0261−0271  Effect of debris on seasonal ice melt (2016−2018) on Ponkar Glacier, Manang, Nepal … Reeju Shrestha, Rijan B. Kayastha, Rakesh Kayastha

Abstract: Supraglacial debris is widely present on glaciers in alpine environments and its distribution greatly affects glacier melt. The present study aims to determine the effect of debris on glacier ice melt on Ponkar Glacier, Manang District, Nepal. We estimated ice melt under various debris thickness using Energy Balance (EB) model and conductive heat flux methods, which are compared with in-situ observations. Four stakes are installed on the glacier at different debris thickness of 11−40 cm. Meteorological data from March 2016 to May 2018 are obtained from the Automatic Weather Station (AWS) installed on the glacier surface at an elevation of 3,881 m a.s.l. for the energy balance calculation. Debris surface temperature and different debris depths are also measured on the glacier. The calculated ablation rates from the conductive heat flux method are 0.9, 1.62 and 0.41 cm/d on pre-monsoon, monsoon and post-monsoon, respectively, with mean debris thermal conductivity 1.04 W/(m∙K). The net radiation shows little variation between the seasons, while turbulent heat flux varies in the season. Sensible heat flux was found to be highest in post-monsoon season due to a larger temperature gradient between surface and air.

0272−0283  Processes of runoff in seasonally-frozen ground about a forested catchment of semiarid mountains … PengFei Lin, ZhiBin He, Jun Du, LongFei Chen, Xi Zhu, QuanYan Tian

Abstract: Climate warming increases the variability in runoff of semiarid mountains where seasonally-frozen ground is widely distributed. However, what is not well understood are the processes of runoff, hydrological drivers, and freeze-thaw cycles in seasonally-frozen ground in semiarid mountains. To understand how freeze-thaw cycles affect runoff processes in seasonally-frozen ground, we monitored hydrological processes in a typical headwater catchment with seasonally-frozen ground in Qilian Mountain, China, from 2002 to 2017. We analyzed the responses of runoff to temperature, precipitation, and seasonally-frozen ground to quantify process characteristics and driving factors. The results show that annual runoff was 88.5 mm accounting for 25.6% of rainfall, mainly concentrated in May to October, with baseflow of 36.44 mm. Peak runoff occurred in June, August, and September, i.e., accounting for spring and summer floods. Runoff during the spring flood was produced by a mix of rainfall, melting snow, and melting seasonally-frozen ground, and had a significant correlation with air temperature. Runoff was mainly due to precipitation accumulation during the summer flood. Air temperature, average soil temperature at 0−50 cm depth, and frozen soil depth variable explained 59.60% of the variation of runoff in the thawing period, while precipitation variable explained 21.9%. Thawing-period runoff and soil temperature had a >0.6 correlation coefficient (P <0.05). In the rainfall-period, runoff was also affected by temperature, soil moisture, and precipitation, which explained 33.6%, 34.1% and 18.1%, respectively. Our results show that increasing temperature and precipitation will have an irreversible impact on the hydrological regime in mountainous basins where seasonally-frozen ground is widely distributed.

