Windthrow Areas Research Articles

Windthrow Impact on Alpine Forest Humipedon: Soil Microarthropod Communities and Humus Dynamics Five Years after an Extreme Windstorm Event

The ecological impact of windthrow disturbance on humipedons and soil microarthropod communities is examined in two areas of the Italian Alps (Val di Fassa and Cansiglio) five years after the Vaia Storm. The following soil coverage conditions were identified: herbaceous vegetation (G), decaying wood (W), no vegetation (B) in windthrow areas; and these were compared with conditions in adjacent undisturbed intact forests (IF) and, only in Val di Fassa, with permanent meadows (M). Soil pH, soil organic matter content (SOM), humus systems and microarthropod communities were analyzed. In Val di Fassa, SOM loss was observed in windthrow areas vs. IF, moving toward a Mull humus system, while G evolved toward M-like conditions, W maintained a thicker O horizon and lower pH and B exhibited severe soil erosion and the lowest SOM. In Cansiglio, windthrow areas showed a slower transition to a Mull system, with a trend toward increasing pH and decreasing SOM. A clear relationship between microarthropod communities and humus systems could not be established because the consistency and biological origins of the humus diagnostic horizons were not considered. Microarthropod communities under different conditions exhibited significant dissimilarity, with varying responses across groups; Shannon and QBS-ar indices remained stable except for a significant decrease in B. Community dissimilarity thus appears to be enhanced by post-windthrow disturbance, suggesting that destructive windstorms may also present an opportunity for enriched microarthropod diversity.

Salvage logging and subsequent post‐windthrow management diminish forest bird communities for two decades

Abstract Post‐disturbance forest management is known to impair biodiversity, including bird communities, but most studies focus on short‐term effects of salvage logging, without recognition of the cumulative, lasting impact of collective post‐disturbance silvicultural practices. We tracked bird community succession in a temperate pine forest from 5 to 19 years after wind disturbance in managed and unmanaged windthrow areas, covering the period from gap creation to early canopy regeneration and comparing it to nearby production forest unaffected by wind disturbance. Bird communities of unmanaged windthrow were consistently the richest in terms of bird abundance and richness. They hosted comparable forest bird diversity to unaffected production stands throughout the study period, as well as a substantial diversity of farmland birds. Managed and unmanaged windthrows followed two distinct successional pathways and did not converge. Despite the bird communities in both windthrows gradually resembling those found in undisturbed forests as the canopy regenerated, each type of windthrow and the unaffected production forest maintained distinct communities until the end of the study. Synthesis and applications. Restraining from any active post‐windthrow management sets bird succession on a distinct pathway, leading to unique and diverse bird communities. We advocate viewing natural disturbances as cost‐effective ecosystem restoration tools, provided no active management is implemented. Furthermore, we advise against using the term ‘salvage logging’ to refer to collective post‐disturbance silvicultural practices, as its varying interpretation may lead to growing confusion as the number of long‐term studies increase.

Topoğrafya ve Meşcere Yapısının Rüzgâr Devriği Zararlarına Etkisinin Araştırılması: Düzce Orman İşletme Müdürlüğü Örneği

Aim of study: The aim of the study was to determined the tree volume and damage level in windthrow areas and to assess the impact of topographic factors and forest structure on windthrow damaged.
 Area of study: Our study was conducted within the Düzce Forest Management Directorate.
 Material and methods: The windthrow areas within the boundaries of Düzce Forest Management Directorate were obtained from extraordinary yield reports. According to windthrow data verified using Google Earth, the borders for each damage were determined and transferred to ArcMap. The relationships between windthrow areas and enviromental parameters were determined using digital maps and forest management plans. Correlation analysis was applied to find out the relationship between windthrow areas and topographic and forest characteristics. Additionally, variance analysis was performed to determine if there were differences in terms of dominant aspects and forest types between windthrow areas and amounts. T-tests were conducted to determine if there were differences between windthrow areas and amounts and the dominant wind direction. Based on the statistically significant results, an intersect analysis was applied to environmental parameters to generate a windthrow susceptibility map.
 Main results: Windthrow occurred mostly in the southwest aspect, in the Fir-Beech species and in the cd age classes. A statistically significant relationship (p

