Table of Content

15 December 2023, Volume 40 Issue 12 Previous Issue    Next Issue

Weather and Climate

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Climate dry-wet conditions, changes, and their driving factors in Xinjiang DONG Hanlin, WANG Wenting, XIE Yun, Aydana YESINALI, JIANG Yuantian, XU Jiaqi 2023, 40 (12):  1875-1884.  doi: 10.13866/j.azr.2023.12.01 Abstract ( 209 )   HTML ( 36 )   PDF (9015KB) ( 209 )   Based on daily observations from 56 meteorological stations from 1961 to 2019, this study analyzed dry-wet conditions, changes, and their underlying driving factors in Xinjiang. The main findings are as follows: (1) In the past 59 years, the Xinjiang climate has changed significantly from dry to wet, with the aridity index (AI) changing at a rate of 0.01·(10a)-1 (P < 0.01). The number of stations with a significant upward trend of AI accounted for 57.1%. (2) The annual precipitation in Xinjiang increased significantly at a rate of 8.6 mm·(10a)-1 from 1961 to 2019, consistent with the change in AI. Conversely, the annual reference evapotranspiration (ET0) showed a significant decreasing trend at a rate of -15.7 mm·(10a)-1. However, it is worth noting that ET0 transitioned around 1990. ET0 continued to decrease before 1990 and then switched to a fluctuating upward trend. (3) Wind speed and relative humidity primarily influenced ET0 variation. Wind speed exhibited a consistent decreasing trend across the entire region, while approximately half of the stations observed a decline in relative humidity. The combined effect of these factors significantly decreased ET0 at nearly 50% of the stations in Xinjiang. Moreover, trends in relative humidity from increasing to decreasing trends and wind speed from decreasing to increasing around 1990 contribute to the differences in ET0 trends between the two periods. The conclusions achieved here provide valuable insights into understanding the dry-wet changes and their underlying driving factors in Xinjiang and have implications for the rational development and use of water resources in this region. Figures and Tables | References | Related Articles | Metrics

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Multi-time scale change characteristics and influencing factors of total solar radiation in Dunhuang City WANG Yunpeng, LI Hongying, YAO Yubi, LI Dongliang, FAN Qiwei, LIU Xiangping 2023, 40 (12):  1885-1897.  doi: 10.13866/j.azr.2023.12.02 Abstract ( 152 )   HTML ( 25 )   PDF (4349KB) ( 204 )   Using ensemble empirical mode decomposition and the M-K mutation test, the multi-times cale characteristics of the evolution of total solar radiation in Dunhuang city were analyzed based on the meteorological data of total solar radiation, relative humidity, total cloudiness, and dust days in Dunhuang city between 1971 and 2020. The key meteorological factors influencing solar radiation in Dunhuang city were explored. The results show the following: (1) There was a significant upward trend of annual total solar radiation in Dunhuang city between 1971 and 2020, with a linear climate propensity rate of 49.6 MJ·m-2·(10a)-1, and the multiyear average annual radiation was 6354.0 MJ·m-2, belonging to the area with the most abundant solar resources. The annual radiation was lowest in the 1970s and highest in the 2010s. Dunhuang has four distinct seasons of solar radiation, with radiation increasing at rates of 32.5, 13.4, 2.9, and 1.1 MJ·m-2·(10a)-1 in summer > spring > fall > winter, respectively. The total solar radiation in Dunhuang city in the last 50 years was dominated by interannual variations of 2.9 and 7.1 years and interdecadal variations of 16.7 years. (2) Monthly solar radiation varied in a “single-peak” pattern, with a sharp increase in March, a peak in May, a gradual decrease in June, and a yearly minimum in December. The hourly distribution of total solar radiation is monomodal, with the maximum occurring between 12:00 and 13:00 a.m. (3) The annual, spring, and summer solar radiation changes were abrupt in 1997, 2000, and 1982. (4) Meteorological factors affecting solar radiation at Dunhuang can be attributed to three factors: atmospheric transparency, illumination, and humidity, and the correlation between each meteorological factor and solar radiation varies according to the seasons. Figures and Tables | References | Related Articles | Metrics

