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1.
Climatic change during the last 4000 years in the southern Tarim Basin,Xinjiang, northwest China 总被引：1，自引：0，他引：1
In this study, a ca. 4000 cal. yr ancient lacustrine (or wetland) sediment record at the southern margin of Tarim Basin is used to reconstruct the history of climate change. Six radiocarbon dates on organic matter were obtained. δ18O and δ13C of carbonate, pollen and sediment particle size were analysed for climate proxies. The proxies indicate that a drier climate prevailed in the area before ca. 1010 BC and during period 1010 BC–AD 500 climate then changed rapidly and continuously from dry to moist, but after about AD 500 climate generally shows dry condition. Several centennial‐scale climatic events were revealed, with the wettest spell during AD 450–550, and a relatively wetter interval between AD 930–1030. Pollen results show that regional climate may influence human agricultural activities. Spectral analysis of mean grain size (MGS) proxy reveals statistically pronounced cyclic signals, such as ca. 200 yr, ca. 120 yr, ca. 90 yr, ca. 45 yr and ca. 33 or 30 yr, which may be associated with solar activities, implying that solar variability plays an important role in the decadal‐ and centennial‐scale climate variations in the study area. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
2.
“北方海上丝绸之路”作为中国古代与东亚各国进行贸易往来的重要海上通道,促进了宋元时期海上丝绸之路的大发展并成就了明朝大航海的辉煌,研究其始发港的变迁与原因对“海上丝绸之路研究体系”的完善和“21世纪海上丝绸之路”的建设具有重要意义,但目前鲜有研究。基于古代典籍、地方志和历史地图的记载,结合前人对历史时期中国环境变化的认识,对隋唐至明清时期长江三角洲地区“北方海上丝绸之路”主要始发港的变迁与原因进行研究。结果表明: (1)隋唐—明清时期中国长江三角洲地区先后兴起了3个“北方海上丝绸之路”主要始发港,扬州港盛于隋唐,上海港盛于唐宋,明州港(今宁波港)盛于宋元; (2)气候变冷引起的北方少数民族南犯,中原地区经济和政治中心南迁,北方海上丝绸之路的始发港由登州(今蓬莱)迁到了长江三角洲地区; (3)随泥沙堆积,雁形式沙洲发育,河口分汊东伸南移,长江河口海岸由喇叭形的河口湾演化为三角洲,这是引起始发港由扬州港向东迁往上海港、乃至明州港的根本原因; (4)长江河口沙洲的发育,引起了长江扬州港段和上海港段水系的变化,使得2个港作为始发港时,港口的具体位置不断地随河势变化而调整; (5)对外贸易政策的变化亦对始发港的兴衰与变迁起到一定的促进或阻碍作用。 相似文献
3.
“北方海上丝绸之路”作为中国古代与东亚各国进行贸易往来的重要海上通道,促进了宋元时期海上丝绸之路的大发展并成就了明朝大航海的辉煌,研究其始发港的变迁与原因对“海上丝绸之路研究体系”的完善和“21世纪海上丝绸之路”的建设具有重要意义,但目前鲜有研究。基于古代典籍、地方志和历史地图的记载,结合前人对历史时期中国环境变化的认识,对隋唐至明清时期长江三角洲地区“北方海上丝绸之路”主要始发港的变迁与原因进行研究。结果表明: (1)隋唐—明清时期中国长江三角洲地区先后兴起了3个“北方海上丝绸之路”主要始发港,扬州港盛于隋唐,上海港盛于唐宋,明州港(今宁波港)盛于宋元; (2)气候变冷引起的北方少数民族南犯,中原地区经济和政治中心南迁,北方海上丝绸之路的始发港由登州(今蓬莱)迁到了长江三角洲地区; (3)随泥沙堆积,雁形式沙洲发育,河口分汊东伸南移,长江河口海岸由喇叭形的河口湾演化为三角洲,这是引起始发港由扬州港向东迁往上海港、乃至明州港的根本原因; (4)长江河口沙洲的发育,引起了长江扬州港段和上海港段水系的变化,使得2个港作为始发港时,港口的具体位置不断地随河势变化而调整; (5)对外贸易政策的变化亦对始发港的兴衰与变迁起到一定的促进或阻碍作用。 相似文献
4.
