Table of Content

15 June 2023, Volume 40 Issue 6 Previous Issue    Next Issue

Weather and Climate

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Characterization of the evolution of drought events in China based on 3D identification LYU Xiaoyu, GUO Hao, MENG Xiangchen, BAO Anming, TIAN Yunfei, ZHU Li 2023, 40 (6):  849-962.  doi: 10.13866/j.azr.2023.06.01 Abstract ( 503 )   HTML ( 57 )   PDF (20005KB) ( 293 )   Globally, China is one of the country’s most frequently and severely affected by drought. These frequent drought events have subsequently caused serious economic, social development, and ecological environment losses. Drought simultaneously leads to alterations in both space and time, and this paper aims to identify drought events and quantify their spatial and temporal dynamic evolution using a three-dimensional clustering algorithm for mainland China, from 1981-2020. The three-dimensional clustering algorithm can be used to effectively identify drought events and describe their dynamic processes. From 1981-2020 there were 102 drought events lasting 2 months or more in mainland China. Spatially, the trajectory of drought events was found to show a tendency to develop from east to west. Temporally, there are high time overlaps between different drought events. In addition, drought events with wide coverage and high severity were concentrated in the period from 2005-2010. The findings of this paper will help to elucidate the spatial and temporal evolution patterns of drought events and provide scientific references for drought monitoring and drought risk management in mainland China. Figures and Tables | References | Related Articles | Metrics

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Anomaly temporal-spatial distribution of solar radiation in Northwest China YAO Yubi, ZHENG Shaozhong, DONG Hongchang, SHI Jie, ZHANG Min, XIA Quan 2023, 40 (6):  863-873.  doi: 10.13866/j.azr.2023.06.02 Abstract ( 247 )   HTML ( 17 )   PDF (7628KB) ( 453 )   The temporal variation, spatial distribution, and temporal and spatial evolution characteristics of the total radiation in Northwest China were studied using meteorological observation data from 169 national meteorological stations in Northwest China, over the past 60 years. The Qaidam Basin in the Northwest of Qinghai and the west of Gansu were the most abundant areas for solar energy resources, the smaller areas in the south of Shaanxi and the southeast of Gansu were found to be resource rich areas, and the other large areas are resource rich areas. From 1961 to 2020, the total radiation showed an upward trend in Southwest Xinjiang, the border area between Gansu and Xinjiang, and smaller areas in northern Gansu and northern Shaanxi, while the total radiation showed a downward trend in most regions of Northwest China. The eigenvector field of EOF mode 1 shows that the total radiation oscillation intensifies from west to east, and the high load area for each component is mainly concentrated in the middle and east, which is the region where the total radiation is prone to be abnormal and the oscillation is strong and sensitive. The eigenvector field of the second EOF mode presents a dipole type from west to east. Qinghai and most of the Gansu are positive regions, which are also the regions with the strongest total radiation and abnormal oscillation. According to the different modal spatial differentiation structure types for the REOF eigenvectors, the study area can be divided into three sub regions, namely: “Eastern northwest anomaly type” which is affected by the East Asian monsoon; “Central northwest anomaly type” which is the marginal region and mainly affected by the East Asian monsoon; and “Western Northwest anomaly type” which is mainly affected by the westerlies. The mutation points for total radiation reduction in the three subregions occurred in 1973, 2017, and 2008 respectively. Figures and Tables | References | Related Articles | Metrics

