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With the increasing frequencies of extreme weather events caused by climate change, the risk of forest damage from insect attacks grows. Storms and droughts can damage and weaken trees, reduce tree vigour and defence capacity and thus provide host trees that can be successfully attacked by damaging insects, as often observed in Norway spruce stands attacked by the Eurasian spruce bark beetle Ips typographus. Following storms, partially uprooted trees with grounded crowns suffer reduced water uptake and carbon assimilation, which may lower their vigour and decrease their ability to defend against insect attack. We conducted in situ measurements on windthrown and standing control trees to determine the concentrations of non-structural carbohydrates (NSCs), of phenolic defences and volatile monoterpene emissions. These are the main storage and defence compounds responsible for beetle´s pioneer success and host tree selection. Our results show that while sugar and phenolic concentrations of standing trees remained rather constant over a 4-month period, windthrown trees experienced a decrease of 78% and 37% of sugar and phenolic concentrations, respectively. This strong decline was especially pronounced for fructose (-83%) and glucose (-85%) and for taxifolin (-50.1%). Windthrown trees emitted 25 times greater monoterpene concentrations than standing trees, in particular alpha-pinene (23 times greater), beta-pinene (27 times greater) and 3-carene (90 times greater). We conclude that windthrown trees exhibited reduced resources of anti-herbivore and anti-pathogen defence compounds needed for the response to herbivore attack. The enhanced emission rates of volatile terpenes from windthrown trees may provide olfactory cues during bark beetle early swarming related to altered tree defences. Our results contribute to the knowledge of fallen trees vigour and their defence capacity during the first months after the wind-throw disturbance. Yet, the influence of different emission rates and profiles on bark beetle behaviour and host selection requires further investigation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Simple Summary: The most important disturbances in European forests are windstorms and fire. In 2004, 12,000 ha of High Tatra Mts. (Slovakia) forests were seriously damaged by strong winds. Furthermore, in 2005 the area of 250 ha of not cleared forest from fallen wood biomass after windstorms was burned down. Our study brings an overview on the influences of irregular wind and fire disturbances and subsequently human activities upon the structure of thrips communities there, where eight study plots with different after-calamity management were chosen. There were two study plots that were affected by wind and subsequent management with the extraction of fallen wood biomass and influenced by fire that were characterized by low species richness. In comparison, not cleared habitats from fallen wood biomass with significantly higher species richness of thrips and higher values of diversity were characterized mainly by the presence of grass-living species Chirothrips manicatus and Limothrips denticornis. The meadow communities with longer development and higher values of diversity were inhabited by the species-rich community mainly with Thrips fuscipennis, T. brevicornis, T. flavus, and T. tabaci. Gradually, in the process of secondary succession these thrips assemblages will be probably replaced by the thrips of the shaded and long-term forests that are mainly composed of Oxythrips bicolor, O. ajugae, and Thrips pini. Strong winds, fire, and subsequent forest management impact arthropod communities. We monitored the diversity and changes in the community structure of forest thrips assemblages in the context of secondary succession and anthropogenic impact. There were eight study plots that were affected to varying degrees by the mentioned disturbances that were selected in the Central European spruce (Picea abies (L.) Karst.) forests in Slovakia. The soil photoeclectors were used to obtain thrips in the study plots during two vegetation seasons. The thrips assemblages and their attributes were analyzed by non-metric multidimensional scaling (NMDS). The significant changes in community structure, composition, stratification, species richness, and diversity of thrips assemblages that were caused by natural- (wind) and human-induced disturbance (forestry and fire) were observed in our research. Our analyses revealed a clear relationship between different thrips assemblages and impacted environment. Moreover, our results indicate that silvicolous thrips species may be useful for indicating changes and disturbances in forest ecological systems. [ABSTRACT FROM AUTHOR]

The anticipated increase in extreme disturbance events due to climate change is likely to expose Norway spruce (Picea abies (L.) Karst.) dominated forests in northern Europe to new conditions. Empirical data on the resilience of such natural (unmanaged) forests to disturbance and the long-term patterns of regeneration in its aftermath are currently scarce. We performed a quantitative assessment of natural forest stands in north–western Latvia to identify and characterise the patterns of stand structure 44 years after a stand-replacing disturbance and investigated the effects of legacies on regeneration. The spatial distribution of tree species and their dimensions were assessed in 71 circular sample plots (500 m2 each) in natural forest areas, where Norway spruce dominated prior to the windthrow and salvage logging was not carried out. Spatial indices (species mingling index, size differentiation index, and aggregation index) were used to characterise stand structure and diversity. The different initial states (age and coverage of surviving trees) of stands affected eventual tree species dominance, size differentiation, degree of mingling and aggregation. Our results demonstrate a close relationship between disturbance legacies and spatial indices. The pre-storm understory and canopy survivors decreased species mingling, whereas survivors increased size differentiation. The size differentiation increased also with a higher degree of species mingling. Leaving differential post-storm legacies untouched promotes a higher structural and species diversity and therefore supports the management approach of preserving canopy survivors. [ABSTRACT FROM AUTHOR]