Social responses to climate change over human history have been widely discussed in academia over the last two decades. However, the transformation of the human–environment nexus crossing prehistoric and historic periods and the processes associated with it are not yet clearly understood. In this study, based on published works on radiocarbon dating, archaeobotany, zooarchaeology, and archaeological sites, together with a synthesis of historical documents and highresolution paleoclimatic records, we trace the extent to which human settlement patterns in the Hexi Corridor in northwestern China evolved in conjunction with climate change over the last 5,000 years. A total of 129 Neolithic, 126 Bronze Age, and 1,378 historical sites in the Hexi Corridor(n=1,633) were surveyed. Our results show that, in the Late Neolithic and Bronze Age periods(～2800–100 BC), climate change contributed to the transformation of subsistence strategies and the subsequent changes in human settlement patterns in the Hexi Corridor. The warm-humid climate in ～2800–2000 BC promoted millet agriculture and helped the Majiayao, Banshan, and Machang Cultures to flourish. The cold-dry climate in ～2000–100 BC resulted in the divergence and transformation of subsistence strategies in the Xichengyi–Qijia–Siba and Shajing–Shanma Cultures and in a shift in their settlement patterns. However, in the historical period(121 BC–AD 1911), human settlement patterns were primarily determined by geopolitics related to the alternating rule of regimes and frequent wars, especially in the Sui–Tang dynasties. We also find that trans-Eurasian cultural exchange since ～2000 BC improved social resilience to climate change in the Hexi Corridor, mediating the human–environment nexus there. Our findings may provide insights into how human societies reacted to climate change in arid and semi-arid environments over the long term. 相似文献
5.
Climate Change and Silk Road Civilization Evolution in Arid Central Asia: Progress and Issues 总被引：1，自引：0，他引：1
Fahu Chen Guanghui Dong Jianhui Chen Yongqi Gao Wei Huang Tao Wang Shengqian Chen Juzhi Hou 《地球科学进展》2019,34(6):561-572
Arid central Asia is one of the regions most sensitive to global climate change, as well as the region with dramatically hydrological changes and fragile ecosystems. The region includes the main body of the ancient Silk Road, which played a key role in the cultural exchange and the rise and fall of Silk Road civilization. Scientific assessment of the risks faced by the sustainable development of human society in the arid central Asia under the background of global warming is a major scientific issue that has received much attention. The study of the relationship between cultural exchange, development of Silk Road civilization and climate change can provide a scientific basis for understanding the evolution rules of human-land relationship on different timescales in this area. This study summarized the research progress in the history of cultural exchanges, the rise and fall of Silk Road civilization, climate change during the Holocene, forcing mechanisms of climate and hydrological change on different timescales, as well as the process and rule of human-environment interaction. On this basis, we proposed that the study of the temporal and spatial patterns of Holocene climate change and the evolution of Silk Road civilization in arid central Asia, as well as the research on the interaction mechanisms between human and environment, are obviously insufficient. Solving the problems of regional imbalance of climate change and cultural evolution in arid central Asia and strengthening the cross-disciplinary study of geoscience and archaeology are effective ways to promote the study of climate change and changes of Silk Road civilization, which has important scientific and practical significance for understanding the evolution of human-land relations in the region, coping with the challenges of climate change, and serving the “One Belt, One Road” strategy. 相似文献
6.
亚洲中部干旱区是对全球气候变化响应最为敏感的地区之一,也是水文变化剧烈和生态环境脆弱的地区。该地区包括了古丝绸之路的主体,在东西方交流和丝路文明兴衰历史中发挥了关键的作用。科学评估全球增温背景下亚洲中部干旱区人类社会可持续发展面临的风险,是广受关注的重大科学问题。东西方交流和丝路文明发展历史及其与气候环境变化关系的研究,可为认识该地区不同时间尺度人地关系演变的规律提供科学依据。通过总结东西方交流与丝路文明兴衰历史、亚洲中部干旱区全新世气候变化过程、多时间尺度气候一水文变化机制以及人与环境相互作用的过程与规律等领域的研究进展,提出目前亚洲中部干旱区全新世气候环境变化时空格局和丝路文明演化的过程,以及人与环境相互作用机制的研究存在明显不足。破解亚洲中部干旱区气候变化和文化演化研究区域不均衡问题,加强地学与考古学等多学科交叉研究,是推进气候变化与丝路文明变迁研究的有效途径。这对理解该地区人地关系演化规律、应对气候变化带来的挑战、服务国家“一带一路”倡议具有重要的科学价值和现实意义。 相似文献
7.
