Bioindication of the dangerous geomorphological processes’ activity centers (on the example of the central part of the Chornohora massif)

Abstract

Rapid climate change in the Ukrainian Carpathians has triggered the intensity and recurrence of geomorphological processes that in turn has changed the vertical structure of landscape complexes. Forest ecosystems serve apparent indicators of the processes. Accordingly, the study aims to identify the spatio-temporal features of avalanche processes, landslides, rock falls using bioindication in the central part of the Chornogora massif in the Ukrainian Carpathians. The main reasons for the intensification of current geomorphological processes include 1) climatic changes and variability in the course of precipitation and air temperatures in the cold season, 2) terrain features (slope, slope exposure and surface type), 3) vegetation features, etc. Snow avalanche activity is influenced by the fluctuation of diurnal temperature within -1 to +5 ° C. Temperature features of the territory have a direct impact on the formation of the structure of snow, stratigraphy, and thickness. One of the important factors triggering snow avalanches are the steepness of the slopes equal to 30-45. The main reasons for the manifestation of such are the force of gravity, which itself affects the movement of rocks from the slopes from elevated to low terrain. The causes of landslides and rock falls are sharp daily changes in air temperature, heavy rainfall, permafrost, melting snow, weathering and more. In mountainous areas, such processes are quite common, and they are associated with morphological, lithological, climatic and other conditions associated with the passage of these processes. The description of the five most intense centers of avalanches was identified and compiled based on the surveys of the Bystrets local residents and the detected deformations and damages of forest formations. The most intensive events were distinguished in 1977, 1995, 1998 and 2001. These avalanche events have caused the greatest changes in the landscape complexes of the central part of the Chornohora. The area occupied by the avalanche flows and the area of damaged forests were detected with the satellite images. According to the remaining tree material (trunks up to 1 m high), the main tree species damaged by the destructive force of the avalanche were identified. In addition, in the period of 2014-2018, 7 avalanche streams have taken place in the central part of the Chornohora. We also discovered a new avalanche centre, in addition to those mentioned earlier. This centre is located on the northeastern slope of the Gomul peak (1788 m). 57% of all the detected snow avalanches are considered epigenetic, 29% are syngenetic and 14% are polygenic. Most of them are associated with either the advection of warm Mediterranean air or local radiation warming of the surface air layer. The results of the survey of avalanche sites indicate a determinative role of tree-shrub formations in the indication of the destructive forces and consequences of avalanches. The restoration of landscapes after snow avalanche processes is also accompanied by the replacement of forest ecosystems with shrubs and the loss of valuable ecosystems, which may lead to the search for climatic explanations for such changes. Other geomorphological processes studied during the expeditions in 2019-2020 are landslides and rock falls. During the survey of the central part of the Chornohora massif for the manifestation of the processes, one active landslide was detected within the forest belt at the altitudes of 1000-1600 meters a.s.l l. Traces of bifurcations, scars and tilted tree species witness the landslide activity. The number of detected damaged trees reaches 20 units per 40 m2. Identified damaged coniferous formations serve valuable data for perspective dendrogeomorphological studies to reconstruct snow avalanches and other geomorphological processes of the past, as well as to distinguish local climate features.