, the analysis of influencing factors, and vegetation conservation and restoration in the oasis-desert ecotone. Figures and Tables | References | Related Articles | Metrics

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Floristic characteristics of the genus Allium Linnaeus in Xinjiang, China ZHANG Qiaoguan,ZHANG Daoyuan,LIU Huiliang 2022, 39 (2):  522-540.  doi: 10.13866/j.azr.2022.02.20 Abstract ( 643 )   HTML ( 23 )   PDF (806KB) ( 438 )   The Allium Linnaeus is an important plant resource of great value with many species. It is situated in Central Asia and the hinterland of the Eurasian continent. Xinjiang of China harbors a wide plant diversity of Allium Linnaeus. To probe into the plant resources and the floristic characteristics of Allium Linnaeus in Xinjiang Province, combining and verifying monographs, literature, bibliographies with specimens from this genus can provide some profound support and outline for taxonomy, classification, biodiversity conservation as well as proper and sound utilization of Allium plants. We hope this study can help further research into this genus (Allium Linnaeus). Based on previous and present references, studies, records, and information about Allium Linnaeus, Allium plants from Xinjiang Province comprise about 58 species, 1 subspecies, 2 varieties, and 6 cultivated species. The floristic characteristics of Allium Linnaeus in Xinjiang Province are summarized as follows: (1) Allium plants of Xinjiang Province are mainly distributed in the Tianshan Mountains, Ili, Tacheng, Altay, and Kashgar, with most of them inhabiting the deserts, steppes, the dry slopes, gravel grounds, mountains, alps, and forest floor (or forests). (2) In terms of the areal-types of geographical elements, the II C5b elements (the Junggar subregion, of the temperate desert) has the largest percentage composition, followed by the I A2 (the Altay region), II C5a (the Tacheng-Ili subregion), I A3 (the Tianshan region), II C6c (the Kashgar subregion). (3) From the perspective of the vegetation regionalization of Xinjiang, the Allium plant species in the vegetation provinces with the IB1, IIA2, IIA1, IIB3 make up most vegetation regionalization types in Xinjiang; the IIB1, IA1, IIB2 follow this; and with a relatively few occurrences in the vegetation province II B4, I C1. (4) Both horizontal distribution and vertical distribution of Allium Linnaeus in Xinjiang are differentiated. (5) The common Allium species in Xinjiang and the adjacent countries (especially in Kazakhstan and Russia) were significantly more than other neighbouring regions. Also, the number of the common Allium species presented a slight distinction. It indicated a higher similarity in the common Allium species among Kazakhstan, Russia, and Xinjiang of China, reflecting the distinctive connection, exchange, interrelation, and affinity with other neighboring floristic components. Henceforth, holistic, comprehensive, multidisciplinary, and sufficient research integrating with molecular phylogeny (phylofloristics), phylogenetic, evolutionary processes, history, and information (historical floristic phytogeography), phylogenetics, and molecular biogeography are proposed. Figures and Tables | References | Related Articles | Metrics

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Biomass allocation patterns of an ephemeral species (Erodium oxyrhinchum) in different habitats and germination types in the Gurbantunggut Desert, China ZHANG Yuanyuan,MENG Huanhuan,ZHOU Xiaobing,YIN Benfeng,ZHOU Duoqi,TAO Ye 2022, 39 (2):  541-550.  doi: 10.13866/j.azr.2022.02.21 Abstract ( 396 )   HTML ( 3 )   PDF (3745KB) ( 323 )   Ephemeral plants are an important plant group in desert ecosystems; they have diverse habitats, and many species also have isochronous germination characteristics. The accumulation and distribution of plant biomass can reflect its response and adaptability to the environment; therefore, studying the biomass allocation pattern of ephemeral plants under different environmental conditions is helpful to further understand the survival strategies of these plants. This study investigated Erodium oxyrhinchum samples germinated in the summer in bare sand and in the spring in three natural habitats (i.e., bare sand, algal crust, and lichen crust). The aboveground and underground biomass were obtained by the whole-plant excavation method. Differences in the plant biomass distribution and allometric growth among the four types [i.e., Bare Sand-Spring Germination (BS), Algal-Spring Germination (AS), Lichen-Spring Germination (LS), Summer Germination in Bare Sand (SG)] were systematically compared and analyzed to explore the variability and conservatism of their resource allocation strategy. The aboveground, underground, and total biomass of individual plants was highest for BS, followed by AS, then followed by LS and SG, who were equal. The root to shoot ratio (R/S) of SG was similar to that of LS and AS, all of which were higher than BS. The aboveground and underground biomass of BS and SG plants both showed an isometric relationship, whereas that of AS and LS represented allometric relationships; nonetheless, a common allometric scaling exponent (0.8843) existed in all four types. The R/S for AS and LS decreased allometrically as individual plant size increased, while the R/S for BS and SG remained relatively constant. In short, the biomass allocation of Erodium oxyrhinchum may be affected by the external environment and individual development, and showed obvious plasticity, which reflected a trade-off between the conservatism and plasticity of resource allocation. Figures and Tables | References | Related Articles | Metrics

