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Forest ecosystems, vital for maintaining global biodiversity and ecological balance, are increasingly threatened by fragmentation. This study addresses the critical issue in the Tuchola Forest of Poland, examining the effects of natural and human factors on forest fragmentation. Our objective was to identify the most suitable dataset for monitoring forest fragmentation from 2015 to 2020, ascertain the primary drivers of fragmentation, and map the areas at high risk. Utilizing the PALSAR (25 m resolution) and Dynamic World (10 m resolution) datasets, we discovered PALSAR's enhanced ability to detect changes in forest structure, particularly evident after a significant windstorm in 2017. This dataset proved crucial in highlighting the escalating trend of forest fragmentation, reinforcing its importance for environmental monitoring and policy formulation. Our analysis identified key factors influencing fragmentation, such as proximity to croplands, tree height and age, wind speed, and vegetation water content, with areas near croplands and having younger, shorter trees being most susceptible. Employing a Weight-of-Evidence (WOE) Bayesian modeling technique, we mapped forest fragmentation susceptibility, demonstrating our methodology's effectiveness through high accuracy validation (AUC of 0.82 and Kappa Index of 0.68). Our innovative approach in mapping susceptibility to fragmentation, especially after extreme weather events, marks a pioneering contribution in Poland. This research advances the understanding of forest fragmentation dynamics and offers a scalable model for global application, emphasizing the urgent need for targeted conservation strategies to preserve the integrity of forest ecosystems amidst climatic risk and anthropogenic pressures.

The disruption of extreme weather events can significantly impact the operation of nation’s critical infrastructures. With the growing trend of extreme weather events in the Caribbean region, evaluating hazard effects of wind storms on power distribution systems becomes increasingly important for disaster preparedness and fast responses in utilities. These catastrophic events disable critical paths of electricity overhead infrastructure, resulting in extended power outages and loss of critical services. In this article, probabilistic wind storm models for the study region have been built by mining the 169-year storm events recorded in the Hurricane Database from the National Hurricane Center of the National Oceanic and Atmospheric Administration. In addition, a simulation approach is presented to evaluate the impacts of wind storms over the power distribution system under different levels of hazards using a random storm trajectory generator and geographic information system data. Extensive studies for the Puerto Rico’s electrical distribution system indicate that our models and procedure effectively estimate the number of affected customers and load loss due to a wind storm impact. [ABSTRACT FROM AUTHOR]

[Display omitted] • Pioneered comprehensive analysis of Tuchola Forest fragmentation via PALSAR and Dynamic World datasets. • Devised Weight of Evidence model to map susceptibility to fragmentation accurately. • Identified key drivers of forest fragmentation including proximity to croplands, tree age and height, wind speed, and vegetation water content. Forest ecosystems, vital for maintaining global biodiversity and ecological balance, are increasingly threatened by fragmentation. This study addresses the critical issue in the Tuchola Forest of Poland, examining the effects of natural and human factors on forest fragmentation. Our objective was to identify the most suitable dataset for monitoring forest fragmentation from 2015 to 2020, ascertain the primary drivers of fragmentation, and map the areas at high risk. Utilizing the PALSAR (25 m resolution) and Dynamic World (10 m resolution) datasets, we discovered PALSAR's enhanced ability to detect changes in forest structure, particularly evident after a significant windstorm in 2017. This dataset proved crucial in highlighting the escalating trend of forest fragmentation, reinforcing its importance for environmental monitoring and policy formulation. Our analysis identified key factors influencing fragmentation, such as proximity to croplands, tree height and age, wind speed, and vegetation water content, with areas near croplands and having younger, shorter trees being most susceptible. Employing a Weight-of-Evidence (WOE) Bayesian modeling technique, we mapped forest fragmentation susceptibility, demonstrating our methodology's effectiveness through high accuracy validation (AUC of 0.82 and Kappa Index of 0.68). Our innovative approach in mapping susceptibility to fragmentation, especially after extreme weather events, marks a pioneering contribution in Poland. This research advances the understanding of forest fragmentation dynamics and offers a scalable model for global application, emphasizing the urgent need for targeted conservation strategies to preserve the integrity of forest ecosystems amidst climatic risk and anthropogenic pressures. [ABSTRACT FROM AUTHOR]

