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Natural disturbances have significantly intensified across European forests, with bark beetle outbreaks being the most rapidly escalating disturbance type. Since 2018, the Czech Republic (Central Europe) has become a Europe's disturbance epicentre due to the unprecedented outbreak of spruce bark beetle Ips typographus in the forests dominated by Norway spruce Picea abies. Here we provide novel insights into the impacts and dynamics of this disturbance from 2016 to 2022. The investigation is based on annual forest change maps developed by the classification of optical and Synthetic Aperture Radar satellite imagery. We identified seven major outbreak foci across the country, where the outbreaks culminated between 2018 and 2021. Most of the outbreak waves exhibited a symmetric shape, characterized by a three-year build-up phase, a single culmination year, and the subsequent decline. The substantial proportion of spruce remaining in the outbreak areas after the culmination point implies that resource depletion is an improbable cause for the outbreak's retreat. In the year of retreat, the proportion of spruce in the forest ranged between 26% and 36% in most of the outbreak areas. The disturbance dynamics manifested a transition from the emergence of new tree mortality spots in the early outbreak phase to their short-range expansion, suggesting density-dependent changes in bark beetle dispersal during the studied period. The core disturbance zone, pinpointed in 2022, covered an area of 9,000 ​km2 and experienced a 38% loss in forest cover. Within this area, forest fragmentation increased significantly, leading to a greater forest patch complexity and reduced connectivity among the patches. The presented findings can serve as a glimpse into the future for other European regions, revealing the potential impacts of natural disturbances amplified by climate change.

This study investigates the isolated decomposition of spruce and lodgepole conifer needles to enhance our understanding of how needle litter impacts near-surface terrestrial biogeochemical processes. Harvested needles were exported to a subalpine meadow to enable a discrete analysis of the decomposition processes over 2 years. Initial chemistry revealed the lodgepole needles to be less recalcitrant with a lower carbon to nitrogen (C:N) ratio. Total C and N fundamentally shifted within needle species over time with decreased C:N ratios for spruce and increased ratios for lodgepole. Differences in chemistry correlated with CO2 production and soil microbial communities. The most pronounced trends were associated with lodgepole needles in comparison to the spruce and needle-free controls. Increased organic carbon and nitrogen concentrations associated with needle presence in soil extractions further corroborate the results with clear biogeochemical signatures in association with needle chemistry. Interestingly, no clear differentiation was observed as a function of bark beetle impacted spruce needles vs those derived from healthy spruce trees despite initial differences in needle chemistry. These results reveal that the inherent chemistry associated with tree species has a greater impact on soil biogeochemical signatures during isolated needle decomposition. By extension, biogeochemical shifts associated with bark beetle infestation are likely driven more by changes such as the cessation of rhizospheric processes than by needle litter decomposition.

Under the effect of climate change, we can expect continuing trend in increasing frequency and severity of disturbances in Norway spruce forests. We are lacking the information to what extent is the pre-disturbance forest structure resilient to stand-replacing disturbance and if it can be carried over to the next generation of forest stand. Therefore following questions arise: How does the pre-disturbance spatial pattern influence the spatial structure of natural regeneration? Does the spatial pattern remain preserved even after nearly complete canopy dieback? We did repeated measurement of forest structure in Trojmezná primary forest (Šumava National Park) ~3 and ~13 years after bark beetle disturbance. Density of trees (height =1.3 m) increased over the years, in 2011 the mean density was 416 ind.ha-1 while in 2021 the mean density was 2 205 ind.ha-1. The tree species composition was dominated by Norway spruce (92.8%) with a mix of rowan (6.8%), which decreased from 15.3% since 2011. Young trees were strongly aggregated to themselves as well as to snags and stumps. Significant clustering around dead wood occurred at shorter distances (around 2 m), the effect weakened with the increasing distance. This implies that the new generation of forest stand mirrors the former parent stand, keeping its spatial structure preserved even after stand replacing disturbance. [ABSTRACT FROM AUTHOR]