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Stoichiometric characteristics of leaves and fine roots in Alhagi sparsifolia in response to the addition of nitrogen and water YU Yang,ZHANG Zhihao,YANG Jianming,CHAI Xutian,ZENG Fanjiang 2022, 39 (2):  551-559.  doi: 10.13866/j.azr.2022.02.22 Abstract ( 359 )   HTML ( 6 )   PDF (7010KB) ( 276 )   Nitrogen and water are important factors affecting the growth of desert plants; nitrogen deposition and drought, the main driving factors of global climate change, will directly change the availability of these two resources in soil. Presently, our understanding of how N deposition and drought affect the chemometric characteristics of desert plants remains limited. Thus, a pot experiment was conducted on 1-year-old seedlings of Alhagi sparsifolia, a dominant plant of the southern edge of the Taklamakan Desert. Different amounts of N fertilizer and water were added to simulate different levels of the N deposition rate (0, 3.0, 6.0, and 9.0 g·m-2·a-1) and water conditions (drought or well-watered conditions) to explore the effects of these two factors on the stoichiometric characteristics of the leaves and fine roots of A. sparsifolia. The results show the following: (1) N and water addition independently or interactively affected the nutrient status of leaves and fine roots of A. sparsifolia, except for P content in leaves. Nitrogen addition significantly decreased the contents of N, Mn, Zn, and Cu in leaves under drought conditions but increased the absorption of these elements by fine roots to a certain extent; (2) microelements such as Mn, Zn, Cu, and Fe were enriched in the fine roots of A. sparsifolia, but macroelements such as N, P, and K were more distributed in the leaves; (3) applying 3.0 g·m-2·a-1 N under drought stress and adding 6.0 or 9.0 g·m-2·a-1 N under well-watered conditions can significantly alleviate the N limitation of fine roots of A. sparsifolia (N:P<14); (4) the nutrient elements of leaves and fine roots of A. sparsifolia have complex interactions within and between organs. The occurrence rate of this relationship between organs is greater than that within organs, followed by that in fine roots, and the lowest in leaves. These results show that A. sparsifolia can coordinate the relationship between aboveground and underground nutrients under the background of fluctuations in environmental resources. Exogenous N input can improve the nutrient status of fine roots of A. sparsifolia. These results provide further scientific reference for the efficient nutrient management and restoration of desert vegetation. Figures and Tables | References | Related Articles | Metrics

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Study on physical and chemical properties and shear strength characteristics of root-soil composite system with different degradation degrees of alpine grassland in the source region of the Yellow River YANG Fucheng,LIU Changyi,HU Xiasong,LI Xilai,FU Jiangtao,LU Haijing,SHEN Ziyan,XU Tong,YAN Cong,HE Weipeng 2022, 39 (2):  560-571.  doi: 10.13866/j.azr.2022.02.23 Abstract ( 340 )   HTML ( 3 )   PDF (9011KB) ( 227 )   This study was to exhibit the effects of alpine grassland degradation on the physical and chemical properties of the soil and the shear strength of the root-soil composite system in the source region of the Yellow River. The alpine grassland in Henan County, Qinghai Province, was selected as the study site. The variation in characteristics of soil density, water content, soil nutrient element content, and shear strength of plant root-soil composite system at different stages of deterioration of grassland was obtained through laboratory experiments. The test results showed that under the same degradation status and sampling depth, the average soil density in the test area of Nanqi Village was 1.02-1.29 times that of Qilong Pasture. The soil water content showed a decreasing trend with the deterioration worsening. Soil pH value increased with increasing deterioration, and soil organic matter content, total nitrogen content, and total phosphorus content decreased. As a result, the shear strength of the root-soil composite system decreased with worsening damage. In Qilong Pasture and Nanqi Village, shear strength in the upper layer (0-10 cm) and lower layer (10-20 cm) were reduced by 72.05% and 48.77%, and 77.26% and 81.37%, respectively. The amount and dry weight of roots in the root-soil composite system decreased gradually with grassland degradation rising. In Qilong Pasture and Nanqi Village, the root amount in the upper and lower layers decreased by 79.28%, 75.93%, and 92.48%, 39.59%, respectively. Finally, according to the WWM model and Pearson correlation analysis, the reduction of roots and nutrient element content significantly reduced the shear strength of the root-soil composite system. Therefore, the study results provide practical guiding significance for the rational prevention and control of grassland degradation, soil erosion, and shallow landslides in the source region of the Yellow River. Figures and Tables | References | Related Articles | Metrics