Land and Water Resources

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Characteristics of hydrological and water resources in the Shiyang River Basin and their effects on land desertification CHAI Huixia, AN Zhishan, PAN Jiapeng 2023, 40 (12):  1898-1906.  doi: 10.13866/j.azr.2023.12.03 Abstract ( 116 )   HTML ( 12 )   PDF (6276KB) ( 131 )   In this article, using the parameters of hydrological, water resources, and the desertification area of the Shiyang River basin in different periods, the basin hydrology, water resources, desertification, and its changes in the relationship between them were quantitatively studied. It provides the data and the theoretical basis for hydrological, water resource features, and land desertification in this area. The research showed that although the precipitation in the Shiyang River basin had increased from 2005 to 2021, the variability was large and remained at a low level, with an average annual precipitation of only 234.70 mm. From 1993-2004, the annual precipitation at the Caiqi hydrological station reduced, whereas the annual sediment transport increased. The annual precipitation at the Zamusi hydrological station increased from 1999 to 2021, whereas the annual sediment discharge decreased. From 2005 to 2021, the total amount of water resources in the Shiyang River basin decreased by 0.24×108 m3 ·a-1, but water consumption and water consumption remained at high levels of 24.70× 108 m3 and 17.07×108 m3, with high water consumption and consumption in agriculture, forestry, and fruit industries, exacerbating the irrationality of water resource utilization in the basin. From 1975 to 2014, the total area of desertified land in the basin reduced, but the land changes in different periods and desertification types remained quite different, and the situation of desertification prevention and control in the basin was still grim. Figures and Tables | References | Related Articles | Metrics

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Main nutrient characteristics and influencing factors of farmland soil in the Loess Plateau of the Shaanxi Province HE Junqi,BAI Hanwei,XU Yiwei,NI Lili 2023, 40 (12):  1907-1917.  doi: 10.13866/j.azr.2023.12.04 Abstract ( 103 )   HTML ( 9 )   PDF (12380KB) ( 95 )   To explore the main soil nutrient characteristics and influencing factors of farmland in the Loess Plateau of Shaanxi, spatial analysis was conducted on the content of SOM, TN, AP, and AK using GIS and geostatistics methods based on the data from 5096 farmland sampling points with a depth of 0-20 cm in the study area. A geographic detector model was used to explore the degree to which 18 influencing factors explained the spatial variation of nutrients. The results showed that the average contents of SOM, TN, AP, and AK were 14.43 g·kg?1, 0.92 g·kg?1, 18.21 mg·kg?1, and 190.28 mg·kg?1, respectively, showing moderate variation. The four best-fit models for nutrients were all exponential models, with moderate spatial correlation among each nutrient. The combined effect of structural and random factors causes spatial differences in the nutrient content. The global spatial correlation of nutrients is TN > SOM > AK > AP. The regional differences in nutrient content are significant, indicating a gradually increasing trend from north to south. The single-factor effects of annual sunshine duration, annual average temperature, fertilizer use, and geomorphic type have stronger explanatory power for spatial variation in nutrient content but lesser than that of the interaction between the two factors. Research has shown that it is necessary to increase fertilizer input in the northern Shaanxi region, perform intensive cultivation in the Guanzhong region, and consider multiple factors in farmland construction. Figures and Tables | References | Related Articles | Metrics