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Recharge sources and potential source areas of atmospheric PM2.5 in Xinjiang XU Junli, HAN Haidong, WANG Jian 2023, 40 (6):  874-884.  doi: 10.13866/j.azr.2023.06.03 Abstract ( 261 )   HTML ( 15 )   PDF (11326KB) ( 103 )   Using the air pollutant mass concentration data in Xinjiang from March 2021 to February 2022, the evolution characteristics of PM2.5 concentration and its potential contribution source area were analyzed. The results showed that: (1) The concentration of PM2.5 in Xinjiang was significantly high, especially in winter, the average was as high as 86.16 μg·m-3, which had certain potential risks to human health. Influenced by the near-surface air stability, the PM2.5 concentration was higher at nighttime and lower in the daytime, but supplemented by (similar) valley winds, the PM2.5 concentration exhibited a significant double-peak pattern in the Hami Basin and the Tarim Basin. (2) The PM2.5 in the economic belt of the northern slope of the Tianshan Mountains was mainly dominated by the emission from the surrounding oil and gas fields and the dust from strong winds during the transportation process, while the source of PM2.5 in other areas, where human activities were relatively weak, was mainly controlled by the dust from strong winds, supplemented by the combustion of oil and natural gas. (3) The overall low concentration of PM2.5 in each path in the source region of the Irtysh River indicates that the impact of pollutants on environmental quality could be ignored. The high concentration of PM2.5 in the NB area was mainly affected by the local atmospheric circulation, but the airflow passing through the oil and gas industry area was a key factor leading to the formation of haze and floating dust weather. Although there are differences in the material supply paths between the Hami Basin and the Tarim Basin, their PM2.5 potential contribution source areas were all mainly distributed in the Kongqi River Basin and Lop Nur on the eastern edge of the Taklimakan Desert. (4) Exogenous airflow evolved into convergent/divergent airflow due to the topography of the basin, supplemented by (quasi) valley winds to promote the mixing of pollutants, which could be the key factor for the similar evolution trend of PM2.5 in the economic belt of the northern slope of the Tianshan Mountains and Tarim Basin. Figures and Tables | References | Related Articles | Metrics

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Atmospheric environmental capacity characteristics and influencing factors of Ningxia over the past 60 years CUI Yang,WANG Dai,GAO Ruina,AN Xingqin 2023, 40 (6):  885-895.  doi: 10.13866/j.azr.2023.06.04 Abstract ( 149 )   HTML ( 6 )   PDF (13959KB) ( 98 )   This study has aimed to evaluate the characteristics of the atmospheric environmental capacity and its influencing factors in Ningxia. The temporal and spatial distribution of the A value of the atmospheric environmental capacity and its main meteorological influencing factors were analyzed using daily fixed time historical observation data from meteorological stations between 1961 and 2018, based on the box model principle. The atmospheric environmental capacity in 2018 was also evaluated and zoned. The results showed that the A value of the atmospheric environmental capacity showed a decreasing trend in all seasons, with a rate of -0.47×104~-0.24×104 km2·(10a)-1. The annual average A value was largest in the summer, followed by the spring, and then autumn and winter. The monthly A value showed a single peak pattern, with a maximum in August and minimum in December. It was generally high in the south and low in the north in space, and influenced by the topography of Helan Mountain and Liupan Mountain, regional precipitation, and other climatic factors. The low value center for A was located in Yinchuan and Shizuishan City, while the high value center was located in the south of Guyuan City. Wind speed and mixed layer height changes had a significant influence on the interdecadal evolution trend of the atmospheric environmental capacity of A in the Ningxia Hui Autonomous Region. There were obvious seasonal and regional differences on the impacts of precipitation and wind speed. For example, wind speed had a greater contribution to the A value in spring in the north, and precipitation had a greater contribution to the A value in summer and autumn in the south. This was affected by high energy consuming industries such as metallurgy, thermal power, the chemical industry, and construction and vehicle emissions. Pingluo County and Litong District were the critical overload and overload areas for the SO2 and NOx atmospheric environments, and the counties south of Litong District were high bearing areas in Ningxia. Figures and Tables | References | Related Articles | Metrics

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Spatial-temporal variability of eolian dust in Egypt, North Africa XUE Yibo, ZHANG Xiaoxiao, LEI Jiaqiang, LI Shengyu, WANG Yongdong, YOU Yuan 2023, 40 (6):  896-904.  doi: 10.13866/j.azr.2023.06.05 Abstract ( 182 )   HTML ( 21 )   PDF (6449KB) ( 298 )   The Sahara region of northern Africa is seriously affected by drought and desertification, and eolian dust activity disasters are considered severe. The arid and semi-arid regions of Egypt in northern Africa were the focus of this study. Based on daily observation data from meteorological stations between 1990 and 2020, and the data obtained from satellite remote sensing products, the spatiotemporal variability characteristics of eolian dust activity disasters in Egypt and their possible associations were assessed. The main influencing factors of eolian dust activity disasters were further discussed. The frequency of eolian dust activities in Egypt varied from 20 to 65 d·a-1 over the past 30 years, showing an overall declining trend with fluctuations. The annual average total suspended particulate (TSP) concentration in Egypt fluctuates was 400-1200 μg·mg-3 and showed an overall decreasing trend over the past 30 years. The highest TSP concentration occurred during spring in Egypt and reached over 2300 μg·m-3. Eolian dust activity in Egypt has a high intensity level when compared to other arid and semi-arid regions of the world; Egypt has the highest frequency of blowing dust, followed by dust in suspension, dust storm, and severe dust storm. The blowing dust that occurs in spring and summer accounts for more than 60% of the total eolian dust weather throughout the year. Ambient TSP concentrations in Egypt are highly correlated with the frequency of eolian dust activity due to wind erosion; There has been a deceasing trend in surface wind speed over the past 30 years, and wind erosion is an important factor affecting air quality in the oasis areas. The frequency of eolian dust activity is significantly negatively correlated with the Atlantic multidecadal oscillation with a correlation coefficient of -0.67. This work provides theoretical basis and data support for a comprehensive understanding of the spatial-temporal characteristics of eolian dust weather in Egypt, North Africa, and the prevention of dust storm disasters. Figures and Tables | References | Related Articles | Metrics

