Risk assessment of mountain tourism on the Western Sichuan Plateau,China

As an important site for tourism activities,mountainous areas may generate greater tourism risks than plain areas due to potential natural disasters,social issues,scenic area management,and tourist behavior.Western Sichuan Plateau is mostly mountainous area and tourism is its pillar industry,Therefore,the assessment of the tourism risks on the Western Sichuan Plateau is of academic value and practical significance.In this study,we use statistical and remote sensing data,fishbone diagram,and the entropy weighting method to construct a tourism risk evaluation model and classify risks into different levels,and we also use a geographic information system(GIS)for spatial mapping to quantify and spatialize the results.The objectives are 1)to identify the risk sources in the Western Sichuan Plateau and analyze their causal mechanisms,precisely reveal the distribution of tourism risks in the study area;2)improve the precision of tourism risk evaluation in scenic areas and analyze the causes and spatial distribution patterns of tourism risks and propose targeted management measures.This study found that the evaluation results of the four elements of hazard,exposure,vulnerability,and disaster prevention and mitigation capacity on the Western Sichuan Plateau showed significant spatial variability,depending on the natural conditions and the quantity difference of tourism resources in different regions.In addition,the tourism risk is low in most areas of the Western Sichuan Plateau,and disaster prevention and mitigation capacity is higher in areas with high tourism risk where attractions are densely populated and tourism is concentrated.Our study can provide a reference for future analyses of tourism risks in mountainous tourist areas such as in China and worldwide.

A Middle Pleistocene Glaciation Record from Lacustrine Sediments in the Western Tibetan Plateau and Discussion on Climate Change

The Tibetan Plateau is an important area for studying global climate change,but the answers to many scientific problems remain unknown.Here,we present new information from the lacustrine sedimentary record in the western Tibetan Plateau,related to the third most-recent glaciations.Continuous sediment data,including sporopollen,particle size,total organic carbon,mass susceptibility,CaCO_(3),CaSO_(4),BaSO_(4)contents and chronological data,were reconstructed and revealed that climate and environmental conditions obviously and distinctly changed between 600 and 700 thousand years ago.In comparison,the data obtained from the Guliya ice core in this area also corresponds to the global glacial climatic characteristics recorded in basin sediments in the eastern and southeastern regions of the plateau and to the information obtained from ice cores in the Antarctic and Arctic regions.In this study,we conclude that the main reason for the glaciations and new tectonic movement must be a geomagnetic polarity reversal 774 thousand years ago(from Matuyama to Brunhes).Indeed,the results of this study suggest that the described reversal event might have influenced the current global climate pattern and will continue to impact climatic changes in the future.

Climate Regionalization for Morchella esculenta Cultivation in the Western Sichuan Plateau Based on GIS

Based on the meteorological data and DEM data in the producing areas of Morchella esculenta in the western Sichuan plateau from 1991 to 2020, the biological characteristics of M. esculenta, as well as the survey of production in the planting area, the correlation between M. esculenta production and the climatic ecological conditions at an altitude of 1 200-3 000 m in the western Sichuan plateau was comprehensively analyzed by using the inverse distance weight method, analytic hierarchy process, climate risk assessment model and geographic information system(GIS), and restrictive or high impact climatic ecological factors were selected as the suitability zoning indicators to carry out the analysis of climatic ecological suitability and planting zoning. The results show that the climatic factors affecting M. esculenta cultivation in the western Sichuan plateau were mainly temperature, temperature difference between day and night, and humidity, and the main meteorological disaster was freezing disaster. Under the influence of vertical changes in temperature, topography and cold damage, the growing areas of M. esculenta in the western Sichuan plateau were mainly distributed in the Minjiang River basin and the river valley along the Dadu River basin at an altitude of 1 200-2 000 m, and were distributed in strips and branches along the rivers. The suitable areas were mainly distributed in Wenchuan, Lixian, Maoxian, Kangding, Jiulong and Luding counties(cities), which were the main producing areas of M. esculenta, but the area was small, accounting for only 3.5% of the study area;the sub-suitable areas were mainly distributed in some towns of Danba, Xiaojin, Wenchuan, Lixian, Maoxian, Heishui and Jiuzhaigou counties, accounting for 36.0% of the total area, and they were the main planting areas of M. esculenta.

