Quantitative analysis on the dynamic characteristics of megadunes around the Crescent Moon Spring, China

The Crescent Moon Spring is a precious natural heritage. However, the dynamic characteristics of megadunes around the Crescent Moon Spring are not well known. This paper quantitatively studied the character- istics and changes of megadunes around the Crescent Moon Spring by interpreting aerial photographs taken in 1985 and 2004 and analysing the dune crestlines and the wind data collected from 2011 to 2012. Results revealed that pyramid dunes were formed by a complex wind regime. The Crescent Moon Spring was not buried by shifting sands because of the stable wind regime and relative stability of pyramid dunes. The crestlines of the dunes around the spring moved northward between 1985 and 2004. The south-facing slip faces were also exposed to wind ero- sion, whereas the other faces were under deposition, thus indicating that the southerly wind was relatively en- hanced. Limiting the scale of tall windbreaks and architectures in the Dunhuang oasis at the north of the spring was necessary to maintain the dynamic equilibrium of the wind regime and sand transport.

Bacterial diversity in the sediment of Crescent Moon Spring,Kumtag Desert,Northwest China

Desert lake, a unique oasis in desert ecosystems, harbours different bacterial communities. Thus, it is considered as a hub of bacterial diversity. In this study, bacterial diversity in the sediment of Crescent Moon Spring, Kumtag Desert, Northwest China was analyzed using high-throughput amplicon pyrosequencing analysis. The sequences of the most abundant OUTs （Operational Taxonomic Units） in the sediment of Crescent Moon Spring were compared with the sequences of those most abundant OUTs of various origins from NCBI GenBank database to detect the origins of bacteria in the sediment of Crescent Moon Spring. Also, bacterial compositions between sediment of Crescent Moon Spring and other desert and lake ecosystems （including desert lakes） worldwide were compared using cluster analysis to determine the possible factors affecting bacterial compositions. In total, 11,855 sequences were obtained and 30 phyla were identified. At the phylum level, the dominant phylum was Proteobacteria with α-Proteobacteria being the first dominant class and the second dominant phylum was Planctomycetes. Our finding that α-Proteobacteria being the first dominant class of Proteobacteria and Planctomycetes being the second dominant phyla are somewhat contradictory with reports from other desert lake sediments. This difference could be resulted from water hydration and conductivity, as well as oligotrophic conditions of Crescent Moon Spring. At the genus level, Rhodobacter, Caldilinea, Planctomyces, and Porphyrobacterwere the dominant genera in the sediment of Crescent Moon Spring. Comparisons on sequences of the most abundant OUTs （including OTU3615, OTU6535, and OTU6646） between sediment of Crescent Moon Spring and various origins from NCBI GenBank database indicate that the origins of bacteria in the sediment of Crescent Moon Spring are likely from the underground water. Furthermore, cluster analysis on comparisons of bacteria compositions between sediment of Crescent Moon Spring and other desert and lake ecosystems （including desert lakes） worldwide shows that at regional scales, bacterial compositions may be mainly affected by geographical patterns, precipitation amounts, and pH values. Collectively, our results provide new knowledge on the bacterial diversity in desert lake ecosystems.

Morphological variation of star dune and implications for dune management: a case study at the Crescent Moon Spring scenic spot of Dunhuang, China

Aerial photographs and 3-D laser scans of a 90-m high star dune at the Crescent Moon Spring scenic spot in Dunhuang,China,are used to investigate the changes in dune morphology on timescales from months to decades.The result revealed that relative-equilibrium airflow strength in three wind directions of northeast,west and south was an important condition for the stability of star dunes with limited migration.Transverse and longitudinal airflows exerted a crucial impact on variation processes of star dune morphology.Controlled by transverse airflows,the easterly winds,the east side was dominated by wind erosion;and strong deposition occurred on the south-south-east arm with a maximum deposition rate of 0.44 m/a in the 46-a monitoring period,causing the east side becoming steep and high.Controlled by longitudinal airflows,the westerly winds,the west-north-west side was mainly eroded and the north arm migrated from west to east with a rate of 0.30 m/a,causing the dune slope becoming gentle and elongate.The local air circulation(southerly winds)exerted a significant impact on the development process of the star dune.Due to the influence of human activities,the south side present surface processes from a concave profile to a convex profile in 46 a,which is a potential threat to the Crescent Moon Spring.The results indicate that rehabilitating the airflow field at most is a crucial strategy to the protection of Crescent Moon Spring from burial.Opening up the passage of easterly,westerly and southerly winds through intermediately cutting the protection forest,demolishing the enclosed wall and changing the pavilion into a porous pattern have been suggested to protect the Crescent Moon Spring from burial.