Land and Water Resources

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Soil bacterial networks in Pinus sylvestris var. mongolica plantations of the Hulunbuir Desert ZHANG Songan, LIU Xuan, ZHAO Peishan, GAO Guanglei, ZHANG Ying, DING Guodong, LIU Ye, REN Yue 2023, 40 (6):  905-915.  doi: 10.13866/j.azr.2023.06.06 Abstract ( 165 )   HTML ( 9 )   PDF (9452KB) ( 479 )   To elucidate soil bacterial network interactions within Pinus sylvestris var. mongolica plantations in the Hulunbuir Desert. P. sylvestris plantations representing three different age groups (25 a, 34 a, and 43 a) and two soil layers (0-10 and 10-20 cm) were selected to assess their soil bacterial networks using molecular ecological network analysis and data from a referenced grassland. The numbers of network edges increased, the average path length reduced from 25 a to 43 a. While the number of network edges reduced and the average path length increased with soil layers from 0-10 cm to 10-20 cm. Compared with the grassland, the P. sylvestris plantations had a lower network edge, and the soil bacterial network was less complicated. The soil bacteria were found to belong to the Acidimicrobiales, RB41, and MB-A2-108 in the 25 a plantation, Gaiellales in the 34 a plantation, and Gaiellales, RB41, Subgroup_7, Subgroup_6, and DA101_soil_group in the 43 a plantation, Latescibacteria in the grassland. The soil bacterial network was significantly positively correlated with ammonia nitrogen, total nitrogen, microbial carbon content, and urease activities and significantly negatively correlated with invertase and catalase activities, soil water content and available phosphorus (P < 0.05). The soil organic matter had both positive and negative effects (P < 0.05). The soil bacterial network complexity and compactness increased from 25 a to 43 a. The opposite was found for the soil layers from 0-10 cm to 10-20 cm. Compared with the grassland, the soil bacterial network of the P. sylvestris plantation was less complicated. The keystone soil bacteria species were different among the three stand ages, and were greatest in stand 43 a. There were more keystone species in the plantation than the grassland. Soil physicochemical properties and enzymatic activity derived the soil bacterial network, and soil organic matter was the major influencing factor. This improved information contributed to a deep understanding of the soil bacterial community and provided a scientific and technological basis for the sustainable management of P. sylvestris plantations in the Hulunbuir Desert. Figures and Tables | References | Related Articles | Metrics

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Effects of changing rainfall frequency on the soil carbon, nitrogen, and phosphorus ecostochimetrics in the Gahai wet meadow, Gannan GUAN Yuqi, LI Guang, PAN Xue, XU Guorong, WEI Xingxing, LIU Hao, WU Jiangqi 2023, 40 (6):  916-925.  doi: 10.13866/j.azr.2023.06.07 Abstract ( 129 )   HTML ( 3 )   PDF (7282KB) ( 248 )   Rainfall is an important factor affecting water supply and soil respiration in wetland areas. Increases in extreme rainfall variability caused by global climate change are thus expected to impact wetland ecosystems. To investigate this, the changes in soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in response to altered rainfall frequencies (weekly, fortnightly, three-weekly, four-weekly, and control irrigation treatments) were assessed in a wet meadow in the Gahai-Zecha Nature Reserve on the north-eastern edge of the Tibetan Plateau. The SOC was found to increase with increasing rainfall frequency, while TP and TN decreased. SOC and TN decreased with increasing soil depth and TP was inconsistent across the different soil layers. As a result, the ratios of C:P and N:P decreased with the soil layers, but the ratio of C:N did not show a significant change. The ratios of C:N, C:P, and N:P did not show significant responses to the rainfall treatments. The SOC, TN, and TP showed obvious seasonal variations, as the SOC showed an increasing and then decreasing trend, the TN showed a decreasing and then increasing trend, and the TP content showed an “M”-shaped decreasing trend. The results suggest that continuous changes in global rainfall, including an increased rainfall frequency, will aggravate the loss of nitrogen and phosphorus in the shallow soil of the alpine wet meadow, likely resulting in aggravated damage due to eutrophication in the water environment surrounding the alpine wet meadows. Figures and Tables | References | Related Articles | Metrics