In north-eastern Switzerland, near the village of Appenzell, the Laseyer wind storm recurrently forces the operators of the local train service to stop the service into the narrow Schwende valley. In fact, a train derailment on 19 January 2007 was attributed to the strong cross-valley winds occuring during a Laseyer event. This event further highlighted a very characteristic feature of this wind storm: the regional wind aloft (as measured at the station Ebenalp) was westerly, and thus opposing the easterly winds needed in the valley (measured at Wasserauen) to lift the coach off the railway tracks. In this study, wind observations at several sites are used to detect and characterize Laseyer events between 1998–2009. Two main conclusions are: (i) strong easterly winds at Wasserauen occur almost exclusively concurrently with strong westerly winds on Ebenalp, whereby the directional window of the westerly winds on Ebenalp is very narrow (265°–295°); (ii) the gust speeds at Wasserauen increase abruptly at the Laseyer's onset, a smoother maximum in gust speeds on Ebenalp is discernible, and, remarkably, the free-tropospheric mean wind speed measured at the nearby Säntis mountain peak exhibits a mimimum – indicating that the Laseyer wind is typically associated with a transient meso-scale flow situation. Potential mechanisms leading to the Laseyer wind storm are presented, including rotor circulations, recirculation bubbles, vortex shedding and gravity waves. No conclusive answer can be given, but it is argued that classic rotors and gravity waves play only a minor role due to the narrowness of the valley.

Windstorms are forest disturbances which generate canopy gaps. However, their effects on Mediterranean forests are understudied. To fill that research gap, changes in tree, cover, growth and soil features in Pinus halepensis and Pinus sylvestris plantations affected by windthrows were quantified. In each plantation, trees and soils in closed-canopy stands and gaps created by the windthrow were sampled. Changes in tree cover and radial growth were assessed by using the Normalized Difference Vegetation Index (NDVI) and dendrochronology, respectively. Soil features including texture, nutrients concentration and soil microbial community structure were also analyzed. Windthrows reduced tree cover and enhanced growth, particularly in the P. halepensis site, which was probably more severely impacted. Soil characteristics were also more altered by the windthrow in this site: the clay percentage increased in gaps, whereas K and Mg concentrations decreased. The biomass of Gram positive bacteria and actinomycetes increased in gaps, but the biomass of Gram negative bacteria and fungi decreased. Soil gaps became less fertile and dominated by bacteria after the windthrow in the P. halepensis site. We emphasize the relevance of considering post-disturbance time recovery and disturbance intensity to assess forest resilience within a multi-scale approach.

Wind storms such as hurricanes increase the outage rate of overhead transmission lines and hence can seriously affect the security of power systems. Therefore, it is very important to estimate the overhead transmission line outage rate for a power system that might be jeopardized by wind storms. In this paper, we propose a new method for estimating the outage rate of overhead transmission lines, with two primary advantages. First, the proposed method describes the relationship between the outage rate and the weather factors by a fragility curve customized for overhead transmission lines to ensure that the relationship is precisely represented. Second, the proposed method takes the conductor strength reduction and different physical properties of overhead transmission lines into consideration to increase outage rate estimation accuracy. We test the proposed method by estimating the outage rate of overhead transmission lines in a regional power system based on both historical and simulated wind storms. The test results show that the proposed method generates a more accurate estimation than the conventional approaches. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