Contact to nature and greenspace is important for emotional well-being and can promote human health. Forest landscapes provide such access to greenspace, especially in protected areas. However, forested protected areas are impacted by natural disturbances such as bark beetle infestations. On the one hand, such disturbances have positive impacts on ecological processes and biodiversity. On the other hand, they have allegedly negative impacts on the recreational value of a landscape. Limited knowledge about the public’s perception of forests subject to natural disturbances still hampers forest management to balance ecological functions and visitors’ recreational experience. Thus, our aim was to determine how attitudes towards nature influence the personal well-being in a naturally disturbed landscape. We investigated self-reported well-being and attitudes towards nature in a standardized questionnaire-based survey of 1008 German inhabitants in an experimentally adapted landscape visualization. Self-reported well-being was generally highest in landscapes with relatively few bark-beetle-killed trees. This was especially the case for people who felt included with nature and preferred an appreciative use or preservation of nature. Conversely, people who had previously visited a national park with visible bark beetle infestations rated their personal well-being highest in landscapes with larger proportions of beetle-killed trees. Our results indicate that it is necessary to analyze people’s knowledge about and relations to forest landscapes as well as concepts of nature conservation, natural landscapes, and biodiversity to gain a better understanding of people’s perceptions of natural disturbances.

This study investigates the isolated decomposition of spruce and lodgepole conifer needles to enhance our understanding of how needle litter impacts near-surface terrestrial biogeochemical processes. Harvested needles were exported to a subalpine meadow to enable a discrete analysis of the decomposition processes over 2 years. Initial chemistry revealed the lodgepole needles to be less recalcitrant with a lower carbon to nitrogen (C:N) ratio. Total C and N fundamentally shifted within needle species over time with decreased C:N ratios for spruce and increased ratios for lodgepole. Differences in chemistry correlated with CO2 production and soil microbial communities. The most pronounced trends were associated with lodgepole needles in comparison to the spruce and needle-free controls. Increased organic carbon and nitrogen concentrations associated with needle presence in soil extractions further corroborate the results with clear biogeochemical signatures in association with needle chemistry. Interestingly, no clear differentiation was observed as a function of bark beetle impacted spruce needles vs those derived from healthy spruce trees despite initial differences in needle chemistry. These results reveal that the inherent chemistry associated with tree species has a greater impact on soil biogeochemical signatures during isolated needle decomposition. By extension, biogeochemical shifts associated with bark beetle infestation are likely driven more by changes such as the cessation of rhizospheric processes than by needle litter decomposition.

The tree natural regeneration and seed bank that survives a large-scale stand-replacing disturbance fully determines the future forest structure until new generation trees reach seed maturity and the supply of seeds is restored. We asked the following questions: (i) Does the advance regeneration stage prevail in the stand? (ii) Does the tree species composition changed after disturbance? (iii) Does the regeneration height structure change depend on elevation and characteristics of the previous stand? Mean seedlings (<130 cm) density was 4000 individuals per hectare 5 years after the disturbance; rowan covered 2% of the regeneration. The density of saplings (≥130 cm) was 252 individuals per hectare, of which 19% were rowan individuals. The advance regeneration consisted of 88% of all individuals. Microsites mostly preferred were soil covered by mosses (32% of individuals), the tree base of living mature trees and snags (28% of individuals), and dead wood (27% of individuals). The density of saplings significantly decreased with increasing elevation; for seedlings, this trend was not significant. Even an elevation gradient of 100 m can have a major impact on the growth rate of the regeneration. Although the variability of stand characteristics was high, no significant effect was recorded for any of the height categories of spruce and rowan with regard to the density of the regenerated stand. Our results provide the example of stands, where structure of regeneration after the disturbance is not explained by previous stand characteristic. Lower saplings density in higher elevation is probably caused by limiting growth conditions such a cold. High heterogeneity of regeneration structure must depend on many other factors. [ABSTRACT FROM AUTHOR]