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Land graveling characteristics and monitoring indicators of the Alxa Plateau WEN Wenjie, PEI Hao, BA Gen, WU Yongjun, LIU Zhiming 2023, 40 (6):  926-936.  doi: 10.13866/j.azr.2023.06.08 Abstract ( 193 )   HTML ( 7 )   PDF (12933KB) ( 86 )   Foundation data from which to develop indicators to monitor and evaluate the graveling land of the Alxa Plateau is required. To address this, the characteristics of surface gravel coverage (Gc), surface gravel mass per unit area (Gm), gravel mass content in the 0-5 and 5-10 cm soil depths [Gmc (0-5 cm), Gmc (5-10 cm)], and their relationships in the land graveling areas of the Alxa Plateau were assessed and analyzed using one-way analysis of variance, Duncan multiple comparisons, univariate linear regression, and correlation analysis. The average total Gc was 39.49% and the average total Gm was 3544.04 g·m-2. The Gc and Gm values at 4-8 and 8-16 mm were significantly higher when compared with the other particle sizes (P < 0.05). The coefficients of variation for Gc and Gm with a particle size of 4-8 mm were the smallest and most stable. The spatial distribution patterns of the Gc and Gm showed gradual increases from east to west and south to north. Different particle sizes (total) of the Gm and Gc showed extremely significant linear regression (P < 0.01 ), Gm could also be a good evaluation of the land graveling level. According to the classification threshold at the graveling level for Gc, the corresponding classification for Gm was determined. Except for the 2-4 mm and > 32 mm particles, the correlations between particle sizes in the Gc, Gm, and Gmc in the 0-5 cm soil layer were significantly greater when compared with the 5-10 cm soil layer, and the correlations between total Gc, Gm, and Gmc in the 0-5 cm soil layer were significantly greater when compared with the 5-10 cm soil layer. A surface gravel coverage threshold of 25% was determined for the Gobi, which is a graveling land type. The results of this study provide indicator data on which to base the monitoring and assessment of graveling land in the Alxa Plateau and other regions. Figures and Tables | References | Related Articles | Metrics

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Response mechanisms of nitrate and ammonia nitrogen concentrations to hydrological processes in the riparian hyporheic zone of pastoral areas XUE Dongyuan, HU Haizhu, ZHANG Jinning, REN Jiawei 2023, 40 (6):  937-948.  doi: 10.13866/j.azr.2023.06.09 Abstract ( 153 )   HTML ( 6 )   PDF (8611KB) ( 309 )   In pastoral and irrigated agricultural areas, nitrogen-containing livestock, poultry manure, and nitrogen fertilizers can enter the surface water and groundwater from the soil, and this is the main source of non-point source pollution in basins. The riparian hyporheic zone acts as an effective barrier to reduce the nitrogen pollution load. Understanding the mechanisms of the migration, transformation, and removal of nitrogen in riparian hyporheic zones is key to controlling nitrogen pollution in the whole basin. In this study, an upper reach of the Xilin River, located in typical pastoral areas, was selected and its water levels, ammonia (NH4+) and nitrate (NO3-) concentrations, as well as the related environmental factors of the river water and riparian groundwater during the summer flood season, were continuously monitored. Based on the high-solution measurements, a water flow and nitrogen reactive transport model of the riparian hyporheic zones was established using FEFLOW. The model fitted using the measured data was found to accurately reproduce the water level dynamics and two main nitrogen concentrations in the riparian hyporheic zone. The results indicate that there is a high risk of nitrogen pollution in the riparian zones during the summer flood season. The NH4+ concentration in the riparian zones can increase from 0.2 mg·L-1 before rainfall events to 7.23 mg·L-1 after rainfall events, and the NO3- concentration can increase from 1 mg·L-1 to 8.27 mg·L-1. Both measured and simulated results show that the nitrogen dynamics in the hyporheic zone are closely related to hydrological processes such as rainfall events and groundwater-surface water exchange. During rainfall events, NO3- with high mobility was found to infiltrate from the river and the ground surface into the riparian zone due to the leaching effect, resulting in a significant increase in the concentration. Meanwhile, the groundwater-river water exchange enhanced by rainfall events can further regulate NO3- and NH4+ concentrations in the riparian hyporheic zone by controlling the input of nutrients and affecting the biogeochemical nitrogen cycles. This study preliminarily reveals the buffering mechanisms of pastoral riparian zones in the hydrological and biogeochemical processes involving nitrogen and provides scientific references for the nitrogen pollution control in pastoral areas. Figures and Tables | References | Related Articles | Metrics

