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High Mountain Areas (high + mountain_area)
Selected AbstractsPLANT COLONIZATION IN CONDESA NIVATION HOLLOW, SIERRA DE GUADARRAMA (SPANISH CENTRAL SYSTEM)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2009JULIO MUÑOZ JIMÉNEZ ABSTRACT. The purpose of this study was to determine plant distribution at a nivation hollow located in a Mediterranean high mountain area and to analyse the effects of snow cover, wind exposure, proximity to moisture and the characteristics of the substrate on the vegetation. We analyse these factors and interpret concurrent effects due to recent climate change. The nivation hollow, called Ventisquero de la Condesa, is located at 2258 m a.s.l., 40°47,10,N and 3°58,35,W, in the Sierra de Guadarrama (Madrid, Spain). We established 579 small sample plots in the study area, and grouped them into 29 transects where snow duration, wind exposure, availability of meltwater, geomorphologic instability and surface rockiness were examined directly and indirectly. The types of plants and the number of individuals per species were registered for each plot to establish ecological affinities among the 28 distinguishable species. Six showed the highest level of chionophily while nine showed the lowest adaptation to snow cover duration. A statistical study incorporating other variables applied in the research revealed that wind exposure, moisture capture and the intensity of geomorphologic dynamics have a highly significant correlation with nivation, while surface rockiness is a virtually independent factor. Due to environmental changes caused by recent global warming, several plant species, especially adapted to survival in snow conditions, coexist in the hollow with saxicolous plants that have invaded the site from adjacent grass and shrublands. [source] The triggering of debris flow due to channel-bed failure in some alpine headwater basins of the Dolomites: analyses of critical runoffHYDROLOGICAL PROCESSES, Issue 13 2008C. Gregoretti Abstract The debris deposits at the bottom of very steep natural channels and streams in high mountain areas can be mobilized by runoff, triggering a water,sediment mixture flow known as debris flow. The routing of debris flow through human settlements can cause damage to civil structures and loss of human lives. The prediction of such an event, or the runoff discharge that triggers it, assumes an interest in risk analyses and the planning of defence measures. The object of this study is to find a method to determine the critical runoff value that triggers debris flow as a result of channel-bed failure. Historical and rainfall data on 30 debris flows that occurred in six watersheds of the Dolomites (north-eastern Italian Alps) were collected from different sources. Field investigations at the six sites, together with the hydrologic response to the rainfalls that triggered the events, were performed to obtain a realistic scenario of the formation of the debris flow there occurred. Field observations include a survey along the channel of the triggering reach of debris flow, with measurements of the channel slope and cross-section and sampling of debris deposits for grain size distribution. Simulated runoff discharge values based on the rainfall recorded by pluviometers were then compared with values obtained through experimental criteria on the initiation and formation of debris flow by bed failure. The results are discussed to provide a plausible physical-based method for the prediction of the triggering of debris flow by channel-bed failure. Copyright © 2007 John Wiley & Sons, Ltd. [source] Landscape patterns of indicator plants for soil acidity in the Bavarian AlpsJOURNAL OF BIOGEOGRAPHY, Issue 10 2003Sebastian Schmidtlein Abstract Aim, Electronic distribution atlases and lists of ecological indicator values are becoming important tools in plant geography. In this contribution, we combine a geographical and an ecological data bank, and map out patterns of indicator value spectra (instead of single or average values) across a physiographically complex landscape. For our study, we select indicators of soil pH and carbonate content as key environmental factors that strongly affect overall plant diversity patterns in the temperate zone. Our goal is to relate the distribution and diversity of plant groups that are indicators of soil pH and carbonate content to environmental controls at the landscape-scale, and thus contribute to a causal understanding of species pools. Location, We studied the Bavarian Alps, which represent the German portion of the Northern Alps. Methods, Based on the existing floristic survey, we calculated relative frequencies of nine classes of indicator plants for soil pH and carbonate content in grid cells. The resulting attribute matrix (cells by indicator class frequencies) was subjected to principal components analysis and to k-means clustering. Results were compared and mapped out in the grid array of the whole region, resulting in continuous and discrete representations of species pool structure. We used a geographical information system to derive physiographical landscape properties from a geological map and a digital elevation model, and analysed their statistical relationship with the shapes of indicator spectra. Results and Main conclusions, Averages of indicator values for soil pH and carbonate content follow the geological structure quite closely. Surprisingly, the diversity of indicator plant groups does not appear to be a function of geological or topographic heterogeneity. Rather, it seems to be related to areas of high elevation with uniform geology. The effect is a matter of additional acidophytes in high mountain areas and, in the high calcareous Alps, extreme calciphytes, while species with intermediate requirements are rarer than usual. For explanation, we suggest two facts: (1) a frequent lack of mature soils at high elevations and (2) particularities in soil genetic processes occurring under the harsh climatic conditions of high mountains. [source] Assessment of Geological Security and Integrated Assessment Geo-environmental Suitability in Worst-hit Areas in Wenchuan QuakeACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2009Wenpeng LI Abstract: The Wenchuan earthquake in 2008 and geo-hazards triggered by the earthquake caused large injuries and deaths as well as destructive damage for infrastructures like construction, traffic and electricity. It is urgent to select relatively secure areas for townships and cities constructed in high mountainous regions with high magnitude earthquakes. This paper presents the basic thoughts, evaluation indices and evaluation methods of geological security evaluation, water and land resources security demonstration and integrated assessments of geo-environmental suitability for reconstruction in alp and ravine with high magnitude earthquakes, which are applied in the worst-hit areas (12 counties). The integrated assessment shows that: (1) located in the Longmenshan fault zone, the evaluated area is of poor regional crust stability, in which the unstable and second unstable areas account for 79% of the total; (2) the geo-hazards susceptibility is high in the evaluation area. The spots of geo-hazards triggered by earthquake are mainly distributed along the active fault zone with higher distribution in the moderate and high mountains area, in which the areas of high and moderate susceptibility zoning accounts for 40.1% of the total; (3) geological security is poor in the evaluated area, in which the area of the unsuitable construction occupies 73.1%, whereas in the suitable construction area, the areas of geological security, second security and insecurity zoning account for 8.3%, 9.3% and 9.3% of the evaluated area respectively; (4) geo-environmental suitability is poor in the evaluated area, in which the areas of suitability and basic suitability zoning account for 3.5% and 7.3% of the whole evaluation area. [source] | ||||||||||