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Summary The quantification of the intensities of tree growth responses to the impact of geomorphic processes is a modern research trend in dendrogeomorphology. It enables a more sensitive assessment of the activity of the studied geomorphic process compared to the traditional use of growth disturbances. The advanced definitions of individual intensity classes of growth disturbances are based exclusively on macroscopic observations. This study evaluates the possibility of anatomical quantification of compression wood (CW) intensity in the case of common spruce (Picea abies (L.) Karst.) and compares it with subjective macroscopic evidence of CW with respect to stem tilting intensity. In total, 25 disturbed (tilted) individuals of P. abies occupying a landslide active during July 1997 were sampled, and 21 of them were analysed. The intensity of external disturbance (stem tilting) was compared against the macroscopic (intensity and duration) and microscopic (quantitative change of the tracheid lumen area and the cell wall proportion) parameters of compression wood suitable for practical application in common dendrogeomorphic analysis. Generally, the macroscopic indices of CW were strongly correlated with stem tilting. The intensity of the anatomical growth response was stronger in the earlywood zone than in the latewood zone. Nevertheless, their dependence on stem tilting was not detected. Results suggest that CW classification based on the quantification of anatomical changes is not possible for dendrogeomorphic purposes. Nevertheless, based on the obtained results, the present study suggests preferring the most intensively tilted trees during future dendrogeomorphic research to obtain the most intensive macroscopic and subjective observable anatomical evidence for studying compression wood.

Background and Aims Understanding the mutual co-ordination of vegetative and reproductive growth is important in both agricultural and ecological settings. A competitive relationship between vegetative growth and fruiting is often highlighted, resulting in an apparent trade-off between structural growth and fruit production. However, our understanding of factors driving this relationship is limited. Methods We used four scions grafted onto a series of size-controlling rootstocks to evaluate the relationships between the annual fruit yield and radial growth of trunks, branches and roots. To assess tree radial growth, we measured ring widths on extracted tree cores, which is an approach not frequently used in a horticultural setting. Key Results We found that the yield and radial growth were negatively related when plotted in absolute terms or as detrended and normalized indices. The relationship was stronger in low vigour trees, but only after the age-related trend was removed. In contrast, when trunk radial growth was expressed as basal area increment, the negative relationship disappeared, suggesting that the relationship between trunk radial growth and fruit yield might not be a true trade-off related to the competition between the two sinks. The effect of low yield was associated with increased secondary growth not only in trunks but also in branches and roots. In trunks, we observed that overcropping was associated with reduced secondary growth in a subsequent year, possibly due to the depletion of reserves. Conclusions Our results show that variation in annual fruit yield due to tree ageing, weather cueing and inherent alternate bearing behaviour is reflected in the magnitude of secondary growth of fruit trees. We found little support for the competition/architecture theory of rootstock-induced growth vigour control. More broadly, our study aimed at bridging the gap between forest ecology and horticulture.

Complex detailed analysis—3D extension of tension wood, Anatomical intensity and tree-ring eccentricity—of one Fagus sylvatica L. individual provides unique insight into tree growth response to landsliding Compression wood formation and tree ring eccentricity of coniferous trees have often been used to date past geomorphic events because of their well-defined tree ring boundaries and visible reaction wood. On the other hand, complex analysis of the ability of tree rings and anatomy of broadleaved trees to detect past geomorphic events is rather rare. Although analysis of broadleaved trees has some limitations, a combination of both approaches (tree ring anatomy and eccentricity) can provide a suitable dendrogeomorphological tool for dating and understanding past landslide events. From an example of a young Fagus sylvatica L. individual, vertical variability of growth responses in the whole stem was detected. The sampled individual was tilted as a direct response to a landslide event caused by intense rainfall in July 1997. It was found that the growth responses of the sampled individual varied with increasing height. By analysing 14 cross sections in the tree stem, it was detected that the sampled individual started to form tension wood (TW) immediately in 1997. This response was also confirmed by the decrease of the vessel lumen area (VLA). The largest decrease of the VLA was in axes A and D. As a result of TW formation, the sampled individual started to form eccentric tree rings. It was observed that with the increasing height of the tree, the number of tree rings with TW and VLA decreased. The formation of TW and eccentricity, but not VLA, also depends on the stem tilting intensity. According to our experimental results, a combination of both approaches can provide a suitable tool to detect the moment of tree growth responses and therefore date landslide movement events.