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Dynamic prediction and regulation of the water resource carrying capacity in the Guanzhong region based on the LMDI-SD coupling model JIA Qiong, SONG Xiaoyu, SONG Shuhong, LIU Xiaodi, QIN Lin, LIU Hui 2023, 40 (12):  1918-1930.  doi: 10.13866/j.azr.2023.12.05 Abstract ( 80 )   HTML ( 8 )   PDF (5722KB) ( 41 )   To realize the dynamic prediction and quantitative regulation of water resource carrying capacity, an LMDI-SD coupling model based on the LMDI decomposition method, system dynamics (SD), and orthogonal test method was established. The coupling model uses the LMDI decomposition method to identify the driving factors of water consumption change, establishes the SD model to predict the water resource carrying capacity, takes the key driving factors of water consumption change of each department as the regulation index, comprehensively regulates the economic and social water use, and selects the optimal regulation scheme combined with the orthogonal test method. Applied to the dynamic prediction and regulation of water resource carrying capacity in the Guanzhong region between 2020 and 2035, the results show that the following: (1) the intensity effect is the key driving factor for the decrease in agricultural water consumption and the increase in domestic and ecological water consumption in the Guanzhong region between 2010 and 2019, whereas the scale effect is the key driving factor for the increase in industrial water consumption; (2) under the current development mode, the water resource bearing pressure of the whole Guanzhong region and cities will increase yearly from 2020 to 2035, and will be in an overloaded state by 2035 as the increase in total water consumption is far greater than the available water supply; (3) the Han to Wei River Diversion Project effectively alleviated the contradiction between supply and demand of water resources in the Guanzhong area from the supply side. However, compared with the rapidly growing demand, water resources in some cities remain limited; therefore, they should be regulated from the demand side; (4) by restricting the expansion speed of industrial development, improving the level of agricultural water use, and slowing down the growth trend of domestic and ecological water use, the water resources in the Guanzhong region can be bearable from 2020 to 2035. The LMDI-SD coupling model constructed in this study has good practical application value for regional water resource planning and management within the framework of sustainable development. Figures and Tables | References | Related Articles | Metrics

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Effect of sand barrier fixation on the formation and development of biological soil crust YAN Peiying,QU Jianjun,WANG Lide,XIAO Jianhua,ZHANG Yuan,WANG Xiaohong,GUO Shujiang 2023, 40 (12):  1931-1937.  doi: 10.13866/j.azr.2023.12.06 Abstract ( 103 )   HTML ( 5 )   PDF (6035KB) ( 86 )   The biological soil crust is important for maintaining stability in desert ecosystems. Therefore, the use of sand barriers as auxiliary measures to promote the formation and development of biological soil crust in arid areas is of great significance. In this paper, the effects of sand fixation by sand barriers (straw checkerboard, nylon grids, and covered nets) on the formation and development of biological soil crusts were studied using microbial high-throughput sequencing combined with soil physical and chemical properties determination. The results showed that the crust thickness under the covered nets was the thickest, although the colors of the crust in the straw checkerboard and nylon grids were similar to that of the algae crust. The proportions of clay and powder particles in the crust of the three types of sand barriers for sand fixation were significantly higher than that of the moving sand. The nutrition degree of the crust in the covered nets was the highest, indicating the highest degree of soil formation. From the composition analysis of fungi, bacteria, and blue-green algae in crusts from the three types of sand barrier, it was found that the proportions of Cyanobacteria and Leptolyngbya in the crust in the covered nets were higher than those in the crust in the straw checkerboard and nylon grids. In contrast, the proportions of Dothedeomycotes and Microcolleus were lower, and the number of unique microbial OUT was highest. Based on the previous process of soil crust formation and microbial succession in arid areas, it was inferred that the degree of crust development in the cover nets was likely higher than that in the straw checkerboard and nylon grids and that their formation and development trajectory differ. Therefore, among the three types of sand barriers, the covered nets for sand fixation were more suitable for biological soil crust formation and development. Figures and Tables | References | Related Articles | Metrics

