Authority in Charge: Chinese Academy of Sciences
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                    Geography, Chinese Academy of Sciences;
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15 September 2021, Volume 38 Issue 5 Previous Issue   
Weather and Climate
Spatial heterogeneity of annual precipitation δ18O over the Tibetan Plateau based on the use of a geographical detector
XI Wentao,GAO Jing
2021, 38 (5):  1199-1206.  doi: 10.13866/j.azr.2021.05.01
Abstract ( 68 )   HTML ( 12 )   PDF (6959KB) ( 41 )  

The annual precipitation δ18O from 24 stations over the Tibetan Plateau was analyzed based on the use of a geographical detector, which was applied to probe the spatial heterogeneity of precipitation δ18O and to quantitatively understand the drivers. This method was used to successfully reflect the spatial heterogeneity of the annual precipitation δ18O over the Tibetan Plateau. The latitude, altitude, longitude, and precipitation amounts respectively explained 0.82, 0.71, 0.57, and 0.49 of the spatial variation in annual precipitation δ18O. Additionally, the combined effects of different factors enhanced the explanation of spatial variation. The possible influences of latitude, precipitation amount, altitude, and temperature on annual precipitation δ18O and seasonal variations in influential factors that cause the spatial heterogeneity of precipitation δ18O were discussed. We conclude that latitude has the strongest explanatory power in relation to the spatial heterogeneity of annual, summer, and winter mean precipitation δ18O over the Tibetan Plateau.

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Characteristics of the radiation balance and surface albedo of a typical alpine wetland in Qiangtang Plateau
QIANG Yaohui,WANG Kunxin,MA Ning,ZHANG Yinsheng,GUO Yanhong
2021, 38 (5):  1207-1215.  doi: 10.13866/j.azr.2021.05.02
Abstract ( 40 )   HTML ( 16 )   PDF (6522KB) ( 32 )  

The energy exchange process and its effects on wetlands in the Qiangtang Plateau have an important impact on the local climate. This study is based on the radiation data observed from June 2017 to June 2020 in Xainza—a typical alpine wetland located in the Qiangtang Plateau—and comprehensively analyzes the characteristics of seasonal, monthly, daily, and hourly weather radiation and albedo. The results show that all the radiation components present obvious seasonal “U”-shaped patterns. The maximum downward shortwave radiation is 301.1 W·m-2, and, in June the maximum upward longwave radiation is 371.5 W·m-2, yet the minimum of both appeared in January. Downward shortwave radiation, upward and downward longwave radiation, and net radiation all show obvious seasonal patterns, characterized by “U”-shaped changes. The hourly value of shortwave radiation in each season is the highest in spring, followed by summer and autumn, and the lowest is detected in winter. Longwave radiation and net radiation are highest in summer and lowest in winter. The radiant flux on sunny days in each season is relatively smooth, and the changes in cloud cover and precipitation are irregular; the average yearly surface albedo is 0.23, the lowest detected in summer and the highest in winter, reaching up to 0.63 on snowy days. These results can contribute to revealing the dynamic changes of the radiation budget occurring on the typical alpine wetland of Xainza, in the Qiangtang Plateau, and to clarifying the influence of such variation on the thermal effect.

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Analysis of the characteristics of the easterly low-level jet in Tarim
YANG Xia,ZHOU Hongkui,ZHAO Keming,XU Tingting
2021, 38 (5):  1216-1225.  doi: 10.13866/j.azr.2021.05.03
Abstract ( 33 )   HTML ( 4 )   PDF (5397KB) ( 22 )  

The low-level jet has an important effect on the occurrence and development of events such as rainstorms, sandstorms, and severe convection. We analyzed conventional sounding data from 1981 to 2020 to determine the characteristics of the low-level jet in the east wind of Tarim. Our findings reveal that, from 1981 to 2020, there was a decreasing trend in the days, mean wind speed, and vertical wind shear of the easterly low-level jet, whereas there was an increasing trend in the mean height of this jet. The easterly low-level jet in Tarim occurred on 74.2 days per year, on average. The low-level jet of the East wind appears 74.2 days per year, its annual average wind speed is 16.3 m·s-1, and its average height is 1555.1 m. The vertical wind shear in the upper layer was 9.94×10-3 s-1 and that in the lower layer was 7.33×10-3 s-1. The number of days, wind speed, and vertical wind shear were highest in spring, followed by summer, and lowest in winter, whereas the height was greatest in winter, followed by autumn, and lowest in spring. There was a considerable monthly difference in the low-level easterly jet in Tarim; the days and vertical wind shear of the upper layer were at the maximum in May and the minimum in December. The average wind speed was at its maximum in May and its minimum in December. The average height was greatest in January and lowest in April. The vertical wind shear at the lower level was at its maximum in April and its minimum in December. The average duration of the easterly low-level jet in Tarim was 2.3 days, with the longest duration in summer and the shortest in winter. There was a rapid decline in the frequency of the easterly low-level jet as the duration increased. The most frequent easterly low-level jets were those that lasted for one day; these accounted for 48% of the total frequency. Those with a duration of less than three days accounted for 76.0% of the total. In conclusion, the easterly low-level jet in Tarim, which is located in the inland arid region, belongs to the large-scale low-level jet, which is different from the low-level jet in China’s monsoon region.

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Comparative analysis of different types of precipitation characteristics in the northern foot of Qilian Mountain under the influence of topography
FU Shuangxi,ZHANG Hongfen,YANG Lijie,ZHAO Yujuan,ZHANG Kexin,CHEN Qi
2021, 38 (5):  1226-1234.  doi: 10.13866/j.azr.2021.05.04
Abstract ( 41 )   HTML ( 7 )   PDF (6657KB) ( 757 )  

The effects of precipitation on Qilian Mountain and the process of heavy rain in different terrains were evaluated using data from the Zhangye CINRAD/CC Doppler radar, conventional meteorological observation, and L-band second radiosonde. The different types of heavy rain formation mechanisms and physical conditions depend on the effect of terrain on the precipitation. The large value area for every type of precipitation is concentrated in the mountainous area or the northern slope of the mountain. The forced uplift effect caused by terrain elevation was significant. The blocking, convergence, and uplift of minor local terrains are more prominent in the process of strong convective precipitation. The training effect produced by the overall uplift due to the significant topography and the convergence effect caused by the small local topography resulted in a short-time heavy precipitation process. In systematic cold air affecting precipitation, the main topographic action form is the strong airflow echo in the bearing layer, which is continuously generating and is being maintained for a long time under the influence of a “pocket” topographic shape. The representational terms of upper-level cold cloud precipitation and lower-level warm cloud precipitation differed in the radiosonde data.