Bembix rostrata (Hymenoptera: Crabronidae) is a conspicuous digger wasp, which is one of the most threatened species of bees and wasps in central Europe. Its distribution is restricted to sites with grey dunes or similar habitats, which B. rostrata needs for nesting. In the years 2012–2014, we have studied the ecological factors influencing the presence of this species in two localities in the Czech Republic, where this species is still relatively abundant. We found that B. rostrata needs continuity in the characteristics of the locality in time because B. rostrata avoids settling in newly emerging localities with the appropriate substrate. The decline in localities of B. rostrata in the Czech Republic correlated with habitat loss due to afforestation, incorrect conservational management, and isolation of the localities. The newly formed anthropogenic sites with fine-grained loose substrates, such as sandpits or fly ash deposits, were not colonised by B. rostrata. This is in sharp contrast with another species of the genus, Bembix tarsata, which is also endangered, but successfully settled in many bare sand patches on former lignite spoil heaps in the north-west of the country. We found that both species hunt Diptera as a prey for their larvae; both are generalists with a preference for species of the family Syrphidae. Unexpectedly, we found workers of the honeybee Apis mellifera captured as a prey for larvae of B. rostrata. Implications for insect conservation Newly applied management tools, such as army vehicles use, manual sand scraping, or plant cover removal, have a positive effect on populations of B. rostrata, as well as on other species with similar ecological requirements.

Detailed knowledge of the occurrence of debris flows in the past is key to understanding their linkage to changing climatic variables and their occurrence in the future. For a comprehensive understanding of the origin of these processes, regional reconstruction is optimal rather than detailed analysis of isolated catchments. This study presents the results of a dendrogeomorphic reconstruction of debris flows across an entire medium-high mountain range in Central Europe covering more than 500 km

Knowledge of the spatial distribution of landslides is essential for forestry, landscape planning or hazard assessment. In fact, dendrogeomorphic approaches are a useful tool to construct past landslide behaviour due to the known location of the sampled trees. The position of trees on the landslide surface can influence the detection of spatial patterns of landslide reactivation and significantly affect the amount and intensity of recorded landslide signals within a series of tree rings. This is due to the presence of different morphological zones with different movement mechanisms that generate landslide bodies. In this study, data from 1030 tree-ring series originating from 515 trees occupying ten different complex landslide sites in the Outer Western Carpathians were used to test the spatial distribution of landslide signals during reactivation events and to investigate the specific influence of six different landslide morphological zones on tree growth, with the aim of revealing the most valuable sites for future sampling at the landslide surface. Spatial patterns of landslide reactivation were tested using the Moran index. Signals from tree rings generally do not tend to cluster spatially. Thus, the analysis of spatial patterns can be used as a very stringent condition for verifying landslide events in the case of a limited number of tree-ring signals. Moreover, this analysis is only suitable for block-type landslides (not for flow-type landslides). Furthermore, this research presents a general model of the influence of movement mechanism on tree growth in the different morphological zones forming complex landslide areas. Finally, recommendations for future sampling strategies regarding tree location within specific morphological zones are made based on the results obtained. In general, trees on subhorizontal landslide blocks or in the plastic shallow movement zone should be preferred as opposed to trees on steep landslide sections or in the source zone, which should be avoided.

This study represents the first palaeoflood discharge estimation using dendrogeomorphic evidence from two ungauged catchments in southern Crete. Dendrogeomorphological methods, rainfall-runoff and hydraulic modelling were applied to estimate the palaeoflood discharge of the 2000 flood event. We developed two scenarios (QHydraulic, QRR) of peak discharges in the short reaches of the Ilingas and Sfakia catchments. Scenario QRR was based on the results of the uncalibrated rainfall-runoff model HEC-HMS. The calculated discharges were equal to 35.9 m3 s−1 in the Ilingas reach and 7.6 m3 s−1 in the Sfakia reach. The second scenario, QHydraulic was based on the output of the two-dimensional hydraulic model IBER, which was calibrated using six palaeostage indicators obtained during a field survey. The reconstructed discharge for the QHydraulic scenario was equal to 26.3 m3 s−1 in Ilingas and 11.2 m3 s−1 in Sfakia. Deviation (26.7% in Ilingas and 32.1% in Sfakia) between the scenarios were attributed mainly to the uncertainties of in flood reconstruction using the palaeostage indicators and uncalibrated rainfall-runoff model. We further investigated uncertainty in Manning’s roughness coefficient, which caused deviations in peak discharges with the range of these deviations defined within ± 40% in the Ilingas reach and ± 36% in the Sfakia reach.

Landslides are dangerous and destructive geomorphic processes that cause annual damage to human infrastructure or even loss of life. As recovery is very costly, knowledge of past landslide activities, a detailed analysis of triggers and prediction of future landslide development are important. Dendrogeomorphic (tree-ring-based) dating is the best solution of chronological data obtaining in forested areas, where trees annually produce increment rings. A moving landslide mass affects trees that grow on its surface. Trees respond to this influence in different ways that are recordable and subsequently visible in tree ring series. Thus, tree rings represent an ideal natural archive of past landslide behaviour. Depending on the tree species, the length of a landslide chronology can be several centuries with sub-annual resolution. Although dendrogeomorphic approaches have some limitations, provided data are unique because they represent insight into the past without the need for long-term monitoring. Nevertheless, trees as landslide archives are suitable for medium-magnitude events because excessively small movements can be disregarded and catastrophic movements destroy trees. This review introduces details regarding tree-landslide interactions, provides a historical overview of applied methods, presents and assesses methodical approaches and summarises basic advantages and contributions to the knowledge of landslide chronology, spatial behaviour and triggers. Finally, limitations, the potential for subsequent research directions and calls for future fundamental studies in new world regions are presented.

