Rockfall hazard in the Daisekkei Valley, the northern Japanese Alps, on 11 August 2005

This paper describes a rockfall event in the Daisekkei Valley of Mount Shirouma-dake (2,932 m), the northern Japanese Alps. The rockfall occurred on a steep cliff comprising well-jointed felsites and produced debris of ≥8,000 m³. Most debris was deposited on an elongated snowpatch located immediately beneath the cliff, and it caused casualties among people who were trekking along a trail on the snowpatch. Additionally, a large rock block slipped 1 km on the snowpatch. The rockfall could have been due to the differential retreat of the rockwall, which contains areas of high- and low-density joints. Seasonal and diurnal freeze–thaw activities and snow avalanches and wash appear to be important factors responsible for the retreat. Although some rock blocks that can collapse further remain on the rockwall, the position of the mountain trail in the Daisekkei Valley is fixed. Fundamental reform of tourism systems for climbers, including education on natural hazards, is required.     

藏北高山嵩草草旬植被和多样性在沙漠化过程中的变化

为确定沙漠化对高山嵩草草甸植被组成、结构和物种多样性的影响，了解高寒区草甸沙漠化的原因，选择西藏那曲安多县南部沙漠化严重区域为调查区，按照沙漠化的不同程度设置样地，系统调查了轻度、中度、重度和极重度沙化草甸的植被变化，结果表明：中度、重度和极重度沙化区的植被与轻度沙化草甸有显著的差异；在中度和重度沙化区，高寒草甸的建群种高山嵩草已被家畜不喜食或更具抗性的植物种所取代，而在极重度沙化的流动沙丘上无植被生长；从过牧的退化草甸到半流动、流动沙丘，植物种多样性呈显著的降低趋势。轻度沙化草甸物种数、个体密度和丰富度指数最多；中度沙化草甸的Shannon-Wiener指数和均匀度指数最大，而优势度指数最小；在沙化过程中，高寒草甸的植被盖度显著下降，地上生物量也在下降，虽然轻度、中度和重度沙化草地的地上生物量显著高于极重度沙化区，但前者之间却无显著差异。地下根系生物量也呈显著下降的趋势。过牧是造成高山嵩草草甸沙化的主要原因。     

利用卫星ETM与样方统计数据研究西鄂尔多斯珍稀濒危植物种群分布规律

使用1999年8月30m分辨率的ETM遥感数据、DEM数据和25个典型的4^4m^2的地面实测样方统计数据、数字化了1994年的珍稀淑危植物分布图，用遥感技术西鄂尔多斯珍稀濒危植物群落进行了水平和垂直带分布规律的研究。图像处理采用遥感弱信息提取技术，识别了建群植物及其种群组合特征；并结合三维景观影像对珍稀植物种群生存生境的地貌、土壤等条件的相关性进行了分析，揭示了垂直、水平地带分异规律，建立了相关分析模型。研究结果为珍稀濒危植物动态监测和物种多样性保护提供了新的技术方法和分析决策依据。     

Researches on Plants from the Lower Devonian Xujiachong Formation in the Qujing District, Eastern Yunnan

Fossil plants Hedeia sinica Hao et Gensel 1998, Huia gracilis Wang et Hao 2001 and Guangnania cuneata Wang et Hao are described from the Lower Devonian Xujiachong Formation, the Qujing district, eastern Yunnan, China. They contribute to our knowledge of the flora in this district. Based on the occurrence of common plants (Hedeia, Huia, Guangnania and Zosterophyllum australianum) and their horizons, it is proved for the first time that the mid-lower assemblage of the Xujiachong flora is comparable with the Early Devonian ((late) Pragian) Posongchong flora of southeastern Yunnan and the upper Baragwanathia flora of Australia. In view of this fact and the stratigraphic sequence, the mid-lower part of the Xujiachong Formation is considered to be of (late) Pragian age. Through comprehensive analyses of plant, bivalve and fish assemblages and the lithology, the upper part of the Xujiachong Formation is dated to be of early Emsian age. The Xujiachong flora belonged to the northeastern Gondwana palaeophytogeogr     

Chemical Characteristics of Stream Draining fromDudu Glacier: An Alpine Meltwater Stream inGanga Headwater, Garhwal Himalaya

I-DtjcrONAlpine environment enjoys a distinct set of physicochemical conditions asl compared to other aqueous systems. Thehydrochemical characteristics of meltwater draining from thisenvironment are different from the other aqueous ecosystemsdue to their mountainous nature and extreme cold climatic conditions. The high concentration of various chemical constitu.ents in meltwater shows the intensive chemical weathering inthe basin. The rapid physical weathering due tO grinding actionof the gl…     