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Prediction of annual precipitation in the Northern Slope Economic Belt of Tianshan Mountains based on a EEMD-LSTM model
YANG Qian,QIN Li,GAO Pei,ZHANG Ruibo
2021, 38 (5):  1235-1243.  doi: 10.13866/j.azr.2021.05.05
Abstract ( 26 )   HTML ( 9 )   PDF (5765KB) ( 31 )  

Precipitation prediction is both an essential and challenging component of modern climate prediction. In the precipitation prediction in Xinjiang, the research and application of coupling models are very limited. Therefore, this paper attempts to establish the ensemble empirical mode decomposition (EEMD) and long short-term memory (LSTM) neural network coupling models to predict precipitation in the Northern Slope Economic Belt of Tianshan Mountains. Firstly, the precipitation data recorded in the study area during 55 years, from 1965 to 2019, were decomposed into four stationary components and trend terms using the EEMD, and the quasi period of each component was obtained by spectral analysis, which provided the basis for the subsequent training of the LSTM model. Then, each EEMD component was trained into the LSTM network model, and the models were used for predictions. The reconstruction and comparison of the results revealed that the average relative error and root mean square error of the 2010-2019 model were 13.38% and 38.03 mm, respectively. Therefore, it is inferred that the EEMD-LSTM coupling model can achieve a better precipitation prediction accuracy in the study area. The model was used to predict annual precipitation in the Northern Slope Economic Belt of Tianshan Mountains from 2020 to 2029; within this period, six years presented more and four years presented less precipitation. Year 2025 is predicted to be an extremely humid year with more than 20% of precipitation in excess; while 2021 is anticipated as an extremely dry year, with expected precipitation amounting to less than 200 mm. This study explored a new method of precipitation prediction in an arid area, and provided a reference for meteorological disaster prevention and mitigation.

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Temporal and spatial characteristics of 0 cm surface temperature in Shaanxi Province during 1958 to 2017 under climate change
XIAO Weiwei,AN Bin,SHI Jiaqi
2021, 38 (5):  1244-1253.  doi: 10.13866/j.azr.2021.05.06
Abstract ( 40 )   HTML ( 6 )   PDF (5643KB) ( 36 )  

We analyzed the temporal and spatial variation characteristics of 0 cm surface temperature in Shaanxi Province during 1958 to 2017 based on monthly surface and air temperature data from 18 meteorological observation stations, by using linear fitting, Mann-Kendall nonparametric tests and spatial interpolation. The results indicated that annual and seasonal 0 cm surface temperature had a significant upward trend (P<0.01) except summer during 1958 to 2017 in Shaanxi Province. The climate tendency showed a trend as winter [0.42 ℃·(10a)-1]>spring [0.38 ℃·(10a)-1]>annual [0.27 ℃·(10a)-1]>autumn [0.23 ℃·(10a)-1]>summer [0.07 ℃·(10a)-1]. We observed that the abrupt changes in annual and seasonal surface temperatures were concentrated at the end of 1990s. After the mutation, the largest warming range was in spring, followed by winter, annual, summer, and autumn. Moreover, we found that the annual and seasonal surface temperatures showed a spatial distribution of “high in the South and low in the north”. The annual, spring, and winter surface temperatures of all meteorological stations showed a significant upward trend (P<0.05), while 33% of stations in summer and 83% in autumn had the same characteristics. Additionally, annual and seasonal surface-air temperature difference showed an upward trend except summer during 1958 to 2017 in Shaanxi Province. The climate tendency showed a trend as winter [0.17 ℃·(10a)-1]>spring [0.1 ℃·(10a)-1]>annual [0.07 ℃·(10a)-1, P<0.01]>autumn [0.02 ℃·(10a)-1, P<0.01]>summer [-0.01 ℃·(10a)-1]. Finally, there is a significant positive correlation between the annual average temperature, four seasons temperature and 0 cm surface temperature in Shaanxi Province in recent 60 years, which is characterized by autumn>spring>annual>summer>winter.

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Analysis of spatial and temporal distribution characteristics of cloud water resources in Qinghai Province from 2014 to 2018
ZHANG Yuxin,MA Xueqian,HAN Huibang,ZHANG Pengliang,LIU Na
2021, 38 (5):  1254-1262.  doi: 10.13866/j.azr.2021.05.07
Abstract ( 29 )   HTML ( 5 )   PDF (5834KB) ( 14 )  

Based on the ERA5-hour reanalysis data (with a horizontal resolution of 0.25°×0.25°), the precipitation, water vapor, hydrocoagulation, and aerial cloud water resources of Qinghai Province were analyzed from 2014 to 2018, using the CCR-MEM and EOF methods. The results showed that the annual precipitation distribution in Qinghai Province was characterized by a greater decline in the southeast and a more limited decline in the northwest, and the spatial distribution was extremely uneven. The water vapor distribution zones were mainly the Qaidam (Qinghai Lake) and Hehuang Valley in the north, the Hoh Xil (Zhiduo) heterotopia distribution zone in the southwest and the Bayan Kera Mountain-Yellow River bend area in the southeast. The distribution characteristics of hydrocoagulants and precipitation were more similar in the southeast than in the northwest, and more in the windward slope of the mountain range.The average precipitation efficiency of water vapor and water condensate was 0.3% and 14%, respectively. The total cloud water resources measured 70.8 billion tons, and were most abundant in the south and southeast of Sanjiangyuan area. The cloud water resources from the southern foot of Qilian Mountain to the extension zone of Xining were the second highest in this area In the decomposition of the EOF method, the main spatial distribution of cloud water resources showed a step-like change in the northeast and southwest. It is urgent to carry out targeted weather modification operations, based on the transport of water vapor and hydrocoagulants and on the distribution characteristics of cloud water resources, combining different regions and different landforms.

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Isotopic characteristics and water vapor sources of precipitation in the Kashi River Basin
ZENG Kangkang,YANG Yuhui,HU Yicheng,FENG Xiancheng
2021, 38 (5):  1263-1273.  doi: 10.13866/j.azr.2021.05.08
Abstract ( 56 )   HTML ( 3 )   PDF (9760KB) ( 45 )  

Using the precipitation isotopic data from July 2017 to June 2018 in the mountainous area of the Kashi River Basin, in addition to the meteorological data of and precipitation in this mountainous area, we have analyzed and discussed the seasonal variation characteristics of δ18O, δD, and d-excess in precipitation, along with the relationship between δ18O and temperature and precipitation. We used a hysplit model to trace and analyze the water vapor source of atmospheric precipitation in this mountainous area. Our findings reveal that: (1) The hydrogen and oxygen isotopes in the precipitation of the Kashi River Basin fluctuate over a wide range, with obvious seasonal variation; i. e., enrichment in summer and depletion in winter. This is due to high temperatures and a strong evaporation fractionation in summer and low temperatures and a weak evaporation fractionation in winter; (2) The intercept and slope of the local meteoric water line equation in the study area are higher than are those of the global meteoric water line, indicating that the local recycled water vapor has a strong effect on high-altitude rivers. The relationship between δ18O and δD in different precipitation types is obviously different. In summer, the evaporation fractionation of δD is greater than is that of δ18O, and both the slope and the intercept of the local meteoric water line are smaller. In winter, the evaporation fractionation of δD is obviously weakened, and the slope and intercept of the snowfall local meteoric water line are both larger; (3) There is an obvious temperature effect on the isotopes of precipitation in the Kashi River Basin. In summer, the temperature is high and the isotope are enriched. The annual precipitation effect is not significant, but there is a certain precipitation effect in autumn; (4) On the annual scale, there is a relatively large surplus of deuterium, indicating that it is affected greatly by the water vapor from the Atlantic Ocean and the local recycling water vapor. In seasonal terms, the precipitation comes from the Atlantic Ocean in summer and autumn, and the deuterium surplus is high, whereas the precipitation comes from the Arctic Ocean in winter and spring, and the deuterium surplus is low; (5) In summer and autumn the precipitation comes mainly from westerly circulation and local recycled water vapor. The precipitation formed by Atlantic water vapor accounts for 68.6% of the total annual precipitation, whereas the precipitation formed by local recycled water vapor accounts for 17.1%. In winter, the precipitation is affected by westerly circulation and the Arctic air mass, and the precipitation formed by Arctic water vapor accounts for 14.3% of the total annual precipitation.