Enrichment of Mantle-derived Fluids in the Formation Process of Granitoids: Evidence from the Himalayan Granitoids around Kunjirap in the Western Qinghai-Tibet Plateau

Taking the Himalayan granitoids around Kunjirap in the western Qinghai-Tibetplateau as an example, the authors present in this paper the characteristics of the granitoids richin mantle-derived fluid components and discuss their rock-forming mechanism. The research resultsindicate that the rock assemblage of the studied granitoids involves diopside syenite-diopsidegranite-biotite (monzonitic) granite, consisting mainly of K-feldspar, oligoclase, quartz,iron-phlogolite, diopside and edenite. The rocks are rich in mantle-derived fluid components ofvolatiles including F, alkali metal elements such as K, Na, Rb, Sr and Ha, and radiogenicheat-producing elements such as U and Th. They were generated by the influx of mantle-derived fluidsinto the lower crest to give rise to partial melting during the lithosphere thinning in theQinghai-Tibet plateau.

Analysis of Land Use Change in Western Yunnan Plateau——Taking Midu County as an example

The research of land use/land cover change （LUCC） is the core content of global environmental change research and an important part of the sustainable development research. Taking the Midu County of western Yunnan Plateau as the example, GIS technology was used to make the spatial overlay with the land use database in 2009 and land change survey database in 2014 of Midu County, so as to analyze the changes of land use of the county, and reveal the law of land use change, with the aim to provide the basis for further rational utilization of land resources.

The Impact of Atmospheric Heat Sources over the Eastern Tibetan Plateau and the Tropical Western Pacific on the Summer Rainfall over the Yangtze-River Basin

The variability of the summer rainfall over China is analyzed using the EOF procedure with a new parameter （namely, mode station variance percentage） based on 1951-2000 summer rainfall data from 160 stations in China. Compared with mode variance friction, the mode station variance percentage not only reveals more localized characteristics of the variability of the summer rainfall, but also helps to distinguish the regions with a high degree of dominant EOF modes representing the analyzed observational variable. The atmospheric circulation diagnostic studies with the NCEP/NCAR reanalysis daily data from 1966 to 2000 show that in summer, abundant （scarce） rainfall in the belt-area from the upper-middle reaches of the Yangtze River northeastward to the Huaihe River basin is linked to strong （weak） heat sources over the eastern Tibetan Plateau, while the abundant （scarce） rainfall in the area to the south of the middle-lower reaches of the Yangtze River is closely linked to the weak （strong） heat sources over the tropical western Pacific.

Effects on Asian Monsoon of Gigantic Qinghai－Xizang Plateau and Western Pacific Warm Pool

A GCM study is performed of the effects on Asian summer monsoon initiation of the Qinghai-Xizang Plateauand western Pacific warm pool. results show that the Plateau, being a prominent sensible heat source, acts as a basicfactor for the formation of the monsoon circulation, the northward transported low-latitude and low-level warm,moist flow in relation to the sensible heating experiences dynamic lifting on the south and east sides of the highland,releasing vast quantities of latent heat through condensation, whereby the monsoon circulation pattern is furthermodulated; the temperature contrast between the Pacific warm pool and the Australian / marine continents serves asanother basic factor for the northern SW summer monsoon genesis over the South-China Sea-the western Pacific,which, however, falls into a category of winter monsoon on a physical basis.

Ice rafting history and paleoceanographic reconstructions of Core 08P23 from southern Chukchi Plateau, western Arctic Ocean since Marine Isotope Stage 3

Multiproxy investigations have been performed on Core 08P23 collected from the Chukchi Plateau, the western Arctic Ocean, during the Third Chinese National Arctic Expedition. The core was dated back to Ma-rine Isotope Stage （MIS） 3 by a combination of Accelerator Mass Spectrometric （AMS） carbon-14 dating and regional core correlation. A total of five prominent ice-rafted detritus （IRD） events were recognized in MIS 2 and MIS 3. The IRD sources in MIS 3 are originated from vast carbonate rock outcrops of the Canadian Arctic Archipelago and clastic quartz in MIS 2 may have a Eurasian origin. Mostδ18O andδ13C values of Neogloboquadrina pachyderma （sinistral） （Nps） in Core 08P23 are lighter than the average values of surface sediments. The lighterδ18O andδ13C values of Nps in the two brown layers in MIS 1 and MIS 3 were resulted from meltwater events; and those in the gray layers in MIS 3 were caused by the enhanced sea ice formation. Theδ18O values varied inversely withδ13C in MIS 2 indicate that the study area was covered by thick sea ice or ice sheet with low temperature and little meltwater, which prevented the biological productivity and sea-atmosphere exchange, as well as water mass ventilation. The covaried light values ofδ18O andδ13C in MIS 1 and MIS 3 were resulted from meltwater and/or brine injection.