The semiochemical push‐and‐pull technique can reduce bark beetle damage in disturbed Norway spruce forests affected by the Vaia storm

Abstract In a 2‐year field study conducted in the South‐Eastern Alps following a large windthrow disturbance, we tested a large‐scale use of a semiochemical push‐and‐pull strategy to protect susceptible Norway spruce edge trees from the European spruce bark beetle, Ips typographus (Coleoptera: Curculionidae, Scolytinae). Slot traps baited with aggregation pheromones (‘pull’) and three repellent semiochemicals (‘push’) were used in both years. In 2020, 26 windthrown areas were classified into three levels of infestation risk, and each was randomly assigned to one of three experimental protocols: eight push‐and‐pull sites; nine trap‐only sites and nine control sites. In 2021, the trials were repeated in 22 clear‐cuts of infested spruce forests, applying two protocols: 16 push–pull and 6 control sites. Fifty traps and 1500 repellent dispensers were used in 2020, and 26 traps and 1500 repellent dispensers were used in 2021. The push‐and‐pull technique performed well in post‐windthrow conditions (2020 trials), especially at high infestation risk, with significantly lower damage to forest edges when compared with untreated sites. The use of pheromone‐baited traps alone was not enough to avoid colonization of forest edges, especially in high‐risk sites. When the push‐and‐pull protocol was applied in clear‐cut areas (2021 trials), the technique was less effective and did not significantly reduce the number of infested trees along the forest edge. Possible interactions with climate conditions are also discussed.

Modeling deadwood for rockfall mitigation assessments in windthrow areas

Abstract. Studying how deadwood mitigates the rockfall hazard in mountain forests is key to understanding the influence of climate-induced disturbances on the protective capacity of mountain forests. Both experimental quantification and numerical process modeling are needed to address this question. Modeling provides detailed insights into the rock–deadwood interaction and can therefore be used to develop effective forest management strategies. Here, we introduce an automatic deadwood generator (ADG) for assessing the impact of fresh woody storm debris on the protective capacity of a forest stand against rockfall. The creation of various deadwood scenarios allows us to directly quantify the mitigation potential of deadwood. To demonstrate the functionality of the proposed ADG method, we compare deadwood log patterns, deadwood effective height, and mesoscale surface ruggedness observed in field surveys in a natural windthrow area with their simulated counterparts. Specifically, we consider two sites near Lake Klöntal, Switzerland, where a major windthrow event occurred in 2019. We perform rockfall simulations for the time (a) before, (b) directly after, and (c) 10 years after the windthrow event. We further compare the results with (d) a simulation with complete clearing of the thrown wood: in other words, a scenario with no standing forest remaining. We showcase an integration of deadwood into rockfall simulations with realistic deadwood configurations alongside a diameter at breast height (DBH)- and rot-fungi-dependent maximum deadwood breaking energy. Our results confirm the mitigation effect of deadwood, which significantly reduces the jump heights and velocities of 400 kg rocks. Our modeling results suggest that, even a decade after the windthrow event, deadwood has a stronger protective effect against rockfall than that provided by standing trees. We conclude that an ADG can contribute to the decision-making involved in forest and deadwood management after disturbances.