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Applied Climate
Heatwave changes and the potential causes in Xinjiang from 1961 to 2018
ZHANG Taixi,FAN Jing,LI Yuanpeng,YU Xingjie
2021, 38 (5):  1274-1284.  doi: 10.13866/j.azr.2021.05.09
Abstract ( 33 )   HTML ( 3 )   PDF (4802KB) ( 30 )  

Given the background of global warming, heatwave changes have attracted considerable attention: High temperature events not only cause severe drought, which greatly harms ecological vegetation and agricultural production, but also have a substantial effect on the production activities of water conservancy, industrial and mining enterprises, and human health: Xinjiang is one of the areas in China with a high incidence of extreme high temperature, and there have been frequent extreme high temperature events in this area in recent years: These events in Xinjiang have the characteristics of a wide range of influence, long duration, high outbreak intensity, and an early start and a late finish: The daily maximum temperature data are used to ascertain the heatwave changes in Xinjiang based on the quality-controlled station data from April to September of 1961 to 2018: Moreover, the NCEP reanalysis data and the sea surface temperature observations are employed to understand the potential reasons for heatwave changes: We have taken the temperature from 1981 to 2010 as the climatic mean: Our findings reveal that there was a significant increase in the number of heatwave days in Xinjiang under the local warming and wetting climate: This increase was more pronounced for extreme heatwaves (Tmax ≥ 40 °C), whereas we found a decreasing trend for the occurrence of moderate heatwaves (37 °C > Tmax ≥ 35 °C): We found that the first heatwave is beginning earlier than previously (mid-April at the earliest), and the last heatwave is finishing later than before (late September at the latest): The increase of heatwave is most pronounced in April; however, it makes a limited contribution to the total heatwave change: In North Xinjiang, the abrupt transition occurs earlier than does that in South Xinjiang: We further show that there is a strong correlation between circulation changes and the heatwave days in Xinjiang: When the 200 hPa geopotential height over Balkhash Lake and its surrounding areas is higher (lower) than normal, the number of heatwave days in Xinjiang is larger (smaller): The variation of 200 hPa geopotential height over Balkhash Lake and its surrounding areas can be traced back to anomalies in the sea surface temperature (SST) in the equatorial Atlantic: The South Asian High would control a larger area, from Balkhash Lake to Mongolia, when the equatorial Atlantic SST is higher, which could result in more heatwave days in Xinjiang: As the reasons for the delay of the initial high temperature of some stations with reduced high temperature days in Xinjiang and the mechanism of influence of SST on high temperature events in Xinjiang remain unclear, the above problems require further study.

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Characteristics of summer extremely high temperature in Ningxia in connection with Arctic sea ice
WANG Dai,WANG Suyan,WANG Fan,LI Xin,YANG Jianling
2021, 38 (5):  1285-1294.  doi: 10.13866/j.azr.2021.05.10
Abstract ( 25 )   HTML ( 3 )   PDF (4573KB) ( 5 )  

The study of the relationship between the extremely high temperature in the Ningxia area and Arctic sea ice within the current climate change scenarios is a great significance to reveal the impact of Arctic sea ice on summer extreme temperatures. Based on maximum temperature data derived from meteorological stations in Ningxia, NCEP/NCAR reanalysis and Arctic sea ice data from 1961 to 2017, the extremely high temperature index was calculated, and its threshold was defined as the 90th percentile of daily maxima, centered on a 31 day window. Subsequently, the climatic characteristics of the summer extremely high temperature in Ningxia, and its relationship with Arctic sea ice were analyzed using the statistical methods of regression, correlation, resultant and so on. Results show that, in the area, the total intensity, frequency of events and the longest lasting days with extremely high temperature in summer had a significantly increasing trend since 1961, and presented obvious interdecadal changes. In particular, the period from the late 1990s to the mid-2000s was the fastest growing interval. After the late 2000s, the increasing trend slowed down, but the interannual variation rate remained high. In addition, the above mentioned extremely high temperature index in summer generally increased across Ningxia, and strengthened in the 2000s and 2010s, in particular, the increase in the northern region was greater than that in the central and southern regions. In the intenser year of extremely high temperature intensity in Ningxia, the northern region of China was control under the positive anomaly field with 500 hPa geopotential height field, and Ningxia was in the south of it. This impeded the cold air in the north from flowing through, which resulted in high temperature detected in summer in Ningxia. In the weak year, the circulation mode over Ningxia was high in the west and low in the east, which was advantageous to the high latitude cold air inflowed southward, but disadvantageous to enhanced extremely high temperature. In the early spring, when the sea ice density in the Greenland Sea, Barents Sea, and Kara Sea is high, to excited the wave train on the 500 hPa geopotential height field steadily propagated from north to south and west to east, that resulting in the Ural Mountain High Ridge weakened, and the middle and high latitude area of Eurasia dominated by zonal circulation, and then caused the strong summer extremely high temperature intensity in Ningxia. The present study aimed to deepen the understanding of the variation of summer extremely high temperature in the Ningxia region, as well as to provide atheoretical basis for their prediction.

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Spatiotemporal characteristics of extreme precipitation in Shaanxi Province based on the regional L-moments method
LUO Zhiwen,WANG Xiaojun,LIU Mengyang,KE Hang,WAN Ting,YIN Yixing
2021, 38 (5):  1295-1305.  doi: 10.13866/j.azr.2021.05.11
Abstract ( 17 )   HTML ( 2 )   PDF (7877KB) ( 4 )  

Extreme precipitation can cause severe disasters in arid and semi-arid regions, such as in the Shaanxi Province of Northern China. To investigate the spatiotemporal characteristics of extreme precipitation in the Shaanxi Province, this study adopted the daily precipitation data of 58 meteorological stations from 1971 to 2015 with no missing observations and relatively uniform distribution and used the maximum precipitation on the 1st, 3rd, 5th, and 7th day to represent the extreme precipitation. The regional L-moments method was further applied to study the temporal and spatial characteristics of the extreme regional precipitation, which involves the screening and processing of precipitation data, identification of homogeneous regions, goodness-of-fit test, quantile estimation for each region, comparison between at-site and regional estimation, deriving regional growth factors, and mapping of the spatial patterns of extreme precipitation. The results and conclusions of the study were: (1) Shaanxi Province can be divided into six hydrometeorological homogeneous regions, among which GEV distribution in each homogeneous region has the best simulation effect, and the estimated optimal quantiles of each homogeneous region are in good agreement with the measured value of the same frequency. (2) The estimated extreme precipitation quantiles calculated by the regional analysis method have better robustness and accuracy compared with the single-station analysis method, especially more significant in calculating extreme precipitation over a long period. (3) When the return period is once every 2 years, the regional growth factor of southern Shaanxi is greater than that of northern Shaanxi; when the return period is once every 5 years, the opposite is true, and with the increase of the return period, the regional growth factor and the difference between southern Shaanxi and northern Shaanxi also increase. (4) In the 100-and 50-year return periods, extreme precipitation is large in the south, centered in the east, the Xianyang-Shangluo region in the middle, the northwest corner of Yan’an in the west, and the west of Yulin are small. The distribution characteristics of extreme precipitation are related to the unique geographical characteristics of Shaanxi Province, especially the east-west Qinling Mountains, which block the water vapor transmission to the north, causing differences in extreme precipitation between the north and south.