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Effects of irrigation and salinity treatments on the soil bacterial community and plant physiological characteristics of Cyperus esculentus farmland in Horqin Sandy Land WU Rui, CAO Hongyu, GAO Guanglei, YU Minghan, DING Guodong, ZHANG Ying, ZHAO Peishan 2023, 40 (12):  1938-1948.  doi: 10.13866/j.azr.2023.12.07 Abstract ( 99 )   HTML ( 4 )   PDF (9131KB) ( 52 )   To reveal the soil bacterial community structure and its effects on Cyperus esculentus, affected by different irrigation and salinity treatments in the Qian Gorlos Irrigation District, a random plot sampling experiment was conducted using two-factor, three-level (irrigation level: 50%, 70%, and 100% standard irrigation quota; salt level: control group, mild salinity stress, and moderate salinity stress). Comparative analysis of soil bacterial community characteristics in C. esculentus cropland under different irrigation and salinity treatments was performed. Simultaneously, the molecular ecological network of soil bacteria was constructed to determine the keystone species and its interrelationship with C. esculentus growth. Results showed that (1) The dominant phyla of soil bacteria in C. esculentus cropland were Proteobacteria (22.85% ± 3.80%), Acidobacteriota (20.02% ± 3.21%), and Actinobacteriota (18.85% ± 2.41%). The dominant genera were RB41, Sphingomonas, and Rubrobacter. Bacterial alpha diversity differed insignificantly under different irrigation or salinity treatments (P > 0.05). With increasing irrigation, the relative abundance of Proteobacteria gradually increased, whereas that of RB41 gradually decreased. The same trend was observed with increasing salinity stress. (2) The co-existence relationship between bacterial species was stronger in 100% standard irrigation quota treatments, with a positive correlation rate of 78.05%. Additionally, the degree of interactions and tightness of connections between bacterial species was highest at 50% standard irrigation quota treatments. The highest ecological network complexity and degree of interactions among bacterial communities were found in control group soils, and stronger co-existence relationships among bacterial species were found in moderate salinity soils, with a positive correlation rate of 75.31%. (3) The number of keystone species increased with increasing irrigation. Additionally, the RB41 genus appeared under 70% and 100% standard irrigation quota treatments. Significant differences were observed in keystone species under different salinity stresses. At an S2 salinity gradient, the number of keystone species reached a maximum, with the emergence of the dominant genera RB41 and Lysobacter. The keystone species were Rubrobacter, RB41, Dongia, Steroidobacter, Nitrospira, Lysobacter, and Luteolibacter. (4) Variations in irrigation significantly affected plant height, crown size, number of tillers, above-ground dry weight, carboxylase activity, proline, and superoxide dismutase activities of C. esculentus plants (P < 0.05). Changes in salt application significantly affected plant height, above-ground dry weight, abscisic acid, soluble sugar, peroxidase activity, and malondialdehyde in C. esculentus (P < 0.05). The final screening was performed to conclude that Lysobacter, Nitrospira, Lysobacter, Dongia, RB41, Steroidobacter, and Luteolibacter were significantly associated with the growth and physiological traits of C. esculentus (P < 0.05). The soil bacterial community composition, molecular network, and keystone species were changed as a result of different irrigation or salt treatments, and keystone species were significantly associated with the growth of C. esculentus. This improved information contributes to a better understanding of the soil bacterial community structure and its ecological function in C. esculentus cropland and provides a theoretical basis for adaptive planting and stable and high yield of C. esculentus. Figures and Tables | References | Related Articles | Metrics

Plant Ecology

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Vegetation change characteristic research of different evolution stages in Minqin Xishawo desert areas MAN Duoqing, LI Delu, LIU Mingcheng, ZHANG Dekui, TANG Jinnian, CHEN Fang, FU Guiquan, YANG Xuemei, DING feng 2023, 40 (12):  1949-1958.  doi: 10.13866/j.azr.2023.12.08 Abstract ( 90 )   HTML ( 6 )   PDF (3263KB) ( 123 )   Through eco-measurement and research at the Xishawo desert pasture in Minqin for 60 a, it was found that desert vegetation flora has experienced four main stages with ground water-table decline, they were the degraded meadow steppe and Tamarix flora, Tamarix and Nitraria flora, Nitraria and degraded Tamarix flora, and Nitraria flora, the plant diversity and coverage dcreased in the processing, eco-degradation and desertification developed remarkably; with rain-fed area enlargement, desert herbal plants grew when precipitation was higher in the year, the plant diversity and coverage increased, and vice versa; some desert shrubs were relatively stable, its population growth and development improved when precipitation was over 140 mm, 100-140 mm for basic growth, and < 100 mm degraded gradually; most plant species of windbreak and sand-fixation afforestation degraded under drought conditions, Haloxylon ammodendron had strong eco-adaptability as an introduced species, it has developed into the biggest man-made windbreak and sand-fixation forest in Minqin desert areas, its big density and drought land were the main reasons for degradation, and sustainability could be increased under low density afforestation according to local plant carry capacity. Recently, with the integrated program implementation in the Shiyang River watershed area, eco-water has been increased, groundwater table has increased in some surroundings, some micro-wetlands have formed, original desert meadow steppe has reoccured, and their ecosystems are developing positively; however, ground water table still reduces slowly in most desert areas, and desertification has developed. Figures and Tables | References | Related Articles | Metrics