Impact of Surface Sensible Heating over the Tibetan Plateau on the Western Pacific Subtropical High: A Land–Air–Sea Interaction Perspective

The impact of surface sensible heating over the Tibetan Plateau （SHTP） on the western Pacific subtropical high （WPSH） with and without air-sea interaction was investigated in this study. Data analysis indicated that SHTP acts as a relatively independent factor in modulating the WPSH anomaly compared with ENSO events. Stronger spring SHTP is usually fol- lowed by an enhanced and westward extension of the WPSH in summer, and vice versa. Numerical experiments using both an AGCM and a CGCM confirmed that SHTP influences the large-scale circulation anomaly over the Pacific, which features a barotropic anticyclonic response over the northwestern Pacific and a cyclonic response to the south. Owing to different background circulation in spring and summer, such a response facilitates a subdued WPSH in spring but an en- hanced WPSH in summer. Moreover, the CGCM results showed that the equatorial low-level westerly at the south edge of the cyclonic anomaly brings about a warm SST anomaly （SSTA） in the equatorial central Pacific via surface warm advection. Subsequently, an atmospheric Rossby wave is stimulated to the northwest of the warm SSTA, which in turn enhances the at- mospheric dipole anomalies over the western Pacific. Therefore, the air-sea feedbacks involved tend to reinforce the effect of SHTP on the WPSH anomaly, and the role of SHTP on general circulation needs to be considered in a land-air-sea interaction framework.

Cenozoic uplift of the Tibetan Plateau:Evidence from the tectonic-sedimentary evolution of the western Qaidam Basin

Geologists agree that the collision of the Indian and Asian plates caused uplift of the Tibet Plateau. However, controversy still exists regarding the modes and mechanisms of the Tibetan Plateau uplift. Geology has recorded this uplift well in the Qaidam Basin. This paper analyzes the tectonic and sedimentary evolution of the western Qaidam Basin using sub-surface seismic and drill data. The Cenozoic intensity and history of deformation in the Qaidam Basin have been reconstructed based on the tectonic developments, faults growth index, sedimentary facies variations, and the migration of the depositional depressions. The changes in the sedimentary facies show that lakes in the western Qaidam Basin had gone from inflow to still water deposition to withdrawal. Tectonic movements controlled deposition in various depressions, and the depressions gradually shifted southeastward. In addition, the morphology of the surface structures in the western Qaidam Basin shows that the Cenozoic tectonic movements controlled the evolution of the Basin and divided it into （a） the southern fault terrace zone, （b） a central Yingxiongling orogenic belt, and （c） the northern fold-thrust belt; divided by the XI fault （Youshi fault） and Youbei fault, respectively. The field data indicate that the western Qaidam Basin formed in a Cenozoic compressive tectonic environment caused by the India--Asia plate collision. Further, the Basin experienced two phases of intensive tectonic deformation. The first phase occurred during the Middle Eocene--Early Miocene （Xia Ganchaigou Fm. and Shang Ganchaigou Fro., 43.8- 22 Ma）, and peaked in the Early Oligocene （Upper Xia Ganchaigou Fro., 31.5 Ma）. The second phase occurred between the Middle Miocene and the Present （Shang Youshashan Fro. and Qigequan Fro., 14.9-0 Ma）, and was stronger than the first phase. The tectonic--sedimentary evolution and the orienta- tion of surface structures in the western Qaidam Basin resulted from the Tibetan Plateau uplift, and recorded the periodic northward growth of the Plateau. Recognizing this early tectonic--sedimentary evolution supports the previous conclusion that northern Tibet responded to the collision between India and Asia shortly after its initiation. However, the current results reveal that northern Tibet also experi- enced another phase of uplift during the late Neogene. The effects of these two stages of tectonic activity combined to produce the current Tibetan Plateau.

Ocean Ridge Granite and Its Geochemical Characteristics in Western Qinghai-Xizang Plateau

In our work, ocean ridge granite, i.e., Oytag plagiogranite massif, was discovered in western Qinghai\|Xizang plateau. It intruded into the basic lava of the Oytag ophiolite suite and it was formed a little later than the (ultra) mafic rocks of the Oytag ophiolite suite. The Oytag plagiogranite possesses the geochemical characteristics of mantle\|source granite and was formed in the \!supra\|subduction zone" (SSZ) ocean ridge environment, like the ocean ridge granite of Troodos, Cypus.