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Temporal distribution and variation characteristics of sandstorms in Hotan Prefecture
Mamatabdulla Emer,Ayxamgul Mamat,Sayran Wayli,CHEN Tianyu,Bupatima Aibaidulla,Ayxam Mamattuhti,MAO Weiyi
2021, 38 (5):  1306-1317.  doi: 10.13866/j.azr.2021.05.12
Abstract ( 32 )   HTML ( 4 )   PDF (5462KB) ( 21 )  

Using the sandstorm monitoring data of four weather stations from 1961 to 2018, we have analyzed the temporal distribution characteristics and variation trend of sandstorm frequency and duration in Hotan. We also discuss the causes of long-term variation in sandstorms. Our chief findings reveal that Hotan has one of the highest occurrences of sandstorms in China, at 20.4 days per year. The frequency is highest in spring and summer, and the peak is in May. The sandstorms in December are the longest in duration, and those in June are the shortest. The sandstorms that occur most often are those lasting for 1-30 min. Although sandstorms in Hotan might occur at any time of the day, we found that most appeared between 18:00 and 23:00, and those that occurred in the middle of the midnight to morning lasted the longest. In the Hotan region, sandstorms can appear from 16 different wind directions; the wind speed and frequency of sandstorms coming from the western path are higher than are those from the other paths. And those sandstorms in the study region can be caused by the wind which was at the maximum average speed of 3.0 m·s-1, and 87.5% of the storms occurred while the wind has not reach the standard. Over the last 58 years, the number of annual sandstorm days, the number of annual gale days, and the annual average maximum wind speed in Hotan have decreased significantly. Sandstorm frequency peaked in the 1960s and has decreased sharply since the 1990s. The durations of the sandstorms in the 1970s-1980s were the longest during the past century; the durations have shortened significantly since the 2000s. The decline in the frequency of sandstorms in Hotan Prefecture is related to the decreasing local gale frequency, the weakening of the daily maximum wind speed, and the improvement of the vegetation cover.

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Drought-wet variation of Changling Mountain in Southeast of Tengger Desert since 1872
QI Jing,JIAO Liang,CHEN Ke,QI Changliang,XUE Ruhong
2021, 38 (5):  1318-1326.  doi: 10.13866/j.azr.2021.05.13
Abstract ( 20 )   HTML ( 4 )   PDF (7121KB) ( 16 )  

The Changling Mountain in the Southeast of Tengger Desert, which is sensitive to climate change was selected as the study area. The correlation between PDSI (Palmer Drought Index) from May to July and tree-ring width chronology were strongthe (r=0.621, P<0.001). Drought was the main controlling climatic factor of the growth of dominant species Picea crassifolia in Changling Mountain through the analysis of correlation between tree-ring width chronologies and climate factors. By setting up a linear regression equation of tree-ring width chronology and PDSI, the drought-wet variation in the past 146 years was reconstructed. At the same time, there were four dry periods in all (1882-1894, 1915-1936, 1966-1978, and 1989-2015) in the past 146 years based on the reconstructed PDSI interannual variation. The period analysis results showed that the reconstructed sequence had periods of around 2 a, 2.6-3 a and 11 a, indicating that the driving factors of drought-wet variation were El Nino Southern Oscillation and sunspot activity in the study area. The research results provide a scientific basis for discussing the drought and wet variation rules in Northwest China and predicting changes in the subalpine forest ecosystem under the condition future climate change.

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Analysis of meteorological factors affecting drought in a desert steppe of the northern foot of Yinshan Mountain
YUCHI Wensi,MIAO Henglu,WANG Xingtian,GAO Tianming,WU Jiabin
2021, 38 (5):  1327-1334.  doi: 10.13866/j.azr.2021.05.14
Abstract ( 31 )   HTML ( 3 )   PDF (2593KB) ( 11 )  

Steppe is a key part of the ecological environment construction in the west region, and its ecosystem is very fragile. In recent years, desert steppe drought disasters occur frequently. Taking the Yinshanbeilu National Field Research Station of Desert Steppe Eco-Hydrological System in Inner Mongolia as the experimental area, the precipitation changes at different slope positions are monitored, the relationship and function between meteorological factors and drought index PA value are analyzed, and a regression model is constructed. The results show that: (1) the precipitation at different slope positions of the desert steppe at the north foot of Yinshan Mountain is: downhill>middle slope>uphill, and the corresponding drought index PA value is: uphillPA > middle slopePA>downhillPA (2) From the observation of each time scale, monthly scale analysis shows that there are different degrees of drought at each slope position, and the drought frequency is high; Seasonal scale analysis shows that light drought occurred only in winter; The annual scale analysis found that the region did not reach the drought threshold in recent 5 years. Overall, the average annual precipitation in this area is sufficient and there is no drought disaster. (3) The multiple regression model constructed according to the main meteorological factors such as precipitation, air temperature and wind speed and the drought index PA value is: YPA=78.799+0.255x1-3.395x2-1.831x3, R2=0.994, the fitting degree of the model is high, which can better reflect the drought situation in the region. It provides a theoretical basis for further studying the relationship between multi meteorological factors and various drought indicators, as well as constructing drought evaluation system.

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Soil Resources
Spatial distribution characteristics of grain size of surface soil in the sand-resitant belt of Minqin Oasis marginal
ZHAO Peng,ZHU Shujuan,DUAN Xiaofeng,CHANG Zhaofeng,KANG Caizhou,WANG Fanglin,WANG Yuqi,GAO Decai
2021, 38 (5):  1335-1345.  doi: 10.13866/j.azr.2021.05.15
Abstract ( 26 )   HTML ( 2 )   PDF (7985KB) ( 9 )  

Soil particle size is an important characteristic parameter of sand drift activity. Through field investigation and indoor test, this paper explored the grain size characteristics of surface soil at the windbreak and sand fixation forest with different spatial distribution, to evaluate the function of the sand barrier belt on the edge of Minqin Oasis. According to the results, the grain size composition in the surface soil of Haloxylon ammodendron-Artemisia desertorum-Agriophyllum squarrosum fixing forest in Baqu was mainly fine sand, medium sand, and very fine sand, which accounts for 33.47%, 26.08%, and 18.18%, respectively. The grain size composition in the surface soil of Nitraria tangutorum-Artemisia desertorum-Bassia dasyphylla fixing forest in Quanshanqu was dominated by fine sand, silt, and very fine sand, which accounts for 29.62%, 21.17%, and 18.87%, respectively. The grain size composition in the surface soil of Nitraria tangutorum-Phragmites australis- Salsola collina fixing forest in Huqu mainly consisted of fine sand, silt, and very fine sand, which accounts for 36.66%, 27.98%, and 22. 83%, respectively. Average particle size, Baqu (2.55 Φ) > Quanshanqu (3.5 Φ) > Huqu (3.94 Φ). Grain size sorting in Baqu (1.58 Φ) was poor, grain size sorting in Quanshanqu (2.29 Φ) and Huqu (2.10 Φ) were also very poor. The frequency curve of grain size in Quanshanqu and Huqu is of double peak type, while that in Baqu is of single peak type. The skewness is extremely positive, and the kurtosis is very narrow. The cumulative distribution curve of grain size shows that the aeolian sand activity in Baqu is more frequent and intense than that in the Quanshanqu and Huqu. The specie composition of the desert vegetation community determines the function of windbreak and sand fixation in the sand-blocking belt and then affects the grain size distribution of the topsoil. It suggested that forestation tree species with strong sand-fixing ability should be selected when the ecological protection system of sand-blocking belt is restored.

