Arid Zone Research

New characteristics of spatio-temporal evolution of extreme climate events in Xinjiang under the background of warm and humid climate

WU Xiaodan,LUO Min,MENG Fanhao,SA Chula,YIN Chaohua,BAO Yuhai

2022, 39 (6): 1695-1705. doi: 10.13866/j.azr.2022.06.01

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Based on the daily meteorological data from 1982 to 2020, the spatial and temporal variability characteristics of extreme climate events in Xinjiang were analyzed using the methods of trend analysis, correlation analysis, Hurst index, and relative importance. The results indicate that the extreme temperature indices in Xinjiang show a warming trend, and the proportion of stations with different extreme temperature indices show a warming trend of 50.98%-100%. The temperature of the cold index was higher than that of the warm index, and the warming trend in southern Xinjiang is more significant than that in northern Xinjiang. Except for the continuous drought index, CDD, the overall extreme precipitation indices showed no significant upward trend, and the proportion of stations with an upward trend was 61.76%-85.29%. The increase in extreme temperature frequency indices, total precipitation, and moderate and light rain days significantly contributed to the warming and humidification trend in Xinjiang. Except for freezing days ID and annual mean rain days precipitation intensity SDII, the changes of other extreme climate indices were sustainable, and the extreme precipitation and warming trend of most extreme temperatures, especially the cold index, were more obvious at high altitudes.

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Comparison of downscaling methods for TRMM 3B43 precipitation data in the Qinghai Lake Basin and its surrounding areas

LI Yankun,GAO Liming,ZHANG Lele,WU Xueqing,LIU Xuanchen,QI Wen

2022, 39 (6): 1706-1716. doi: 10.13866/j.azr.2022.06.02

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Using multiple linear regression (MLR), principal component stepwise regression (PCSR), and Kriging, the TRMM 3B43 precipitation data in the Qinghai Lake Basin and surrounding areas with a resolution of 0.25° were downscaled to a resolution of 0.01°. The measured precipitation data of 20 meteorological stations in the study area were selected, and the correlation coefficient, root mean square error, and relative deviation (Bias) were used to evaluate the downscaling results. Downscaling methods for the study area. The results show a consistent spatial distribution of precipitation in the study area based on TRMM and the three downscaling methods. The annual average precipitation and the three seasons of spring, summer, and autumn are all high in the north, low in the west and northwest, and winter precipitation. The performance was high in the south and northwest and low in the middle. With increased altitude, the precipitation in the study area showed an overall trend of first increasing and then decreasing with 3800 meters as the boundary. The results of the accuracy evaluation show that the Kriging accuracy on the annual scale has the best performance. On the spatial scale, the TRMM and the three downscale data have the best accuracy in the eastern region. On the quarterly scale, the data precision is PCSR > Kriging > TRMM > MLR. On the monthly scale, the PCSR data accuracy is the best. The effect of altitude on the TRMM and the three downscaling data in the study area is small. However, with increasing altitude, the remote sensing data gradually underestimates the precipitation phenomenon, which may be due to the underestimation of precipitation and convection during microwave precipitation rate inversion underestimation of precipitation. From the comprehensive precipitation spatial distribution consistency analysis and precision evaluation, it is considered that PCSR is the most suitable downscaling method for TRMM 3B43 precipitation data in the Qinghai Lake Basin and surrounding areas.

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Selection of cloud model simulation parameters and analysis of microphysical structure characteristics of the precipitation process in the Qilian Mountains

ZHANG Wenyu,REN Jing,FU Danhong,KONG Lingbin,TIAN Shuo

2022, 39 (6): 1717-1727. doi: 10.13866/j.azr.2022.06.03

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Using the measured data and cloud model, the precipitation process of a typical stratocumulus system in the Qilian Mountain is numerically simulated. The influence of parameter selection on the simulation results is discussed, and its microphysical structure characteristics are analyzed. The results show that the optimal parameter of the Qilian Mountain cloud model is the Thompson scheme. The content distribution of various aquatic products shows a single peak. The values of graupel and snow mixing ratios near 01:00 and 4.5 km can reach 0.1 g·kg^-1 and 0.7 g·kg^-1, respectively. There is abundant supercooled water in this height layer. From the spatial distribution and temporal correlation of the five aquatic products, the melting of graupel and snow has a significant contribution to rainwater formation. In the vertical direction, the cloud system presents a layered structure of “catalysis supply”: The highest layer above 8 km is the coexistence area of ice crystals and snow, and the supercooling area above the zero-layer (4.5 km), with graupel particles, cloud water, and rainwater at the same time. This cloud structure is conducive to forming precipitation and artificial precipitation enhancement in the Qilian Mountain.

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Various characteristics of the mesoscale convection system of a convective rainstorm in the Hetao area of Inner Mongolia

HUANG Xiaolu,LI Ruiqing,LI Linhui,LIN Hongjie,YAO Lebao

2022, 39 (6): 1728-1738. doi: 10.13866/j.azr.2022.06.04

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Based on conventional observation data, FY4A satellite cloud pictures, Doppler radar data, and reanalysis data, the occurrence and various characteristics of the mesoscale convective system (MCS) of the heavy rain process in the Hetao area of Inner Mongolia on July 19, 2018, were analyzed. The results show that: (1) The stable and less moving subtropical high, the 500hPa upper trough, the low-level shear line, the low-level southwest jet, the 300 hPa upper-altitude jet, and the surface low pressure provide a favorable circulation background. (2) The stable low-level southwest jet provides enough water vapor transport. Pseudo-equivalent potential temperature high energy tongue, deep warm cloud layer, high-intensity CAPE, cold advection intrusion behind the upper trough, and the unstable air layer together provide better environmental conditions for the heavy rainstorm. (3) The two successively developed MCS caused the heavy rain process. The convective rainstorm is mainly caused by the slow movement of the east-west MCS along the Yinshan Mountains, 20 mm·h^-1 heavy rain appears at the edge of upwind cloud clusters and the strong TBB gradient areas. (4) The east-west echo moves slowly along the direction of the echo wavelength axis. The strong echo moves slowly from west to east to form a significant “train effect,” causing continuous heavy rain for more than five hours. The north-south direction echo lasts longer, but its moving direction is vertical to the direction of the echo wavelength axis, and the moving speed is faster, so the intensity of the rainstorm produced is weaker than the east-west direction. (5) The surface convergence line is the main factor that triggered the MCS occurrence and development, Hetao area complex terrain, and the pulsation of the low-level jet both promote the effect. The almost overlapping distribution of the surface mesoscale convergence line and the Yinshan Mountains are favorable to the continuation of rain and the convective rainstorm.