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Spatiotemporal characteristics of vegetation carbon use efficiency and its sensitivity to climate in the Yellow River Basin in Shaanxi Province WANG Juan, WANG Zhao, GUO Bin, HE Huijuan, DONG Jinfang 2023, 40 (12):  1959-1968.  doi: 10.13866/j.azr.2023.12.09 Abstract ( 80 )   HTML ( 5 )   PDF (17498KB) ( 43 )   Vegetation carbon use efficiency (CUE) can objectively reflect the efficiency of vegetation in sequestering atmospheric carbon and the response of vegetation to climate change. Using MOD17, land use, and meteorological data, this study applied methods, such as the Hurst exponent, correlation analysis, and sensitivity analysis to explore the spatiotemporal variability of vegetation CUE and its sensitivity to climate factors in the Shaanxi section of the Yellow River Basin from 2001 to 2021. The results showed that (1) From 2001 to 2021, the gross primary productivity, net primary productivity (NPP), and vegetation CUE in the Shaanxi section of the Yellow River Basin exhibited an increasing trend, with an average CUE value of 0.51. (2) The study area was only 14.21% of the region, exhibiting a decreasing trend. The high-value areas of vegetation CUE are primarily concentrated in the windbreak and sand-fixation areas and the Grain for Green Project areas of northern Shaanxi. The areas where vegetation CUE indicated a decreasing trend accounted for 59.96%, most of which transitioned from an increasing trend to a decreasing trend. (3) Overall, temperature and precipitation correlated negatively with vegetation CUE, but the relationship with precipitation is more significant. Regions with positive correlations with temperature and precipitation are distributed in northern Shaanxi’s windbreak and sand-fixation areas. Sensitivity analysis of temperature and precipitation showed that the threshold values were 10 °C and 500 mm, respectively. When the temperature is below 10 °C and the precipitation is below 500 mm, the vegetation CUE increases with increasing temperature and precipitation. The relationship between vegetation CUE and climate factors is more significant and sensitive in arid areas, such as the conversion of farmland to forests and windbreak and sand-fixation areas in northern Shaanxi. Figures and Tables | References | Related Articles | Metrics

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Seasonal changes of NDVI in the arid and semi-arid regions of Northwest China and its influencing factors WU Wanmin, LIU Tao, CHEN Xin 2023, 40 (12):  1969-1981.  doi: 10.13866/j.azr.2023.12.10 Abstract ( 137 )   HTML ( 20 )   PDF (20110KB) ( 100 )   The study of vegetation dynamics and its influencing factors can reveal the response mechanism between vegetation cover dynamics and climate change and has important significance for regional vegetation restoration and ecological sustainability. Based on MODIS multitemporal remote sensing satellite data, this study investigated the quarterly changes in vegetation cover in the arid and semi-arid regions of Northwest China from 2000-2020 using variation coefficient, Theil-Sen median trend analysis, Mann-Kendall significance test, correlation analysis, and Hurst index. The study found that: (1) The spatial variability of the Normalized Difference Vegetation Index (NDVI) was high in winters, and the high fluctuation areas were mainly in the grasslands and unused land areas in the Daxinganling region of Xinjiang and Inner Mongolia. (2) NDVI fluctuates more with the seasons and is most obvious in forests and cultivated areas. (3) NDVI is mainly improving, with the largest improvement in springs (84.63%), the smallest in winters (72.52%), and the most significant improvement in the woodland areas. (4) Surface temperature and precipitation influenced NDVI in all seasons (Significance = 0.05), with precipitation changes significantly affecting NDVI trends in summers and weakly during winters and surface temperature changes significantly affecting NDVI trends in springs and weakly in autumns. (5) The future NDVI also mainly shows an improving trend, with an area of 70.89%; notably, the degraded areas are sporadically distributed in the Tarim and Junggar Basins of Xinjiang. This study’s results provide theoretical references for ecological restoration and management in the arid and semi-arid regions of Northwest China and the response to local climate warming and humidification. Figures and Tables | References | Related Articles | Metrics

