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We present a comparative study of large wood (LW) mobility in two steep channels (0.06

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Dendrogeomorphology is an established discipline that is commonly used to date natural hazards, including landslides, debris flows, rockfalls, snow avalanches, and flash floods, by examining tree-ring records. Anthropogenic impacts frequently alter the present landscape, resulting in changing frequencies or increased spatial extents of geomorphic processes, such as subsidence-induced landslides or rockfalls caused by mining activities. In such cases, dendrogeomorphic records from afforested sites may provide information where ground movement monitoring is lacking. Additionally, the temporal occurrence of subsidence can vary greatly, ranging from gradual to abrupt movements. While radar interferometry can currently measure subsidence rates, such data typically covers short time periods and are less precise in forested areas. Comparing tree-ringbased data with in situ monitoring may clarify the sensitivity and reliability of dating methods in these particular conditions of continuous ground movement. We conducted dendrogeomorphic analyses at various sites in the Czech Republic with geomorphic activity caused by past or current underground mining of black coal or ore. We discovered over 20 rockfall events in three stopes that emerged after medieval ore mining, with increased rockfall activity in the Eastern Sudetes since the 1980s. Furthermore, we obtained the years of exposures from ten roots, revealing ground subsidence and the opening of tension cracks, and even the lateral retreat of the flanks of minor depressions. We also employed dendrogeomorphic techniques to detect subsidence-induced surface displacements in the Upper Silesian Coal Basin, which has been affected by underground coal mining. Chronological data were compared with in-situ monitoring and among various sites with lower and higher subsidence rates. Most events occurred in the 1930s, 1970s, 1990s, and late 2000s, with a peak of activity in 1973 and other notable events in 1986, 1995-1997, and 2005-2011. Moreover, not only the timing of mining operations, but also site-specific factors such as soil, morphology, and precipitation events, are essential for characterizing surface displacements in the forested post-mining landscape. [ABSTRACT FROM AUTHOR]

Gully erosion is a worldwide issue that is often caused or accelerated by inappropriate land management. This study comprehensively evaluates accelerated gully erosion in fluvioglacial sediments left by a Pleistocene ice sheet in northeastern Czechia. Geomorphic mapping of an area of approximately 2 km² revealed gullies up to 3.5 m wide and deep, with their heads starting at the boundaries of fields and pastures. One of the causes of accelerated gully erosion are considered to be anthropogenic interventions, mainly melioration measures, or natural piping that cause concentrated subsurface runoff. Dendrogeomorphic methods were used to determine the development of the gully system. Trees respond to erosion processes by changing the anatomy of the cells in the newly grown root rings. When we determine the time of anatomical change onset, we are able to identify the year of erosion processes. Microscopic analysis and dating of 102 cross-sections from 28 exposed tree roots revealed 18 years of gully incision since 1985, with increased activity from 2007 to 2014. The mean incision rates ranged between 1–20 cm/year but could reach 1 m during individual events. To determine predispositions of gully erosion a geophysical survey with the use of Ground Penetrating Radar (GPR) was carried out. A total of 17 GPR profiles were conducted in the agriculture field above the gully systems. The geophysical survey confirmed the presence of subsurface structures (possibly the melioration measures in the area) and their possible connectivity to the gully systems. The combination of concentrated subsurface and surface runoff is considered to have a significant effect on the expansion of gullies in the present. [ABSTRACT FROM AUTHOR]

Debris flows (DFs) occurring in both natural and anthropogenic-disturbed areas may severely disturb trees along their paths. In the last decades, dendrogeomorphic investigations were largely applied to reconstruct the spatiotemporal activity of DFs in natural areas, while studies regarding the effects on tree growth patterns of contaminated sediments originating from mining areas and transported by DFs are lacking. In this study, we apply the dendrogeomorphic methods to reconstruct the spatiotemporal pattern of DF activity but also to analyse the growth of disturbed trees in the mining area of Călimani Mountains (Eastern Carpathians, Romania). During the second half of the twentieth century, in the central part of the Călimani Mountains, the mining activities for sulfur-rich ore extraction and processing resulted in significant environmental changes of the slope and channel morphology. Sediment transfers by DFs originating from the spoil heap talus area and following the stream channels started during the mining period (1970-1997), and are still ongoing today, more than two decades after the cessation of the mining activities. Norway spruces (Picea abies (L.) Karst.) living either along the channels or on the margins of two sediment retention reservoirs, and heavily disturbed by DFs, were sampled using Pressler borers and a chainsaw. Several tree-growth anomalies at macroscopic at microscopic scales were identified and allowed the reconstruction of past DF events in this mining-disturbed area. The study confirms the usefulness and potential of dendrogeomorphic approach for tracking sediment transfers not only in natural environment, but also in anthropogenic-disturbed surroundings. Therefore, the tree-ring approach must be seen as a novel and very precise information tool, which can be applied either to calculate sedimentation rates and for the monitoring of the magnitude and extent of sediment transfers in mining areas. Further dendrogeomorphic investigations on various coniferous and broadleaved tree species living in similar mining environments will confirm their high potential for the reconstruction of the dynamics of hydrogeomorphic processes. Keywords: Debris flows (DFs), dendrogeomorphology, mining area, sediment transfer, Călimani Mountains (Eastern Carpathians, Romania) [ABSTRACT FROM AUTHOR]