Winter microclimatic regime of low-altitude scree slopes and its relation to topography: case study from the Ceske Stredohori Mts. (N Czech Republic)

Abstract

Many low- to mid-altitude Central-European scree slopes display microclimatic regimes with thermal anomalies throughout the year. These anomalies favour stenoecious species, some of them considered to be glacial relics. In this study, we present a pilot study focusing on the evaluation of topographical factors (elementary landforms, slope profile, clast size) that predispose the formation of different microclimatic regimes at screes that have similar physico-geographical characteristics. We carried out detailed geomorphologic mapping at four scree slopes in the Ceske Stredohori Mts. (Northern Czech Republic). The mapping was supplemented with snow cover monitoring, observations of microclimate-induced features (ice holes with cold air exhalation and vents of warm air), and temperature measurements from the prolonged winter period of 2007-2008. The results showed distinct differences in the microclimatic regime of the four study sites. A concave foot slope built by large boulders was the major factor inducing cold exhalations and the persistence of ice and snow. Slope inclination and vegetation patterns played a limited role. Warm vents within the upper part of the screes were strictly related to specific landforms (terminal lobes and elevations) and to mid-size clasts. The results are discussed using a geomorphologic evaluation of sites in the region that display thermal anomalies. The regional analyses indicate that the warm vents are mainly located on the southern slopes (due to higher incoming solar radiation) and at higher altitudes. The screes with cold air exhalations (freezing screes) are located at lower altitudes and on slopes with different orientations.