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Numerical study on the effect of low-level jet on two rainstorms on the east side of the Helan Mountain

CAO Yiqing,LONG Xiao,LI Chao,WANG Siyi,ZHAO Jianhua

2022, 39 (6): 1739-1752. doi: 10.13866/j.azr.2022.06.05

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Comparative analysis of two rainstorm processes was conducted using methods of synoptic diagnosis and numerical experiment with the NCEP 1°×1° reanalysis, and Ningxia regional automatic station observation, and FY-2E satellite data. These rainstorms occurred on the east side of the Helan Mountain from July 18 to 19, 2018 and June 4 to 5, 2017, which were all accompanied by low-level jet. (1) The “7·18” process is a short-term rainstorm, which is produced by the interaction of a high-altitude trough and southerly low-level jet under the circulation background of “high in the east and low in the west” at 500hPa, while the “6·04” process is a large-scale continuous precipitation process formed under the influence of the stable large-scale trough and the southeast low-level jet. (2) The difference in the impact of the low-level jet on the two rainstorms may be due to the different distribution patterns of the low-level jet. The low-level southerly jet before the “7·18” heavy rain mainly played the role of transporting water vapor. When the low-level jet strengthened and interacted with the Helan Mountains, the rainstorm was induced, and the southerly low-level jet was deflected into the southwest low-level jet. The low-level jet and the rainstorm process promoted each other to strengthen the precipitation. The northern part of Ningxia is always located on the southeast side of the mesoscale vortex and the left side of the southwest low-level jet during the “6·04” rainstorm. It is a favorable dynamic condition for the rainstorm. (3) Results of the numerical sensitivity experiment indicate that the precipitation intensity is weakened in the two rainstorms after decreasing intensity of the low-level jet; the reduced areas are located near the Helan Mountain and the central area of Ningxia plain, respectively. Among them, the south wind component of the low-level jet has an important impact on the precipitation intensity. (4) Results of diagnostic analyses show that the impacts of the low-level jet strengthen the dynamic effects of vertical movement at the windward slope for the “7·18” process, and the impact on the “6·04” process is mainly reflected in the dynamic convergence and uplift on the left side of the low-level jet. The influence of water vapor transport in the “7·18” process is greater than that in the “6·04” case.

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Circulation pattern and LLJ characteristics of 20 rainstorm events in the eastern region of the Helan Mountain

LI Chao,LONG Xiao,CAO Yiqing,WANG Siyi,HAN Zifei,WANG Hui

2022, 39 (6): 1753-1767. doi: 10.13866/j.azr.2022.06.06

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The eastern region of the Helan Mountain is an area prone to extreme rainstorms in Northwest China. To further explore the distribution of circulation patterns and evolution characteristics of the low-level jet systems during a rainstorm occurrence in this region and improve the accuracy of rainstorm forecasts and the ability of disaster prevention and mitigation in this region. Based on the encrypted surface precipitation observation and NCEP/NCAR reanalysis data, this paper comprehensively analyzed the formation mechanism of 20 heavy rainfall events in the eastern piedmont of the Helan Mountain from 2009 to 2020. The results show that: According to the characteristics of the 500 hPa circulation situation, the main rainstorm processes in this area can be classified into two: “Northwest side of the subtropical high” and “In front of upper trough” category rainstorm. The rainstorm of “In front of upper trough” category occurs under the combined action of the high-altitude westerly trough, the high-altitude jet stream, and the low-altitude water vapor convergence field. During the precipitation process on the northwest side of the subtropical high, the eastern foot of Helan Mountain is located on the northwest side of the western Pacific subtropical high. The edge of the subtropical high brings abundant water vapor, and the combination of high and low-altitude dynamics strengthens this type of precipitation. Obvious differences exist in the LLJ systems corresponding to the two types of precipitation processes. During the precipitation process of the “Northwest side of the subtropical high” category, the LLJ shows the characteristics of northward intensification and southward retreat and weakening. The LLJ axis is mainly located on the left side of the Helan Mountains. Its main effect on such rainstorm process is reflected in the transport of water vapor and the increased wind speed on the windward slope. “In front of upper trough” category rainstorm’s LLJ is characterized by eastward movement and weakening, and the jet axis is mostly located on the right side of the Helan Mountains. The development and evolution of mesoscale cyclones generated by LLJ dynamics play an important role in triggering and maintaining such rainstorms.

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Exploring the interaction between the heat island effect and pollution island effect in Xi’an, China

JIANG Ziqi,WANG Xuhong,FENG Zihao,CUI Siying,YANG Xia

2022, 39 (6): 1768-1781. doi: 10.13866/j.azr.2022.06.07

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Surface/Canopy Urban Heat Island (SUHI/CUHI) effect and Atmospheric/Near-surface Urban Pollution Island (AUPI/NSUPI) effect interact and influence each other, significantly threatening the urban ecological environment. Based on the spatial coupling analysis and attribution method, the impact of AUPI on SUHI under radiation effect and CUHI on NSUPI under turbulence mixing in Xi’an city from 2003 to 2020 were explored using land surface temperature, air temperature, Aerosol Optical Depth (AOD), and PM_2.5 data. The results indicated that: (1) Due to the difference in aerosol radiation effect between day and night in winter, SUHI intensity in winter is <0.2 K. The strong aerosol radiation cooling effect causes low ground temperature in urban areas and cooler in urban areas than in rural areas. When the SUHI intensity is greater than 2.2 K at night, the long-wave radiation effect of aerosol is enhanced, and the pollutant particles suspended in the urban space become the “insulation layer” of the city. (2) Significant CUHI in spring and summer enhanced atmosphere turbulent mixing, causing the diffusion of pollutant particles near the surface in urban regions. PM_2.5 concentration and NSUPI intensity decreased correspondingly on urban surfaces. In autumn and winter, the atmospheric inversion layer obstructed air ascending movement driven by the CUHI effect. PM_2.5 particles aggregated and accumulated in near-surface urban areas, and NSUPI was enhanced accordingly. Additionally, the contribution of haze to surface heat island by attribution quantitative analysis suggested that AOD in rural or urban areas was significantly negatively correlated with SUHI at night and correlation coefficients were -0.431 and -0.386, respectively. This suggested that the main radiation effect of haze on the surface heat environment at night was the cooling effect, while the weakening or strengthening effect of haze on the local climate of urban heat islands was mainly attributed to the positive or negative difference in AOD in urban and rural areas. The UHI and UPI effects are inseparable. It is very important to promote the comprehensive study of urban climate and pollution for constructing a green urban ecological environment.