Plant Ecology

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Potential geographical distributions of Tugarinovia in China under climate change scenarios ZHAO Yanfen, PAN Borong 2023, 40 (6):  949-957.  doi: 10.13866/j.azr.2023.06.10 Abstract ( 145 )   HTML ( 6 )   PDF (6933KB) ( 179 )   Tugarinovia is a genus that is endemic to the Alashan Desert in China. It is crucial for the conservation of Tugarinovia to predict the impact of climate change on its potential geographical distribution. This study was based on 34 sites of distribution of Tugarinovia in China and 22 environmental variables. The current and future (2050s and 2070s) changes in the pattern of distribution of Tugarinovia under three shared socio-economic paths (SSP1-2.6, SSP2-4.5, and SSP5-8.5) in China were simulated using a maximum entropy (MaxEnt) model. The ability of model to predict these changes was verified by the area under curve (AUC) value under the receiver operating characteristic (ROC) curve, and the primary environmental factors that affect its distribution were analyzed using the Jackknife method and comprehensive contribution rate. The results showed the following: (1) The MaxEnt model has high simulation accuracy (AUC=0.992), and altitude, the warmest quarterly precipitation, the coldest quarterly precipitation, and annual average temperature are the dominant environmental factors that affect the geographical distribution of the Tugarinovia. (2) Currently, the suitable and highly suitable areas for Tugarinovia are both limited, with a suitable area of 37.08×104 km2 and a highly suitable area of 6.89×104 km2, which are primarily distributed along the Yinshan and Helan Mountains in a fragmented manner. (3) The future three climate scenarios suggest that the highly suitable areas of Tugarinovia will overall increase and display a significant increase under the SSP5-8.5 climate scenario. The centroid of its suitable area mainly migrates to the east (Alxa Left Banner). Figures and Tables | References | Related Articles | Metrics

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Nutrient addition and disturbance effects on the community composition and assembly in a desert steppe QIAO Jingjuan, ZUO Xiao’an, YUE Ping, WANG Guolin, WANG Jingyuan, WANG Zezhou 2023, 40 (6):  958-970.  doi: 10.13866/j.azr.2023.06.11 Abstract ( 198 )   HTML ( 10 )   PDF (8361KB) ( 305 )   The effects of short-term nutrient additions (NPKμ, 10 g·m-2) and disturbances on the species diversity, functional traits, soil properties, and community assembly mechanisms of the herbaceous community in the Urat desert steppe were examined. A mixed linear model, principal component analysis, and null model methods were utilized and both disturbance and interaction treatments were found to significantly reduce species richness and β diversity. Short-term nutrient additions significantly reduced soil pH but increased soil electrical conductivity. Six functional traits of the dominant species (i.e. Stipa glareosa, Peganum harmala, Salsola collina, Corispermum mongolicum) and six community-weighted mean significant changes under the disturbance and nutrient addition treatments were identified. The disturbance and nutrient additions promoted the transformation of the dominant species in the community from conservative strategies to acquisitive strategies. The results of the two null models revealed that community assembly under the control tended to be a stochastic process, while the disturbance and interaction treatments tended to be deterministic processes, and that of the nutrient addition treatments tended to be weaker deterministic processes. Plant communities in the desert steppe responded and adapted to the nutrient additions and disturbances through changes in the dominant species and their crucial functional traits. Figures and Tables | References | Related Articles | Metrics