敦煌月牙泉湖成因与地质保护

月牙泉是甘肃敦煌市的胜景,自20世纪60年代以来泉湖水位逐年下降,近年来有加速下降的趋势,为拯救月牙泉投入了大量的人力、物力和财力,但收效甚微。在前人研究的基础上,通过现场调查,提出了对泉湖地质成因的新认识及研究思路和拯救措施的新构想。在详细分析研究泉湖区水文地质结构的基础上,采取适当的阻水帷幕技术,即可减少泉湖排泄流量,保持稳定水位。同时应加强区域地下水资源规划和管理,切实改变区域地下水位持续下降的局面,维持生态环境的健康发展。

敦煌月牙泉的蓝藻类

1981年,1983年,1989年3次在敦煌月牙泉共采集蓝藻标本12号,经鉴定隶属于2科9属15种。

敦煌月牙泉湖近百年水位变化及其原因分析

敦煌月牙泉形成于第四纪全新世,距今约12 ka。因泉湖地处鸣沙山环抱之中,形似月牙并兼具沙水共生的淡水泉湖特征,成为世界瞩目的自然地理环境的重要地质遗迹。对月牙泉湖近百年水位动态变化进行了综合分析,认为月牙泉湖水位动态变化的综合原因可归结为气候和人为因素。1960年开始农业打井灌溉、党河水库和渠系的修建导致地下水补、排失衡,到2001年月牙泉湖水位下降9.98 m,年均下降0.24 m,致使区域性地下水位的下降是造成月牙泉湖水位下降的主要原因,气温的升高加大蒸发量是月牙泉湖水位动态变化的次要原因。通过月牙泉人工补水工程,2018~2019年月牙泉湖水位上升1.58 m,湖水域面积由9472.59m^2逐渐扩大到13334.75m^2,昔日古人心中美丽的月牙泉面貌再次展现在我们的眼前。

中国当代“舞剧邻界批评”举隅——中国当代舞剧批评研究随笔之五

舞剧是以舞蹈为主要表现手段的综合性戏剧样式。所谓“舞剧邻界批评”是指深度参与这个“综合性戏剧样式”的各方—主要是音乐、戏剧、美术等相关艺术领域的学者对舞剧的批评。作为“中国当代舞剧批评研究随笔”系列的第五篇,举隅的批评文章出自六位学者:三位来自音乐界(两位作曲家和一位乐评家),两位来自戏剧界,一位来自美术界。六篇批评文章对舞剧的透彻分析和美学提升,对于我国当代舞剧批评而言具有很好的示范作用。

敦煌鸣沙山月牙泉景区风沙环境分析

基于月牙泉周边7个气象站点同步风况资料,探讨月牙泉周边起沙风况、输沙势以及主导输沙方向的空间分布特征。结合月牙泉周边沙山、建筑物、树木等的方位特点,剖析了近年来月牙泉受沙害困扰的缘由。由于受南北两高大沙山的夹击,该区北风相对较少,西风和南风较强,南侧沙山的北移最为突出,直接威胁月牙泉的存亡。