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Impact of climatic factors and human activities on the net primary productivity of the vegetation in the Pisha sandstone area WANG Yi’en, RAO Liangyi 2023, 40 (12):  1982-1995.  doi: 10.13866/j.azr.2023.12.11 Abstract ( 81 )   HTML ( 7 )   PDF (18829KB) ( 37 )   As a highly serious soil and water loss area in the Loess Plateau, vegetation growth plays an important role in controlling soil erosion and maintaining ecological balance. This study calculated the net primary productivity of vegetation NPP and 18 extreme climate indices in the Pisha sandstone area from 2001 to 2021 based on the CASA model and Rclimdex 1.0, respectively. Trend analysis, correlation analysis, random forest importance ranking, and residual analysis were used to study the spatial-temporal variation of NPP and its response to climate factors in the Pisha sandstone area. The relative contributions of climate factors and human activities to the NPP in the Pisha sandstone area were also calculated. The results showed that (1) NPP variation in all regions of the Pisha sandstone area from 2001 to 2021 had a significant increasing trend, but in the future, 82.5% of the NPP in the Pisha sandstone area will change to a decreasing trend. (2) On the annual scale, NPP correlated positively with average annual temperature, total annual precipitation, and extreme heavy precipitation index and correlated negatively with cold night days TN10P and diurnal temperature range DTR. On the seasonal scale, the increase in average temperature and warm night days in spring was conducive to increase NPP, and there is a lag effect. Increasing the number of warm days in summer was unconducive to vegetation growth, and the NPP has a three-month lag response to the number of warm days in summer. Extreme heavy precipitation in summer was conducive to NPP increase, whereas summer drought was unconducive to vegetation growth, and NPP has a three-month lag response to the number of continuous dry days. (3) Both climate change and human activities contribute positively to NPP in the Pisha sandstone area. The climate contribution of the bare area and the covered sand area is dominant (62.13% and 60.06%, respectively), whereas that of the covered soil area is dominated by human activities (60.40%). Figures and Tables | References | Related Articles | Metrics

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Differences and spatial variation in the stem xylem structural traits of Reaumuria soongarica and Calligonum mongolicum SHEN Hui, ZHANG Jing, PENG Lan, TAO Ye, ZANG Yongxin, ZHANG Yuanming 2023, 40 (12):  1996-2006.  doi: 10.13866/j.azr.2023.12.12 Abstract ( 85 )   HTML ( 10 )   PDF (9324KB) ( 70 )   Xylem structure traits are the basis for plant adaptation to different water conditions and are core plant traits in response to changes in environmental conditions. The typical shrubs Reaumuria soongarica and Calligonum mongolicum in the northwest desert region were selected as the subjects for comparison between stem xylem structure and functional traits to understand the differences or similarities of different species in the same habitat and the xylem structure plasticity of the same species under different environmental conditions. The results showed that (1) Xylem structure traits of R. soongarica and C. mongolicum were significantly different. The mean vessel diameter and vulnerability index of C. mongolicum were significantly higher than those of R. soongarica, whereas the opposite was true for vessel density and vessel grouping index. (2) The patterns of xylem structure traits in response to climate change differed between R. soongarica and C. mongolicum. The mean vessel diameter and vessel thickness-to-span ratio of C. mongolicum significantly reduced with increasing mean annual precipitation and aridity index, whereas that of R. soongarica were unrelated, and only the theoretical hydraulic conductivity had a significant positive correlation with the mean annual precipitation and aridity index. (3) There was a trade-off between efficiency and safety in the xylem hydraulic conductivity system of R. soongarica, whereas none was observed in C. mongolicum. (4) The trait network analysis results indicated that the central traits of both R. soongarica and C. mongolicum were mean vessel diameters. Changes in mean vessel diameter mediate changes in the trait network. Xylem structure traits between R. soongarica and C. mongolicum were significantly different, with R. soongarica having a more conservative water use strategy than C. mongolicum. Figures and Tables | References | Related Articles | Metrics