Early detection of Ips typographus infestations by using Sentinel-2 satellite images in windthrow affected Norway spruce forests in Smolyan region, Bulgaria

Strong winds uprooted more than 100 thousand m3 of coniferous trees in natural forest stands nearby the town of Smolyan (the Western Rhodopes) in January 2018. Although damaged trees were quickly removed from the stands, the European spruce bark beetle (Ips typographus) attacked the healthy Norway spruce trees near the windthrow areas in August 2020. Our hypothesis was that the trees were infested by the pest in previous years when no symptoms of attacks were observed. This study was conducted in three spruce stands, located near the windthrow areas and attacked by I. typographus, and in three control (healthy) stands located 5-10 km from the affected areas. We used satellite images captured by Sentinel-2 in September 2017-2020. It was established that in September 2017 (a year before the windthrow), the mean values of the Normalized difference vegetation index (NDVI) in the attacked stands were concentrated between 0.60 and 0.75 (with a maximum at 0.70), indicating that the trees were in good health. During the period 2018-2020 the distribution of mean values of NDVI was stretched between 0.35 and 0.75, which is an indication of evidence of pest attacks on the individual trees. The detail comparison of pixel values of the NDVI in the attacked and control sample plots was made on the base of images captured on 27.06.2020. The mean NDVI values in the three control plots (0.74-0.79) were much higher than the mean values in the sample plots attacked by the pest (0.57-0.65). These results showed that the values of NDVI based on satellite remote sensing data of Sentinel-2 can be used for early detection of I. typographus infestations in spruce stands around the windthrows. These data are important for rapid planning and implementing the sanitary feelings that reduce the pest population.

Contribution to the Knowledge of Fungi of the Kampinos National Park (Central Poland): Part 6 – With Particular Emphasis on the Species Occurring on Windthrown Areas

Abstract We identified 17 species of fungi that are new to Kampinos National Park. Sixteen were found during surveys of areas damaged by a strong wind in 2017. The remaining species was found outside the windthrow area. Descriptions of four species new to Poland ( Cortinarius subcompar , Hyaloscypha quercicola , Hypocrea tremelloides , and Trechispora aff. invisitata ) are also provided. The current number of macromycetes taxa identified in Kampinos National Park is 1,654.

UAV Video-Based Approach to Identify Damaged Trees in Windthrow Areas

Disturbances in forest ecosystems are expected to increase by the end of the twenty-first century. An understanding of these disturbed areas is critical to defining management measures to improve forest resilience. While some studies emphasize the importance of quick salvage logging, others emphasize the importance of the deadwood for biodiversity. Unmanned aerial vehicle (UAV) remote sensing is playing an important role to acquire information in these areas through the structure-from-motion (SfM) photogrammetry process. However, the technique faces challenges due to the fundamental principle of SfM photogrammetry as a passive optical method. In this study, we investigated a UAV video-based technology called full motion video (FMV) to identify fallen and snapped trees in a windthrow area. We compared the performance of FMV and an orthomosaic, created by the SfM photogrammetry process, to manually identify fallen and snapped trees, using a ground survey as a reference. The results showed that FMV was able to identify both types of damaged trees due to the ability of video to deliver better context awareness compared to the orthomosaic, although providing lower position accuracy. In addition to its processing being simpler, FMV technology showed great potential to support the interpretation of conventional UAV remote sensing analysis and ground surveys, providing forest managers with fast and reliable information about damaged trees in windthrow areas.

Novel indices for snow avalanche protection assessment and monitoring of wind-disturbed forests

Windstorms are natural disturbances predicted to increase in frequency in the future, with a consequent increased risk of damage to forests. Such damage severely affects the forest structure and, therefore, its protection capacity. Previous studies analyzed post event conditions and the recovery time of abated forest within study areas smaller than 10 ha, while not accounting for larger spatial scales. In this study, we propose a new methodology to provide tools for the spatial assessment and monitoring of protection forests against snow avalanches affected by large-scale windstorms. Four indices have been used: (i) vegetation height model, (ii) surface roughness, (iii) stored volume height and (iv) adapted tree parameters, of which the latter two have been specifically developed for this goal. We selected and periodically recorded two windthrow areas using photogrammetric surveys (deriving dense point clouds) to assess the performance of the proposed indices and to investigate the long-term changes in protective effects (Disentis, CH) and the influence of snow cover (Franza, IT). Stored volume height and the adapted tree parameters were the best indices to capture the forest conditions and standing trees, respectively. The stored volume height was further used to estimate forest protective capacity in relation to the snow cover height. Analyzing the Disentis (CH) area, we concluded that the minimum level of protective capacity occurs ten years after the storm event. After 29 years, the forest protective capacity against natural hazards increased again as forest recovery proceeded. However, special attention should be given to gaps between growing trees that may be critical for potential avalanche formation as wood decays. This study provided new insights into the long-term protective efficiency of windthrow forests, introducing two new indices to spatially assess and monitors their evolution.