干旱区山地森林流域径流变化规律及其驱动机制  蔺鹏飞，何志斌，杜军，陈龙飞，朱喜，田全彦

气候变化增加了干旱区山地径流的变异性，而山地径流的变异性对科学地认识变化环境下内陆河流域水资源的管理至关重要。本文基于典型小流域多年观测数据，定量研究了气候变化背景下典型小流域径流变化规律，并探讨了其驱动机制。结果表明祁连山区流域径流过程是受水文气象要素综合控制和影响下的产物，温度主要影响春汛融雪径流过程，降水主要影响夏汛降雨径流过程。径流量主要集中在5~10月，占全年径流总量的89.2%，且径流主要来自高海拔地区（冰川积雪带、寒漠带、高寒草甸、灌丛）。年径流变化过程在6月、8月和9月存在峰值，即存在春汛和夏汛过程，且春汛洪峰峰值明显小于夏汛。春汛融雪径流过程主要由降雨、积雪和季节性冻土融化所产生的混合洪水组成，平均气温、0~50 cm平均土壤温度和冻土冻融厚度对春汛期径流过程起主导作用，贡献率达59.6%。而夏汛径流过程主要是由于降水累积过程形成，夏汛期间的降水既要补充前期土壤中缺失的水分，满足植物对土壤水分的急需，同时以壤中流形式向河道中缓慢汇流，形成河道汇流。夏汛径流与降雨量高度相关，贡献率达到18.1%，而温度等其他要素对径流过程的总贡献率为33.6%。研究结果表明温度和降水的变化将对季节性冻土分布的山区森林流域的水文情势将产生不可逆的影响。

0284−0294  Calculation of salt-frost heave of sulfate saline soil due to long-term freeze−thaw cycles … Tao Wen, Sai Ying, FengXi Zhou

Abstract: Based on salt-frost heave tests of sulfate saline soil under repeated freeze−thaw cycles, this paper discusses the mechanism of the salt-frost heave under long-term freeze−thaw cycles. The results show that the salt-frost heave can be restricted considerably by loads, and there is a critical load for the salt-frost heave cumulative effect. Under this load, peak values of salt-frost heave approach a constant, and the residual values become 0. There is no longer structure heave or cumulative effect of saline soil exposed to freeze−thaw cycles under the critical load. Taking cumulative effect into account in calculations of salt-frost heave, a salt-frost heave model under freeze−thaw cycles is developed.

多次冻融下硫酸盐渍土地基盐冻胀量的计算  文桃，应赛，周凤玺

本文推求了盐冻胀量的关系式，对不同荷载下的硫酸盐渍土进行了多次冻融条件下盐冻胀试验，探讨了多次冻融条件下硫酸盐渍土的盐冻胀机理和规律。结果表明，荷载能有效抑制盐冻胀变形，存在抑制盐冻胀累加性的临界荷载。在盐冻胀累加性临界荷载下，硫酸盐渍土多次冻融下的盐冻胀累加性消失，峰值盐冻胀量为常数，而残余盐冻胀量为0。考虑盐冻胀累加性，建立了多次冻融条件下硫酸盐渍土盐冻胀计算模型。

0295−0305  Seedling germination technique of Carex brunnescens and its application in restoration of Maqu degraded alpine grasslands in northwestern China … JianJun Kang, WenZhi Zhao, CaiXia Zhang, Chan Liu, ZhiWei Wang, HaiJun Wang

Abstract: Carex brunnescens (Pers.) Poir. is considered to be the only clonal herb found to date that can develop and form fixed dunes in Maqu alpine degraded grasslands of northwestern China. However, due to strong dormant characteristics of C. brunnescens seeds, the sand-fixing effect of the plant is severely limited. This study explores a technique that can rapidly promote the seed germination of C. brunnescens, and also investigates the adaptation and sand-fixing effect by cultivating C. brunnescens seedlings to establish living sand barriers in the sand ridges of moving sand dunes. Results show that the seed germination rate obtained a maximum of 63.7% or 65.1% when seeds were treated with 150 mg/L gibberellic acid (GA3) for 24 h followed by soaking in sulfuric acid (98% H₂SO₄) for 2.5 min or sodium hydroxide (10% NaOH) for 3.5 h, and then germinated (25 °C in daytime and 5 °C at nighttime) in darkness for 10 d. After breaking seed dormancy of C. brunnescens, the living sand barrier of C. brunnescens (plant spacing 15−20 cm; sand barrier spacing 10−20 m) was established in the perpendicular direction to the main wind in the middle and lower parts of the sand ridges on both sides of the moving sand dunes. When the sand ridges were leveled by wind erosion, the living sand barrier (plant spacing 15−20 cm; sand barrier spacing 0.5−1.0 m) of C. brunnescens was reestablished on the wind-eroded flat ground. Finally, a stable sand-fixing surface can be formed after connecting the living sand barriers on both sides, thus achieving a good sand-fixing effect. These findings suggest that rapid seed germination technology combined with the sand−fixing method of C. brunnescens can shorten the seed germination period and make the seedling establishment become much easier which may be an effective strategy to restore and reconstruct Maqu degraded grasslands.