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Differences in the response to soil drought in Atriplex canescens and Tamarix ramosissima HU Huanqiong, LI Li, YU Jun, LIANG Hailian, LYU Ruiheng 2023, 40 (12):  2007-2015.  doi: 10.13866/j.azr.2023.12.13 Abstract ( 93 )   HTML ( 4 )   PDF (3636KB) ( 68 )   To construct shelter forests in arid areas, selecting plant species with strong stress tolerance and adaptability is key. By simulating a pot water control experiment with different drought gradients, the ecological adaptability of the introduced plant Atriplex canescens and the native plant Tamarix ramosissima willow to drought stress were compared. The results showed that (1) With an increase in drought degree, the water content in the A. canescens and T. ramosissima leaves reduced gradually, and the water retention capacity, proline content, and relative conductivity gradually increased. The soluble sugar and malondialdehyde contents of A. canescens and T. ramosissima were the maximum in mild and severe drought, respectively, and the increase rate was greater in T. ramosissima. (2) The POD activity of A. canescens and T. ramosissima increased gradually, and under severe drought, the percentage increase of T. ramosissima compared with the control was approximatelythree times that of A. canescens; SOD activity was greatest under moderate drought, and the percentage increase in T. ramosissima compared with the control was approximatelyfive times that of A. canescens. The changes in the activity of both enzymes of T. ramosissima were greater than those of A. canescens. (3) The chlorophyll content of A. canescens and T. ramosissima were mildly dry > control > moderate drought > severe drought, the net photosynthetic rate, transpiration rate, stomatal conductance, and intercellular carbon dioxide concentration of T. ramosissima gradually decreased, and mild drought slightly promoted chlorophyll and photosynthetic capacity of A. canescens. (4) The correlation and principal component analysis results indicated that the relationship between the T. ramosissima traits was closer under drought stress, and the relationship between traits and traits was difficult to change in A. canescens, which was relatively conservative. Conclusion: A. canescens is less affected by drought stress, and its drought adaptability is slightly stronger than that of T. ramosissima. Figures and Tables | References | Related Articles | Metrics

Ecology and Environment

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Geomorphologic characteristics of the co-existence zone of barchan and parabolic dunes in western Hunshandake Sandy Land REN Xiaozong,WANG Songsong,WANG Yamei,LUO Jinhong,MA Yongtao 2023, 40 (12):  2016-2030.  doi: 10.13866/j.azr.2023.12.14 Abstract ( 200 )   HTML ( 9 )   PDF (19146KB) ( 111 )   Barchan and parabolic dunes can be transformed into each other and coexist in the same area, resulting in a unique landscape in which typical barchan dunes coexist with embryonic barchan and parabolic dunes. It is helpful to understand the causes of their formation and execute targeted desertification prevention and control projects after studying their spatial distribution, morphological characteristics, and migration. Based on the Esri historical image service (World Imagery Wayback), the morphological parameters of the dunes in the coexistence zone of the barchan and parabolic dunes, west of Hunshandake Sandy Land, were extracted in three periods: January 15, 2008, June 4, 2011, and September 20, 2016, and the direction and velocity of the dune migration were calculated. The results indicate that typical barchan dunes are concentrated in 15 areas related to the dry lake bed in the western part of the sandy land, whereas embryonic barchan and parabolic dunes are sequentially distributed around the periphery of the dry lake bed. The appearance of the dry lake bed was a key factor in the development of the typical barchan dunes in the Hunshandake Sandy Land. Therefore, more attention should be paid to the desertification caused by the lake drying up. The analysis of morphological parameters of sand dunes in the fifth zone, where the co-existence of barchan and parabolic dunes is typically found, indicates that the typical barchan and embryonic barchan dunes significantly differ from embryonic parabolic dunes. The correlation analysis between the morphological parameters of sand dunes indicates that toss slope length, lee slope length, and bottom area are inherited from the barchan to parabolic dunes, with horns experiencing the greatest changes during this process. Furthermore, the migration directions of the three types of dunes are almost equal but have varying migration velocities, as well as the factors that affect the migration of sand dunes. The most significant impact on the embryonic parabolic dunes, whose vegetation cover is relatively high, was the vegetation cover, whose variation was consistent with that of NDVI during the same period. The most significant impact on the typical barchan and embryonic barchan dunes, whose vegetation cover is relatively low, was wind speed, whose variation was consistent with that of DP and RDP during the same period. Additionally, other factors, including terrain, sand sources, and human activities, can influence the morphology and migration of barchan-parabolic dunes. Figures and Tables | References | Related Articles | Metrics