Capacity Planning of Timber Harvesting in Windthrow Areas

Digitization can help the forest industry to improve cost efficiency and to reduce possible environmental impacts. In the context of this study, models were implemented using the example of windthrow processing, which enables a capacity planning for carrying out timber harvesting. For capacity planning, it is necessary to estimate the time required by the harvesting systems. For this purpose, existing productivity models were analyzed, the models were validated and adjusted, and the time required for each harvesting system and calamity area was calculated using stand and terrain parameters. Depending on the scenario and the preferred harvesting system, the time for harvesting the timber in an almost 200-hectare windthrow area in a case study region in Carinthia (Austria) varied. The harvesting with cable yarder and tractor takes about 26,000 machine hours and 86,000 man-hours. Harvesting operations with cable yarder and harvester-forwarder has proven to be the most productive with a duration of around 20,000 machine hours and 70,000 man-hours. Depending on the scenario, in windthrow areas, forest workers are needed for 28 to 42 min to fell, delimb, buck and extract 1 m3 of timber to the forest landing.

Detection of Windthrown Tree Stems on UAV-Orthomosaics Using U-Net Convolutional Networks

The increasing number of severe storm events is threatening European forests. Besides the primary damages directly caused by storms, there are secondary damages such as bark beetle outbreaks and tertiary damages due to negative effects on the market. These subsequent damages can be minimized if a detailed overview of the affected area and the amount of damaged wood can be obtained quickly and included in the planning of clearance measures. The present work utilizes UAV-orthophotos and an adaptation of the U-Net architecture for the semantic segmentation and localization of windthrown stems. The network was pre-trained with generic datasets, randomly combining stems and background samples in a copy–paste augmentation, and afterwards trained with a specific dataset of a particular windthrow. The models pre-trained with generic datasets containing 10, 50 and 100 augmentations per annotated windthrown stems achieved F1-scores of 73.9% (S1Mod10), 74.3% (S1Mod50) and 75.6% (S1Mod100), outperforming the baseline model (F1-score 72.6%), which was not pre-trained. These results emphasize the applicability of the method to correctly identify windthrown trees and suggest the collection of training samples from other tree species and windthrow areas to improve the ability to generalize. Further enhancements of the network architecture are considered to improve the classification performance and to minimize the calculative costs.

Biological Legacies and Rockfall: The Protective Effect of a Windthrown Forest

Windstorms represent one of the main large-scale disturbances that shape the European landscape and influence its forest structure, so post-event restoration activities start to gain a major role in mountainous forest management. After a disturbance event, biological legacies may enhance or maintain multiple ecosystem services of mountain forests such as protection against natural hazards, biodiversity conservation, or erosion mitigation. However, the conservation of all these ecosystem services after stand-replacing events could go against traditional management practices, such as salvage logging. Thus far, the impact of salvage logging and removal of biological legacies on the protective function of mountain stands has been poorly studied. Structural biological legacies may provide protection for natural regeneration and may also increase the terrain roughness providing a shielding effect against gravitational hazards like rockfall. The aim of this project is to understand the dynamics of post-windthrow recovery processes and to investigate how biological legacies affect the multifunctionality of mountain forests, in particular the protective function. To observe the role of biological legacies we performed 3000 simulations of rockfall activity on windthrown areas. Results show the active role of biological legacies in preventing gravitational hazards, providing a barrier effect and an energy reduction effect on rockfall activity. To conclude, we underline how forest management should take into consideration the protective function of structural legacies. A suggestion is to avoid salvage logging in order to maintain the multifunctionality of damaged stands during the recovery process.