Bees and wasps inhabiting steppe formations are, according to recent red lists, among the most endangered species, quickly disappearing from local faunas of central European countries. Several species, which are specialised nesters in empty gastropod shells, show the opposite pattern. Based on their distribution maps, we found that these species are recently more common and widespread than in the past. In contrast, the bee species nesting in the ground showed clearly the opposite result. They are much rarer now than in the past. Climatic data suggest that the bees nesting in gastropod shells have expanded towards higher altitudes and/or areas of lower mean July temperature. The main reasons of these distributional shifts are (i) unfavourable nature conservation management practices during the twentieth century, resulting in the successional shifts of steppe formations towards shrubs and mesic grasslands, (ii) human-driven change of many sites towards wood plantations or crop fields, and (iii) the increase of the number of available gastropod shells (i.e. nesting resources for shell-nesting bees) in steppe habitats as the response to the mentioned successional changes.

As the use of the increment borer is supposed to be invasive, there is a question of how coring affects subsequent growth or the health of various tree species. Ten Picea abies (L.) Karst. trees in the Beskydy Mts. (Czech Republic) were analysed nine years after coring by an increment borer (June 2011) to determine their anatomical and growth responses to the coring. Cores (13 per tree) were extracted at regular vertical and horizontal distances to evaluate the spatio-temporal pattern of the responses. Sixty percent of trees reacted to the increment boring by creating a vertical crack at the end of year 2011. Traumatic Resin Ducts (TRDs) appeared in all trees relatively soon after coring, with a predominance in the vertical axis. In the horizontal axis, TRDs gradually disappeared with increasing distance from the old coring hole. Overall the spatio-temporal occurrence of TRDs varied in the tree trunk. The immediacy of the response was indirectly dependent on the distance from the 2011 core. Trees responded by growth release the following year after coring as well. The duration of growth disturbances reached three years on average. The results show that P. abies trees are not critically endangered by increment borer coring.

Catastrophic landslides represent one of the most dangerous natural hazards. Detailed knowledge about the pre-landslide behaviour of the affected slope is crucial for effective modelling of the landslide origin in the future or even for creating an early warning system. As precise retrospective reconstruction of slope movements in the pre-landslide period is very limited, dendrogeomorphic methods can be effective tools for these purposes due to the high sensitivity of trees to slope movements and the spatial aspects of data provided by the position of affected trees. This study presents the results of tree ring-based analysis of slope movements preceding three selected catastrophic landslides of different types in the Outer Western Carpathians (Girova 2010—translational rockslide; Brodska 1997—earthflow; Hluboce 2006—rotational rockslide). Three aspects of pre-landslide slope movements were analysed in detail (frequency, intensity, spatial distribution). In total, 300 tree ring series from 150 trees disturbed by pre-landslide movements were used for these purposes. The Girova landslide was preceded by an increasing frequency and intensity of movements but without any spatial pattern. The Brodska landslide was preceded by a low frequency of low-intensity movements without any temporal trends but with significant clustering several years before the landslide. The Hluboce landslide was preceded by a decreasing frequency of movements with increasing intensity and concentration in the source zone. The character of pre-landslide movements is probably influenced by the presence of old landslide structures on the affected slope and by the mechanism of the movements themselves.

The mechanisms and velocities of landslide movements are important information for assessing hazards associated with landslides. This contribution introduces a new approach in reconstructing the past rate of landslide displacement using dendrogeomorphic methods. The principle of this method is based on the analysis of exposed roots in tension cracks or scarps of active landslides. The identification and dating of anatomical changes in root ring series in various root segments, induced by gradual root exposure due to crack spreading, enable the estimation of the rate of root exposure and the calculation of the displacement rate of landslide blocks. We analysed anatomical reactions of 87 root cross sections in tension cracks of an active landslide the Moravskoslezske Beskydy Mts. in the Outer Western Carpathians. Microscopical analysis of microcuts from cross sections showed the reduction in the earlywood vessel sizes, indicating the year of root exposure. We identified 17 years of exposure between 1997 and 2015. We calculated the individual displacement rates of the landslide expressed as the segment rate between the two adjacent samples of tension crack spreading and the mean spreading rate for all roots crossing one tension crack. The average total spreading rate for each tension crack was 3.2 cm year−1, with a maximum of 4.3 cm year−1 and a minimum of 1.7 cm year−1. Although this new approach has some uncertainties and limitations, it remains a low-cost technique that allows us to reconstruct the minimal past rate of landslide displacement without the need of long-term monitoring.