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Relationship between tensile properties and microstructure of single root of three riparian plants ZHANG Yu,ZHU Haili,ZHANG Ke,LI Guorong,LIU Yabin 2022, 39 (2):  572-583.  doi: 10.13866/j.azr.2022.02.24 Abstract ( 377 )   HTML ( 2 )   PDF (5678KB) ( 530 )   We aimed to analyze the tensile properties of single roots and the micromechanical mechanism of revetment by three dominant alpine meadow plants (Blysmus sinocompressus, Kobresia capillifolia, and Potentilla fruticose) in the source area of the Yellow River. The mechanical properties of single roots of these three plants and their relationship with microstructure were quantitatively analyzed through a single root tensile test and paraffin section test. As the root diameter increased (from less than 0.5 mm, 0.5-1.0 mm, to greater than 1.0 mm), the single root tensile resistance and elongation increased, whereas the single root tensile strength and Young’s modulus decreased. The tensile stress-strain curve for single roots followed a single peak curve trend. The average tensile strength of the single roots of Potentilla fruticose shrubs was 1.56 and 1.25 times greater than that of the cyperaceous Blysmus sinocompressus and Kobresia capillifolia, repsectively, whereas the average single root elongation of Blysmus sinocompressus was 1.06 and 1.36 times greater than that of Kobresia capillifolia and Potentilla fruticose, respectively. The single root tensile strength of cyperaceous plants was mainly related to the vascular column area ratio, whereas the single root tensile strength of Potentilla fruticose shrubs was closely related to the proportion of epidermis and secondary xylem. The ability to resist root system deformation in Blysmus sinocompressus and Kobresia capillifolia was stronger than that of Potentilla fruticose; therefore, these two cyperaceae plants play a role in reinforcing the soil, and slowing down the speed of deformation and failure of the river bank. Moroever, the stiffness and tensile strength of the Potentilla fruticose root system were higher, which play a role in soil consolidation and bank protection. Our results provide scientific support for screening the dominant revetment species in the source region of the Yellow River. Figures and Tables | References | Related Articles | Metrics

Ecology and Environment

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Contribution of climatic change and human activities to changes in net primary productivity in the Loess Plateau YANG Dan,WANG Xiaofeng 2022, 39 (2):  584-593.  doi: 10.13866/j.azr.2022.02.25 Abstract ( 673 )   HTML ( 25 )   PDF (4842KB) ( 343 )   In this study, we used the CASA model to produce a net primary productivity (NPP) dataset for the Loess Plateau from 2000 to 2018. Based on correlation and residual analyses, we quantified the relative contribution of climate change and human activities to NPP, with a goal of providing a scientific basis for the formulation of local ecological protection strategies and improving watershed ecological security. The distribution pattern of NPP in the Loess Plateau from 2000 to 2018 was high in the southeast and low in the northwest. The portion of NPP that followed an increasing trend was mainly distributed in the core area of the Grain for Green Program, accounting for 86.86% of the total NPP, whereas the portion of the NPP that followed a decreasing trend was distributed in the northwestern arid zone, accounting for 13.14% of the total NPP. The contribution rates of climate change and human activities to NPP were 48.78% and 51.22%, respectively. Climate change plays an important role in vegetation change in sparsely populated and underdeveloped areas, whereas human activities play an important role in vegetation change in areas with large populations and better economic development. The Loess Plateau, an arid and semi-arid region, has a more sensitive vegetation response to climate change. With the increasing frequency of human activities, climate and human activities jointly determine the vegetation changes. This study contributes to the understanding of the effects of climate change and human activities on the dynamic changes of vegetation. It provides a scientific basis for vegetation restoration and high-quality development of the Loess Plateau. Figures and Tables | References | Related Articles | Metrics