Annually resolved June–July–August (JJA) temperatures from ca. 570 BC to AD 120 (±100 a; approximately 690 varve years) were quantified from biogenic silica and chironomids (Type II regression; Standard Major Axis calibration‐in‐time) preserved in the varved sediments of Lake Silvaplana, Switzerland. Using 30 a (climatology) moving averages and detrended standard deviations (mean–variability change, MVC), moving linear trends, change points and wavelets, reconstructed temperatures were partitioned into a warmer (+0.3°C; ca. 570–351 BC), cooler (?0.2°C; ca. 350–16 BC) and moderate period (+0.1°C; ca. 15 BC to AD 120) relative to the reconstruction average (10.9°C; reference AD 1950–2000 = 9.8°C). Warm and variable JJA temperatures at the Late Iron Age–Roman Period transition (approximately 50 BC to AD 100 in this region) and a cold anomaly around 470 BC (Early–Late Iron Age) were inferred. Inter‐annual and decadal temperature variability was greater from ca. 570 BC to AD 120 than the last millennium, whereas multi‐decadal and lower‐frequency temperature variability were comparable, as evident in wavelet plots. Using MVC plots of reconstructed JJA temperatures from ca. 570 BC to AD 120, we verified current trends and European climate model outputs for the 21st century, which suggest increased inter‐annual summer temperature variability and extremes in a generally warmer climate (heteroscedasticity; hotspot of variability). We compared these results to MVC plots of instrumental and reconstructed temperatures (from the same sediment core and proxies but a different study) from AD 1177 to AD 2000. Our reconstructed JJA temperatures from ca. 570 BC to AD 120 showed that inter‐annual JJA temperature variability increased rapidly above a threshold of ～10°C mean JJA temperature. This increase accelerated with continued warming up to >11.5°C. We suggest that the Roman Period serves with respect to inter‐annual variability as an analogue for warmer 21st‐century JJA temperatures in the Alps. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
8.
位于华北平原北部的北京,东西北三面环山,形如海湾,中间为一小平原,是地质历史演变成的一块风水宝地。自春秋战国时期作为燕都蓟城,经秦、汉、晋、隋、唐、五代、宋(辽、金)等历代变迁,于金贞元年建都,至其后的元、明、清,多作为都城,先后定名为中都、中都永安府、大都、大都路总管府、北平府、北京、京师顺天府。自辽代起北京城范围比今北京大。北京城地域演变是社会经济发展和人们生活需求自然形成的,它应对现今城市规划布局、人才建设具有重要的参考价值。 相似文献
9.
在佛经与我国史籍中均记载有一种名为＂火珠＂的宝石,但其宝石学成分究竟是什么,历来争论颇大。三国时期,＂火珠＂开始从外国进口,被帝王看作是祥瑞的标志。晋代时期其用于装饰皇太子的玉具剑。隋唐时期,其价值进一步提升,专用于装饰皇帝的玉具剑。自唐朝末年开始,＂火珠＂一词的宝石学意义逐渐减弱。探讨＂火珠＂有助于了解中国古代宝石的使用情况,对构建中国古代宝石学具有重要意义。从＂火珠＂的产地、颜色、稀有性等宝石学特征以及与出土宝石实物比照,对其成分进行了较详细的论证。结果发现,＂火珠＂是巴利文＂Phalika＂（＂颇黎＂）以及梵文＂Sphatika＂（＂塞颇胝迦＂）的意译。＂火珠＂也就是＂颇黎＂,并不是我国常见的水晶,最可能为无色刚玉。 相似文献
10.