Dendrogeomorphic methods are frequently used for the analysis of past landslide behaviour and have become the standard approach used to date landslide activity. Unfortunately, many questions related to the application of tree-rings to landslide analysis remain unsolved. This study points to the significance of dividing a large complex slope deformation area into homogenous zones to obtain as much relevant chronological data as possible and to help with a more precise landslide hazard assessment. The multidisciplinary approach included geophysical measurement and geomorphic mapping. The clay mineral content in weathered slope sediments was analysed to verify the presence of expanding minerals contributing to slope instability. Furthermore, 713 samples from 271 trees and 18 tree roots were analysed to create event chronologies for each zone. The results provided evidence about the different behaviours of each zone. The intensity of tree responses to slope movement significantly changed even within one isolated zone. Chronological data were used to identify landslide triggers using rainfall characteristics and indices for climate variability and extremes. The results suggested a significant contribution of spring rainfall to landslide activity. In addition, shallow landslides movement was dependent on above-average rainfall characteristics compared to the movement of deep-seated blocks. Tree-ring-based chronologies of individual zones were used to characterise the general concept of complex slope deformation development.

Investigations of mass movement hazards need to be supported by accurate data regarding past frequencies of landslide reactivations. Dating landslide events using tree rings is a reliable approach for vegetated slopes in temperate climates. Despite the enhanced use of dendrogeomorphic research during recent decades, little is known about the specific responses of Larix spp. to landslide movements. We investigated the active section (~0.6 ha) of a complex landslide in the Vsetinske vrchy Mts. (Outer Western Carpathians) that is overgrown by a forest stand composed of European larch (Larix decidua Mill.) and Norway spruce (Picea abies (L.) Karst.). Using the dendrometric and dendrogeomorphic data identified from 74 trees (33 L. decidua and 41 P. abies), including the number and types of growth disturbances (GDs) and compiled event chronologies, we compared the responses of both tree species to the same landslide reactivations. We observed the same mean tree stem inclination for both tree species, whereas the inclination azimuths differed. L. decidua generally showed a higher number of stem bends compared to P. abies. Similar proportions of subjectively identified GDs (compression wood, CW, and abrupt growth suppression, GS) and mathematically identified GDs (tree-ring eccentricities) were observed in both tree species. However, the total number of GD.tree−1 was slightly higher in L. decidua (4.1) than in P. abies (3.2). A higher abundance of GS was identified in L. decidua at the expense of CW compared to P. abies. The event chronology based on the mathematical approach revealed slightly more landslide signals than for the subjective approach, mainly in L. decidua. However, the largest known landslide reactivation (in 1997) was recorded in all cases in both tree species. Based on the CW analysis, it was shown that larger stem inclinations are associated with longer persistence of CW in P. abies (rather than L. decidua), resulting in the possible masking of younger landslide events. By contrast, P. abies compensates for that limitation by having a generally shorter mean duration of CW than L. decidua. Overall, it seems that the complexity of landslide movements and root system architecture influenced the number and character of GDs in both tree species. In addition, we did not find any relationships between the measured dendrometric parameters and number of GDs to better assess the most suitable trees for dendrogeomorphic dating prior to sampling. Therefore, we recommend sampling both tree species when they overgrow the same landslide body so that the final event chronology will be more robust and possible limitations of one tree species can be eliminated by the benefits of the second.

The chronological aspects of landslide research are of great interest regarding the hazard assessment of landslide triggers. Dendrogeomorphic methods provide a good ratio of chronology length and dating resolution. An alternative to the standard dendrogeomorphic approaches used in landslide research (based on reaction wood analysis – a reaction to stem inclination) is the analysis of tree-ring eccentricity. This study tests three frequently used dendrogeomorphic approaches based on tree-ring eccentricity and verifies the results by comparing them with the results obtained by the standard dendrogeomorphic expert approach. In total, 125 individual Fagus sylvatica L. trees growing on the block-type landslide of Lipova straň in the foothills of the Orlicke hory Mts. (central Europe) were sampled and used for the analysis. The first tested approach identifies landslide signals based on the analysis of mean eccentricity values from two moving windows. The second tested approach determines landslide signals from a series of eccentricity values based on the use of an eccentricity threshold from reference trees. The last tested approach organizes the eccentricity values into categories and identifies landslide signals based on the defined temporal patterns of the individual categories. The limitations of each approach are revealed, and recommendations for increasing the robustness of each approach are presented. Moreover, the sensitivity of F. sylvatica trees to landslide signals was tested using each approach. The obtained results suggest the need for a specific sampling design (regarding tree age) for each tree-ring eccentricity-based approach.

Snow avalanches (SA) and debris flows (DF) are among the widespread geomorphic processes in high mountains. One of the most reliable method for determining their historical occurrence is related to dendrogeomorphical analyses. Sampling focused only on one process suffers from the noise caused by disturbances induced by the other process. Thus, the aim of this paper is to find specific parameters of stem scars that significantly differ when they are caused by different processes. For this purpose, six parameters of 102 sampled scars on mountain pine (Pinus mugo var. mugo) individuals growing on the polygenic debris fan in the High Tatra Mountains were recorded. For the verification of origin of scars from historically known DF and SA events, the intra-seasonal dating of callus tissue using microcuts was performed. 50 DF scars and 52 SA scars were identified and analysed. Several significant differences were identified, which serve as recommendations for a future sampling strategy. DF scars were significantly longer, wider, and occurred at lower distances above the ground in comparison with SA scars. DF scars expressed a significant negative relationship between scar length and its distance above the ground. The selection of scars with described parameters for a pointed analysis of SA or DF could help with sampling of scars caused by the analysed process.