In November 2004 a large windstorm affected forests dominated by Norway spruce (Picea abies (L.) H. Karst, 1881) in the High Tatras National Park, Slovakia, and was followed by a wildfire (2005) and bark beetle outbreak. In this study we investigate temporal changes of breeding bird community (their species richness, density and diversity) as well as different nest-position guilds, in relation to disturbance type. Bird species composition was surveyed in two periods (2006 and 2007, and 2017 and 2018) using the point count method on four plots differing by disturbance type – undisturbed forest, unlogged windthrow, salvage logged windthrow and burnt salvage logged windthrow. A total of three visits per point and breeding season were performed at forty point count sites. We also assessed the successional shift in habitat characteristics between the two monitored periods. In total, 55 bird species and 2059 individuals were recorded on the plots during the study. We observed no effect of disturbance type on mean species richness, abundance and Simpson's diversity per point; however, those characteristics did significantly increase over the study duration. While differently disturbed points had previously differed in their (nest-position) guild number and diversity, the differences between them disappeared over time. We found different trajectories of temporal change in the composition of the species communities and guild diversity in relation to disturbance type, but in a similar direction. During the first period, the greater the initial differences in the severity of disturbance among the disturbance types, the greater the differences were in the composition of bird communities; however, the differences gradually diminished as the forests regenerated. Alterations in habitat structure caused by natural and anthropogenic disturbance and by subsequent succession were the most probable reasons for the altered bird communities and observed patterns of recovery. [ABSTRACT FROM AUTHOR]

The tree diameter distribution was used to characterize the impact of forest disturbances and the ecosystem dynamics during the process of regeneration in the absence of any management 44 years after the event. In addition, the impact of salvage logging after windthrow remains unknown, especially on long-term responses. In this study, comparisons were made between the "unsalvaged" and "salvaged" post-storm management scenarios. The study was conducted in Slitere Natural Park in the Northwest part of Latvia, where large-scale windthrow occurred on November 2, 1969. The three-parameter Weibull function was used to describe the diameter distribution of Norway spruce (Picea abies (L.) Karst.) stands formed after large-scale wind storm in two site types (on fertile mineral soils: with normal moisture regime (fresh)—Oxalidosa—and with periodic excess water (wet)—Myrtilloso-sphagnosa) and where salvage logging was or was not carried out (management scenarios). The naturally regenerated stands remained Norway spruce dominated and were independent of the post-storm management scenarios; still, they were significantly affected by a forest type. The three-parameter Weibull distribution function suited well to actual diameter distributions of the sample plots. Diameter distributions significantly differed between the forest types: In Myrtilloso-sphagnosa (wet) forest stands, it was a negative exponential and in Oxalidosa (fresh) stands unimodal and positively skewed. We did not detect distribution differences caused by salvage after a large-scale disturbance, indicating that other factors (like ecological importance of deadwood, a risk of insect outbreaks to neighboring areas, etc.) need to be considered, when deciding on the post-storm management. [ABSTRACT FROM AUTHOR]

• A dataset from 317´000 annual tree observations during 37 years is presented. • Drought and high N deposition increase the risk of uprooting and stem breakage. • Wind damage under drought and high N deposition endangers the sustainability of Picea abies. Damage by wind in forests has increased in recent decades, counteracting possible growth increases by nitrogen (N) deposition. This is also shown by the long-term forest monitoring data from this study. The main factors affecting uprooting and stem breakage in Fagus sylvatica (L.) (9′846 individual beech trees in 102 plots) and Picea abies (Karst.) (9′168 Norway spruce trees in 72 plots) have been analysed by binomial mixed regression models. Our long-term forest observations showed that drought increased uprooting of beech and increased both uprooting and stem breakage of Norway spruce. In beech, high N deposition interacted with drought, resulting in increased uprooting under drought. In Norway spruce, N deposition increased stem breakage directly. Foliar potassium (K) deficiency increased uprooting of both beech and Norway spruce. Moreover, we found an indirect effect of soil acidification in increasing uprooting of beech by decreasing foliar calcium (Ca) concentrations. In Norway spruce, the soil acidification effect was confounded by foliar K concentrations. In beech, stem breakage increased with higher temperature which can be explained by a temperature-mediated growth increase of white rot fungi. In contrast, temperature was negatively related with stem breakage in Norway spruce, which may be interpreted as an inhibition of the heartrot fungus Heterobasidion at higher temperatures.In summary, drought and high N deposition increase the risk of mechanical damage to both beech and Norway spruce and thus endanger sustainable growth rates. We therefore suggest that wind damage must be taken in account in productivity calculations and carbon budgets of temperate forests. [Display omitted] [ABSTRACT FROM AUTHOR]