黄土高原近两千年来土地利用和环境的变迁 总被引：7，自引：0，他引：7
在220～1368A.D.期间内累计有859年,全部黄土高原在非汉族的管辖之下;而其余289年,该地区的某些部分依然被非汉族所控制。非汉族进入黄土高原以后,土壤侵蚀速度随放牧地的扩张而减小。在隋朝和唐朝期间(581～907A.D.),黄土高原的生态环境较当今温暖湿润,植被更为繁茂,林地约占整个黄土高原面积的25%。在明朝和清朝期间(1368～1911A.D.),黄土高原的大部分森林被破坏,土壤侵蚀速度随自然植被损毁而增大 相似文献
11.
塔里木盆地是中国最大的内陆盆地,它经过长期海陆变迁和盆山耦合作用形成。从元古代到晚二叠纪,一直处于海洋环境,几经海侵海退,有大量海相沉积。从二叠纪末开始,全区抬升,海水退出,盆地进入陆地发展阶段,以湖相和河流相沉积为主,仅在西部边缘有泻湖相沉积;至渐新世,印度板块与欧亚板块在帕米尔地区碰撞拼合,盆地彻底与古特提斯海分离,形成统一的内陆盆地。盆地的气候环境从晚白垩世就已向干热发展,形成了广泛的红色沉积和膏盐;上新世以来,青藏高原及其他山地快速隆升,对盆地的环境格局产生重大影响,盆地腹地出现荒漠化,风成沙堆积面积扩大;第四纪时,干旱化气候进一步加剧,塔克拉玛干沙漠逐渐形成;一些天然绿洲在盆地周围和河流流域相伴而生,从而奠定了今天塔里木盆地的环境格局。古时绿洲大部分是丝绸之路的连接点和集结地,在距今约2000年前的汉朝还比较繁荣,后来变成了废墟和荒漠,塔克拉玛干沙漠的南缘向南推进约100～150km,而注入盆地(沙漠)的河流向上游收缩几百公里。 相似文献
12.
A proxy climate record from a raised bog in County Fermanagh, Northern Ireland, is presented. The record spans the interval between 2850 cal. yr BC and cal. yr AD 1000 and chronological control is achieved through the use of tephrochronology and 14C dating, including a wiggle‐match on one section of the record. Palaeoclimatic inferences are based on a combination of a testate amoebae‐derived water table reconstruction, peat humification and plant macrofossil analyses. This multiproxy approach enables proxy‐specific effects to be identified. Major wet shifts are registered in the proxies at ca. 1510 cal. yr BC, 750 cal. yr BC and cal. yr AD 470. Smaller magnitude shifts to wetter conditions are also recorded at ca. 380 cal. yr BC, 150 cal. yr BC, cal. yr AD 180, and cal. yr AD 690. It is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest Europe. Harmonic analysis of the proxies illustrates statistically significant periodicities of 580, 423–373, 307 and 265 years that may be related to wider Holocene climate cycles. This paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing. Relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
13.
应用第四纪地质学和海相生物等化石数量统计,以天津马棚口海岸带BQ1孔化石鉴定与统计结果,对古气候、古事件进行对比研究。通过岩芯编录,在岩性层中划分出4个海相层、5个过渡层、9个海面波动。结合研究区广泛分布的贝壳堤和牡蛎礁,利用其大量的测年资料,重现了6道海岸线;根据海相化石个体统计数,画出全新世气候演化曲线,与孢粉和物候所画的古气候演化曲线大体一致。研究历代海陆变迁,必然涉及到历史上长期争论不休的西汉大海侵等问题,谭其骧（1965）圈定的大海侵范围、海岸线分布以及考古结果几乎都能联系在一起,因此,大海侵之谜终于尘埃落定。考古界对河北平原自东汉—金的空白也有了初步答案,同时,发现中国朝代兴衰与气候冷暖有明显的对应,从而建立了气候分期。 相似文献
14.
从史料记载看中国历史时期海面波动 总被引：5，自引：0，他引：5
广泛采用文字类海面变化“代用资料”是历史时期小尺度海面波动研究的重要手段，将史籍中有关海面波动的记载与考古学和沉积地层学证据相结合进行综合分析，可以初步认定：我国历史时期2ka年来，西汉至两晋为相对高海面时期（西汉晚期为显著高海面时期）；晋末至隋末为相对低海面时期，唐至南宋为相对高海面时期，尤其是8世纪，11世纪后期至13世纪初期出现显著高海面，而其间的唐末至五代，南宋后期至元初曾出现过海面下降；元明清时期总体为相对低海面时期，但在元中后期至明初，16世纪上半叶，17世纪末至18世纪初分别出现几次相对高海面。 相似文献
15.