A Study on Forest Species Diversity and Its Ecological Service Function in the Plateau Area of Western Sichuan

This paper presents a study on species diversity and its ecological service function in the plateau area in western Sichuan. The results show that species diversity in the plantations on the cutover land has a tendency to increase and that its ecological service function is to be improved with stand age growing. The species diversity in forest communities is also gradually increased on different succession stage till reaching a climax level. But the species diversity in the climax community is slightly decreased before it reaches a relatively constant status. Ecological service function of diversity is gradually strengthened with the progress of succession. In addition, species diversity in a stand in a similar site and at a same age differs among forest types. Species diversity index within a coniferous and broad-leaved mixed forest is larger than that within a coniferous forest. Meanwhile, species diversity enriches as the tree density increases.

Deep Drilling Campaign in the Western Qaidam Basin,NE Tibetan Plateau and their Revealed Global Temperature Forcing of Salt Formation in the Late Miocene-Quaternary

The Qaidam Basin in the NE Tibetan Plateau has contributed the largest amount of potash in China.However,how the potash was formed has long been a subject of debate.Here we carried out a deep drilling

川西高原和攀西地区不同级别短时强降水环境参量特征对比分析

利用2010—2021年5—9月川西高原和攀西地区62个国家级自动站逐小时观测资料及时间分辨率为1 h的ERA5再分析资料,对比分析了两区域不同级别短时强降水发生发展过程中水汽、热力和垂直风切变等环境参量特征。结果表明:川西高原和攀西地区短时强降水主要集中在6—8月,午后至前半夜是川西高原短时强降水的高发时段,攀西地区则表现出明显的夜雨特征。就川西高原而言,较好的水汽、热力条件和较强的垂直风切变、上升运动均有利于高级别短时强降水的产生;不同级别短时强降水的CAPE值差异显著,1100 J·kg^(−1)可作为判断是否出现20 mm·h^(−1)以上短时强降水的参考阈值。就攀西地区而言,不同级别短时强降水在暖云层厚度、700 hPa比湿、700 hPa假相当位温、CAPE、0~3 km垂直风切变等环境参量的值域分布上均存在明显差异;当700 hPa比湿大于13 g·kg^(−1)、CPAE值超过1100 J·kg^(−1)、0~3 km垂直风切变达到10 m·s^(−1)时,极易出现50 mm·h^(−1)以上的短时强降水。

川西高原某隧道幔源气逸出机理及防控研究

川西高原地区特殊的构造和岩性为幔源气提供了赋存环境。本文针对幔源气成因、出气段落超前地质预报探测原则、检测与监测进行了阐述,总结了幔源气出气段工作思路:(1)辨识幔源气类型及其不同浓度下的危害;(2)树立“物钻结合,长短结合”的超前地质预报理念;(3)加强气体的检测与监测,加强幔源气的通风管理。通过以上探测及防控手段,实现了对岩浆岩幔源气的可防可治,保证了施工安全。研究成果可为类似地质背景环境的隧道施工提供针对性探测及防控思路。

川西高原土地利用碳储量估算及多情景预测

[目的]区域碳储量与土地利用密切相关。在“双碳”目标下,从碳储量视角开展重点区域土地利用变化预测研究,对协调与优化区域土地利用格局、提高区域生态系统未来固碳潜力具有重要参考价值。[方法]以川西高原为研究区,以2000年、2010年和2020年土地利用为数据源,预测不同情景下2030年土地利用,结合修正的土地利用碳密度数据和InVEST模型估算区域碳储量变化。[结果](1)从各地类相对研究区的面积占比变化看,2000—2020年草地从65.20%逐步缩减到63.65%,林地从31.73%不断扩张到32.92%,未利用地先减后增且净增0.57%,水域和耕地先增后减均净减0.11%,湿地持续增加,共净增0.07%;研究区2000年、2010年、2020年碳储量分别为24.26×10^(8),24.29×10^(8),24.27×10^(8) t,呈先增后减趋势。(2)与2020年相比,2030年自然发展情景下碳储量减少3.19×10^(5) t,在耕地保护情景、生态保护情景、耕地生态联合保护情景下将分别固碳4.29×10^(6),9.72×10^(6),9.60×10^(6) t。[结论]扭转未利用地的扩张趋势,在保持耕地面积的基础上继续稳步推行生态保护政策,提高川西高原陆地生态系统固碳潜力并助力其成为重要“碳汇”区域应成为川西高原国土空间规划和管控的关注重点。