玛曲高寒草地褐鳞苔草种子萌发技术及其在退化草地恢复中的应用  康建军，赵文智，张彩霞，刘婵，王志伟，王海军

褐鳞苔草是目前玛曲高寒退化草地发现的唯一能够发育并且形成沙丘的克隆草本植物。然而，由于褐鳞苔草种子具有较强的休眠特性，导致这种优良植物的固沙效果受到严重限制。本研究旨在探索一种促进褐鳞苔草种子快速萌发的技术，并通过培育褐鳞苔草幼苗在流动沙丘的沙垄上建立褐鳞苔草活沙障，研究其适应性和固沙效果。结果表明：在常温下，用98%的H₂SO₄泡种2.5 min或者用10% NaOH泡种3.5 h后，在25/5 °C（12 h/12 h）变温且避光的条件下，经150 mg/L赤霉素（GA₃）浸泡24 h，可快速破除褐鳞苔草种子休眠并使其在10 d内种子发芽率分别达到63.7%和65.1%。打破褐鳞苔草种子休眠后，在流动沙丘两侧沙垄中下部垂直于主风方向建立褐鳞苔草活沙障（株距15~20 cm，沙障间距10~20 m）。待沙垄风蚀拉平后，在风蚀平地上再建植褐鳞苔草活沙障（株距20 cm；间距：0.5~1.0 m），并且连接左右两侧活沙障可形成稳定的固沙面，进而起到较好的固沙效果。以上研究表明，褐鳞苔草种子快速萌发技术与固沙技术相结合可以缩短种子萌发期，使种子育苗变得更加容易，成为恢复和重建玛曲退化草地的有效策略。

0306−0316  Variation in water source of sand-binding vegetation across a chronosequence of artificial desert revegetation in Northwest China … YanXia Pan, XinPing Wang, Rui Hu, YaFeng Zhang, Yang Zhao

Abstract: Water is the most important limiting factor in arid areas, and thus water resource management is critical for the health of dryland ecosystems. However, global climate change and anthropogenic activity make water resource management more difficult, and this situation may be particularly crucial for dryland restoration, because of variation in water uptake patterns associated with artificial revegetation of different ages and vegetation type. However, there is lacking longterm restorations that are suitable for studying this issue. In Shapotou area, Northwest China, artificial revegetation areas were planted several times beginning in 1956, and now form a chronosequence of sand-binding landscapes that are ideal for studying variability in water uptake source by plants over succession. The stable isotopes δ¹⁸O and δ²H were employed to investigate the water uptake patterns of the typical revegetation shrubs Artemisia ordosica and Caragana korshinskii, which were planted in different years. We compared the stable isotope ratios of shrub stem water to groundwater, precipitation, and soil water pools at five layers (5−10, 10−40, 40−80, 80−150, and 150−300 cm). The results indicate that Artemisia ordosica derived the majority of their water from the 20−150 cm soil layer, whereas Caragana korshinskii obtained water from the 40−150 cm soil layer. The main water sources of Artemisia ordosica and C. korshinskii plants changed over time, from deeper about 150 cm depth to shallow 20 cm soil layer. This study can provide insights into water uptake patterns of major desert vegetation and thus water management of artificial ecosystems, at least in Northwest China.