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Soil carbon and nitrogen content and path analysis under different land use patterns on the southern slope of Qilian Mountains
DIAO Erlong,CAO Guangchao,CAO Shengkui,YUAN Jie,YU Min,CHEN Zhen,ZHANG Zhuo,TONG Shan,ZHAO Meiliang
2021, 38 (5):  1346-1354.  doi: 10.13866/j.azr.2021.05.16
Abstract ( 24 )   HTML ( 3 )   PDF (2541KB) ( 5 )  

Taking the soils under four different land use types on the southern slope of Qilian Mountain as the research object, we used field sampling, laboratory analysis, and one-way ANOVA to analyze the TC and TN contents in surface (0-20 cm) and deep (20-50 cm) layers of soil. A path analysis method was used to reveal the direct and indirect effects of environmental factors on soil TC and TN. The results were as follows. (1) As a direct effect, the soil carbon and nitrogen interaction was significant, but pH had little direct effect on soil carbon and nitrogen content. As an indirect effect, soil water content had a positive effect on TC content in surface soil mainly through TN, whereas pH had an indirect negative effect on TC content in deep soil mainly through TN. Temperature had an indirect negative effect on soil TN content mainly through precipitation, whereas bulk density had an indirect negative effect on soil TN content mainly through TC. (2) Soil carbon and nitrogen content showed obvious “surface polymerization.” The content of soil carbon and nitrogen decreased as soil depth increased. The carbon and nitrogen content of forest soil was the highest; these contents were significantly higher than those found in soil from grassland and cultivated land(P<0.05) but were not significantly different from the contents in shrub soil(P<0.05). The soil nitrogen content in the study area was higher than the national soil nitrogen content grading standard, which could provide sufficient nitrogen nutrient elements for the growth of vegetation in this area. (3) Soil carbon and nitrogen content was affected by the natural environment and human activities. Although this study focused on the effects of natural environmental factors on soil carbon and nitrogen content, the effects of human activities on these contents were not considered; thus, the impact of human activities should be further analyzed future research.

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Distribution characteristics of soil organic carbon in Xilin Gol steppe and its influencing factors
CHANG Shuai,YU Hongbo,CAO Congming,MA Zice,LIU Yuexuan,LI Xiang
2021, 38 (5):  1355-1366.  doi: 10.13866/j.azr.2021.05.17
Abstract ( 25 )   HTML ( 4 )   PDF (9031KB) ( 13 )  

Soil organic carbon (SOC) is an important indicator of soil nutrient content and quality. The study of SOC in different steppe types assists ecological restoration and rational land use projects. This study was conducted in the Xilin Gol steppe, and used the Kriging interpolation, correlation analysis, unary linear regression, and principal component analysis to explore the spatial differentiation of SOC and identify its influencing factors. The results showed that: (1) In the meadow steppe, SOC content in 0-10 cm, 20-30 cm, and 40-50 cm soil layers was 23.28 g·kg-1,12.71 g·kg-1, and 9.28 g·kg-1, respectively; in the typical steppe it was 16.75 g·kg-1, 10.75 g·kg-1, and 7.20 g·kg-1, respectively; in the desert steppe, the content was 1.62 g·kg-1, 2.00 g·kg-1, and 1.73 g·kg-1, respectively. Also, results showed that the SOC content in the meadow and typical steppes gradually decreased with the increase of soil depth, while there was no significant difference between different soil layers in the desert steppe. (2) Different steppe types had different influences on SOC content. For the same soil layer depth, the SOC content order was basically meadow steppe>typical steppe>desert steppe. The SOC content in the horizontal direction was consistent with the distribution of vegetation coverage, showing a trend of gradual decrease from southeast to northwest. (3) Correlation analysis showed that SOC was significantly (P<0.01) and negatively correlated with altitude, temperature, and pH; and significantly (P<0.01) and positively correlated with precipitation, soil water content, available nitrogen, and available phosphorus. It had no significant correlation (P>0.05) with slope, aspect, and available potassium. (4) The main factors affecting SOC were available nitrogen, precipitation, and temperature; the secondary factors were soil water content and available potassium. Therefore, attention should be paid to the control of nitrogen intake and hydrothermal conditions in different steppe types.

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Effects of early sowing and tillage measures on nitrogen and phosphorus in the soil supporting spring wheat in the semi-arid area of the Loess Plateau
LIU Shuainan,LI Guang,SONG Liangcui,YUAN Jianyu,XIE Mingjun,WEI Xingxing
2021, 38 (5):  1367-1375.  doi: 10.13866/j.azr.2021.05.18
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To study the effects of early sowing and tillage measures on soil nitrogen and phosphorus in a farmland ecosystem, 0-40 cm of soil supporting spring wheat (Triticum aestivum) in the semi-arid region of the Loess Plateau was collected and analyzed. Under early sowing and normal sowing conditions, the different tillage measures were as follows: traditional tillage (T), traditional tillage + straw returning (TS), no tillage (NT), and no tillage + straw mulching (NTS). Results were as follows. (1) Under different treatments, the contents of N (TN, $NO_3^--N$, and $NH_4^+-N$) and P (TP) in spring wheat-related soil had the characteristics of surface aggregation. The average value of soil N:P (1.713) was lower than the national average value (5.2) and the coefficient of variation was 26.99%-77.28%, which belonged to the medium variation level. (2) In the 0-40 cm soil layer, the TN,$NH_4^+-N$, and N:P levels of early sowing spring wheat were significantly lower than the levels found with normal sowing (i.e., by 23.1%-32.5%), which was not conducive to the accumulation of TN and $NH_4^+-N$, whereas $NO_3^--N$ and $NO_3^--N$:N levels were significantly higher in early sowing spring wheat than the levels achieved with normal sowing (i.e., by 30.5% and 41.5%, respectively), which was conducive to the retention of $NO_3^--N$ in the soil. (3) The contents of TN and TP under straw mulching conditions (NTS and TS) were higher than those under NT and T, but the contents of available nitrogen ($NO_3^--N$ and $NH_4^+-N$) showed the opposite trend. (4) Under different treatments, the contents of TP in the soil tended to be stable during the growth period, whereas the contents of N changed significantly at the tillering and flowering stages. Therefore, selecting suitable sowing times and tillage management measures will help to improve the accumulation and transformation efficiency of N and P elements in crop soil and will accelerate the restoration process of farmland ecosystems in the semi-arid area of the Loess Plateau.