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Population dynamics of natural Haloxylon ammodendron in the eastern margin of Badain Jaran Desert MAO Mao, MENG Zhongju, DANG Xiaohong, ZHAO Feiyan, WANG Dehui, CHAI Xiangxian 2023, 40 (6):  971-978.  doi: 10.13866/j.azr.2023.06.12 Abstract ( 194 )   HTML ( 12 )   PDF (5909KB) ( 227 )   The purpose of this study was to analyze the population structure and dynamic characteristics of the natural Haloxylon ammodendron forest in Badain Jaran Desert, revealing the renewal process and future development trend of this Haloxylon species. This work also involved preparation of a static life table, survival rate curves, mortality and disappearing rate curves, population dynamic change index, and a time-series forecasting model. The results showed that: (1) The age structure of this species belongs to the “J” type, with abundant seedlings. (2) The survival curve belongs to the Deevey-II type, and the disappearance and mortality rates have similar trends, both with maximum and minimum values at ages X VII, and IV. (3) The number dynamic change index is greater than 0, indicating that this species has a growing population. (4) The results of time-series prediction analysis showed that the number of individuals will increase. Studies have shown that the natural H. ammodendron population is a stable growing population. In view of the low survival rate of young in this population, it is recommended to manually intervene in the growth of H. ammodendron seedlings to improve their survival rate. Figures and Tables | References | Related Articles | Metrics

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Differences in moss crust development between Artemisia ordosica and Salix pasmmophia shrubs MO Qiuxia, SONG Wei, BU Chongfeng, WANG Chun, WANG Heming, LI Yahong 2023, 40 (6):  979-987.  doi: 10.13866/j.azr.2023.06.13 Abstract ( 139 )   HTML ( 5 )   PDF (6727KB) ( 89 )   The soil properties and moss crust development indices in typical Artemisia ordosica and Salix pasmmophia shrub land plots in the sandy area of Mu Us Sandland have previously been analyzed in combination with allelopathic tests of the extracts from the different shrub organs. The results showed that moss crust development in A. ordosica shrub land was better than that in S. pasmmophia shrub land, but the reason is unclear, and elucidating it is the aim of this investigation. A significant difference in the moss crust coverage between the two kinds of shrubs (P < 0.05) was identified. The total moss crust coverage and sub-canopy and inter-canopy crust coverage were as follows: A. ordosica > S. pasmmophia, and the total moss crust coverage and subcanopy and intercanopy crust coverage in the A. ordosica shrub land were 1.6, 2.9, and 1.1 times higher than those in the sand S. pasmmophia shrub land, respectively. Furthermore, there was no significant difference in moss crust thickness between the two kinds of shrubs (P > 0.05). Pearson correlation analysis showed that the moss crust coverage in the sub-canopy was significantly positively correlated with the soil water content, moss crust thickness in the sub-canopy was significantly positively correlated with silt content, and inter-canopy moss crust coverage was significantly positively correlated with soil water and clay content (P < 0.05). The higher soil water, clay, and silt contents in the A. ordosica shrub land promoted the development of moss crusts. The aqueous extracts from the roots, stems, and leaves of the A. ordosica and S. pasmmophia inhibited the development of moss crusts; that is, the allelopathic synthesis effect (SE) was negative. Specifically, the allelopathic inhibitory effect of the 0.2 g·mL-1 aqueous extract of the S. pasmmophia leaves was the strongest, with an SE of -0.95. The inhibitory effect was significantly higher than that of the A. ordosica leaves (SE = -0.65). It can be inferred from the results that the higher soil water, clay, and silt contents in the A. ordosica shrub land and the significant allelopathic inhibition of the S. pasmmophia leaves on the moss crusts led to the improved development of moss crusts in A. ordosica shrub land when compared with S. pasmmophia shrub land. Figures and Tables | References | Related Articles | Metrics