人工植被恢复过程中固沙植物水分来源变化特征研究  潘颜霞, 王新平, 虎瑞，张亚峰, 赵洋

水分是干旱地区最重要的限制因子，水资源管理对旱地生态系统健康至关重要。全球气候变化和人类活动使得水资源管理更为困难，尤其在干旱植被恢复区，不同年龄和类型的人工植被的吸水模式发生了变化，这就需要长期的植被恢复过程来综合研究这一问题。在我国西北腾格里沙漠南缘的沙坡头地区，从1956年开始进行了多次人工植被种植，形成了不同时间序列的人工植被景观，是研究人工植被演替过程中水分来源变化的理想试验地。本文利用稳定同位素¹⁸O和²H研究了不同年代人工植被固沙区典型植物油蒿和柠条根系的水分吸收特征，我们比较了降水、不同深度 (5~10、10~40、40~80、80~150和150~300 cm) 土壤水、地下水和灌木茎干水的稳定同位素值。结果表明，半灌木油蒿主要吸收20~150 cm土层的水分，灌木柠条的水分主要来自40~150 cm土层；且油蒿和柠条的主要水分来源随固沙时间的变化而改变，固沙60余年后，植物的主要水分来源从150 cm土层逐渐变化到20 cm土层。本文可为研究我国北方主要荒漠植被的水分吸收规律及人工生态系统的水分管理提供依据。

0317−0328  Variation characteristics and prediction of pollutant concentration during winter in Lanzhou New District, China … DongYu Jia, XiaoXia Li, XiaoQing Gao, LiWei Yang 

Abstract: PM_2.5 and PM₁₀ were the main air pollutants during winter in Lanzhou New District, China. In this paper, WRF model output combined with hourly monitoring data of pollutant concentration was used to analyze characteristics of the concentration change and to study the relationship between meteorological elements and PM₁₀/PM_2.5 in Lanzhou New District in January, 2018. Meanwhile, the concentration changes of PM_2.5 and PM₁₀ were predicted by wavelet analysis combined with BP neural network. The results show that: (1) Due to the cold front process in winter, PM_2.5 was negatively correlated with the water vapor mixing rate. PM₁₀ was positively correlated with air temperature and negatively correlated with air pressure. (2) There was an inversion layer in the atmosphere near the high value day of PM_2.5 and PM₁₀, the surface was controlled by low pressure, low wind speed, and the situation of low value day of PM_2.5 was the opposite. On the day of high value of PM₁₀, the air temperature below 600 hPa was higher, and the wind speed near the surface was also higher. (3) Wavelet analysis combined with BP (Back Propagation) neural network had a good prediction effect on PM_2.5, which could basically reflect the hourly change of PM_2.5 concentration. However, the simulation effect of PM₁₀ was poor, and the input parameters of surrounding pollutants should be added to improve the prediction effect.

兰州新区冬季污染物浓度的变化特征和预测研究  贾东于，李晓霞，高晓清，杨丽薇

PM_2.5和PM₁₀是兰州新区冬季的主要污染物。本文利用WRF模式结合污染物浓度小时监测数据，分析兰州新区2018年1月污染物浓度的变化特征，同时结合气象要素探究其对PM₁₀和PM_2.5的影响。最后，利用局地气象要素作为输入参量通过小波分析结合BP神经网络预测PM_2.5和PM₁₀的浓度变化。结果表明：(1)在冬季，由于受到冷锋过境的影响，PM_2.5与局地气象要素相关性较好。其中，PM_2.5与水汽混合速率呈负相关。PM₁₀与气温呈正相关，而与气压呈负相关。(2) 冬季重污染和轻污染日与局地天气条件密切相关。在PM_2.5高值日，大气中存在逆温层，地表受低压、低风速控制，而PM_2.5低值日的情况正好相反。在PM₁₀高值日，600 hpa高度以下气温较高，地表附近风速也较高，说明研究区域的PM₁₀浓度主要受到扬尘影响。(3)通过研究发现小波分析结合BP (Back Propagation)神经网络对PM_2.5有较好的预测效果，可以反映PM_2.5浓度的小时变化。但PM₁₀的预测效果较差，在之后的研究中需要进一步增加地形、地势和海拔高度等输入参数来提高预测效果。