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Changes in runoff from major rivers and analysis of its causes in the Shule River Basin from 1956-2021

WANG Xueliang,CHEN Rensheng,LIU Junfeng,HAN Chuntan

2022, 39 (6): 1782-1792. doi: 10.13866/j.azr.2022.06.08

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Based on the measured runoff from the hydrological stations of Shule River, Shiyou River, and Dang River from 1956 to 2021, as well as the meteorological station of Tuole and reanalyzed meteorological data, the characteristics of runoff changes of the three rivers and their causes were analyzed using Sen’s slope estimator and Mann-Kendall test. The results showed that the runoff changes of the three rivers showed an upward trend from 1956 to 2021, among which the Shule River and the Dang River showed significantly increasing trends, while the Shiyou River showed a non-significant increasing trend. The years of abrupt change for the three rivers were 1998, 2007, and 1982, respectively. The runoff increased significantly after the abrupt change, in which the Shule River increased by 60%, while the Shiyou River and the Dang River increased by approximately 20%. Runoff from the Shule River and Shiyou River was abundant during the study period after the 2000s, while runoff from the Dang River increased slowly after the 1980s and showed a historical abundance value in the early 2020s. The combined effect of increased fluctuating precipitation and accelerated glacier melting due to accelerated temperature rise after 1986 resulted in an increasing trend of both average annual and seasonal runoff for these three rivers.

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Study on influence degree of phreatic evaporation based on hydrogen and oxygen isotope characteristics

JIANG Lei,ZHAO Yi,ZHANG Pengwei,HE Liang,BAI Xiang

2022, 39 (6): 1793-1800. doi: 10.13866/j.azr.2022.06.09

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The arid oasis area plays an important role in ecological protection and water conservation in Xinjiang. The groundwater in the area provides precious freshwater resources and is the main source of water for plants. It is important to study soil water transport, the relationship between soil water and groundwater transformation, and plant water in arid oasis areas, by studying the influencing degree of phreatic evaporation. To study the soil profile characteristics of typical vegetation growing areas, such as Populus euphratica and Tamarix ramosissima, in arid oasis area of the lower reaches of the Tarim River, environmental isotope, soil physical, and chemical analysis methods were used in this paper. The results showed that there are strong phreatic evapotranspiration and capillarity in the lower reaches of the Tarim River. It greatly influences the fractionation of hydrogen and oxygen isotopes, soil moisture content, and soil salinity. From the diving face up, as height increases, the stable isotope values of hydrogen and oxygen in soil water decreased gradually and reached a minimum value at 1-1.5 m and then gradually increased. Gradually, the soil moisture content decreases, and the rate of decrease slows down at 1-1.5 m. The soil salinity generally remains stable near the water table, and the salt content gradually increases at 1-1.5 m. Integrate soil profile data of different vegetation growing areas, the influence depth of phreatic evapotranspiration is 1-1.5 m in autumn. Using the fractionation characteristics of hydrogen and oxygen isotopes to study the phreatic capillary height and evaporation depth in arid oasis areas, it is possible to get the information that traditional hydrogeology and phreatic evaporation experiments cannot get. In the next step, it is necessary to summarize the water-salt transport law and its movement model under different evapotranspiration conditions.

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An evaluation of water environmental carrying capacity in Kyrgyzstan based on sustainable development goals

WANG Weilu,LIU Tie,LUO Geping

2022, 39 (6): 1801-1809. doi: 10.13866/j.azr.2022.06.10

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Kyrgyzstan is an important transportation hub for the countries along The Belt and Road Initiative in China, which is rich in mineral resources, has an underdeveloped economy, has frequent human activities, and has relatively weak ecological environmental protection, resulting in major water environmental problems. Drawing on the evaluation indicators of the 2030 Sustainable Development Goals, this study uses the entropy and the analytic hierarchy methods to determine the weights of the indicators, analyzes the change trend of the carrying capacity of the water environment in Kyrgyzstan from 2006 to 2020 using the principal component analysis method, and determines the main influencing factors affecting the carrying capacity of the water environment in Kyrgyzstan using the vector model method. The results show that the carrying capacity of the water environment in Kyrgyzstan from 2006 to 2020 shows an overall enhancement trend. The water environment and socio-economic subsystems promote the continuous increase in the carrying capacity of the water environment, while the water ecology and water resource subsystems limit the carrying capacity of the water environment. Population density, water shortage, water body area, and per capita share of renewable water resources are the main influencing factors limiting the water environment’s carrying capacity. Increasing the rate of urbanization, improving the efficiency of water use, reducing the discharge of wastewater, and increasing the rate of wastewater treatment are effective ways to improve the water environment’s carrying capacity in Kyrgyzstan.

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Analysis of various characteristics and driving factors of gray water footprint in Gansu Province

YIN Mingcai,ZHU Hao,HU Yuanzhao,LI Zhenzhong,ZHANG Jishi

2022, 39 (6): 1810-1818. doi: 10.13866/j.azr.2022.06.11

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This study examines the change in the gray water footprint in Gansu Province from 2011 to 2020 and uses the STIRPAT model to analyze the driving factors of the greywater footprint. The results show that the greywater footprint has been declining over the last ten years. The overall decrease was 378.53 billion m³; the maximum decline was 81%. The life, agricultural, and industrial greywater footprints accounted for 43%, 38%, and 19%, respectively. The graywater footprint of the planting industry is greater than that of animal husbandry. The overall intensity of the greywater footprint shows a downward trend, indicating that water resource utilization has increased yearly. According to the degree of water pollution and residual graywater footprint, the water pollution level in the Gansu Province from 2011 to 2016 was greater than one, and the water pollution is relatively severe. The research shows that the residual ash water footprint was negative from 2017 to 2020, indicating that the water quality shows an upward trend. Water environmental problems have been improved, and water resources continue to increase. From the driving factors of greywater footprint in the Gansu Province, urbanization level; per capita GDP; first, second, and third industrial output value; the intensity of greywater footprint; and total retail sales of social consumer goods will all promote the increase of greywater footprint, and the influencing coefficients are 0.142, 0.126, 0.052, 0.382, 0.132, 0.916, and 0.1, respectively. According to the size of the impact coefficient, relevant policies can be developed to reduce the graywater footprint of the Gansu Province, reducing the pressure on the water environment.