Windthrows promote higher diversity of saproxylic beetles (Coleoptera: Passalidae) in a Central Amazon forest

Abstract Natural disturbances change environmental conditions that play an important role in controlling biodiversity. Large‐scale windthrows (i.e. snapped and uprooted trees) promoted by convective systems cause severe tree mortality and can alter the dynamics of several insect taxons in forests. We assessed the effect of large‐scale windthrows resulting from a squall line event in January 2005 on strictly saproxylic beetle assemblages in Central Amazonia. Using a paired sampling design comparing windthrown and old‐growth forest, we investigated the responses of different metrics of Passalidae diversity (richness, abundance and composition). We found a higher richness and abundance of species in windthrown areas compared with old‐growth forest, and a correlation between species composition and the tree mortality gradient. Differences in the richness and composition of the Passalidae assemblage between disturbed and old‐growth forest suggest that the tree mortality gradient created by windthrows promotes the diversity of saproxylic beetles in Central Amazonia.

Extending deep learning approaches for forest disturbance segmentation on very high‐resolution satellite images

AbstractAccurate remote detection of various forest disturbances is a challenge in global environmental monitoring. Addressing this issue is crucial for forest health assessment, planning salvage logging operations, modeling stand dynamics, and estimating forest carbon stocks and uptake. Substantial progress on this problem has been achieved owing to the rapid development of remote sensing devices that provide very high‐resolution images. Concurrently, image processing algorithms have witnessed rapid development owing to the extensive use of artificial neural networks with complex architectures and deep learning approaches. This opens new opportunities and perspectives for applying deep learning methods to solving various problems in environmental sciences. In this study, we used deep convolutional neural networks (DCNNs) to recognize forest damage induced by windthrows and bark beetles. We used satellite imagery of very high resolution in visual spectra represented as pansharpened images (RGB channels). When predicting forest damage, we obtained accuracies higher than 90% on test data for recognition of both windthrow areas and damaged trees impacted by bark beetles. A comparative analysis indicated that the DCNN‐based approach outperforms traditional pixel‐based classification methods (AdaBoost, random forest, support vector machine, quadratic discrimination) by at least several percentage points. DCNNs can learn a specific pattern of the area of interest and thus yield fewer false positive decisions than pixel‐based algorithms. The ability of DCNNs to generalize makes them a good tool for delineating smooth and ill‐defined boundaries of damaged forest areas, such as windthrow patches.

A satellite-derived database for stand-replacing windthrow events in boreal forests of European Russia in 1986–2017

Abstract. Severe winds are among the main causes of disturbances in boreal and temperate forests. Here, we present a new geographic information system (GIS) database of stand-replacing windthrow events in the forest zone of European Russia (ER) for the 1986–2017 period. The delineation of windthrow areas was based on the full Landsat archive and two Landsat-derived products on forest cover change, namely the Global Forest Change and the Eastern Europe's forest cover change datasets. Subsequent verification and analysis of each windthrow was carried out manually to determine the type of related storm event, its date or date range, and geometrical characteristics. The database contains 102 747 elementary areas of damaged forest that were combined into 700 windthrow events caused by 486 convective or non-convective storms. The database includes stand-replacing windthrows only with an area > 0.05 and > 0.25 km2 for the events caused by tornadoes and other storms, respectively. Additional information such as weather station reports and event descriptions from media sources is also provided. The total area of stand-replacing windthrows amounts to 2966 km2, which is 0.19 % of the forested area of the study region. Convective windstorms contribute 82.5 % to the total wind-damaged area, while tornadoes and non-convective windstorms are responsible for 12.9 % and 4.6 % of this area, respectively. Most of the windthrow events in ER happened in summer, which is in contrast to Western and Central Europe, where they mainly occur in autumn and winter. Due to several data and method limitations, the compiled database is spatially and temporally inhomogeneous and hence incomplete. Despite this incompleteness, the presented database provides a valuable source of spatial and temporal information on windthrow in ER and can be used by both science and management. The database is available at https://doi.org/10.6084/m9.figshare.12073278.v6 (Shikhov et al., 2020).