Storms and wind damage are the main cause of biomass loss in forests of Northern Europe, as well as they are synergic with the disturbances causing intense water and temperature stress. This highlights the necessity for climate-smart management at landscape level coupling ecological demands of forestry species with their wind resistance. Silver birch (Betula pendula Roth.), which is highly plastic species, appears to be promising for a wider application under such conditions, as it is believed to tolerate wide range of weather conditions. Though silver birch can be sensitive to water deficit and windthrow, local information on its wind tolerance in sites with different moisture regimes is advantageous. Mechanical stability of 71 mid-aged silver birches (Betula pendula Roth.) growing in seven dry (Hylocomiosa) and five periodically waterlogged (Myrtilloso-sphagnosa) sites with mineral soils in Latvia (hemiboreal lowland conditions) were assessed by the destructive static pulling tests. Site type had a significant, yet intermediate effect on the stability of silver birch. As expected, trees under periodically waterlogged conditions were more prone to collapse under static loading, however, they showed a better resistance to primary failure (beginning of wood structure deformation). Uprooting was the most common form of tree collapse. Surprisingly, considering similar root depths, stem breakage was more frequent in the periodically waterlogged than dry sites (21.9 vs. 5.1%, respectively), indicating high loading resistance of roots, supporting high plasticity and wind resistance of the studied metapopulation of silver birch. Nevertheless, in the periodically waterlogged sites, the difference between forces needed to cause primary and secondary (collapse) failures of stem decreased with age/size, implying necessity for optimization of rotation length. Accordingly, quantification of wind resistance can aid climate-smart selection of species for forest regeneration depending on landscape, suggesting birch as wind resistant option under periodically waterlogged conditions.

Understanding how wind and trees interact during wind storms is crucial for better predicting forest wind damage. The complexity of this interaction is enhanced by the fragmented environment of forests. Here, we present an unprecedented field experiment (TWIST) where both the wind dynamics and the tree motion in the edge region of a maritime pine forest have been recorded simultaneously during four non-destructive wind storms. For three of them, the instrumented trees were under stand flow while for one of them they were under an edge flow. Our measurements demonstrate that the well-known characteristics of stand-flow dynamics remain valid under high wind conditions. Only the sub-canopy flow appeared more intermittent as canopy-top turbulent structures penetrate easier within the canopy due to the tree foliage reconfiguration. Under similar storm intensity, the tree motions were lower under edge flow than under stand flow due to the lower turbulence of the former flow while the mean wind speed was higher. This result demonstrates the importance of considering both the turbulence and the mean wind speed in wind risk models. No impact of tree motion other than tree reconfiguration were observed on the stand flow dynamics. On the other hand, for the edge flow, our measurements reveal a peak in frequency on the wind velocity fluctuations related to the fundamental tree vibration mode. This peak was especially visible at canopy top and in the upper trunk space under high wind conditions. Compared to the stand flow, we suspect that the velocity fluctuations induced by the tree motion emerge in the edge flow due to the lower background turbulence. Our edge storm was nonetheless not strong enough for tree motion to enhance flow turbulence and for trees to enter into resonance. These findings may suggest a higher susceptibility of near-edge trees to reach resonance than stand trees due to the motion of upwind trees in a lower background turbulence. [ABSTRACT FROM AUTHOR]

Storms cause major forest disturbances in Europe. The aim of this study was to model tree-level storm damage probability based on the properties of a tree and its environment and to examine whether fine-scale topographic information is connected to the damage probability. We used data documenting effects of two autumn storms on over 17 000 trees on permanent Finnish National Forest Inventory plots. The first storm was associated with wet snowfall that damaged trees, while exceptionally strong winds and gusts characterized the second storm. During the storms, soils were unfrozen and deciduous trees were without leaves. Generalized linear mixed models were used to study how topographical variables calculated from digital elevation models (DEM) with resolutions of 2 and 10 m (TOPO2 and TOPO10, respectively) were related to damage probability, in addition to variable groups for tree (TREE) and stand (STAND) characteristics. We compared models containing different variable groups with Akaike information criteria. The best model contained the variable groups TREE, STAND, and TOPO2. Increase in slope steepness calculated from the high-resolution DEM decreased tree-level damage probability significantly in the model. This suggests that the local topography affects the tree-level damage probability and that high-resolution topographical data improves the tree-level damage probability models. [ABSTRACT FROM AUTHOR]