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Analysis of temporal and spatial evolution and influencing factors of soil erosion in Ordos City

ZHAO Mengen,YAN Qingwu,LIU Zhengting,WANG Wenming,LI Gui’e,WU Zhenhua

2022, 39 (6): 1819-1831. doi: 10.13866/j.azr.2022.06.12

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The spatial-temporal variation and influencing factors of soil erosion in Ordos City were studied to provide a reference for ecological environment management and soil and water conservation in mining areas. Based on the RUSLE model and geographic detector method, hydraulic soil erosion in Ordos City from 2000 to 2019 was studied, and its influencing factors were analyzed in this paper. The results showed that: (1) The average soil erosion in 2000, 2005, 2010, 2015, and 2019 was 3865.49 t·km^-2·a^-1, 2932.85 t·km^-2·a^-1, 2890.21 t·km^-2·a^-1, 3711.10 t·km^-2·a^-1, 4308.21 t·km^-2·a^-1, respectively. The average soil erosion decreased first and then increased during the 20 years. Increased mining activity was the main reason for the increased soil erosion. (2) The soil erosion in the 20 km buffer zone of the coal mine area developed in a good direction, and the ecological control measures in the mining area were effective and feasible. (3) Slope had the strongest explanatory power on soil erosion in Ordos City and was identified as the leading factor. The synergy of the two factors had enhanced the explanatory power for soil erosion. The soil erosion situation in Ordos City was mainly slight and mild erosion. >35° slope interval, 0-0.3 vegetation coverage interval, and industrial and mining land was an area prone to soil erosion. Therefore, increasing vegetation coverage can effectively prevent soil erosion.

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Effects of different plantations on soil aggregates in the Nayman sand region

WU Ji,YANG Guang,HAN Xueying,WEN Yaqin,YANG Yiwen,LI Wenlong,LIU Yi

2022, 39 (6): 1832-1841. doi: 10.13866/j.azr.2022.06.13

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Abstract To analyze the composition of soil aggregates and their stability changes in different plantation forests in the Nayman sand region and to select the best forest type for soil and water conservation as well as wind and sand stabilization, the soil in the understorey of poplar, oil and camphor pine plantation forests in the Nayman sand region was used as the research object, and the composition of soil aggregates in the 0-20 cm, 20-40 cm, and 40-60 cm soil layers was investigated using dry and wet sieving methods, and the soil stability evaluation index was used to evaluate soil condition. The results showed that: (1) the content of large agglomerates in the three plantation sites differed significantly between the dry and wet sieve results. Their PAD values further indicated that water-stable agglomerates were more representative in reflecting agglomerate stabilty in plantation forests in the Nayman sand region, and the number of large agglomerates with R_>0.25 was significantly higher in the 0-20 cm soil layer than in the 40-60 cm under the two sieving conditions. (2) Combining the effects of different plantation forests on soil agglomerates MWD, GMD, D, and R_>0.25 values showed the best structural properties of camphor pine soils, which had the highest water stability and relatively low D values. (3) The soil agglomerate diameter index and the fractal dimension D are clearly linearly related to the content of each grain size, but the positive and negative thresholds of the correlation coefficients differ, indicating that the 2 mm and 0.25 mm grain classes are particularly important dividing lines in the soil agglomeration process, which can be used as intuitive parameters to characterize soil mechanical and water stability, respectively. The combined experimental results indicate that the planting of camphor pine in the ecologically fragile Nayman sand area can effectively improve the soil structure and is suitable for the extension in the sand consolidation work in this area.

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Effects of long-term enclosure on soil aggregate stability and erodibility in Bayinbuluk alpine grassland

YU Guangling,LI Kaihui,ZHOU Jianqin,LI Keyi,CONG Mengfei,HU Yang,WANG Xuyang,JIA Hongtao

2022, 39 (6): 1842-1851. doi: 10.13866/j.azr.2022.06.14

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To evaluate the effects of long-term enclosure measures on the stability and erodibility of soil aggregates, the grassland (alpine meadow, alpine meadow steppe, and alpine steppe) with long-term enclosure (fenced in 1984) and free grazing were selected as the research objects. The composition, mean weight diameter (MWD), geometric mean diameter (GMD), and soil erodibility (K value) of water-stable aggregates in 0-5, 5-10, 10-20, and 20-30 cm soil layers were analyzed. The results showed that: (1) The minimum MWD value appeared in the 0-5 cm soil layer of the alpine meadow under free grazing treatment (1.75 mm). No significant difference was observed in the MWD and GMD of 20-30 cm soil layer under the enclosure and free grazing in an alpine meadow and alpine meadow steppe (P > 0.05), while the difference in alpine steppe was significant (P < 0.05). (2) The K value of 10-20 cm soil under free grazing was 0.136, so the anti-erosion ability was the weakest in all treatments. (3) The redundant analysis found that the changes in total potassium, total phosphorus, and pH were the most important factors affecting soil K value, and soil organic carbon was the most important factoraffecting MWD. (4) The 0-10 cm soil layer of Bayinbuluk alpine grassland was dominated by >2 mm macroaggregates. The long-term enclosure caused stronger stability of soil aggregates in the 0-10 cm soil layer. Moreover, grassland type, enclosure, and soil layer significantly affect the stability and erodibility of soil aggregates. This indicates that long-term enclosure could improve the soil aggregates’ water stability and erosion resistance.

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Discovery of a moss family Schistostegaceae in Xinjiang, China

Mamtimin SULAYMAN,Alanur KAHAR,LIANG Lingwei,Mamurbieke MAKAN,WANG Pengjun

2022, 39 (6): 1852-1855. doi: 10.13866/j.azr.2022.06.15

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This paper reports China’s second record, Xinjiang new record of Schistostega pennata (Hedw.) F. Weber & D. Mohr (Schistostegaceae) collected from Altai Mountains in Xinjiang. Its morphological characteristics and ecological environment are described and discussed.

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Buxbaumia viridis, a newly recorded species in Xinjiang, China and its historical correction in China’s distribution

Gulistan ANWAR,WANG Pengjun,Alanur KAHAR,Mamtimin SULAYMAN

2022, 39 (6): 1856-1861. doi: 10.13866/j.azr.2022.06.16

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Buxbaumia viridis (Moug. ex Lam. & D C.) Brid. ex Moug. & Nestl. is newly reported in Xinjiang based on the specimens collected from Keshikushitai, the 78th regiment of Xinjiang Production and Construction Corps. B. viridis has been recorded incorrectly in Shaanxi Province for more than 100 years, it is the first time to find its existence. In this paper, the morphological characters, distribution and habitat of this species are described, the peristome and spore are observed by scanning electron microscopy. Based on the above observations, a key to the genus Buxbaumia in China and illustrations of B. viridis are presented, and the historical distribution in China is rectified.