Vertical distribution of epiphytic bryophytes depends on phorophyte type; a case study from windthrows in Kampinoski National Park (Central Poland)


 
 
 The vertical distribution of epiphytic bryophytes in European forests are still relatively poorly understood. The aim of the study was to analyse the diversity and vertical zonation of epiphytic mosses and liverworts on selected tree types (Quercus petraea, Betula pendula and Pinus sylvestris) within windthrow areas in the Kampinoski National Park (Central Poland). The investigations were performed in five parts of the trees: the tree base, lower trunk, upper trunk, lower crown, and upper crown. Deciduous trees have more species than pine trees (13 on Quercus and Betula, 8 on Pinus). The type of phorophyte was crucial for the differences in the species composition from the tree base to the upper crown that was observed. The highest richness of bryophytes was recorded on the tree bases, while the lowest was recorded in the upper parts of the crowns. The variability of the habitat conditions in the vertical gradient on the trunk that affected the patterns of the occurrence of species with different ecological preferences was determined using the Ellenberg indicator values. An increase in the value of the light and acidity indicators from the base of the trunk upwards and decreasing tendency in the case of moisture indicator was noted.
 
 

Impacts of windstorm-induced forest loss and variable reforestation on bird communities

With climate change, the area affected by and the intensity of forest disturbances such as windthrow, insect outbreaks and fire will be increasing. Post-disturbance forest management will be varied, and it is difficult to predict how much natural succession will be allowed in comparison to reforestation. Both, disturbance and reforestation will affect forest biodiversity globally, but potential shifts in species distribution, abundance and community composition are poorly understood.We studied the response of breeding bird communities to windstorm-induced forest loss (windthrow followed by salvage logging) and different reforestation strategies in one of Central Europe’s largest contiguous windthrow areas created by storm Kyrill in 2007. A decade after the disturbance, we compared bird species diversity, population densities and community composition on plots in replanted beech, replanted conifers and secondary succession (all salvage-logged after the storm), with undisturbed mature (ca. 50–80 years old) Norway spruce Picea abies as a control, in the setting of a natural experiment.Of the stands blown down, 95% were Norway Spruce. Reforestation strategies varied, with Spruce and non-native conifers planted on twice the area that was replanted with European Beech Fagus sylvestris. Large areas were still dominated by successional tree species a decade after the storm, especially birch Betula spp., mirroring recommendations of sub-national forestry agencies to include secondary succession in future forest development. Birds responded strongly to windstorm-induced forest loss, with a pronounced community turnover. Species associated with high conifer stands reached significantly lower densities on sample plots in disturbed areas. Replanted areas were characterized by mostly ubiquitous bird species. Areas dominated by secondary succession, especially birch, were characterized by high densities of long-distance migrants (often species of conservation concern) and shrubland species, among them several indicator species.Our results suggest that an increase of forest disturbance across Central Europe will lead to a pronounced reorganisation of biodiversity. Strategies that allow more secondary succession, and avoid replanting allochthonous tree species are likely to benefit populations of depleted bird species, even at salvage-logged and cleared disturbance sites.

Planting time, stocktype and additive effects on the development of spruce and pine plantations in Western Carpathian Mts.