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Effects of water stress on rhizosphere organic nitrogen fractions and enzyme activities in the rhizosphere of delayed cultivation grape
YANG Changyu,ZHANG Rui,LIN Baojun,DONG Bo,GAO Yanting,LI Hongxia,ZHAGN Caixia,WANG Xihong
2021, 38 (5):  1376-1384.  doi: 10.13866/j.azr.2021.05.19
Abstract ( 26 )   HTML ( 2 )   PDF (1797KB) ( 2 )  

In order to explore the changes in the basic physical and chemical properties, enzyme activities and organic nitrogen components of the rhizosphere soil of protected grapes under different water stress conditions, and analyze the response relationship between them provide a certain reference basis for the establishment of a reasonable stress irrigation model for the delayed cultivation of grapes in the Hexi area of Gansu Province. Using a completely randomized test design based on a single water stress factor, the Bremner method was employed to determine the characteristics of the variation in organic nitrogen contents in the rhizosphere soil layer of the grapes during the ripening period, and the basic physical and chemical properties of the soil and soil enzyme activity during the whole growth period, under different water stresses (moderate W1, mild W2, and adequate W3 water supply). The results showed: (1) Moderate and mild water stress during the whole growth period had no significant effect on the total nitrogen, ammonium nitrogen, total phosphorus, organic matter, and organic carbon of the rhizosphere soil of the grapes under delayed cultivation, but the soil microbial biomass carbonand nitrogen contents were reduced. The contents of soil nitrate nitrogen and available phosphorus in the early stage of water stress were significantly lower than those observed in adequate water supply conditions. (2) Moderate and mild water stress had no significant effect on the activity of catalase in rhizosphere soil during the whole grape growth period, but showed different levels of inhibitory effects on the contents of urease and invertase in the fruit swelling and coloring stages. (3) The contents of organic nitrogen components in each treatment were present in the following order: non-acid hydrolysis nitrogen>acid hydrolysis amino acid nitrogen>acid hydrolysis ammonium nitrogen>acid hydrolysis unknown nitrogen>acid hydrolysis amino sugar nitrogen; both mild and moderate water stress contributed to the accumulation of total acid hydrolyzed nitrogen in the grapes’ rhizosphere soil, which increased by 21.16% and 10.34%, respectively, compared with contrast. (4) Sucrase had a significant and positive correlation with microbial biomass carbon; RDA analysis showed that nitrate nitrogen and ammonium nitrogen were the most important environmental factors affecting the variation of soil organic nitrogen components, followed by total nitrogen.

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Characteristics of soil ecological stoichiometry of different tree spcies in sub-frigid desert steppe
LOU Boyuan,WANG Yongdong,YAN Jinsheng,Akida Askar
2021, 38 (5):  1385-1392.  doi: 10.13866/j.azr.2021.05.20
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In order to explore the effects of different tree spices on soil nutrients and ecological stoichiometry in sub-frigid desert steppe, combining the method of field investigation and indoor analysis, we analyzed soil nutrients (C、N、P、K) and ecological stochiometry of soil for Nursultan, capital of Kazakhstan of three different tree spcies. The results shouwd that: (1) Soil nutrient content was affected by tree species, but there was no significant difference in ecological stoichiometry among different tree species. (2) Soil organic carbon and total nitrogen contents in different tree species plantations increased significantly after plantation. The differences of soil surface organic carbon and total N contents between coniferous forest and broad-leaved forest were significant. (3) Soil C, N and P contents showed extremely significant positive correlation, and C content was the controlling factor of C: N and C:P, while N content was the controlling factor of N:P. Although the soil nutrient content increased significantly, the overall level was still lower than the global average level, and the local soil nutrient content was still in a state of shortage. N is the limiting factor of nutrient cycle and plant growth in this area. Appropriate application of nitrogen fertilizer in the growth process of plantation can accelerate the growth and ecological restoration process of shelterbelt. This study can provide scientific basis for the protection forest construction and sustainable management in Nursultan, capital of Kazakhstan.

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Plant and Plant Physiology
Nitrogen uptake strategies of short-lived plants in the Gurbantunggut Desert
ZHUANG Weiwei,HOU Baolin
2021, 38 (5):  1393-1400.  doi: 10.13866/j.azr.2021.05.21
Abstract ( 27 )   HTML ( 17 )   PDF (1923KB) ( 9 )  

Investigation into whether there is ecological niche separation of nitrogen (N) utilization by the same living type of plants in desert ecosystems can help in elucidating the survival strategies of desert plants and the influence of N on the survival of these plants. In the Gurbantunggut Desert, four short-lived herbaceous plants—Erodium oxyrrhynchum, Hyalea pulchella, Nonea caspica, and Lactuca undulata—are distributed widely. The uptake of different forms of N by these four plants was investigated at different soil depths in different months. The findings revealed that the N uptake rates of all four species in May were higher than were those in April at different soil depths. As for the uptake rates of different forms of N, that of glycine was lower than that of both nitrate and ammonium N. The highest recovery of nitrate N was achieved by N. caspica in April, up to 52.3%. Meanwhile, the highest recovery of ammonium N was achieved by N. caspica in May, reaching 90.7%. The uptake of 15N by H. pulchella was lower than was that by the other three species. The four short-lived plants could efficiently utilize not only soil inorganic N but also soil organic N, and E. oxyrrhynchum and L. undulata displayed a significant preference for nitrate N uptake. The findings reveal that in the Gurbantunggut Desert ecosystem, short-lived plants have differential and diversified N uptake capacity and can all absorb soluble organic state N sources from the soil.

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Analysis of vegetation variation trend and correlative factors in Junggar Basin
MA Xiaomei,DU Bingchenxi,CHNEG Yongxiang,WU Ling
2021, 38 (5):  1401-1410.  doi: 10.13866/j.azr.2021.05.22
Abstract ( 28 )   HTML ( 3 )   PDF (5299KB) ( 23 )  

To explore the response of vegetation to environmental change, the vegetation dynamic changes and correlative factors in the Junggar Basin were analyzed by using the maximum value composite method, Mann-Kendall, Hurst trend analysis, hydro-thermal coordination analysis, and other methods based on MOD09A1 remote sensing image data from 2000 to 2019. The results showed an increasing vegetation area in the Junggar Basin in the past 20 years due to the warming and wetting of the regional climate, the increase of precipitation in the cold season, and the popularization of drip irrigation technology. The average percentage of area where vegetation presented an increasing trend and a decreasing trend in each season was 85.47% and 12.61%, respectively. The low-lying areas prone to converge water and salt showed a decreasing trend in vegetation. The vegetation and salinization indexes were negatively correlated. Vegetation changes in oasis areas were mainly regulated by human activities. The results of the Hurst trend prediction showed that the future trend of vegetation change in the basin was basically consistent with the trend of vegetation change in the past 20 years. The results of this study have certain reference value for the succession and genesis of plant communities in different habitats of the basin under the background of global warming and human activities.

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Analysis of the magnitude and influencing factors of the hydraulic redistribution of plant roots
YANG Guisen,HUANG Lei,YANG Lizhen,CHEN Jiajia
2021, 38 (5):  1411-1419.  doi: 10.13866/j.azr.2021.05.23
Abstract ( 23 )   HTML ( 3 )   PDF (3174KB) ( 6 )  

The concept of hydraulic redistribution of plant roots (HR) refers to the passive transmission of water between different parts of the soil via plant roots, driven by the water potential gradient at the root-soil interface. It is a physiological regulation strategy employed by plant roots in order to adapt to the spatial heterogeneity of soil moisture. Not only can it optimize the use of water by plants, but it has also a certain impact on the ecosystem’s geochemical cycle. Therefore, the study of HR under water-limited environments is of great significance to understand in depth the ecological hydrological mechanism of plant survival in arid areas and its control strategies. Based on these observations, this paper reviews and analyzes the latest trends and progress in HR research at home and abroad, and compiles a more systematic review encompassing the developmental history of HR, its role in eco-hydrology, its magnitude, universality, and influencing factors. Using data mining to quantitatively describe HR on a global scale, it was found that HR mainly occurs in drier tree plant communities; in addition, HR accounts for 3%-79% of the transpiration process, with an average of 32%. Through the analysis of climatic factors, vegetation andsoil characteristics, and other aspects considered as HR influencing factors, it was found that the aridity index and soil texture have a significant impact on HR (P<0.05). Finally, combined with the new challenges faced by HR in the context of global change, the difficulties faced by current HR research and the frontier issues of science that should be focused on in the ecohydrological effect are proposed. Our study provides some reference for future HR research.