Salvage logging is one of most frequently applied management responses to forest disturbances world‐wide. As forest disturbances are increasing, so too is the application of salvage logging, yet its effects on ecosystems remains incompletely understood. In the Norway spruce (Picea abies (L.) Karst.) forests of Europe, salvaging of windfelled trees is inter alia applied to reduce the risk of bark beetle outbreaks (mainly Ips typographus L.). By preventing further disturbances, salvage logging can conserve live tree carbon (C) in forest landscapes. At the same time salvage logging reduces C stocks in detrital pools via the extraction of disturbed trees, its net effect thus remains unclear.We used the forest landscape model iLand to explore the effect of a wide range of salvaging intensities on (a) subsequent bark beetle outbreaks, and (b) landscape‐scale forest C stocks in a Norway spruce‐dominated production forest in Slovakia under past and future climatic conditions.Climate change resulted in a two‐ to three‐fold increase in bark beetle disturbances throughout the 21st century in our simulations. We found that removing >95% of disturbed trees can effectively buffer the effect of increasing disturbances, dampening bark beetle infestations and increasing live tree C. Total ecosystem C followed a U‐shaped pattern over salvaging intensity, with highest values in no salvage and 100% salvage scenarios.However, realistic rates of salvaging (<95% of disturbed trees detected and removed) had no significant effect on bark beetle dynamics and live tree C, and reduced the total ecosystem C stored in the landscape. Furthermore, the effect of reduced bark beetle disturbance under intensive salvaging was partly offset by increased wind disturbance.Synthesis and applications. Clearing disturbed areas to prevent future disturbances from bark beetles and conserve live tree carbon should only be applied where very high salvaging rates are feasible (i.e. small and concentrated disturbances). Considering that changing disturbance regimes make high‐intensity salvaging increasingly challenging, alternative disturbance management approaches need to be developed. [ABSTRACT FROM AUTHOR]

In this article, we investigated the detection of forest vegetation changes during the period of 2017 to 2019 in the Low Tatras National Park (Slovakia) and the Sumava National Park (Czechia) using Sentinel-2 data. The evaluation was based on a time-series analysis using selected vegetation indices. The case studies represented five different areas according to the type of the forest vegetation degradation (one with bark beetle calamity, two areas with forest recovery mode after a bark beetle calamity, and two areas without significant disturbances). The values of the trajectories of the vegetation indices (normalized difference vegetation index (NDVI) and normalized difference moisture index (NDMI)) and the orthogonal indices (tasseled cap greenness (TCG) and tasseled cap wetness (TCW)) were analyzed and validated by in situ data and aerial photographs. The results confirm the abilities of the NDVI, the NDMI and the TCW to distinguish disturbed and undisturbed areas. The NDMI vegetation index was particularly useful for the detection of the disturbed forest and forest recovery after bark beetle outbreaks and provided relevant information regarding the health of the forest (the individual stages of the disturbances and recovery mode). On the contrary, the TCG index demonstrated only limited abilities. The TCG could distinguish healthy forest and the gray-attack disturbance phase; however, it was difficult to use this index for detecting different recovery phases and to distinguish recovery phases from healthy forest. The areas affected by the disturbances had lower values of NDVI and NDMI indices (NDVI quartile range Q2–Q3: 0.63–0.71; NDMI Q2–Q3: 0.10–0.19) and the TCW index had negative values (Q2–Q3: −0.06–−0.05)). The analysis was performed with a cloud-based tool—Sentinel Hub. Cloud-based technologies have brought a new dimension in the processing and analysis of satellite data and allowed satellite data to be brought to end-users in the forestry sector. The Copernicus program and its data from Sentinel missions have evoked new opportunities in the application of satellite data. The usage of Sentinel-2 data in the research of long-term forest vegetation changes has a high relevance and perspective due to the free availability, distribution, and well-designed spectral, temporal, and spatial resolution of the Sentinel-2 data for monitoring forest ecosystems.