敦煌鸣沙山-月牙泉近地表风沙输移路径及强度

利用鸣沙山-月牙泉景区多点同步风况和输沙通量资料,探讨了近地表流场特征、风沙活动强度及输移路径;基于1985和2009年两期遥感影像,揭示高大沙山动态变化及其对月牙泉的影响。月牙泉主要受南北沙山夹击,尤其是北沙山南移更为突出,直接威胁月牙泉存在。近年来,受地形、周边建筑物和外围树木的影响,月牙泉景区近地表流场改变,导致区域输沙动态平衡破坏。因此,月牙泉风沙防治应从恢复近地表风沙流场角度考虑,遵循风沙动态平衡原则,打通月牙泉景区东风通道,恢复均衡环流结构,这是维系高大沙山与月牙泉共存的关键。

敦煌月牙泉景区沙丘粒度特征

对月牙泉外围沙山表面沉积物进行系统采样,结合区域风况,分析了沙山典型部位的粒度分布及其参数特征。月牙泉北侧金字塔沙丘沙粒较粗,分选性较差,正偏趋势显著;月牙泉南侧线形沙丘以细沙为主,分选性较好,分布属正偏态。北侧金字塔沙丘从西南和西北两个坡面到东侧坡面,粗颗粒减少、分选性变好,但趋势不明显,说明金字塔沙丘未发生明显移动;而南侧线形沙丘自南侧坡面向北侧坡面沙粒粒径变小、分选变好,较细的沙粒被搬运并沉积北侧坡面,搬运作用十分明显,即线形沙丘向月牙泉方向发生明显移动。通过粒度分析风沙动力环境表明,月牙泉风沙危害主要来自南侧沙山北移。

金字塔沙丘近地表流场及其对月牙泉影响研究

对月牙泉景区气象站点资料和积沙量统计分析以及月牙泉北侧金字塔沙丘近地表流场野外观测表明:受地形影响,月牙泉景区和金字塔沙丘各点起沙风玫瑰和输沙势玫瑰在监测期内差别较大。在金字塔沙丘影响下,不同风向下气流发生多次分离和汇集,沙丘近地表气流发生明显变化,携沙气流行进方向发生改变。金字塔沙丘坡面上各点合成输沙势和起沙风与坡面走向呈垂直角度,气流沿坡面爬越沙丘时,动能发生损耗,携沙能力减弱,减少了进入月牙泉的风沙量,减弱了月牙泉的风沙灾害。

气象要素对敦煌鸣沙山月牙泉风景区风沙输移的影响

利用月牙泉及其周边架设的自动气象站观测资料,结合WRF-LES模式模拟月牙泉内山谷风,对该区域风场和输沙进行分析。结果表明：1敦煌地区盛行西北风、东北风和南风,3种风向相互抵消,使得敦煌的沙丘格局基本稳定。2月牙泉的风沙运动春夏季较强而秋冬季较弱,外围区域较中心活跃,在流经月牙泉的过程中,起沙风作用时间损失30%-40%,由于能量的分散及地形的阻碍,风向偏折且风速降低,挟沙风中的一部分沙粒被留在了泉内。3 WRF-LES模拟结果显示,月牙泉和它南北两侧的鸣沙山间可产生日夜相反的山谷风,水体和沙漠的比热容差异导致边界层形成高低压的交错分布,从而驱使空气流动形成山谷风。白天的温差更大,谷风的影响大于山风。山谷风的平均风速约为0.767 m·s-1,由月牙泉吹向南北两侧。此外,山谷风能加强泉内挟沙风的风速,使总输沙量增加了8.48%。

敦煌月牙泉风沙环境及沙山动态监测

通过对月牙泉景区气象站点资料以及周边沙山高度定点长期监测数据的分析,得出景区内由于受周边高大沙山地形因素影响,景区内形成了两组主导风向下的局地环流,两组环流风向相反,物质搬运方向相反。但随着周边环境的变化,环流产生变化,原有输沙平衡遭到破坏,造成了南山和北山对月牙泉形成夹击之势。从沙山高度变化的监测中,除东山高度有降低趋势外,其余各点均表现为增高趋势,与输沙势分析结果保持一致。通过以上分析,从风流场方面揭示出月牙泉夹击之势的形成原因,剖析出沙害的根源,进而为保护月牙泉提供强有力的科学依据,并为揭示飞沙不落月牙泉现象奠定研究基础。