The dating of past landslide events is one of the most crucial aspects of landslide research, leading to a better understanding of past landslide activity. Landslides can be extremely dangerous natural hazards, and thus, solving the relationships between their activity and climate variations is of high importance. For these purposes, data about past landslide activity are fundamental for such analyses. Various methods of landslide absolute dating exist, but the most precise approach that dates back several centuries is based on tree-ring analysis (dendrogeomorphology). Landslide movements can affect the growth of trees in response to specific growth disturbances. Although dendrogeomorphic methods are successfully used for dating other geomorphic processes, their use in landslide research is actually the most frequent. Dendrogeomorphic research on landslides is strongly influenced by general approaches of landslide signal extraction from tree-ring series of disturbed trees and by the type of landslide (varying by morphology, material and mechanism of movement). This study provides an overview of basic aspects of dendrogeomorphic research on landslides, and more specifically, it reviews basic tree-ring-based approaches of landslide dating. Presented review focuses on various landslide types and their effect on dendrogeomorphic dating. This review is built from the extensive database of all accessible dendrogeomorphic studies of landslides from 1893 to 2020. Moreover, recommendations for specific sampling and approach choice in individual landslide types are presented. Finally, limits of tree-ring-based approaches are presented, including provided proposals for further research.

The Czech part of the Outer Western Carpathians (COWC) formed by flysch rocks is among the most landslide-prone areas in Europe. Recent LiDAR-based inventory mapping reveals that the area of the COWC encompasses more than 13,500 landslides, with some geological domains exhibiting > 20% of the surface area covered by landslides. Although mass movements represent crucial geomorphic agents in the COWC, their timing and especially lifespan remain elusive. In this study, we focused on rockslides affecting the flanks of the flysch anticline developed within Paleogene sandstones. The area (“Hradisko” ridge) is well known as the most extensive rock city in the COWC. Structural-geological investigation, kinematic analysis and the application of near-surface geophysics (ERT, GPR and seismic refraction) suggest that rockslides accompanied by toppling and lateral spreads are predisposed by the architecture of bedding planes, joints and inherited faults cross-cutting the anticlinal ridge. Based on 10Be exposure dating of five scarps and rockslide boulders (a total of 25 cosmogenic-dated samples), we were able to reconstruct the long-term history of rock slope failures. Although the obtained ages of headscarp exposures reveal consistent patterns suggesting major mass movement phases at ~ 18 ka and ~ 12 ka, the interpretation of boulder exposure ages is ambiguous. The study area has not been affected by catastrophic slope failure in historic times, but dendrogeomorphic analysis reveals surprisingly strong tree ring signals of mass movements within the last 150 years. These findings suggest that progressive failure is developing within some parts of the rockslide and/or slope portions above the major scarp. We conclude the following: (1) some rockslide spots within the COWC might express a very long history, encompassing the full Late Glacial–Holocene Period; (2) major mass movement activity in the study site temporally coincided with the major climatic changes; (3) rockslides with a very long history still represent potential hazards, although evidence of their active movement is not detected by standard geomorphic mapping techniques and (4) dating of the scarps should be preferred as even a higher number of boulders might be unreliable.

Dendrogeomorphic dating of past landslide events is a valuable tool for the assessment of landslide activity, providing unique data for the analysis of triggers or the modelling of landslide behaviour in the future. Unfortunately, tree-ring-based methods as well as dating approaches suffer from some limitations. One of the less frequently addressed limits of dendrogeomorphic analysis concerns the changing capacity of trees to record landslide events in their tree-ring series with increasing age. This study uses, to date, the most extensive database of tree-ring series (1736) of 868 disturbed individuals of Picea abies (L.) H. Karst. subjected to 20 landslides in the Outer Wester Carpathians for the assessment of their age-dependent sensitivity. The distribution of the total number of 1485 growth disturbances (reaction wood - RW and abrupt growth suppression - GS) throughout all decades of tree life shows evidence of distinct changes in the capacity for trees to record landslide signals with increasing age. The occurrence of RW dominated in the juvenile decades of tree life and then increased again in the 9th decade. The frequency of GS gradually increased and culminated during the 7th and 8th decades. The two intensities of growth disturbance (strong and moderate) expressed temporally balanced ratios, suggesting an effect of disturbance intensity rather than changing tree age. The important factors controlling age-dependent tree sensitivity to landslide movements based on the results seem to be changing stem elasticity, decreasing annual increment rates, root system development and increasing tree body weight. Moreover, this study demonstrates that landslide type (e.g., rigid block vs. plastic flow-like landslides) and bedrock geology distinctly modify age-dependent sensitivity that should be taken into account during the sampling of trees for landslide dating.