This study focused on the evaluation of forest vegetation changes from 1992 to 2015 in the Low Tatras National Park (NAPANT) in Slovakia and the Sumava National Park in Czechia using a time series (TS) of Landsat images. The study area was damaged by wind and bark beetle calamities, which strongly influenced the health state of the forest vegetation at the end of the 20th and beginning of the 21st century. The analysis of the time series was based on the ten selected vegetation indices in different types of localities selected according to the type of forest disturbances. The Landsat data CDR (Climate Data Record/Level 2) was normalized using the PIF (Pseudo-Invariant Features) method and the results of the Time Series were validated by in-situ data. The results confirmed the high relevance of the vegetation indices based on the SWIR bands (e.g., NDMI) for the purpose of evaluating the individual stages of the disturbance (especially the bark beetle calamity). Usage of the normalized Landsat data Climate Data Record (CDR/Level 2) in the research of long-term forest vegetation changes has a high relevance and perspective due to the free availability of the corrected data.

In this article, we investigated the detection of forest vegetation changes during the period of 2017 to 2019 in the Low Tatras National Park (Slovakia) and the Sumava National Park (Czechia) using Sentinel-2 data. The evaluation was based on a time-series analysis using selected vegetation indices. The case studies represented five different areas according to the type of the forest vegetation degradation (one with bark beetle calamity, two areas with forest recovery mode after a bark beetle calamity, and two areas without significant disturbances). The values of the trajectories of the vegetation indices (normalized difference vegetation index (NDVI) and normalized difference moisture index (NDMI)) and the orthogonal indices (tasseled cap greenness (TCG) and tasseled cap wetness (TCW)) were analyzed and validated by in situ data and aerial photographs. The results confirm the abilities of the NDVI, the NDMI and the TCW to distinguish disturbed and undisturbed areas. The NDMI vegetation index was particularly useful for the detection of the disturbed forest and forest recovery after bark beetle outbreaks and provided relevant information regarding the health of the forest (the individual stages of the disturbances and recovery mode). On the contrary, the TCG index demonstrated only limited abilities. The TCG could distinguish healthy forest and the gray-attack disturbance phase; however, it was difficult to use this index for detecting different recovery phases and to distinguish recovery phases from healthy forest. The areas affected by the disturbances had lower values of NDVI and NDMI indices (NDVI quartile range Q2–Q3: 0.63–0.71; NDMI Q2–Q3: 0.10–0.19) and the TCW index had negative values (Q2–Q3: −0.06–−0.05)). The analysis was performed with a cloud-based tool—Sentinel Hub. Cloud-based technologies have brought a new dimension in the processing and analysis of satellite data and allowed satellite data to be brought to end-users in the forestry sector. The Copernicus program and its data from Sentinel missions have evoked new opportunities in the application of satellite data. The usage of Sentinel-2 data in the research of long-term forest vegetation changes has a high relevance and perspective due to the free availability, distribution, and well-designed spectral, temporal, and spatial resolution of the Sentinel-2 data for monitoring forest ecosystems. [ABSTRACT FROM AUTHOR]

This study focused on the evaluation of forest vegetation changes from 1992 to 2015 in the Low Tatras National Park (NAPANT) in Slovakia and the Sumava National Park in Czechia using a time series (TS) of Landsat images. The study area was damaged by wind and bark beetle calamities, which strongly influenced the health state of the forest vegetation at the end of the 20th and beginning of the 21st century. The analysis of the time series was based on the ten selected vegetation indices in different types of localities selected according to the type of forest disturbances. The Landsat data CDR (Climate Data Record/Level 2) was normalized using the PIF (Pseudo-Invariant Features) method and the results of the Time Series were validated by in-situ data. The results confirmed the high relevance of the vegetation indices based on the SWIR bands (e.g., NDMI) for the purpose of evaluating the individual stages of the disturbance (especially the bark beetle calamity). Usage of the normalized Landsat data Climate Data Record (CDR/Level 2) in the research of long-term forest vegetation changes has a high relevance and perspective due to the free availability of the corrected data. [ABSTRACT FROM AUTHOR]