The increase of wood decay due to the fungal pathogen Heterobasidion annosum is expected to increase the vulnerability of tree stands to wind damage due to the decrease in tree anchorage (by wood decay in roots) and stem strength (by wood decay in stem wood). In this work, we developed a framework to simulate the effects of wood decay by Heterobasidion annosum on the vulnerability of Norway spruce ( Picea abies (L.) Karst.) stands to wind damage in terms of uprooting and stem breakage. We also demonstrated the model performance by using tree- and stand-level sensitivity analyses. The increase in the amount of wood decay decreased the predicted wind speeds needed for both uprooting and stem breakage of trees and increased the predicted amount of wind damage. The probability of uprooting was higher than stem breakage for infected trees, which was opposite to the findings for the healthy trees. Because of some simplifications in the modelling due to the lack of proper experimental data (e.g., effects of wood decay on strength of roots and stem in Norway spruce), our model may overestimate the risk of wind damage caused by wood decay. Therefore, further model validation is still needed based on experimental research. [ABSTRACT FROM AUTHOR]

Actual status of mountain forests especialy, of Norway spruce (Picea abies Karst. (L)) stands is a result of combined action between forest management measures and biotic and abiotic risk factors. In this context, tree growth dynamics is a result of multifactor interaction (competition, disturbance, management practice, climate etc.). Wind damage affect the stand structure and normal ecosystem functions including the relationship between individual tree growth and competition processes. Though, it is recorded a diminishing of productive capacity for affected stands as well as a significant diameter increment for remaining standing trees. The correlation between tree growth (cumulate basal area increment in the last 10 years) and competition (Hegyi and Schutz competition indices) was analysed in stands with different windfall intensity. No relationship between tree growth and competition was observed in highly affected stands. Schutz competition index explains better individual tree growth comparing with Hegyi index in low or no-affected stand by windthrow. The variability of the basal area increment (In△g10), explained by competition indices, is rather low (<2%) in the stand that had been highly affected by windfall, regardless of the selected competition index. Thus, significant reduction of the stand density related to number of trees (low density), as a consequence of high intensity windfalls, crown competition has a very small influence on the basal area increment comparing with situations met in low (high density) and moderate (medium density) affected stands. [ABSTRACT FROM AUTHOR]

Ecological patterns vary in space and time. Therefore, when using dynamic models in ecology, the spatial aspect should not be neglected prematurely since it could possibly change the model outcomes to a considerable extent. In view of this problem, we describe here a method how to construct a non-spatial version from a spatially explicit simulation model. The principle idea is to suppress the spatial correlations of cells in a grid in time by continuously re-assigning a random neighbourhood for each cell on the grid. Since this procedure actually eliminates the spatial dimensions, it allows to quantify the unadulterated impact of spatial processes on the model results. To illustrate an important application of this approach in the context of forest management we use a grid-based model that simulates succession of Norway spruce (Picea abies (L.) Karst.) at mountainous sites after blowdown events. The output of this model is compared with the results of the deduced non-spatial version of this model regarding the predicted amount of re-growing trees. The non-spatial version dramatically overestimates the number of spruce trees on different microsites. Thus, the uncritical use of the non-spatial model might give reason to wrong management decisions that are based on too optimistic predictions. In practice, this may lead to dangerous situations, especially in mountain forests serving as protection against avalanches and landslides. This example demonstrates the successful applicability of our approach. Our method can be interpreted as a contribution to an extended sensitivity analysis: it analyses the sensitivity of the results due to structural changes of the model. This sensitivity allows one to estimate the redundancy or the necessity of spatially explicit processes in a model with regard to the parsimony principle of modelling. Since our approach is not dependent on special features of the simulation model used here, it is assumed to be applicable for other spatial models, too, and can thus be considered of general interest for a diligent model analysis. [Copyright &y& Elsevier]