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Analysis of landscape pattern from 1990 to 2019 based on multi-temporal imagery in arid oasis SONG Qi,SHI Zhou,FENG Chunhui,MA Ziqiang,JI Wenjun,PENG Jie,GAO Qi,JIANG Xuewei 2022, 39 (2):  594-604.  doi: 10.13866/j.azr.2022.02.26 Abstract ( 312 )   HTML ( 9 )   PDF (8515KB) ( 407 )   In this study, 226 scenes of Landsat image data of Aral Reclamation Area from 1990 to 2019 were used to compare different classification methods, from which that with the highest accuracy was selected. The landscape pattern changes in the Aral Reclamation Area for more than 30 years were analyzed in terms of patch type level, landscape level, abrupt changes, and spatial distribution, respectively. The best results were obtained for the multi-temporal object-oriented classification, with an overall accuracy of 96.57% and a Kappa coefficient of 0.95. At the patch type level, arable land tends to fragment over 30 years, the dominance of unused land decreases, the landscape shape of parkland and woodland tends to become more complex, and the landscape of water bodies and built-up land tends to become more balanced. At the landscape level, landscape shapes become more complex and fragmented, landscape connectivity decreases, and landscape richness and heterogeneity increase. The Aral Reclamation Area underwent a sudden change in landscape pattern in 2005. In terms of spatial distribution, there is a tendency for the central Tarim River region to spread out in all directions. Figures and Tables | References | Related Articles | Metrics

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Effects of different years of returning farmland on soil moisture and species diversity in Minqin Qingtu Lake area WANG Jia,TIAN Qing,WANG Lide,HE Hongsheng,SONG Dacheng,GUO Chunxiu 2022, 39 (2):  605-614.  doi: 10.13866/j.azr.2022.02.27 Abstract ( 310 )   HTML ( 12 )   PDF (895KB) ( 350 )   Using the spatial instead of temporal method, we investigated the characteristics of soil moisture change and vegetation succession characteristics across different years of abandoned land (returned fields 1 a, 2 a, 4 a, 8 a, 13 a, 20 a, 30 a, 40 a, and CK) in the Qingtu Lake area of Minqin. As the period of abandoned land increased, the soil water content first decreased, then increased and gradually stabilized. Additionally, as the period of abandoned land increased, the number of individuals, number of groups and Margalef richness index tended to decline; the Shannon diversity index and Pielou evenness index increased first, then decreased and gradually stabilized, whereas the Simpson dominance index only minorly changed before stabilizing. Moreover, as the period of returning farmland increased, the plant community followed a succession process: Kochia scoparia→Halogeton arachnoideus→Setaria viridis→Peganum nigellastrum→Suaeda microphylla→Lycium ruthenicum→Reaumuria soongarica→Kalidium foliatum. Overall, the Simpson dominance index and soil water content in the 0-20 cm soil layer showed a highly significant negative correlation, whereas the Shannon diversity index and soil water content in the 0-20 cm soil layer showed a highly significant positive correlation; however, there was no significant correlation with soil water content in the 20-40 cm soil layer. Additionally, there was no significant correlation between group number, Margalef richness index, Pielou evenness index, and soil water content. As such, natural vegetation succession in arid areas depends on the soil water content in the 0-20 cm soil layer. Figures and Tables | References | Related Articles | Metrics

