AbstractThe influence of abiotic conditions on land-use development since the nineteenth century is assessed in case studies from the Czech and Slovak Carpathians. Hypotheses claim that significant land-use changes have occurred, but without pronounced differences because of similar abiotic conditions in the case studies. Abiotic conditions are expressed by physiotopes, which contain information on georelief, lithology, and soil. Our results indicate a high rate of land-use change in both case studies, and a detailed analysis of changes in two sequential periods reveals significant differences in five of the six periods compared in these case studies. Areas along state border seem to be more affected by anthropogenic changes as the proportion of plots with stable land use was only 25.7% in the Czech area (Starý Hrozenkov, Vápenice, and Vy?kovec) compared to 47.6% in the Slovak area (Lietavská Svinná-Babkov). Repeated land-use changes occurred mostly in valley floors and adjacent slopes. Land-use changes in the study areas are only partly explained by the abiotic conditions in physiotope and morphometric attributes, as shown by multiple correspondence analysis. The crucial difference in land use is in different settlement structures, which reflect differences in historical development. 相似文献
The present area of European wetlands is only a fraction of their area before the start of large-scale human colonization of Europe. Many European wetlands have been exploited and managed for various purposes. Large wetland areas have been drained and reclaimed mainly for agriculture and establishment of human settlements. These threats to European wetlands persist. The main responses of European wetlands to ongoing climate change will vary according to wetland type and geographical location. Sea level rise will probably be the decisive factor affecting coastal wetlands, especially along the Atlantic coast. In the boreal part of Europe, increased temperatures will probably lead to increased annual evapotranspiration and lower organic matter accumulation in soil. The role of vast boreal wetlands as carbon sinks may thus be suppressed. In central and western Europe, the risk of floods may support the political will for ecosystem-unfriendly flood defence measures, which may threaten the hydrology of existing wetlands. Southern Europe will probably suffer most from water shortage, which may strengthen the competition for water resources between agriculture, industry and settlements on the one hand and nature conservancy, including wetland conservation, on the other. 相似文献
The soil heave over time associated with a leak in a hot-water line beneath a floor slab of a lightly loaded structure constructed on a natural unsaturated expansive soil in Regina of Saskatchewan, Canada is modelled in this paper using the Modulus of Elasticity Based Method (MEBM). The case history arises from the studies that were initiated by the Prairie Regional Station of the Division of Building Research, National Research Council in 1960s as a part of a comprehensive field study program to investigate the problems associated with construction in/on an expansive soil in the Regina area. There is a good comparison between the results from the MEBM and the published data of measurements and estimations of soil heave over time. The encouraging results of this study suggest that the MEBM is a simple and promising approach for use in conventional engineering practice by geotechnical engineers for estimation of the heave over time of expansive soils. 相似文献
The aim of this interdisciplinary study is to assess the heat risk for Bratislava. The following layers were created to compute the risk index: the hazard layer of air temperature, a mitigation layer of tree vegetation, an exposure layer of population and a vulnerability layer of individuals over 65 years of age. The MUKLIMO_3 model was used to evaluate the field of mean surface air temperature at 9 PM during selected days of the summer heat wave in August 2018. The tree vegetation layer, in the form of percentage per grid cell, was derived from Sentinel-2 satellite data. Population density data are based on mobile positioning data, and elderly population data are based on a gridded database from the statistical census. Input layers were unified into a resolution of 500 × 500 m, and the heat risk index was calculated by summation of the weighted input layers. The results reflect the variability of the population and the elderly population within the city, as well as the variability of the temperature field, which is caused by the joint effect of an urban heat island and topography. The highest values of risk index occur within the broader city centre, with specific hot spots at several places.
Controlling factors for the occurrence of littoral macrophyte species were investigated in Lipno Reservoir (area: 46.5 km2; zmean: 6.6 m; zmax: 22 m; water residence time: 0.6 yr), a dam impoundment with moderately fluctuating water level (amplitude up to 4 m) which is used for hydropower and downstream flow augmentation. The options of supporting littoral macrophyte growth for improving the reservoir's ecological potential were evaluated according to the European Water Framework Directive's definitions. Macrophytes were examined at 115 sites, each 50 m long, along the whole reservoir perimeter at regular 1 km intervals. Sites were surveyed for their phytocoenology, shore morphometry, pedological characteristics of substrate, transparency of water, and anthropogenic impacts. Most of the sites were characterised by a wide eulittoral zone with a tenuous cover of terrestrial hydrophilic, amphibious, and/or emergent macrophytes and a low proportion of silt, clay, and organic fractions in the substrate. Infralittoral submerged and floating-leaved macrophytes were restricted to a few sites within the mouths of the main and side tributaries where transparency was maintained by clear inflow water independent of reservoir pool fluctuations. Water transparency was low (1-2 m) compared to annual changes of water level (2 to >3 m). Multivariate statistical analysis (DCA, CCA) confirmed relationships between the occurrence of macrophyte species and morphological and substrate characteristics of the shore. Improvement of macrophyte cover and establishment of vital infralittoral zones requires improvements in water transparency and changes in reservoir operation, i.e., limiting the range of water level fluctuation to less than ca. 1 m. 相似文献
In connection with the work for the next generation VLBI2010 Global Observing System (VGOS) of the International VLBI Service for Geodesy and Astrometry, a new scheduling package (Vie_Sched) has been developed at the Vienna University of Technology as a part of the Vienna VLBI Software. In addition to the classical station-based approach it is equipped with a new scheduling strategy based on the radio sources to be observed. We introduce different configurations of source-based scheduling options and investigate the implications on present and future VLBI2010 geodetic schedules. By comparison to existing VLBI schedules of the continuous campaign CONT11, we find that the source-based approach with two sources has a performance similar to the station-based approach in terms of number of observations, sky coverage, and geodetic parameters. For an artificial 16 station VLBI2010 network, the source-based approach with four sources provides an improved distribution of source observations on the celestial sphere. Monte Carlo simulations yield slightly better repeatabilities of station coordinates with the source-based approach with two sources or four sources than the classical strategy. The new VLBI scheduling software with its alternative scheduling strategy offers a promising option with respect to applications of the VGOS. 相似文献