River incision and vegetation dynamics in cut-off channels

The consequences of river incision on ecosystems dynamics in cut-off channels were hypothesized to be 1) the reduction of river backflows and overflows of the river in the former channels; 2) the reduction of seepage flows from the river and drainage into the channels; 3) the drainage of the hillslope aquifer by the former channels. The subsequent changes of aquatic plant communities should be 1) the terrestrialization of the higher part of former channels and 2) their change into more oligotraphent ones if the hillslope aquifer is poorer in nutrients than the river. In those reaches where the river bed is aggraded, river backflows in the cut-off channel should increase, as should overflows and seepage, and more eutraphent species should develop. Changes in aquatic vegetation were studied over a ten-year period in four cut-off channels supplied by a nutrient-poor hillslope aquifer and a nutrient-rich river. Two of them were located in an incised reach of the river, one in an aggraded reach and one (reference) in a reach that was neither aggraded nor incised. The vegetation of the reference channel exhibited only minor changes over the ten-year period, indicating that the successional trend is not perceptible at the time scale of the study, and thus that any change observed in the other channels can be ascribed to river incision or aggradation. Terrestrialization expected in the channels located in the incised reach clearly progressed in the downstream parts, but was inhibited by groundwater supplies in the upper parts. As expected, oligotraphent communities progressed or remained dominant in the upper part. The channel located in the aggraded reach of the river exhibited the highest floristic changes. As expected, eutraphent communities progressed in this channel, but unexpectedly, terrestrialization also progressed in the upstream part. Alternative explanations are: 1) aggradation could have instigated more backflows and overflows without modifying significantly the mean water-level and 2) more frequent water overflows could have favoured alluvial deposition and thus terrestrialization.     

浙江天目山自然保护区珍稀濒危植物及其利用与保护

天目山是浙江省珍稀濒危植物最丰富的地区，共有国家保护的珍稀濒危植物２５科、３４属、３７种，其中属二级保护１３种，三级保护２４种．论述了天目山珍稀濒危植物的区系特点、类型及地理分布，列举了它们的一些利用价值，最后提出了保护天目山珍稀濒危植物的一系列建议．     

ON THE LAYER-ZONE OF ALPINE MEADOW ON THEQINGHAI-TIBETAN PLATEAU

RuleofzonalityisoneofthedassicaltheonesinGeOgraphy.Thedifferentiationofzonalityfromaz0nalityindicatesthedevel0pmentofpeople'Scoguhveabilitiestonaturallaw.Longitudinal,latitudinalandaltitudinalzonalitiesbelongt0idealconcePts,however,theywerefavorablet0theformationoftheconcePtofthIeedimensi0nalzonality.UPt0n0wtherehavebeenmanydifferentideasonzonality.ForexamPle,inanarr0wsense,zonality0ulyreferst0thelatitudinalzonality,namely,thequatityofheatorairtemPeraturegraduallyChangs,whichresultsinthezo…     

等高活篱笆试验研究的若干问题*

本文讨论了等高活篱笆技术在设计、管理和效益分析等方面的原则与方法,指出应结合当地的自然条件和社会经济需求,围绕一两种主要功用来应用这种坡地持续利用技术。植物种类选择和篱笆的管理应以篱笆植物的属性、篱笆的形成及农林复合系统中各组分的和谐关系为依据。活篱笆改善生态的功能、社会经济效益宜采用费用-效益分析的方法进行评价。     

The Evolution of Alpine Ultramafic Rocks and Partial Melting of the Upper Mantle

Ultramafic rocks of Tibet and Xinjiang are the products of partial melting of the upper mantle. The evolution of their mineral composition is marked by two parallel evolutionary series: one is the progressive increase of the 100 Mg/(Mg+Fe~(2+) ratio of silicate minerals in order of lherzolite→harzburgite→dunite, i.e. the increase in magnesium; the other is the increase of the 100 Cr/(Cr+Al) ratio of accessory chrome spinel in the same order, i. e. the increase in Chromium. The above-mentioned evolutionary trends are contrary to that of magmatic differentiation. The evolution of fabrics of ultramafic rocks is characterized by progressive variation in order of protogranular texture→melted residual texture, symplectic texture and clastophyritic texture→equigranular mosaic texture and tabular mosaic texture. Experiments of partial melting of lherzolite have convincingly shown that the evolution of Alpine ultramafic rocks resulted from the partial melting of pyrolite. Various subtypes of them represent different degrees of partial melting. The vertical zoning marked by more basic rocks in the upper part and more acid rocks in the lower actually belongs to the fusion zoning of pyrolite.