New findings regarding the ground air circulation by chimney effect in low-altitude permafrost susceptible porous screes (Detunata Goală, Romanian Carpathians)

<p>Seasonally differentiated ground air circulation in low altitude porous talus slopes from temperate regions known as chimney circulation creates the conditions for permafrost development in their lower parts well below the regional permafrost altitudinal limit. So far it was shown that the cold air adsorption and warm air exfiltration areas during winter correspond to the lower and upper areas respectively of talus slopes and that they are quite stable and regular in extent and shape. New aerial survey in early winter at Detunata Goală scree with a complex talus slope-rock glacier morphology performed immediately in the days following light snow falls allowed the precise detection of warm air areas positions, shape and temporal changes within hours and days. Several triangular-shaped stripes were found to occur continuously from lower to upper parts of talus slopes and morphometric analysis on a high resolution UAV-derived DEM revealed that they correspond to 1the central longitudinal axis of debris cones composing the talus slopes. Thermal monitoring of air between the blocks was also performed at the location of these stripes where a thermal gradient was found to occur: the atmospheric/ground air temperature contrast increases upwards and towards the axis of talus cones reaching a maximum of >10 °C (+5.3 °C in the ground versus -5 °C outside). In the rock glacier lobe area, the warm air evacuation is different and presents a linear configuration. This work discusses the relation between the morphometry of the deposit and warm air evacuation areas and their short term thermal regime. Also, it discusses new geophysical investigations results (electrical resistivity tomography and seismic refraction tomography) performed at the end of the warm season of 2020 in the coldest area of the scree.</p>

Efficacy of visual surveys for monitoring populations of talus-roosting bats

Winter cave and mine surveys have been the primary method to monitor status of bat populations but they are not equally effective across regions or species. Many species of bats that roost in rock outcrops during the non-hibernation period are difficult to monitor with existing methods. Visual surveys for bats roosting on talus slopes has been proposed as a means to monitor populations, but efficacy of the method is unknown. We used standardized plot-based visual surveys to quantify presence and abundance of eastern small-footed bats Myotis leibii on talus slopes in Virginia, and studied sources of variation and error. Detection probability for talus surveys was relatively high but varied based on search effort and site characteristics. Both abundance and detection probability varied more among plots within sites than among sites or years. In trials with radio-tagged bats to study the causes of false negatives, 18% of bats roosted where surveyors could not see them, and 18% of bats were visible but overlooked due to human error. Inexperienced surveyors counted slightly fewer bats than the principal investigator, perhaps as an artifact of the dual-observer approach. There also was a slight learning curve among students. Visual surveys have strong potential to aid in the study of bats that roost in talus slopes. Talus surveys, unlike longer established methods to monitor bat populations, provide ways to assess error. We recommend using talus surveys to monitor other rock roosting bat species with poorly understood populations, such as many species in western North America.

Thickness of talus deposits on Fugleberget hillside (SW Spitsbergen) in the light of the theories of slope development in periglacial areas

<p>Periglacial areas are very sensitive to contemporary climate change. Rate of morphogenetic processes depends on numerous factors, including the most important: warming of air and ground, increase of precipitation (extreme rainfalls in particular) and shortening of snow cover duration. The dynamics of above mentioned processes may effectively modify conventional slope development models. The paper shows structure of selected talus slopes on Fugleberget hillside based on field observations and radar (GPR) sounding. Then the results have been compared to the classical slope models. The radar survey in April and May 2014 used RAMAC CU II Malå GeoScience system equipped with 30 MHz RTA antenna (Rough Terrain Antenna). Six GPR profiles of various length have been collected along the talus axes and transversally on Fugleberget hillside and partly on Hansbreen lateral moraine. According to the radar sounding maximum thickness of the debris deposits is 2530 m. Weathered material is getting thicker towards terminal part of the screes and debris deposits overlap marine sediments. The morphometry of the talus slopes shows that their current forms differ from conventional slope models, what can result from significant acceleration of geomorphic processes due to climate change</p>

Postglacial talus slope development imaged by the ERT method: comparison of slopes from SW Spitsbergen, Norway and Tatra Mountains, Poland

Talus slopes are a common sedimentary formation both in polar and high-mountain areas, but their development is still not sufficiently understood. This article discusses the environmental factors that have been influencing development of talus slopes since the deglaciation and their impact on the internal structure of slopes. Case studies of the slopes from SW Spitsbergen and the Tatra Mountains in Poland were compared in order to explore different evolution stages. Slopes’ structure was analysed using geophysical surveys based on two-dimensional electrical resistivity tomography (ERT) with a Wenner-Schlumberger array and an electrode spacing of 5 m, combined with geomorphological observations. The investigated talus slopes represent the paraglacial, periglacial and talus-alluvial environments. New data on the internal structure of talus slopes developing in the present or past glaciated areas adds to understanding talus slope evolution. There are many different views concerning the development of slopes during the paraglacial period, whose analysis seems to be crucial in the background of climate change and their record in slope structures. In addition, the study provided valuable information on the development and degradation of permafrost in slope materials.

On Dryopteris site type forests in Estonia

Fern-rich forest communities are presented in Estonia in mesic or moderately humid nutrient-rich habitats, in areas of drained mire forests, on floodplains and lower parts of talus slopes of the North-Estonian limestone escarpment (klint). In the recent official forest typology only one site type has been distinguished and labelled by the ferns: the Dryopteris site type in the scope of boreo-nemoral forests. The aims of the current study were (i) to clarify whether distinguishing between two fern-rich forest site types, one among the full-drained forests group and another in the boreo-nemoral forests group, is reasonable, and if so, then (ii) what the main characteristics of both considered forest site types are, (iii) what the main environmental factors determining the structure of these communities are, and (iv) what the mutual relationship between those forests and other fern-rich forest communities is. Our results asserted a distinct difference between the full-drained and undrained Dryopteris site type forests distinguished by the former scholars. The undrained boreo-nemoral fern-rich stands have developed in the same place in harmony with habitat conditions, while drained forests have significantly changed. It seems that despite some vagueness due to long-lasting post-drainage succession, it is nevertheless justified to recognise the fern-rich drained stands in Estonian forest typology as representing an autonomous forest site type in the group of full-drained forests. To avoid confusion in nomenclature, in the future, the undrained fern-rich boreo-nemoral forests site type could be named according to the most conspicuous indicator species as the Athyrium (filix-femina) site type and fern-rich stands on full-drained peat soils as the Dryopteris (expansa) site type.