Lacustrine sedimentological and geochemical records for the last 170 years of climate and environmental changes in southeastern China 
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下载免费PDF全文 Kandasamy Selvaraj Bao Zhi Lin Jiann‐Yuh Lou Wei Lan Xia Xiang Tong Huang Chen‐Tung A. Chen 《Boreas: An International Journal of Quaternary Research》2016,45(1):165-179
Reconstruction of modern climate and environmental changes in east Asia using inland natural climate archives can provide valuable insights on decadal–multidecadal climate and environmental patterns that are probably related to both natural and anthropogenic forcing. Here we investigated an 89‐cm‐long sediment core (TH1) from Tian Lake, southeastern China, for sedimentological, physical and geochemical parameters in order to understand climate and environmental changes for the latest two centuries. 137Cs‐ and 210Pb‐based age models show that the fine sand–coarse silt‐dominated core contains ~170 years (c. AD 1842–2011) of continuous sedimentation. Sediments with fine sands, low MS values, high water content, high TOC content and a high C:N ratio from c. AD 1842 to 1897 suggest intense hydrological conditions and strong runoff in the catchment, probably because of a humid climate. From AD 1897 to 1990, sediments with very fine sand and coarse silt, high MS values, low water content and unchanged TOC and C:N ratios indicate normal hydrological conditions and in‐lake algae‐derived organic matter. During this interval, the chemical weathering indicators show stronger weathering conditions compared with sediments deposited during AD 1842–1897, supporting the dominance of weathered surface soil input in the earlier interval and physical erosion dominance in the later period, respectively. Since AD 1990, the continuous decrease of geochemical proxies suggests human‐interacted Earth surface processes in the catchment of Tian Lake. A PCA revealed four dominant geochemical controlling factors – detrital input, trophic status, grain size and early diagenesis –, accounting for 26, 20, 18 and 16% of total variance, respectively. This study for the first time provides lacustrine geochemical evidence for the most recent two centuries of climate and environmental changes in coastal southeastern China, a region that is currently undergoing an inversion of critical zone, i.e. an overturning of its soil profile, owing to swift modernization. 相似文献
16.
Celia Martín-Puertas Blas L. Valero-Garcés M. Pilar Mata Peter Dulski 《Quaternary Research》2009,71(2):108-120
The Iberian-Roman Humid Period (IRHP, 2600-1600 cal yr BP), is the most humid phase of the last 4000 yr in southern Spain as recorded in the sedimentary sequence of Zoñar Lake (37°29′00″N, 4°41′22″ W, 300 m a.s.l.). A varve chronology supported by several AMS 14C dates allows study of the lake evolution at annual scale in response to human impact and climate changes. There are four climate phases within this period: i) gradual transition (2600-2500 yr ago, 650-550 BC) from a previous arid period; ii) the most humid interval during the Iberian-Early Roman Epoch (2500-2140 yr ago, 550-190 BC); iii) an arid interval during the Roman Empire Epoch (2140-1800 yr ago, 190 BC AD 150); and iv) a humid period synchronous with the decline of the Roman Empire (1800-1600 yr ago, AD 150-350). Varve thickness and geochemical proxies show a multi-decadal cyclicity similar to modern North Atlantic Oscillation (NAO) (60, 20 years) and solar variability cycles (11 yr). The timing and the structure of this humid period is similar to that described in Eastern Mediterranean and northern European sites and supports the same large-scale climate control for northern latitudes and the Mediterranean region. 相似文献
17.