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To simulate the growth and physiological responses of Cyperus esculentus seedlings to salt stress in sandy soil

MA Xingyu,HUANG Caibian,ZENG Fanjiang,LI Xiangyi,ZHANG Yulin,DING Ya,GAO Yanju,XU Mengqi

2022, 39 (6): 1862-1874. doi: 10.13866/j.azr.2022.06.17

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To investigate the growth and physiological responses of Cyperus esculentus to salt stress in wind-sand soil, a pot experiment with eolian sandy soil as the growth medium was conducted to examine the effects of different degrees of salt stress (NaCl solution) on the growth, physiological and biochemical characteristics, and the balances of Na⁺ and K⁺ in root and leaves in a greenhouse on days 30 and 50 of stress exposure. The results showed that: (1) When the NaCl concentration was ≤0.5 g·kg^-1, both the aboveground and underground dry weights of C. esculentus seedlings were significantly unaffected. However, plant height declined significantly compared with the non-stress seedlings. When NaCl the concentration was ≥1.0 g·kg^-1, the dry weights of aboveground and underground, plant height, and leaf area decreased significantly with stress time. (2) On day 30, under salt stress, the proline content increased significantly with the NaCl concentration, but soluble and protein contents increased slightly. However, MDA content increased significantly under 0.5 g·kg^-1 NaCl treatment and decreased significantly with increasing NaCl concentration. Under salt stress on day 50, as the NaCl concentration increased, the soluble protein content increased significantly. Then, soluble sugar content increased significantly firstly and then remained stable, while the contents of proline and MDA only increased significantly at 3.5 g·kg^-1 NaCl. (3) The Na⁺ content and Na⁺/K⁺ in leaves and roots increased significantly as the NaCl concentration increased, while the K⁺ content decreased significantly and then remained stable when the NaCl concentration was >1.0 g·kg^-1. These results suggest that increased proline content at the early growth stage, while increased contents of soluble protein and sugar at the late growth stage, contribute to increasing the osmotic adjustment and water-holding capacity and decreasing the MDA content and K⁺ loss, improving the salt tolerance of C. esculentus in sandy soil. The comprehensive evaluation results showed that when the NaCl concentration was ≤0.5 g·kg^-1, no effect of salt stress on the growth of C. esculentus seedling was found, while the plant growth was inhibited significantly when the concentration was >1.0 g·kg^-1.

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Responses of seed germination of Caragana korshinskii to different temperatures and soil water content

YANG Hui,ZHANG Ze,ZHANG Lan,YAN Xingfu

2022, 39 (6): 1875-1884. doi: 10.13866/j.azr.2022.06.18

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Caragana korshinskii is a xeromorphic shrub of Fabaceae distributed in the sandy grasslands of the desert or semi-arid areas in Northwest China, and one of the main shrub species applied widely in the practice of water, soil conservation, wind-break, and sand-fixation. In this paper, different soil water contents (4%, 8%, 12%, 16%, 20%, and 30%) were conducted to investigate the responses of the seed germination of C. korshinskii to different temperatures and soil water content under six constant temperatures (5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, and 30 ℃) controlled using artificial climate incubators. The results showed that: Temperature, soil water content, and their interaction all significantly impacted the germination percentage (GP), germination rate (GR), germination index (GI), and vigor index (VI) of C. korshinskii seeds. Seeds exposed to 10 ℃ had the highest GP of 87.5%, and those to temperatures of 15 ℃, 20 ℃, and 25 ℃ had high GP as well. Then, it substantially declined when the cultivation temperature elevated to 30 ℃. GR, GI, and VI were all minimized at 5 ℃, and they all increased first and declined with elevated temperature, and maximized at 25 ℃ or 15 ℃. With the soil water content elevating, trends of increasing and decreasing were all detected in GP, GI, and VI at all temperatures. The maxima of the above three parameters were observed at 30% soil water content under 5 ℃ while they were detected at 20% or 16% soil water content under other temperatures. With increased soil water content, the GR of seeds cultivated at 5 ℃ increased gradually. However, those of seeds cultivated at other temperatures increased first and then declined. It maximized in 20% soil water content at the temperatures of 10 ℃, 15 ℃, and 20 ℃, while in 16% soil water content at the temperatures of 25 ℃ and 30 ℃. The inhibition effects of higher temperature and soil water content on the germination of C. korshinskii seeds during the summer and autumn may be a protective strategy to ensure some seeds enter soil seed bank and reduce the risk of seedling mortality. Also, the C. korshinskii seeds could germinate at relatively lower temperatures and soil water content during early spring, which may compensate for the above inhibition effects of higher temperature and soil water content on seed germination.

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Forestry structure and spatial distribution pattern of different age tree species in forest area of eastern Altai Mountain

XU Qiao,ZHAO Wanyu,WEI Yan,YE Mao,ZHAO Xinfeng

2022, 39 (6): 1885-1895. doi: 10.13866/j.azr.2022.06.19

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To clarify the spatial distribution pattern of trees in the Fuyun forest area of the Altai Mountain and provide a reference for biodiversity protection and forest management in this area, the tree species composition, tree diameter class structure, habitat characteristics of different tree species in different age forests, and spatial distribution pattern of dominant species in the Fuyun forest region of the Altai mountain were analyzed. The results showed that: (1) Picea obovata, Larix sibirica, Betula pendula, and Populus tremula were the dominant species in the Fuyun forest region, the individual number accounted for 99.99% of the total number, rare species accounted for 0.013% of the total species. (2) The diameter class structure of the dominant species was similar to that of all trees, which was similar to the inverted “U” shape, with medium diameter class individuals in the majority. (3) From the relationship between species distribution and environmental factors, altitude and slope direction have great influence, but the relationship with soil thickness is not obvious. (4) The spatial distribution pattern of the four tree species is cluster distribution, and according to the age groups, their young forests are evenly distributed. The spatial distribution pattern of trees is the result of long-term adaptation between the plant species and its environment，and it can be signals, such as the forest dynamics, plant revival, and expansion of different tree species, and the relationship between trees as well as the environments.

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Research on the spatio-temporal variation of carbon storage in the Xinjiang Tianshan Mountains based on the InVEST model

LU Yayan,XU Xiaoliang,LI Jicai,FENG Xiaohua,LIU Luyuan

2022, 39 (6): 1896-1906. doi: 10.13866/j.azr.2022.06.20

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Understanding the impact of land use change on ecosystem carbon storage is important for protecting mountain ecosystems and regional economic and socially sustainable development in arid areas. Based on the land use data of the Xinjiang Tianshan Mountains from 1990 to 2020, the carbon storage and its spatial distribution pattern of the study area from 1990 to 2020 were estimated using the InVEST model carbon storage module, and the influence of land use change on carbon storage was analyzed. The results showed that: (1) The land use types of the study area were mainly grassland and unused land, followed by permanent glaciers and snow, and forest land, with very little area of shrubs, waters, construction land, and wetlands. (2) The carbon storage showed a continuous trend, with a total increase of 19.49 Tg. Grassland, unused land, and forest land contributed the most to the total carbon storage. (3) The spatial distribution pattern of carbon storage in the last 30 years was relatively stable, and nearly 88% of the regions are significantly unchanged. The spatial distribution pattern was closely related to the vertical natural zone distribution. (4) The transformation of three land use types: grassland, permanent glaciers and snow, and unused land, was the main contributor to the spatial and temporal evolution of carbon storage in the Tianshan Mountains. This study can provide scientific support for carbon balance management and policy formulation of emission reduction and sink enhancement in mountain ecosystems in arid regions. It is also important for building the Green Silk Road and the China-Central Asia community of destiny.