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Root distribution characteristics of three typical plantations in a Loess Hills region
LI Hao,HU Chanjuan,ZHAO Rongqin,GUO Lei,MAN Zhou
2021, 38 (5):  1420-1428.  doi: 10.13866/j.azr.2021.05.24
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The root is the main organ through which plants absorb water and nutrients. The development and distribution of roots have an extremely important impact on plant growth. In order to understand the root distribution characteristics of typical artificial forests in Loess Hills areas and provide a scientific basis for vegetation restoration in the future, a case study was carried out on three artificial forests (Populus tomentosa, Pinus tabuliformis and Armeniaca sibirica), located in Longtan watershed, Anding District, Dingxi City, Gansu Province. The study analyzed root length density, root area density and root biomass density in different soil depths and diameter degrees, and the results showed that: (1) Fine roots of different diameter classes were dominant in all three artificial forests. The root length and root area densities of fine roots and total roots were the following: Populus tomentosa>Pinus tabulaeformis>Armeniaca sibirica, while the root biomass density was the following: Pinus tabulaeformis>Populus tomentosa>Armeniaca sibirica. The Pinus tabulaeformis forest had the highest root length and root area densities of middle roots and coarse roots. (2) In the vertical soil profile, the root length, root area, and root biomass densities of total and fine roots decreased with increasing soil depth. However, the vertical distribution feature of middle and coarse roots was not clear. (3) The root length density, root area density and root biomass density of fine and total roots were significantly and positively correlated with soil total carbon, total nitrogen, organic carbon, and water content. The root length and root area densities of middle roots were significantly correlated with soil total carbon, total nitrogen, total phosphorus, and organic carbon. The root length and root area densities of coarse roots were significantly correlated with soil total carbon. The increase in soil carbon, nitrogen and water contents had a synergistic effect on the growth of the root system to a certain extent.

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Nutrient content of five natural poplar forests in the Irtysh River Basin in Xinjiang
SONG Jingwei,XU Ziran,CHEN Jiaxin,XU Qinghua
2021, 38 (5):  1429-1435.  doi: 10.13866/j.azr.2021.05.25
Abstract ( 21 )   HTML ( 3 )   PDF (594KB) ( 11 )  

Our analysis of the biomass and organ nutrient content of five main Populus natural forests in the Irtysh River Basin in Xinjiang reveals that the average N content of the leaves in the five poplar species is 19.36 g·kg-1 and the average P content is 2.89 g·kg-1. The N content of the leaves is close to the levels found in land plants both globally and domestically, whereas the P content of the leaves is higher than the average levels found in global and domestic land plants. The average leaf N/P ratio is 6.83, which is relatively lower than the average levels seen in both global and domestic land plants; the ratio of leaf N/P is higher than that of the stem; and the ratio of stem N/P stem is higher than that of the root. The leaf K content of P. jrtyschensis is the highest, the stem K content of P. laurifolia is the highest, and the K content in the root system of P. alba is the highest. The biomass distribution ratio of the five natural forests—P. laurifolia, P. jrtyschensis, P. canescens, P. nigra, and P. alba—1:1.03:1.15:1.23:1.37. The P. alba forest has the highest biomass distribution, and the P. laurifolia forest has the lowest biomass distribution.

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Effects of sodium salinity stress types on the germination of Kalidium foliatum seeds and its young seedling growth
LEI Chunying,JI Xiaomin,PENG Muzhi,JIANG Li
2021, 38 (5):  1436-1441.  doi: 10.13866/j.azr.2021.05.26
Abstract ( 34 )   HTML ( 5 )   PDF (2884KB) ( 14 )  

The effects of different types of sodium salt stress on seed germination and seedling growth in the eremophyte Kalidium foliatum were studied by measuring the germination rate, germination index, bud length, and root length. In addition, the mechanism of seed germination and seedling growth when adapting to different types of saline alkali land was explored; this work provides insights into the development desert restoration and forage industry in arid areas through K. foliatum planting. Results showed that NaCl, Na2SO4, NaHCO3, and Na2CO3 significantly inhibited the germination rate and germination index of K. foliatum. According to regression analysis, the critical values of NaCl, Na2SO4, NaHCO3, and Na2CO3 were 325, 267, 245, and 166 mmol·L-1, respectively, whereas the limit values were 671, 580, 569, and 389 mmol·L-1, respectively. In addition, NaCl, Na2SO4, NaHCO3, and Na2CO3 significantly inhibited the growth of K. foliatum shoots and roots. However, seed germination and seedling growth responses differed significantly according to the four sodium salt exposures. For example, the toxicity of alkaline salt was greater than that of neutral salt. In young seedlings, the shoots were more sensitive to salt exposure than were the roots. Furthermore, root length could be used as a parameter to evaluate the salt tolerance of K. foliatum. Finally, according to the degree of salt toxicity on seed germination and seedling growth, the toxicity to K. foliatum can be ranked as follows: NaCl<Na2SO4<NaHCO3< Na2CO3.

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Ecology and Environment
Development and application of the temperature soil moisture precipitation drought index (TMPDI) based on multi-source remote sensing data
MAN Yuanwei,LI Jing,XING Liting
2021, 38 (5):  1442-1451.  doi: 10.13866/j.azr.2021.05.27
Abstract ( 25 )   HTML ( 3 )   PDF (5246KB) ( 18 )  

Drought has a profound social and economic impact on the whole world. Reliable drought monitoring is of great significance to drought prevention and drought relief. In the areas with low vegetation coverage and crop planting rate, the accuracy of using vegetation status or single factor for drought monitoring is low, based on the simple and objective Euclidean distance method in three-dimensional Euclidean geometry space, a new drought index, temperature soil moisture precipitation drought index (TMPDI), was constructed for drought monitoring. Taking Gansu Province as the research area, the TMPDI was verified by using SPI, SPEI, other remote sensing data and wheat yield per unit area. The results showed that: TMPDI was highly correlated with SPI and SPEI(R2>0.64), which reduced the uncertainty of drought monitoring using precipitation or surface temperature, improved the accuracy and effectiveness of soil moisture in agricultural drought monitoring, and accurately describe the temporal and spatial evolution characteristics of drought events. At the same time, it can also better reflect the impact of drought intensity and drought area rates on wheat yield, which proves that TMPDI its high effectiveness and reliability in agricultural drought monitoring.

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Change processes and trends of land use/cover in the Balkhash Lake basin
LIU Wanru,CHENG Chunbo,LUO Geping,HE Huili
2021, 38 (5):  1452-1463.  doi: 10.13866/j.azr.2021.05.28
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The Balkhash Lake basin is an important transboundary basin spanning China’s Xinjiang region (domestic) and Kazakhstan (overseas). Existing since 1972, the Kapuchagai Reservoir, which is the largest water conservancy project within the Balkhash Lake basin has experienced different stages of ecological change, especially since the collapse of the Soviet Union. This study analyzed three periods in which change occurred and trends in Land Use and Land Cover (LULC) starting from the 1970s, 2005 and year 2015, using the Markov model and other methods. Moreover, the differences between internal and external basin characteristics where identified and compared. The results showed that, in the Balkhash Lake basin, LULC changed; both cultivated and wood lands initially showed a decreasing trend between the 1970s and 2005, then an increasing trend afterward (2005-2015). In contrast, the change processes observed in water areas and unused lands showed a completely opposite trend. In addition, grassland and urban land uses maintained a steady increasing trend. This indicates that later changes in LULC had a greater impact on the overall LULC changes throughout the study period. These changes mainly assume a two-way conversion process, so the change process of the whole river basin was always in equilibrium during the study period. The structure and change process of LULC types outside and inside were different: Internal land use types were more evenly distributed than those located externally, and both the single type and regional LULC variation in trends, and the status index indicated that the domestic change process was more stable than that outside the watershed. However, because the external area accounted for 86% of the entire river basin, it dominated the structure and change process of LULC types in the whole area. This study provides a basis for sustainable land resource management and ecological environment protection in the region.