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Temporal and spatial variation characteristics and influencial factors of soil moisture in the Xiangride-Qaidam River Basin CHENG Mengyuan,CAO Guangchao,ZHAO Meiliang,DIAO Erlong,HE Qixin,GAO Siyuan,QIU Xunxun,CHENG Guo 2022, 39 (2):  615-624.  doi: 10.13866/j.azr.2022.02.28 Abstract ( 324 )   HTML ( 5 )   PDF (8924KB) ( 130 )   As a key factor of the ecological environment, soil moisture is an important indicator for soil monitoring and changes to the ecological environment. This study is based on MOD11A2 LST and MOD13A2 NDVI data, and used mathematical statistical analysis methods, including the temperature-vegetation dryness index (TVDI), correlation analysis, and regional statistical analysis. The temporal and spatial distribution of humidity characteristics and its influencing factors were analyzed. The average TVDI value in the vegetation growing season of the Xiangride-Qaidam River basin from 2005 to 2020 was 0.61; the maximum value was noted in 2015 (0.64) and the minimum value occurred in 2020 (0.58). The interannual TVDI value slowly decreased over time; however, it did increase in 2015. The drought situation in the study area was unstable, and remained at a drought level for an extended time period. The area corresponding to different soil moisture levels, in descending order, was as follows: drought > extremely arid > normal > humid > extremely humid, accounting for 30.63%, 25.77%, 22.16%, 16.44%, and 5.01% of the total area, respectively. The spatial distribution of TVDI gradually decreased from northwest to southeast, with obvious regional differences. Moreover, the TVDI value had a negative correlation with altitude, decreasing by 0.11 for every 500 m increase in altitude. The TVDI was positively correlated with the average temperature, but had no obvious correlation with precipitation. Figures and Tables | References | Related Articles | Metrics

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Response of agricultural nonpoint source pollution load in the Ulungur River basin under climate change ZOU Kaibo,ZHANG Yuhu,LIU Xiaowei,XUE Shuhui,YANG Bowen,CUI Yanxin 2022, 39 (2):  625-637.  doi: 10.13866/j.azr.2022.02.29 Abstract ( 445 )   HTML ( 8 )   PDF (5175KB) ( 157 )   Taking the Ulungur River basin in Xinjiang as study area, a nonpoint source pollution distributed hydrological model suitable for the basin was constructed based on the soil and water assessment tool (SWAT), and nine climate change scenarios were set using the scenario setting method. The impact of different climate change scenarios on the river basin runoff and nonpoint source pollution load was analyzed, key affected areas were identified, and a scientific basis for the prevention and control of nonpoint source pollution in the river basin was provided. The results show that (1) the values of the determination coefficient R2 for runoff, total nitrogen and total phosphorus in the regular rate and verification period were all above 0.75, and the Nash coefficient Ens was above 0.55. The established SWAT model could be used for agricultural nonpoint sources in the pollution load simulation applied to the Ulungur watershed. (2) Precipitation, runoff, total nitrogen load, and total phosphorus increased by 20%, 48.01%, 23.19%, and 29.65%, respectively, and the impact on runoff caused by temperature variation was less than that caused by precipitation variation. (3) The average annual total nitrogen load per unit area of each sub-catchment was between 0.01-164.79 kg·hm-2·a-1, and the total phosphorus load per unit area was between 0.01-45.10 kg·hm-2·a-1. The areas where climate change had a greater impact on nonpoint source pollution were mainly distributed in Arda Township in Fuhai County, Turhong Township, Kuerte Township, and Chakurtu Township in Fuyun County, Arele Township, Altobe Town, and Takshken Town, etc. in Qinghe County. Studies have shown that increased precipitation is one of the main factors affecting the agricultural nonpoint source pollution load in the basin. In the future, the prevention and control of this type of pollution should focus on controlling two types of pollution sources, livestock and poultry breeding and farmland runoff. Figures and Tables | References | Related Articles | Metrics

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A multi-scale integrated classification method for landforms YANG Weitao,SUN Jianguo,MA Hengli,HUANG Zhuo 2022, 39 (2):  638-645.  doi: 10.13866/j.azr.2022.02.30 Abstract ( 377 )   HTML ( 8 )   PDF (8849KB) ( 347 )   Landform objects span a broad range of sizes. Existing automatic landform classification methods do not fully consider size, however, which restricts classification accuracy. This study proposes a multi-scale integrated classification method for landform that considers the size of different features. The method consists of three steps: multi-scale segmentation, screening according to scale order, and multi-scale merging. The screening according to scale order is an iterative confirmation process of classified objects based on multi-scale feature extraction and supervised classification, with small scale (small size) priority and probability maximization as criteria. According to experimental results from the Loess Plateau, the method is simple and reliable (overall accuracy reached 75.16% and the Kappa coefficient reached 0.71) and can be used for detailed classification of landform. Figures and Tables | References | Related Articles | Metrics