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Temporal and spatial variation of vegetation ecological quality and its driving mechanism in Aksu prefecture

FANG He,YAN Peiwen,SHI Jian,KANG Juan,LIU Hairong,CHEN Dan,LUO Ji,XU Dong

2022, 39 (6): 1907-1916. doi: 10.13866/j.azr.2022.06.21

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Under the guidance of the theory of “Two mountains”, the construction of ecological civilization has been vigorously promoted in Aksu prefecture. Today a new path of high-quality development giving priority to ecological conservation and green development with Aksu characteristics has been found in Aksu prefecture. The vegetation ecological quality information is an important index to evaluate land ecosystems. Applying remote sensing technology to research vegetation ecological quality spatiotemporal variation offers practical scientific applications for developing eco-civilization. Aksu prefecture is typical sensitive area of climate change and fragile area of vegetation ecological environment in China, thus, it has a great practical significance to study vegetation ecological status in Aksu prefecture. Combined with multi-source remote sensing data and meteorological observation data, in this paper, we explore the temporal and spatial variations of vegetation ecological quality in the growing season (from July to September) and dominant factors of climate change and human activities in Asku prefecture from 2000 to 2021. The main result of this study as follows: (1) Both of fractional vegetation cover (FVC) and net primary productivity (NPP) showed an upward trend, while the "green degree" of vegetation increased significantly in Asku prefecture from 2000 to 2020; (2) The vegetation ecological quality showed a fluctuating upward trend in Aksu from 2000 to 2020. The ecological quality of vegetation in desert and bare land area of oasis edge increased significantly; (3) The dominant factor of VEQI change in most areas of Aksu is human activities, while climate change dominates VEQI change only in a small number of areas such as the north of Wensu county. In this paper, the temporal and spatial variation of vegetation ecological quality and its driving factors in Aksu prefecture in recent 22 years were analyzed by using several vegetation ecological parameters, which could provide data base and technical support for ecological civilization construction.

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Characteristics and drivers of the spatial-temporal change of net primary productivity in the capital area of Kazakhstan from 1994 to 2018

CHEN Yusen,Akida ASKARL,WANG Yongdong,Talgat ABZHANOV,Dani SARSEKOVA,Zhazira ZHUMABEKOVA

2022, 39 (6): 1917-1929. doi: 10.13866/j.azr.2022.06.22

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Clarifying the impacts of climate change and human activity on plant’s net primary productivity (NPP) is crucial for regional ecosystem transformation and sustainable development. Using a simulated scenario experimental design based on the CASA model, five periods of Landsat remote sensing images, and meteorological data spanning the years 1994 to 2018, this paper determines the effects of two factors, human activities and climate change, on plant’s NPP in the capital area. The results indicate that: (1) During 1994-2018, the multi-year average of NPP in the studied area was 226.21 g C·m^-2·a^-1, with a fluctuating rising trend; (2) The execution of the Green Ring Project led to a large positive gain in NPP owing to an increased plantation area (0.38 Tg C·a^-1, P < 0.01).In contrast, the impact of climate change on NPP is more variable, with an overall loss effect (-0.07 Tg C·a^-1, P = 0.34). Under the combined influence of human activity (land use change) and climate change, the NPP of Kazakhstan’s capital area exhibited a considerable positive gain effect (0.27 Tg C·a^-1, P < 0.1); climate change has a lesser impact on plants’ net primary productivity than human activities. (3) Temperature, solar radiation, and precipitation are the most influential climatic elements on NPP. During 1994-2000 and 2006-2012, increased temperature and reduced precipitation caused NPP loss, which dropped from 218.50 g C·m^-2·a^-1, 201.19 g C·m^-2·a^-1 to 189.00 g C·m^-2·a^-1, 188.48 g C·m^-2·a^-1; With the improvement of precipitation circumstances over 2000-2006 and 2012-2018, the mean value of NPP in this area increased significantly, reaching 201.19 g C·m^-2·a^-1, 207.73 g C·m^-2·a^-1 correspondingly. These research findings assist in elucidating the processes of climate change and human activities on NPP and may also serve as a guide to enhance the ecological quality of the desert-steppe area, alleviate the global warming issues, and serve the carbon neutrality goal of Kazakhstan by 2060.

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Remote sensing classification characteristics of typical plant communities in the semi-arid areas of eastern Ningxia

PANG Haiwei,YU Dian,REN Chengbao,ZHANG Yu,ZHENG Caizhi,GUO Jiacheng,BIAN Zhen,SANG Guoqing

2022, 39 (6): 1930-1941. doi: 10.13866/j.azr.2022.06.23

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The vegetation information extraction technology by remote sensing has been widely used in environmental monitoring and ecological protection. It can be seen that this technology has more important significance and application value in desertification frontier areas, such as arid and semi-arid regions. Taking the Haba Lake National Nature Reserve as the research area, the remote sensing extraction of typical plant communities at the regional scale was studied, verifying the applicability of the extraction of plant communities in this area based on the multi-temporal Landsat8 data. Based on the optimal index factor, the optimal band combination was determined. Simultaneously, combined with the object-oriented classification method, eight groups of classification experiments using single-phase and two-phase images with different band combinations were compared and analyzed to explore the influence of multi-temporal data on classification accuracy. The research results show that: (1) Different segmentation parameter settings influence the classification accuracy. Among these, when the compactness factor and shape factor are 0.7 and 0.1, respectively, the optimal classification effect of the experiment can be achieved. (2) The vegetation planted artificially in a large area of the study area has a better classification effect. Natural mixed plant communities, such as Bletilla striata and Achnatherum splendens, easily cause misclassification and mixed classification. (3) According to the final classification accuracy, the classification of multi-temporal data can significantly improve the classification accuracy. Compared with the overall classification accuracy and Kappa coefficient of single-phase data, the maximum improvement is 8.24% and 0.10, which can effectively improve the extraction accuracy of vegetation information in the study area.