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Spatio-temporal patterns variation of ecological vulnerability in Otindag Sandy Land based on a vulnerability scoping diagram
CHEN Zhenqi,ZHANG Jing,ZHANG Yilong,LIU Rui
2021, 38 (5):  1464-1473.  doi: 10.13866/j.azr.2021.05.29
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The question of how to coordinate social and economic development, population growth, resource consumption, and environmental protection has become an urgent topic for regional sustainability development. Identifying the ecological vulnerability (EV) of specific areas is the precondition to achieving effective ecosystem management for sustainability. However, the driving forces of EV, including climate change, environmental protection policies, and land use, may change over a long period of time, affecting the spatio-temporal patterns of EV. Taking Otindag Sandy Land as the research area, we used the “Vulnerability Scoping Diagram” framework to establish the evaluation index system. Using Moran’s I index and principal component analysis (PCA), we evaluated the spatio-temporal distribution patterns of EV of this sandy land, and we also analyzed its driving mechanism from 2000 to 2019. The findings revealed that: (1) the EV of Otindag Sandy Land has exhibited an increasing trend over the past two decades; (2) the EV of this area presents an agglomeration distribution pattern with obvious spatial auto-correlation on spatial extent, in which the high-high cluster of EV is distributed in the western region, and the low-low cluster of EV is located in the eastern region; (3) the heterogeneity of the temporal and spatial distribution of EV is due to the synergistic effect of human activities and climate factors at different levels. According to the factor loadings matrix of PCA, after 2010 or 2015, the influence of indicators such as the population density, the number of livestock, and the per capita grassland area on the EV of this region has either weakened or been restrained by the implementation of ecological restoration projects and ecological policies. Meanwhile climate factors have gradually highlighted the leading role in driving EV in this region. This study provides a theoretical basis for the ecological construction and ecological restoration of Otindag Sandy Land, and puts forward some suggestions and measures for ecosystem management. At the regional level, from the perspective of future spatial planning, the EV in the eastern part of Otindag Sandy Land is mild to moderate, and ecological management measures should focus on harmonizing rational utilization of grassland resources with ecological protection. Meanwhile, the EV in the central and western regions of this area is severe to extreme, and it is thus necessary to strengthen ecological restoration projects and ecological migration to reduce grazing pressure on sandy land. At the local level, while comprehensively considering the demographic factors, pasture size, and grassland quality of herdsmen households, we should optimize grassland property rights and coordinate the interests of herdsmen with the goal of ecological conservation to achieve the fine administrative management “one household, one eco-management measures”.

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Health assessment of plantations in Nursultan, capital of Kazakhstan
YAN Jinsheng,WANG Yongdong,LOU Boyuan,Akida Askar,XU Xinwen
2021, 38 (5):  1474-1483.  doi: 10.13866/j.azr.2021.05.30
Abstract ( 22 )   HTML ( 2 )   PDF (1039KB) ( 3 )  

The study was performed in Nursultan and its surroundings. Its principal aims are to explore the methods of plantation health assessment, analyze different plantations, screen suitable assessment indexes of plantation health, and establish an evaluation model of plantation health, which would provide theoretical support for health assessment in the region. Twenty-five plantation plots and two natural forest plots were analyzed. Shannon-Wiener index (X1), Pielou index (X2), Simpson index (X3), stand spatial structure optimization object function(X4), soil organic matter content (X5), soil total nitrogen content (X6), soil total phosphorus content (X7), soil pH (X8), soil moisture (X9), mean tree height (X10), mean breast diameter (X11), mean height under branches (X12), mean canopy (X13), and forest regeneration (X14) were evaluated. Factor analysis, cluster analysis, discriminant analysis, and stepwise regression analysis were used to comprehensively assess the plantations. Fourteen single indicators were converted into four independent indicators through factor analysis. The contribution rates of the first four factors were 30.482%, 24.374%, 19.711%, and 8.646%, representing 83.212% of the original data variance. The health score value was calculated through the factor score coefficient matrix and the weight of each factor. Cluster analysis was performed on comprehensive health scores, and plots were divided into five categories: (Ⅰ) a high-quality type, (Ⅱ) a satisfied type, (Ⅲ) a moderate type, (Ⅳ) a vulnerable type, and (Ⅴ) an unhealthy type. The results of discriminant analysis and cluster analysis were similar. The accuracy of the self-verification and cross-validation were 100% and 85.185%. The optimal mathematical model for plantation health assessment was established as H=0+0.293X13+0.186X5+0.079X3+0.100X2+0.038X7(R2=0.987). Five indexes for plantation health assessment were selected: Mean canopy, soil organic matter content, Simpson index, Pielou index and soil total phosphorus content. Mean canopy, soil organic matter content, Simpson index, Pielou index, and soil total phosphorus content could be used to assess the health of plantations in the region. The comprehensive assessment value of the five indexes could be calculated to predict healthy conditions by measuring the five indexes under the same conditions.

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Remote sensing evaluation of ecological environment in Urumqi City and analysis of driving factors
Pariha Helili,ZAN Mei,Alimjan Kasim
2021, 38 (5):  1484-1496.  doi: 10.13866/j.azr.2021.05.31
Abstract ( 32 )   HTML ( 4 )   PDF (3852KB) ( 15 )  

The ecological environment quality assessment is essential to the sustainable development of the regional social economy. This paper takes Urumqi, Xinjiang, as the research area, preprocessed the Landsat series data of 2000, 2010, and 2019. The principal component analysis method was used to construct the Remote Sensing Ecological Index (RSEI), and the single factor analysis and the multi-factor interaction analysis method were used in the geographic detector to influence the eight factors of RSEI (population density, land use type, altitude, economics density, green degree, humidity, heat, and dryness). The quantitative detection of the degree of influence was conducted, after which the dominant factors affecting the ecological environment quality of the study area were revealed. The results show that: (1) The average RSEI values of Urumqi in 2000, 2010, and 2019 were 0.21, 0.21, and 0.23, respectively, showing an increasing trend. During the study period, Urumqi's ecological improvement area was greater than the area that deteriorated, indicating the ecological environment quality of Urumqi. In a state of improvement; (2) In the past 20 years, among the eight impact factors in the study area, the single factor heat index has the strongest explanatory power for the spatial differentiation characteristics of RSEI; (3) The spatial distribution characteristics of the ecological environment in the study area are the result of the mutual interaction of multiple influencing factors. Considering the interaction of multiple factors, population density, greenness index, and dryness index are the main influencing factors and key driving forces of the quality of regional ecological environment. Evaluating the quality of the regional ecological environment, understanding the status of the ecological environment and mastering its changing laws do not only aid the promotion of sustainable development of the regional economy but also has important practical significance and reference value for constructing urban ecological civilization.

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