The effect of instream wood on stream hydraulics and geomorphic processes depends on wood and channel dimensions. We investigated abundance and characteristics (i.e., wood orientation, proportion of spanned channel width, stability and decay classes) of large wood (LW; defined here as having a length ≥ 1 m and a diameter ≥ 0.1 m) and small wood (SW; including two categories with length ≥ 0.5 m and diameter ≥ 0.1 m or length ≥ 1 m and diameter ≥ 0.05 m) in three steep, confined headwater channels of medium-high mountain ranges of the Western Carpathians (Central Europe). Results show that SW is more frequent than LW, however, active-channel LW load varied between 26 and 305 m3∙ha−1, whereas SW showed much lower active-channel load (8–16 m3∙ha−1). Differences between LW and SW active-channel volumes were considerably smaller in streams under dominant deciduous canopy. In these streams, morphological steps – created exclusively by SW – were more frequent than LW steps. This higher frequency of SW in streams surrounded by a deciduous tree canopy can be explained by the continuous supply of branches rather than entire dead trees. On the other hand, the volume and frequency of LW was related to the proportion of conifers in the valley corridor. We observe very high active-channel load in two channel reaches for which values exceeded most of those observed in similarly small streams across the globe. We also observe an unusually large proportion of instream wood (both LW and SW) oriented parallel to the flow direction, which might suggest a higher mobility of bed material in the flysch-dominated headwater channels of our study site.

The recent acceleration of gully erosion caused by environmental factors and human impacts has led to an enhanced demand for applied research in risk-prone areas worldwide. We investigated the dynamics of gullies that have recently threatened dwellings and railways in the foreland of the Eastern Sudetes (340–390 m a.s.l. in the NE part of Czechia). Flood countermeasures in a residential area above the study site created conditions conducive to accelerated erosion in the gullies; thus, the main aim of this study was to determine how human interventions changed the spatio-temporal dynamics of the gullies during a short period. Twenty two gullies (with a mean length 48.5 m) have developed on a 1-km-wide escarpment (with a mean slope 25°) composed of glaciogenic sediments of various sizes. Dendrogeomorphic techniques were applied on 23 exposed roots of Tilia cordata Mill. (a tree species that has never been used to detect root exposure). Microsections were prepared using a G.S.L.1 sledge microtome and analysed using the WinCELL Reg software to determine the timing of root exposure. Approximately 90% of the eroded sediments (1287.4 m3) were transported across the railway onto the floodplain and caused damage to dwellings, while approximately 10% created bare accumulations at the gully floors. The most significant pulses of gully erosion occurred during the last 10 years (2007, 2009, 2010, and 2014). The maximum identified gully erosion occurred in 2014 (max. incision: 154 cm; maximum widening: 160 cm). In contrast, the development of the bank failures has been slowly progressing since the early 1990s, with a mean bank eroded area between 0.07 and 0.12 m2 year−1. The analysis of the precipitation characteristics (1963–2016) with the Mann-Kendal trend test revealed no significant trend. However, the last strong erosion event, in May of 2014, was triggered by an extraordinary rainstorm with an hourly intensity of 41.3 mm h−1 (maximum intensity of 2.8 mm min−1). Therefore, the recent increase in gully erosion is the consequence of extreme precipitation and human interventions that have been performed in the study site since 2007 (i.e., damming of the ditches and building of new culverts). The dendrogeomorphic research of exposed T. cordata roots significantly contributed to the identification of the gully erosion pulses and thus can be further applied in other localities.

High-magnitude hydrogeomorphic events in steep streams (e.g., debris flows and debris floods) are capable of transporting considerable quantities of bed material, including large wood, although wood pieces that are longer than the channel width are often perceived as relatively stable elements in narrow headwater channels. We investigated present large wood distribution along 1.7 km of a steep headwater channel (the Klepacský Stream; Eastern Sudetes; NE Czech Republic) surrounded by managed forests and engineered by twelve check dams (presently at various stages of destruction). The total wood volume was measured at 123.0 m3, including wood deposited on adjacent terraces by a high-magnitude hydrogeomorphic event in 2010 representing a ca. 20–30 year recurrence interval. Approximately a half of the total wood volume (58%) was stored in large jams (≥10 large wood pieces) that originated during that event. We observed reach controls (based on transport agents and valley morphology) and local controls (represented by individual check dams) of LW depositional patterns. The uppermost debris flow-affected reach produced high volumes of mobilised wood, including many pieces that were two-to-three times longer than the local active channel width; significantly shorter and thinner pieces were found within large jams in downstream reaches void of debris-flow processes. We also documented that this high-magnitude event was responsible for the notable out-of-channel storage of large wood, which decreases the volume of wood that might be transported by a future event. In addition, 30.5 m3 of large wood, that is ~one-quarter of the total volume measured along the stream, was deposited in relation to twelve damaged check dams despite their lowered trapping efficiency.