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Soil quality evaluation of returning farmland to Manas River irrigation area under the constraints of the“Three Red Lines” strategy of water resources

HUANG Zhou,YANG Guang,SU Jun,LI Xiaolong,LIU Bing,HE Xinlin,QIAO Changlu,LI Pengfei,WANG Chunxia,ZHAO Li

2022, 39 (6): 1942-1951. doi: 10.13866/j.azr.2022.06.24

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The restriction of the “Three Red Lines” strategy of water resources makes the areas dominated by agricultural water gradually conduct “reducing water consumption by returning farmland” measures, which effectively ensures a control index of total water consumption and produces the decline of soil quality of abandoning some land after returning farmland. Taking the returning farmland soil in the Manas River irrigation area in Xinjiang as the research object under the condition of “three red lines,” this paper analyzes the indexes of soil pH value, total dissolved salt, organic matter, total nitrogen, total phosphorus, alkali hydrolyzed nitrogen (AN), and available potassium (AK), and calculates the soil fertility index of returning farmland (RF) and adjacent cultivated plots (CK) by constructing a fuzzy comprehensive evaluation model, and to perform the soil quality evaluation of RF to Manas River irrigation area under the conditions of the “Three Red Lines” strategy. The results show that: (1) The salt content of treatment RF is 10.84% higher than that of CK. Both treatments are moderately saline soil. The salt of treatment RF is mainly accumulated at 40-100 cm. (2) The soil nutrients of RF treatment were lower than CK treatment as a whole, and the difference in alkali hydro nitrogen was the largest, 22.15% lower. (3) The soil fertility evaluation index of the two treatments ranged from 0.49 to 0.77, and the soil quality was above the middle level. The average fertility index of the CK treatment was 6.67% higher than that of the RF treatment. The research results can provide a basis for implementing the land withdrawal scheme under the constraint of the total amount of water resources in the irrigation area and the protection of soil quality.

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Effects of saline water drip irrigation on soil salt accumulation and cotton growth during the whole growth period

GUO Xiaowen,LIU Jiawei,ZHENG Zhiyu,MIN Wei

2022, 39 (6): 1952-1965. doi: 10.13866/j.azr.2022.06.25

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There is a shortage of freshwater resources in arid areas, but saline water resources are abundant. Long-term saline water irrigation will affect soil chemical properties, cotton growth, and yield. By studying the effects of different irrigation water salinity and nitrogen application rates on soil soluble salt ions, soil elements, enzyme activity, cotton growth, and yield, their relationship was analyzed. Three kinds of irrigation water salinity were set in the experiment, which were 0.35 (freshwater), 4.61 (brackish water), and 8.04 (saline water) dS·m^-1, expressed in FW, BW, and SW, respectively. The nitrogen application rates are 0 and 360 kg·hm^-2 respectively, which are expressed as N0 and N360, respectively. The results showed that: (1) compared with fresh water irrigation, brackish water, and saline water irrigation significantly reduced cotton biomass and seed cotton yield. Compared with no nitrogen application, nitrogen application significantly increased cotton biomass and seed cotton yield. (2) With the increase in salinity of irrigation water, the contents of Na⁺, Ca²⁺, Cl^-, and Ca increased significantly, while the contents of $S O 4 2 -$ , $H C O 3 -$ , Mg²⁺, Na, Ni, Co, Cr, K, Fe, Se, and Cu decreased significantly. Under the condition of nitrogen application, the contents of Na⁺, Ca²⁺, Cl^-, and $S O 4 2 -$ increased significantly, while the contents of $H C O 3 -$ , Mg²⁺, K⁺, P, K, Ca, Fe, Se, Zn, Al, and Mg decreased significantly. (3) With the increase in salinity of irrigation water, the activities of sucrase, catalase, dehydrogenase, polyphenol oxidase, hydroxylamine reductase, alkaline phosphatase, and aryl sulfatase decreased significantly, while the activities of nitrate reductase and nitrite reductase increased significantly. Nitrogen application significantly increased soil enzyme activity. Comprehensive analysis showed that saline water irrigation reduced the activities of soil sucrase, catalase, dehydrogenase, polyphenol oxidase, hydroxylamine reductase, alkaline phosphatase, and aryl sulfatase, and reduced the yield of seed cotton. The soluble salt ions Cl^-, SO₄^2-, Na⁺, and Ca²⁺ in saline water were the main driving factors for the change in enzyme activity.

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Simulation and analysis of the effects of precipitation and nitrogen application on the yield and biomass of spring wheat in dryland under elevated temperature

ZHANG Kang,NIE Zhigang,WANG Jun,LI Guang

2022, 39 (6): 1966-1975. doi: 10.13866/j.azr.2022.06.26

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To explore the effects of temperature increase, water decrease, and nitrogen application on spring wheat yield and biomass in semi-arid areas. Based on the meteorological data from 1971 to 2018 in the Anding District, Dingxi City, and the field test data from 2014 to 2018 in the Anjiagou Village, Fengxiang Town, Anding District, Dingxi City, and Gansu Province, this study conducted five temperature gradient (0 ℃,0.5 ℃,1 ℃,1.5 ℃,2 ℃), five precipitation gradient (?20%, ?10%, 0%, 10%, and 20%), and four nitrogen treatments (0 kg?hm^?2, 55 kg?hm^?2, 110 kg?hm^?2, and 220 kg?hm^?2) to analyze the yield and biomass of spring wheat in dryland using regression equation, single factor analysis, and interaction analysis. The wheat yield was analyzed using the relationship between temperature increase and nitrogen application. The results show that: (1) The normalized root mean square error (NRMSE) of wheat yield and biomass simulated by the model was 7.47% and 7.66%, respectively, and the model validity index was 0.91 and 0.85, respectively. The NRMSE of wheat yield and biomass simulated by the model was 1.73%, and the model validity index was 0.98. The results showed that the model could well reflect the effects of temperature, precipitation, and nitrogen application on spring wheat yield and biomass. (2) When the temperature increased, spring wheat yield and biomass showed a parabolic negative effect. Spring wheat yield and biomass presented a downward parabola with a threshold of 122.11 kg?hm^?2 and 129.06 kg?hm^?2, respectively, and the optimal yield and biomass values were 2574.86 kg?hm^?2 and 5777.39 kg?hm^?2, respectively. The increased precipitation has a positive opening parabolic effect on spring wheat yield and biomass. (3) The interaction between the temperature and the nitrogen application rate was negative. The interaction between temperature and precipitation was negative. The interaction between the nitrogen application rate and precipitation was positive. (4) When the yield was optimal at 0 ℃,0.5 ℃,1 ℃,1.5 ℃ and 2 ℃, precipitation should be increased by 20%, and nitrogen application should be 156.2 kg?hm^?2, 149.6 kg?hm^?2, 131.56 kg?hm^?2, 110.0 kg?hm^?2, and 107.8 kg?hm^?2, respectively. (5) The effect order of temperature, nitrogen application, and precipitation on yield is precipitation > nitrogen application > temperature. Reasonable coordination of water and nitrogen can mitigate the negative effect of temperature increase on yield.