Planting of seedlings is the most reliable and speedy way of forest restoration. Routine spring planting of bareroot seedlings is frequently unsuccessful in central Europe. In this study, the effects of planting time and a spring-pre-planting application of ectomycorrhiza-hydrogel additive Ectovit and hydrogel Stockosorb on the development of bareroot and container Norway spruce and Scots pine seedlings on windthrow area in Western Carpathians, northwest Slovakia were estimated. Survival and aboveground growth parameters during three consecutive years and root dry weight, short root frequency, soil and needle nutrients concentration and ectomycorrhizal fungi root colonization and identification 2 years after planting were assessed. Regardless of planting time and additive, the best developed bareroot spruce (2 + 2) survived significantly better than container spruce (2 + 0), container pine (2 + 0) and especially small-size bareroot pine (1 + 0); bareroot pine was found unsuitable for planting in conditions of planting site. Both additives improved survival of spring-planted container spruce in the summer-drought second year after planting. Container spruce survived and grew significantly better following fall compared to spring planting time. Higher number of short roots was observed in spring than in fall planted bareroot spruce. Neither planting time nor additives affected root dry weight and abundance of ectomycorrhizae. No significant effects of the treatments on pine development were found. Except of K deficiency in container spruce, sufficient or overabundant foliar macro-nutrients concentration was detected. Visual morphotyping of short roots and identification of ectomycorrhizae by DNA analysis indicated inefficient ectomycorrhizal inoculation of seedlings with Ectovit.

Mapping forest windthrows using high spatial resolution multispectral satellite images

Wind disturbances represent the main source of damage in European forests, affecting them directly (windthrows) or indirectly due to secondary damages (insect outbreaks and forest fires). The assessment of windthrows damages is very important to establish adequate management plans and remote sensing can be very useful for this purpose. Many types of optical remote sensing data are available with different spectral, spatial and temporal resolutions, and many options are possible for data acquisition, i.e. immediately after the event or after a certain time. The objective of this study is to compare the windthrows mapping capabilities of two multispectral satellite constellations (i.e. Sentinel-2 and PlanetScope) characterized by very different spectral, spatial and temporal resolutions, and to evaluate the impact of the acquisition conditions on the mapping results. The analysed area, with an extent of 732 km2, is located in the Trentino-South Tyrol region (Italy) which was affected by the Vaia storm on the 27th-30th of October 2018, causing serious forest damages. The change vector analysis technique was used to detect the windthrows. For each data source, two pairs of images were considered: 1) pre- and post- event images acquired as close as possible to the event; 2) pre- and post- event images acquired at optimal conditions, i.e. at similar phenological state and similar illumination conditions. The results obtained with the two satellite constellations are very similar despite their different resolutions. Data acquired in optimal conditions allowed having the best detection rate (accuracy above 80 %), while data acquired just after the event showed many limitations. Improved spatial resolution (PlanetScope data) allows for a better delineation of the borders of the windthrow areas and of the detection of smaller windthrow patches.

Investigations of mature Scots pine stands in wind-throw areas in Norway spruce forests in Western Rhodopes

Abstract We investigated the current health condition (defoliation), state of natural regeneration, and mycoflora and phytopathogen-caused attacks in Scots pine forests (Pinus sylvestris L.) planted in the 1960s in areas affected by wind disturbances in the West Rhodope Mountains in Bulgaria. Some damage types (resin outflow and anthropogenic damage) were present to a low extent in the research plots (S – Selishte and PK – Pobit Kamak). Some were missing completely (damage by deer and other animals, the presence of lignicolous fungi and abiotic damage). The most important results of this study were the following: i) the occurrence of the bark beetle pest Tomicus minor Hartig (Coleoptera, Scolytinae) was recorded on average in 4.6 (S) and 2.3 (PK) of fallen shoots under the tree crown within 1 m diameter around the stem; ii) significant damage to tree crowns due to the loss of assimilation organs in Scots pine trees (28% – S and 39% – PK, respectively) was several times higher than that recorded in Norway spruce (Picea abies L.) (10%); iii) tree species composition resulting from natural regeneration showed 95–100% proportion of Norway spruce despite the predominance of Scots pine in the maternal stand. These observations might provide evidence of unsuitable environmental conditions in the studied localities for pine forests on the southern range of the natural P. sylvestris occurrence. Forest management in similar ecological and climatic conditions should aim at significant diversification of the forest stand structure by utilizing tree species suitable for the given ecosystems.