Although large wood (LW) has been intensively studied in forested basins of humid temperate climates, data on LW patterns in different fluvial environments are rather scarce. Therefore, we investigated the dimensions, characteristics, longitudinal distribution, and dynamics of LW along a 4.05-km-long reach of an ephemeral channel typical of European Mediterranean mountainous landscape (Sfakiano Gorge, Crete, Greece). We analysed a total of 795 LW pieces, and the mean observed abundance of LW was generally lower (14.3 m3/ha of active valley floor or 19.6 LW pieces/100 m of stream length) than is usually documented for more humid environments. The number of LW pieces was primarily controlled by trees growing on the valley floor. These living trees acted as important LW supply agents (by tree throws or the supply of individual branches with sufficient LW dimensions) and flow obstructions during large flood events, causing storage of transported LW pieces in jams. However, the downstream transport of LW is probably episodic, and large jams are likely formed only during major floods; after >15 years, we still observed significant imprints of the last major flood event on the present distribution of LW. The geomorphic function of LW in the studied stream can only be perceived to be a spatially limited stabilising element for sediments, which was documented by a few accumulations of coarse clastic material by LW steps and jams.

This article presents a multidisciplinary approach to the assessment of slope deformation at the Lower Hodrusa mining water reservoir, which is part of a UNESCO cultural heritage site. The multidisciplinary approach was used to develop remedial measures. The Lower Hodrusa mining water reservoir is situated in the Hodrusa-Hamre municipality near Banska Stiavnica in the central part of Slovakia. The first mention of the construction of the reservoir is from 1743, and according to historical records, there were problems with slope stability already at that time. Nowadays, to increase the volume of water available for technical operations in the Hodrusa valley, the decision was made to increase the dam’s output capacity. Slope movements were first detected while the reservoir was being drained. A part of the left shore 50 to 150 m from the dam crest moved, damaging adjacent buildings. The Hodrusa-Hamre municipal authorities declared an emergency on 24 August 2015 because of the appearance of cracks in the asphalt surface of the national road and its subsidence. The main discontinuity conformed approximately to the contours of the known landslide area on the south side of the reservoir. The significant deformations involving the 0.20-m subsidence of the service road were reported during heavy rainfall in October 2014. A range of geoscientific disciplines was used to develop a detailed description of the landslide area and to determine the cause of the slope deformation. The depth and course of the shear surface were measured using boreholes and geophysical methods; the historic development of the landslide was analysed using dendrochronological measurements; and the present horizontal and vertical movement of the landslide over one and half years was determined using geodetic monitoring based on a network of stabilised points and inclinometer measurements.

Gully erosion is a widespread natural hazard that causes substantial financial losses every year. Dendrogeomorphic (tree ring-based) methods are a good alternative approach for assessing gully development in forested areas. The majority of previous dendrogeomorphic studies dealing with erosion focused on sheet erosion or erosion rates in the active channels of old, stabilized gullies. This study aims to asses newly originated gully development based on an analysis of exposed tree roots. Moreover, the root exposure data were used to calculate rates of linear and areal gully headcut retreat (GHR). In total, 81 samples (microcuts) from common spruce (Picea abies(L.) Karst) were analyzed for anatomical responses to root exposure. The existence of the shallow channel preceding the gully itself was identified. This GHR reconstruction (for a limited time period of eight years) provides evidence of highly active gully development in the forested area of the Flysch Carpathians that is comparable with results from semi-arid regions.

The degradation of forest ecosystems represents a severe environmental issue in anthropogenically modified landscapes worldwide. We demonstrated the negative impact of contaminated debris flow deposits on riparian forest in the Romanian Carpathians through the innovative combination of several dendroecological approaches. Reconstruction of debris flow activity using 95 individuals of Picea abies (L.) Karst. was performed to identify 11 events during the period 1952–2018. Recent events (e.g., 2007, 2014, 2016–2017) filled the valley floor after the stream was dammed in the 1980s, which deteriorated tree growth. This state was worsened by site acidity (pH = 3.8), low organic carbon, high sulfur content, and high concentrations of several metals in debris flow deposits. Wood anatomical analyses confirmed that trees producing tangential rows of traumatic resin ducts as a possible response to burial by toxic debris material subsequently produced smaller and flatter earlywood tracheids. In particular, the most obvious changes (average decrease in tracheid lumen area by 62.9% over two years) occurred after the 2016 debris flow event. Using inductively coupled plasma optical emission and/or mass spectrometry, we identified peak or increased concentrations of thallium (max. 0.7 mg kg−1), caesium (max. 0.4 mg kg−1), and aluminium (max. 434 mg kg−1) in tree biomass that could be related to debris flow activity in 1996, 2007, and 2016. Regarding the individual-specific responses of sampled trees, we conclude that the forest decline is caused by complex interaction between the depth of tree burial by debris flow deposits, the mechanical weight and chemistry of deposits, and the rate of nutrient and toxic element uptake.