川西北高原区植被覆盖变化及驱动力

[目的]了解川西北高原区植被覆盖变化规律及驱动力,为区域植被保护与恢复建设提供理论参考。[方法]以MODIS NDVI为基础数据,结合Sen氏趋势、Manna-Kendall检验及Hurst模型完成该地区近20年空间分布特征、趋势变化和未来可持续状态分析,以地理探测器对其驱动力进行探索。[结果](1)该地区植被覆盖整体表现为东部相对较好;(2)全时段内,全域80.56%的地区植被覆盖变化趋势为无显著改变,显著改善地区全域面积占比为17.80%;(3)Hurst指数表明,未来全域植被覆盖整体将处于无显著改变的发展状态;(4)高程、年均气温和土壤类型的单因子解释力均在30%以上,它们是驱动植被覆盖分布格局差异形成的主要因素,各因子交互协同作用均为增强效果,各因子适宜植被生长的区间或类型也存在明显差异;(5)自然因素主导了区域植被覆盖空间分布总体格局的形成,而土地利用类型则是驱使其动态变化的关键因素。近20年内,川西高原区植被覆盖变化规律显著,自然因素主导了区域植被覆盖的空间分布格局。[结论]近20年研究区植被覆盖变化规律明显,自然因子虽然主导了植被覆盖的空间布局,但是对其格局变化产生驱动作用的因素主要为人类活动。

四川盆地及川西高原地区FY-3D/VASS温湿度廓线检验

利用2020—2021年探空站及ERA5再分析资料,对FY-3D大气垂直探测系统(VASS)温湿度廓线在四川盆地及川西高原地区的精度进行检验。结果表明:与ERA5数据相比,FY-3D/VASS温度在盆地和高原地区不同季节的平均偏差分别为-0.631~0.500℃和-2.230~-1.234℃,均方根误差分别为2.117~3.222℃和3.077~3.460℃,高原比盆地地区大,在垂直高度上,盆地地区的精度在800~700 hPa较低,高原地区的精度随高度的减小逐渐降低;FY-3D/VASS比湿呈现一致的负偏差,平均偏差在盆地和高原地区分别为-0.775~-0.525 g·kg^(-1)和-1.096~-0.347 g·kg^(-1),均方根误差分别为1.251~2.367 g·kg^(-1)和0.696~1.991 g·kg^(-1),在700~600 hPa的精度较低;通过将两组检验的平均偏差相加,间接建立FY-3D/VASS基于探空温湿度数据的检验结果,其中FY-3D/VASS温度在盆地地区的平均偏差较小,高原地区平均偏低2.440℃左右,比湿在盆地和高原地区平均偏低0.612 g·kg^(-1)左右。上述结果可提升FY-3D/VASS温湿度反演产品在四川盆地及川西高原地区的天气气候应用能力。

川西高原毛垭坝盆地全新世气候变化

在西风带、东亚季风和印度季风的共同影响下,青藏高原不同区域全新世气候变化过程存在显著差异,加强不同区域古气候变化研究对重建青藏高原全新世气候变化过程及理解其变化机制具有重要意义。以青藏高原东部川西高原理塘县毛垭坝盆地全新世地层为研究对象,在14C测年的基础上,通过沉积环境和多个古气候代用指标的分析,重建了全新世气候变化过程。毛垭坝盆地早-中全新世冰水湖沉积物覆盖在末次冰期冰碛物之上,晚全新世为冲洪积物。全新世沉积物在筛除砾石(粒径>2 mm)后的粒度组成以中粉砂以下粒级(粒径<32μm)为主,占比多>80%,是冰川磨蚀作用的产物。磁化率在古土壤层明显增大,结合粒径<1μm粒度组分的出现,可能说明成壤作用生成的强磁性矿物是磁化率值增大的原因。在冰水湖还原环境中磁化率值显著减小,可能与磁性矿物溶解有关。结合总有机碳(TOC)和色度参数的综合分析表明,毛垭坝盆地早全新世气候温干,中全新世暖湿,晚全新世温干,这一变化过程与青藏高原东部全新世气候变化总的趋势相符。在晚全新世气候温干的趋势下,毛垭坝盆地在2 700 a BP古土壤发育,气候温湿。

川西高原绿色韧性公路建设探索与工程实践

从四川盆地边缘向川西高原过渡区域受构造地质作用,地质结构极为复杂,生态脆弱,韧性度差。随着西部大开发如火如荼的进行,川西高原公路交通基础设施建设进一步加强。从国家和行业层面,提出了绿色公路建设理念,但对韧性公路建设很少涉及,特别是针对川西高原公路建设从绿色韧性方面研究,尚无成熟的经验可以借鉴。以汶马、久马高速公路建设为例,从绿色韧性入手,明确绿色韧性建设应用和提升技术,创新性探索提出“绿色和韧性协同,融合发展”的建设理念,并阐述在此理念指导下如何在川西高原韧性度差和生态敏感的公路上,建设韧性度高且绿色环保的相关举措。探索提出如何提供路网韧性和绿色环保建设的措施,以期为川西高原广大公路建设提供借鉴和参考。