Windstorms are among the most severe disturbances that affect mountain forests in central Europe. This study was conducted in a windthrow area resulting from a windstorm of an enormous scale in November 2004 in the Slovakian High Tatras Mountains. In this study, we used dendrochronological methods to determine the age structure and growth pattern of 529 Norway spruce (Picea abies (L.) Karst) and 103 European larch (Larix decidua Mill) during the last 200 years by examining cross sections of stumps. The multiage structure of the spruce indicated that this species regenerated constantly throughout the reconstruction period. The age structure of the larch was distinctly bimodal with only two ca. 20 year periods of regeneration. The initiation of larch recruitment overlapped in time with release pulses and showed severe disturbance events. A sudden and simultaneous production of compression wood and resin pockets in survivor trees indicated that wind was the most probable disturbance factor. The current composition of the stand with coexisting spruce and larch was a result of infrequent and severe windstorms events. Larch benefits from broader openings and regenerates in recruitment pulses once or twice per century, whereas spruce may regenerate constantly taking advantage of small-scale, gap-phase processes. Such a disturbance scenario allows the light-demanding larch to coexist among the more shade-tolerant spruce. [ABSTRACT FROM AUTHOR]

Mortality rate is thought to show a U-shape relationship to tree size. This shape could result from a decrease of competition-related mortality as diameter increases, followed by an increase of senescence and disturbance-related mortality for large trees. Modeling mortality rate as a function of diameter is nevertheless difficult, first because this relationship is strongly nonlinear, and second because data can be unbalanced, with few observations for large trees. Parametric functions, which are inflexible and sensitive to the distribution of observations, tend to introduce biases in mortality rate estimates. In this study we use mortality data for Abies alba Mill. and Picea abies (L.) Karst. to demonstrate that mortality rate estimates for extreme diameters were biased when using classical parametric functions. We then propose a semiparametric approach allowing a more flexible relationship between mortality and diameter. We show that the relatively shade-tolerant A. alba has a lower annual mortality rate (2.75%) than P. abies (3.78%) for small trees (DBH <15 cm). Picea abies, supposedly more sensitive to bark beetle attacks and windthrows, had a higher mortality rate (up to 0.46%) than A. alba (up to 0.30%) for large trees (DBH ≥50 cm). [ABSTRACT FROM AUTHOR]

In natural forest, disturbance changes tree species composition which in turn affects soil properties. Two areas in the Central Forest State Biosphere Reserve, in the Russian Southern Taiga Zone, differed in the intensity of disturbance: Norway spruce was the dominant species at one site, while at the other spruce was mixed with broadleaves. The presence of broadleaves was due to large gaps in the canopy having been formed, which have triggered vegetation succession. At both sites, five plots were selected to evaluate how the presence of broadleaves influences the properties of the soils under spruce. Soil samples were taken close to spruce trees and the O, A and E horizons were analysed. A difference in the distribution of organic matter in the soil horizons was evident, with a higher concentration in the O and A horizons at the spruce dominated site, while a more homogeneous distribution was found under spruce at the site where broadleaves were abundant. The organic matter did not only differ in quantity, but also in quality as estimated by the C/N ratio, and therefore affected the CEC and element relative availability. No differences at the two sites were found for water-extractable and exchangeable elements, but the ratio between the exchangeable and the acid-extractable forms were different, suggesting a higher relative availability of the elements at the spruce dominated site, and thus potentially higher leaching. Both theoretical and empirical studies have suggested that podzolisation and accumulation of organic matter in the O horizon are related to stagnation of ecosystem processes and ecosystem decline. Our data suggest that the presence to windthrow sites and the inclusion of broadleaf species acts to slow or even reverse podzolisation even in spruce dominated sites. [ABSTRACT FROM AUTHOR]

In this study a GIS-based decision support system (DSS) was built for assessing the short-and long-term risk of wind damage in boreal forests. This was done by integrating a forest growth model SIMA and a mechanistic wind damage model HWIND into geographical information system software (ArcGIS 8. 2) as a toolbar (DLL) using ArcObjects in ArcGIS and Visual Basic 6. In this DSS complex problems are solved within program so that forest gaps, edge stands and edges are automatically tracked when the forest structure changes over time as a result of forest growth dynamics and management. This DSS can be used to assess the risk of wind damage to Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and birch (Betula spp. ) stands, regarding the number of stands and area at risk and length of vulnerable edges of these risk stands at certain critical wind speed classes (i.e. corresponding the maximum wind speed a tree/stand can resist). This DSS can helps forest managers to analyse and visualise (charts, maps) the possible effects of forest management, such as clear-cuts, on both the immediate and long-term risks of wind damage at both stand and regional level. [Copyright &y& Elsevier]