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Effects of different irrigation rates on cotton growth and yield formation in Xinjiang

ZHANG Hui,ZHANG Kai,CHEN Bing,YANG Chuan,LIU Ping

2022, 39 (6): 1976-1985. doi: 10.13866/j.azr.2022.06.27

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To study the effects of different irrigation amounts on cotton growth and yield formation in Xinjiang to provide a theoretical basis for water-efficient utilization in high-yield cotton fields in Xinjiang. The field experiment was conducted under drip irrigation under the film. With the normal irrigation volume as the control (3071 m³·hm^-2, I100), three deficit gradients were established, including light deficit (2686 m³·hm^-2, I85), moderate deficit (2421 m³·hm^-2, I75), and severe deficit (1955 m³·hm^-2, I60). The plant height, the number of main stem nodes, the number of fruit branches, boll setting, and shedding characteristics of cotton were measured at different growth stages, the yield components of cotton were measured, and the irrigation water use efficiency was calculated during the harvest period. The results showed that: (1) the bud, flowering, full boll, and boll opening stages of cotton under deficit irrigation treatment were 1-2 days, 2-4 days, 3-8 days, and 4-11 days earlier than that under normal irrigation treatment; (2) Before entering the boll stage, the plant height and internode length of the main stem of cotton showed a trend of first increasing and then decreasing with decreased irrigation amount, and after the boll stage, both decreased with decreased irrigation amount; The number of bolls and fruit set in the middle and lower canopy of cotton decreased with decreased irrigation, and the number of fruit set in the middle canopy significantly differed among different irrigation treatments (P < 0.05); (3) At the harvest stage, the seed cotton yield of I100 treatment was 6090 kg·hm^-2, which was 7.4%-27.3% higher than that of deficit irrigation treatment; The efficiency of irrigation water use increases with decreasing irrigation amount, and the highest is 2.27 kg·m^-3. To sum up, when considering the benefits of agricultural production, efficient utilization of water resources, and the ecological environment, it is recommended to perform moderate deficit irrigation for cotton in Xinjiang to improve the efficiency of irrigation water utilization, save water resources, and achieve the optimization of social, economic, and ecological environment benefits while ensuring high crop yield.

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Recent variations of the Batura, Pasu, and Ghulkin glaciers and their potential impact on the Karakoram highway

LI Zhijie,WANG Ninglian,CHANG Jiawen

2022, 39 (6): 1986-1995. doi: 10.13866/j.azr.2022.06.28

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The Karakoram highway (KKH) is a strategic channel connecting China and Pakistan and promoting the opening up of Xinjiang to the outside world. It is situated on the valley floors of the Pamir-Hindu Kush-Karakoram, where the densest mountain glaciers exist in High Mountain Asia (HMA). The KKH has been affected by glacier hazards for a long time, especially the Batura-Ghulkin section in the middle reaches of the Hunza River. In this study, based on the research documents, field investigation reports, Landsat MSS\TM\ETM+\OLI images, elevation change data sets of HMA, and ITS_LIVE glacier surface velocity data, we reconstructed the historical changes of the Batura, Pasu, and Ghulkin glaciers, including the glacier area, surface elevation, surface velocity, and meltwater runoff over the last 100 years, as well as the impact of glacier variations on KKH. The results show that over the past 100 years, the Batura and Pasu glaciers have generally retreated, with the distance increased between the glacier tongue and KKH, while the Ghulkin glacier has remained stable. Therefore, for the KKH, the current changes in the Batura and Pasu glaciers pose no direct threat. As the Ghulkin glacier is too close to the KKH, particularly the northern glacier tongue, which is only about 170 m, the direct threat to the highway will persist for a long time. For the Batura glacier, the more realistic threat is the migration and reorganization of the meltwater runoff drainage channel (Batura River) from June to July 2021. After the diversion, the water flow will cause strong erosion of the roadbed, which must be attended to by the government. The Pasu glacier has been retreating strongly in the past decades, and the risk of large-scale glacial lake outburst flood has also decreased recently, so the glacier hazard’s threat to the KKH is weakening. With the construction of drainage facilities, the meltwater runoff of the Ghulkin Glacier has been effectively channeled, but the disaster risk contained in the migration and swing of the meltwater channel can not be ignored.

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Dynamic changes and driving factors of the surface freeze-thaw index in Inner Mongolia

ZHANG Haochen,SA Chula,MENG Fanhao,LUO Min,WANG Mulan,GAO Hongdou,ADIYA Saruulzaya

2022, 39 (6): 1996-2008. doi: 10.13866/j.azr.2022.06.29

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Using the trend analysis, correlation analysis and gray correlation, the spatial and temporal variation characteristics and driving factors of the surface freezing index (SFI) and surface thawing index (STI) in Inner Mongolia over the past 40 years were analyzed based on the daily average surface temperature data of 45 meteorological stations in Inner Mongolia from 1980 to 2019, combined with China’s first-generation global land surface reanalysis product (CRA) data and the NDVI data. The study shows that the following: (1) the spatial distribution of annual mean values of the SFI had an increasing pattern from southwest to northeast, while the STI had the opposite pattern, and latitude was the key factor affecting the spatial distribution of the SFI and STI. The SFI and STI showed significant decreasing and increasing trends during the study period, with multi-year variations ranging from 956.1 to 1848.3 ℃·d and 3717.6 to 4442.3 ℃·d, respectively, and rates of change of -156.4 ℃·d·（10a）^-1 and 152.4 ℃·d·（10a）^-1. Compared with the seasonal permafrost zone, the freeze-thaw index in the multi-year permafrost zone was more sensitive to climate warming. (2) The soil SW content, precipitation, and NDVI in the study area showed an increasing trend, and the snow depth showed a decreasing trend over the last 40 years. However, the interannual variation showed different spatial variability, with a warm-dry trend in the multi-year permafrost area and a warm-wet trend in the seasonal permafrost area. The SFI, STI, and influencing factors are mainly negatively correlated. The SFI and the influencing factors were mostly positively correlated in the multi-year permafrost area and mostly negatively correlated in the seasonal permafrost area. The STI was the opposite of the SFI. The change of the SFI and STI in Inner Mongolia was driven by a combination of influencing factors, while 0.4 m of soil water content was the dominant factor affecting the change of the SFI, and NDVI was the dominant factor affecting the change of the STI. The results provide valuable references for permafrost degradation and the production of agriculture and livestock in Inner Mongolia.

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