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Characterization of spatial and temporal changes in the oasis effect and attribution analysis of the Hexi region in the last 20 years HOU Wenbing, LI Kaiming, HUANG Zhuo 2023, 40 (12):  2031-2042.  doi: 10.13866/j.azr.2023.12.15 Abstract ( 111 )   HTML ( 15 )   PDF (9677KB) ( 110 )   The oasis effect is extremely important for improving the climate of arid areas and supporting the self-sustainability and development of oasis systems. In this study, taking the Hexi region of Gansu Province as the study area, the indicators of oasis effect intensity were selected using meteorological and remote sensing data. The geodetector model was adopted to reveal the spatial and temporal characteristics of the oasis effect over the past 20 years, and the influencing factors of the oasis effect intensity were analyzed qualitatively and quantitatively. The results show that (1) from 2000 to 2020, the oasis effect intensity in the study area had an increasing trend in springs, summers, and winters and a decreasing trend in autumns, and the changes in the daytime are similar to those of the corresponding seasons, but with greater intensity. The strongest was in the summer, with an increase of 1.43 ℃; at night. The changes in springs, summers, and autumns were similar to those of the corresponding seasons, but with a lower intensity, and the weak oasis warming island effect appeared in the nighttime of the autumn of 2000 and the winter of 2010; (2) the area share of strong oasis effect “cold island” is the largest in summers, and the change is small, whereas the area share of oasis “warm island” effect is the largest in winter, with a decreasing trend yearly; (3) the intensity of oasis effect in summer had a strong negative correlation with the change in vegetation cover of oasis, with a correlation coefficient of -0.917. Climate and surface factors are the major controlling factors for the intensity of the oasis effect in the Hexi region. The effect of surface albedo is the weakest, and the interaction between factors should not be neglected. Figures and Tables | References | Related Articles | Metrics

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Study on water-holding capacity of litters from typical artificial forests in reclaimed regions of the opencast coal mine in Shanxi Province ZHANG Jianhua, ZHANG Kun, LIU Yong, ZHANG Hong, ZHANG Kaiquan, ZHOU Xiaoyang, XU Longchao 2023, 40 (12):  2043-2052.  doi: 10.13866/j.azr.2023.12.16 Abstract ( 82 )   HTML ( 5 )   PDF (3291KB) ( 84 )   To study the important effects of the water-holding capacity of litter in plantation plants in coal mine dumps on soil and water conservation and ecosystem restoration in mining areas, litter accumulation amount, the thickness, water-holding rate, water-holding capacity, and water absorption rate of different decomposition stages were investigated in four typical plantations of the same age (Populus simonii, Ulmus pumila, Pinus tabulaeformis, and Robinia pseudoacacia forests) in the Antaibao opencast coal mine reclamation area, through field investigation and soaking extraction. The results showed that the litter accumulation amount in the P. simonii forest was higher than that in the R. pseudoacacia and U. pumila forests (P < 0.05). The water-holding capacity and litter rate at different decomposition degrees changed logarithmically with immersion time (P < 0.01). The order of the water absorption rate of litter was R. pseudoacacia forest > U. pumila forest > P. simonii forest > P. tabulaeformis forest, and the water absorption rate showed a significant power function with immersion time (P < 0.01). In conclusion, the litter of the P. simonii forest had the strongest water-holding capacity, whereas the R. pseudoacacia forest had the fastest water absorption rate. Therefore, from the perspective of the water conservation capacity of litter, P. simonii forest should be prioritized and mixed with the R. pseudoacacia forest, which is more conducive to water conservation in the reclamation area of opencast coal mines. Figures and Tables | References | Related Articles | Metrics