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Precise management zoning in arid soil croplands based on multi-source data BAI Jianduo,PENG Jie,SHI Zhou,WANG Yuzhen,LIU Weiyang,LI Hongyi 2022, 39 (2):  646-655.  doi: 10.13866/j.azr.2022.02.31 Abstract ( 357 )   HTML ( 4 )   PDF (10618KB) ( 72 )   According to the spatial heterogeneity of soil salinization, the precise management precise zoning of oasis farmland in the arid area of Southern Xinjiang is of great significance for the adjustment of areas, based on spatial heterogeneity in soil salinization, is important for determining agricultural planting structure structures and fine-scale management. This study selected the topical oasis farmland in arid zone as the study object and used electromagnetic induction data, topographic date, and satellite remote sensing data as for oasis farmland in the data sources. We analyzed arid zone of Southern Xinjiang to analyze the spatial heterogeneity of soil salinization by geostatistical. Geostatistical methods and screened the were used to evaluate vegetation index and salt index in indices for different periods with correlation analysis. The surface apparent electrical conductivity (ECh0.375) of the farmland was used as the main variable, and the deep apparent electrical conductivity (ECh0.75, ECV0.75, ECV1.5), vegetation index (RVI, GRVI, EVI), and soil salinity index (NDSI, S5, SI-T) were used as the auxiliary variables. The study area was partitioned by using an object-oriented multi-scale segmentation algorithm, and the zoning results were evaluated by the mean Coefficient of variation (CV) and Moran’s I. The results showed that there was obvious spatial heterogeneity in the apparent electrical conductivity of each soil layers in the study area, and the auxiliary variables were significantly correlated with the main variable. The average coefficient of variation of each partition was reduced by 60% compared with that of the whole study area, and the. The interval heterogeneity based on multi-source data zoning was higher than that based on single-source data zoning. From the perspective of farmland cultivation, segmentation effects, and zoning evaluation principles, the, management zoning effect that integrated the information of surface and deep soil salinization was the best. And the zoning results were not only consistent with both local farmland management but also met the mechanized operation requirements. The findings can provide certain a technical and methodological reference for precise management zoning of oasis farmland in arid areas of Southern Xinjiang. Figures and Tables | References | Related Articles | Metrics

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Drought characteristics and effects on grain production in Wuwei, Gansu Province DING Wenkui,LI Xingyu,YANG Xiaoling,MA Zhonghua,LI Yanying 2022, 39 (2):  656-664.  doi: 10.13866/j.azr.2022.02.32 Abstract ( 865 )   HTML ( 10 )   PDF (1653KB) ( 207 )   Drought is a serious concern in the worst disaster weather in Wuwei, Gansu Province. Using precipitation data from 1960 to 2019 and grain yield data from 1970 to 2019 in Wuwei City of Gansu Province, variation characteristics of meteorological drought and grain yield, and the relationship between drought and grain yield was analyzed by statistical method in Wuwei City. The results showed that (1) spatial variation of frequency of spring drought, early summer drought and midsummer drought was consistent. Drought occurred more frequently in the northern desert area than in the oasis plain area, and that were more common in the oasis plain area than in the southern mountain area. (2) the frequency of spring drought, early summer drought and midsummer drought was not consistent. The frequency of spring drought increased in Liangzhou and Minqin, but showed a decreasing trend in Gulang, Tianzhu and the whole city. Eearly summer drought did not change in Liangzhou and Gulang, but decreased in Minqin, Tianzhu and the whole city. Midsummer droughts showed no change in Liangzhou, but decreased in Minqin and Gulang, and increased in Tianzhu and the whole city. Frequency of a variety of drought showed an increasing trend with increasing of drought grade. Extreme drought frequency was the most, and light drought took second place on spring drought. Extreme drought frequency was the most, and heavy drought took second place on early summer drought. Medium drought frequency was the most, extreme drought took second place on midsummer drought. (3) the grain production (wheat, maize, and total food) increased significantly with year and age. The annual variation of meteorological production had no obvious regularity, and had a great volatility. The age change of meteorological production increased first, then decreased and then increased. The meteorological yield was basically negatively correlated with ages frequency of various drought. The correlation between meteorological yield and frequency of early summer drought was significant, but the correlations with other droughts were not significant. Meteorological yields were lower in age of more drought frequencies, but meteorological yields were higher in age of less drought frequencies. It indicated that drought was one of the important factors restricting the abundance of grain. Figures and Tables | References | Related Articles | Metrics