Ecology and Environment

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Evaluation of an oasis-urban-desert landscape and the related eco-environmental effects in an arid area ZOU Yi, MENG Jijun 2023, 40 (6):  988-1001.  doi: 10.13866/j.azr.2023.06.14 Abstract ( 216 )   HTML ( 9 )   PDF (16162KB) ( 168 )   Oasis, urban, and desert areas are important landscape types in the inland river basins of arid zones. The Heihe River is the second largest inland river in the northwest arid zone of China. With the socio-economic development of the basin, ecological and environmental problems have become increasingly prominent. In this study, kernel density estimation and landscape structure metrics were applied to analyse the spatio-temporal pattern and transition characteristics of the oasis-urban-desert areas in the Heihe River Basin from 2000-2020. A multivariate regression tree model was used to examine the trade-off and synergy relationships in the oasis-urban-desert landscapes. The remote sensing ecological index (RSEI) and ecological contribution rates of landscape transition, were also used to assess the eco-environmental effects of the oasis-urban-desert landscapes. Deserts were found to be widespread in the Heihe River Basin, oases were concentrated along the middle and lower reaches of the river, and urban areas accounted for the smallest proportion, and their spatial distributions and scale of their structures were found to be closely related to oases. The transition of oasis-urban-desert landscapes in the Heihe River Basin can be summarized into three periods: the domination of agricultural activities (2000-2005), rapid industrial development (2005-2015), and coordinated development transformation (2015-2020). Temperature, GDP, altitude, and precipitation were the main factors affecting the trade-offs and synergies between oasis-urban-desert landscape transitions. From 2000-2020, the eco-environment effects of the landscape transitions were dominated by positive eco-environment effects, with farmland expansion being the dominant factor for positive effects, and the degradation of farmland, water area, and grassland the main factors for negative effects. The findings of this study will provide theoretical guidance for the implementation of future ecological protection and high-quality development strategies for inland river basins in arid zones. Figures and Tables | References | Related Articles | Metrics

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Spatial and temporal evolution of ecological vulnerability and its influencing factors in the Hehuang area QI Runze, PAN Jinghu 2023, 40 (6):  1002-1013.  doi: 10.13866/j.azr.2023.06.15 Abstract ( 207 )   HTML ( 17 )   PDF (12155KB) ( 125 )   An evaluation index system was constructed based on a concept model for exposure sensitivity adaptation ecological vulnerability. A projection pursuit model and genetic algorithm were used to determine the index weight, and the ecological vulnerability index was calculated for the Hehuang region. Spatio-temporal scanning was used to explore the spatial aggregation characteristics and spatio-temporal change laws for ecological vulnerability. The factors influencing ecological vulnerability were explored with the aid of geographical detectors. From 2000 to 2020, the ecological vulnerability of the Hehuang region was found to predominately be light and medium, with obvious regional differences in the spatial distribution. Ecological vulnerability has obvious characteristics for time and local spatial aggregation. High value aggregation and low value aggregation can coexist, and spatial aggregation is mainly distributed in Gansu Province. From 2000 to 2020, the ecological vulnerability of 53.36% of the land decreased. The most influential factor on ecological vulnerability is vegetation coverage, followed by desertification index, net primary productivity of vegetation, drought index, habitat quality index, and altitude. Figures and Tables | References | Related Articles | Metrics

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Spatio-temporal changes and driving forces in the ecological environment of Altay City determined using an MRSEI model LIU Xiao, GUO Peng, QI Jiafeng, DU Wenling, ZHANG Ruqian, ZHANG Kun 2023, 40 (6):  1014-1026.  doi: 10.13866/j.azr.2023.06.16 Abstract ( 215 )   HTML ( 20 )   PDF (17468KB) ( 118 )   To evaluate the ecological environment of Altay City in Xinjiang in a timely, objective, and quantitative manner, an improved remote sensing ecological index (MRSEI) was constructed based on multi-source remote sensing data. The spatial and temporal variation characteristics were then analyzed by combining a standard deviation ellipse and gravity center migration model. A geographical detector model was used to detect the five indicators, which were greenness, dryness, humidity, temperature, and air quality. (1) From 2015 to 2021, the greenness and humidity indexes of Altay City showed a significant positive correlation with the ecological environment in the region. In contrast, the three indexes for temperature, dryness, and air quality showed significant negative correlations. (2) From 2015 to 2021, the average value of the MRSEI in Altay City increased. The spatial migration ability of ecological index areas I and II was strong, while III-V were relatively stable in the spatial structure. The center of gravity for ecological index areas I-IV moved north, while the center of gravity for area V moved south, indicating that the distribution of the high ecological index in the south of Altay City increased significantly. (3) The dominant factors causing the changes in the eco-environmental quality differed each year. The spatial evolution of eco-environmental quality in Altay is the result of multiple factors. (4) The differences in spatial distribution and the differences between the MRSEI and RSEI data are related to the spatial distribution of AOD, indicating that even if Altay City had improved air quality, AOD would still have an impact on the ecological quality of the spatial distribution. From 2015 to 2021, the ecological environment of Altay City was thus found to be affected by many factors and tended to improve toward the south. Figures and Tables | References | Related Articles | Metrics