Two 14C accelerator mass spectrometry (AMS) wiggle‐match dated peat sequences from Denmark and northern England record changes in mire surface wetness reconstructed using plant macrofossil and testate amoebae analyses. A number of significant mid–late Holocene climatic deteriorations (wet shifts) associated with declines in solar activity were recorded (at ca. 2150 cal. yr BC, 740 cal. yr BC, cal. yr AD 930, cal. yr AD 1020, cal. yr AD 1280–1300, cal. yr AD 1640 and cal. yr AD 1790–1830). The wet shifts identified from ca. cal. yr AD 930 are concurrent with or lag decreases in solar activity by 10–50 years. These changes are replicated by previous records from these and other sites in the region and the new records provide improved precision for the ages of these changes. The rapidly accumulating (up to 2–3 yr cm?1, ～1310 yr old, 34 14C dates) Danish profile offers an unprecedented high‐resolution record of climate change from a peat bog, and has effectively recorded a number of significant but short‐lived climate change events since ca. cal. yr AD 690. The longer time intervals between samples and the greater length of time resolved by each sample in the British site due to slower peat accumulation rates (up to 11 yr cm?1, ～5250 yr old, 42 14C dates) acted as a natural smoothing filter preventing the clear registration of some of the rapid climate change events. Not all the significant rises in water table registered in the peat bog archives of the British and Danish sites have been caused by solar forcing, and may be the result of other processes such as changes in other external forcing factors, the internal variability of the climate system or raised bog ecosystem. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
18.
内陆河流域城镇发展的历史过程与机制——以黑河流域为例 总被引：2，自引：0，他引：2
城市的起源与形成是一个极其复杂而漫长的过程,是诸文明要素积累凝聚、从量变到质变的过程.黑河流域的城市大致经历了五个发展阶段:秦汉以前的城市萌芽,两汉时期的奠基期,十六国时期、隋唐时期的第二高峰期,宋以后的衰落期,直到明清以后城市再度复苏.在这一变化过程中,移民屯垦、兴修水利、农牧业的消长与进退、人口迁移与聚集、地缘政治和自然环境的变化是城镇发育与成长的主要驱动力.其中,又蕴含了两个相互交错的正负效应:汉民族的西扩—统一的国家—稳定的地缘政治关系—移民屯垦—兴修水利—农业繁荣—气候暖湿—城镇发展;少数民族东进—地方割据—复杂动荡的地缘政治环境—牧业扩张—气候干冷—沙漠化扩大—城镇衰退.其实质是在特定的地理环境和民族分布格局下,对优势生存空间的争夺. 相似文献
19.
We present a study that reconstructs the ancient courses of the Euphrates in part of the Mesopotamian floodplain west and southwest of the ancient site of Babylon. The focus is on tracing paleochannel courses, determining when these paleochannels were active, and understanding the patterns of avulsion. The research was carried out using a combination of geological, geomorphological, remote sensing, historical, and archaeological approaches. Fieldwork included “ground truthing” of the remote sensing work, manually drilling boreholes (up to 7 m in depth), sedimentary and geomorphological documentation and sample collection for radiocarbon dating. As a result, five main courses of the Euphrates in five different periods have been mapped in this area, including four previously unidentified and/or unlocated migrations that linked the different periods. The main courses are the Purattum Course (before 3100–1000 BC), the Arahtum Course (1000–125 BC), the Sura Course (125 BC to AD 1258), the Hilla Course (13th to 19th century AD), and the Hindiya Course (19th to 20th century AD). There has been an overall migration of the main channel from east to west across the study area over time. The location of avulsion nodes changed along the length of the river, mainly downstream over time, but with a cluster of avulsion events near Babylon and a notable man‐made interference in the 20th century at the Hindiya Barrage. 相似文献
20.
The Tarim Basin is the largest inland basin in China. Its southern margin is a region with the most fragile eco-environment in China. According to archaeological data, historical documents and paleoclimatic information, great changes have taken place in the eco-environment of the region. Such changes are mainly manifested in the temporal-spatial changes of oases and the expansion of desertification extent, which led to the abandonment of some famous ancient cities and the disappearance of the southern route of the Silk Road. At present, desertification of the region is showing an accelerating tendency. This paper analyzes the distribution and evolution laws of oases in the region, deals with their natural and anthropogenic causes, and points out that before the 20th century evolution of the oases gradually occurred under the influence of natural factors, in particular the climatic aridification, while in the 20th century the desertification and environmental degradation of oases are mainly attributed to human activities under the background of arid climate. To halt further degradation of the environment of the oases great efforts should be made to use water and soil resources rationally, develop advantageous resources and protect the natural oases. 相似文献