Recently, dendrogeomorphic methods have been increasingly used for the dating past-flood events, and tree-ring-based approaches are generally considered valuable tools in palaeohydrology. Several limitations of the approach are known, but their effects on the resulting chronologies have not been assessed or quantified. Thus, this study attempts to critically evaluate and quantify the effectiveness of dendrogeomorphology in past-flood analysis. The tree-ring-based methods were tested on two long-term monitored, contrasting catchments in a region in the Outer Western Carpathians. In total, 101 sampled trees provided evidence of 126 growth disturbances, enabling the reconstruction of seven flood events approximately during the last 30 years in each catchment. After the comparison of monitored discharges with tree-ring records, standard dendrogeomorphic indices enabled the detection of approximately half of the flood events with discharges larger than the maximal sensitivity of the approach used (minimal detected discharge corresponding to ca. Q2). Nevertheless, significant differences were identified between the two catchments. Values of dendrogeomorphic indices corresponded well to values of maximal discharges, and increasing the indices thresholds increased the proportion of detected floods in narrow mountainous catchment. In contrast, no effect on the proportion of detected flood events after indices threshold increase was detected in the case of a wide braided channel (in the second catchment). However, the indices values corresponded well to the flood volume. The differences were probably caused by the water-level behaviour in narrow and wide channels. Thus, it seems that the characteristics of channel reaches must be very carefully considered in regard to the interpretation of dendrogeomorphic results of past-flood events.

The knowledge of past landslide movement chronology is crucial for estimating future landslide development or for detailed analysis of triggers. A very precise approach to landslide history detection is based on tree ring analysis (dendrogeomorphology). The detection of landslide movements is based on dating growth responses induced by slope movements. To date, a relatively limited spectrum of tree growth disturbances has been used in landslide research. This study provides new evidence about the possibilities of using tension wood (a growth response to stem tilting) in Fagus sylvatica L. for detection of past landslide movements. Twenty-three disturbed trees growing on a landslide with a known origin (July 1997) were analysed. Parameters of the tension wood and tree rings (vessel lumen area (VLA) and its change, the duration of tension wood, and tree ring eccentricity and its change) were compared with each other and with tree parameters (tilting degree, age, and stem diameter). Tension wood was readily macroscopically identified on the prepared surfaces of increment cores using a stereoscope. Significant relationships were found between the degree of stem tilting and tension wood duration and the magnitude of VLA change. Thus, these two parameters of tension wood can be viewed as potential indicators of landslide-influenced intensity. Tension wood formation seems to be very sensitive to tree stem tilting, as all studied trees with various degrees of stem tilting contained it in the entire tree ring width after 1997. Moreover, the onset of tension wood in 1997 always started in the second part of the tree ring width. This signals the immediate growth response to landslide movements and the possibility of using tension wood for dating with sub-annual (seasonal) resolution. Tree ring eccentricity correlated with the stem tilting degree as well; nevertheless, no relationship with tension wood parameters was found. The findings of this study with the discussed limits provide support for the very effective use of tension wood in the dendrogeomorphology of landslides.

Unlike high-relief mountain areas, low-relief hilly landscapes are usually rarely affected by deep-seated gravitational slope deformations (DSGSDs). However, low-topography flysch thrust fronts can create suitable structural conditions for DSGSDs. The study area of the Kavalcanky ridge represents a relatively low-lying ( 50 m) of the studied DSGSD. Together with slope stability finite element modelling, geophysics suggests that the shear zone of DSGSDs is represented by one of the thrust faults, whereas lateral limits are formed by a set of conjugate strike-slip faults. Radiocarbon dating of bogs within the DSGSD body showed two phases of mass-movement activity corresponding to the Late Glacial-Holocene transition and Middle Holocene. The recent activity was excluded by dendrogeomorphic analysis. We concluded that the structural conditions involving high lithological complexity, tectonic weakening and the presence of major tectonic contacts might create conditions prone to DSGSDs even in relatively low-topography settings with mass movement activity, especially during humid and warmer Late Quaternary periods.

Picea abies L. Karst is undeniably one of the most important tree species growing in Slovakia. In addition to natural mountain spruce forests, monocultures planted in lower areas are also quite common. In this article, we analyze the climate–growth response differences between these two types of spruce stands in the context of local climate change consequences. The study area representing natural mountain spruce forests is located under Osobitá Mt. (Tatra Mountains, Slovakia), while the analyzed low-lying planted monoculture is situated near Biely kríž (Malé Karpaty Mountains, Slovakia). Temporal variation of the dendroclimatological relationships was expressed by the running Spearman correlation coefficient during the observed period 1961–2018. The results showed crucial differences in the dendroclimatological relationships between the selected study areas. For the natural mountain spruce stand, consistent, weak, and positive correlations to the temperature variables were typical, with negative relationships to precipitation during the growing season. In this case, the negative impact of a recent temperature rise was limited. In contrast, the monoculture reacted to the temperature variation during the growing season with fluctuations, while in the case of precipitation, almost no dependence was found. Such incoherency may be a consequence of worsened health conditions, as well as insufficient resiliency to climate-driven stress. The importance of this paper is in its wide applicability, mainly in forestry.