Electrical power transmission networks of many developed countries are undergoing deep transformations aimed at (i) facing the challenge offered by the stochastically fluctuating power contributions due to the continuously growing connections of renewable power generating units and (ii) decreasing their vulnerability to failures or malicious attacks and improving their resilience, in order to provide more reliable services, thus increasing both safety and profits. In this complex context, one of the major concerns is that related to the potentially catastrophic consequences of cascading failures triggered by rare and difficult to predict extreme weather events. In this work, we originally propose to combine an extreme weather stochastic model of literature to a realistic cascading failure simulator based on a direct current (DC) power flow approximation and a proportional re-dispatch strategy. The description of the dynamics of the network is completed by the introduction of a novel restoration model accounting for the operating conditions that a repair crew may encounter during an extreme weather event. The resulting model is solved by a customized sequential Monte Carlo scheme in order to quantify the impact of extreme weather events on the reliability/availability performances of the power grid. The approach is demonstrated with reference to the test case of the IEEE14 power transmission network. [ABSTRACT FROM AUTHOR]

The article deals with the reaction of soil environment to a violent deforestation resulting from a wind storm. As a material, permanent inventory plot located in Training Forest Enterprise Masaryk Forest Křtiny was selected. The plot represents beech high forest, where soil was sampled from four types of sample plots: (1) maternal forest representing situation before the storm; (2) zone of transition from the maternal forest to the open area; (3) reafforested clearing; (4) natural evolution. From each sample plot type, 6 mixed samples of Ah horizon were analysed to assess N-ammonium (N-NH4+) and N-nitrates (NO3−) content and respiration activity. The results show a significant difference between the respiration activities of the particular sample plots, as well as a significant difference in the content of N-ammonium and N-nitrate forms, the maternal forest representing a site of the lowest biological (and respiration) activity on the one hand, and, on the other hand, site of high N-ammonium and low N-nitrate content, respectively. From the results, intensive nitrification caused by the deforestation is evident. The results are to be used as a starting level for a long-term observation of reaction of the forest beech ecosystem to deforestation and selected types of forest management.

In order to recognize the wind erosion situation of a region, the survey of its windiness is not sufficient and the physical characteristics of earth are of importance too. In fact, the outbreak of dust storms in a region is due to the sensitivity of earth and domination of wind in that region. In this investigation we have tried to find a way for determining the regions in which a dust storm is generated. In addition to wind rose that determines the windiness of a region, we have used another graph with the name of storm rose. With this new graph we have tried to find a relationship between the earth surface situations (threshold erosion velocity) and windiness of a region, so that we can reach a more suitable analysis for wind erosion. Studies made in the region show that where the threshold velocity less than 8 m/s (16 knots) is, the land is susceptible for erosion and thus has an important role in generationof dust storms. With the Storm roses drawn, it was also distinguished that most of the dust storms evolved in the region have the directions between west and northwest. So if we want to lessen the damages of flying dust and particles on Yazd city, we should stabilize the dust in the above-mentioned direction and bring them under control.

Esse estudo tem por objetivo realizar um zoneamento das ocorrências de granizo e vendaval no estado do Rio Grande do Sul (RS), entre os anos 1989 e 2009. Foram utilizados os registros de ocorrências dos eventos (com e sem decretação de situação de emergência), obtidos junto à Coordenadoria Estadual de Defesa Civil do RS (CEDEC), a fim de analisar o período de maior freqüência de ocorrências e as regiões mais atingidas por esses eventos. Os resultados mostraram que, em relação aos eventos de granizo a estação mais favorável para sua ocorrência é a primavera (290 eventos), seguida do inverno (132 eventos). As áreas que apresentaram as maiores ocorrências localizaram-se na metade norte do Estado, dentre as quais se destacaram como mais atingidas o Alto Uruguai (217 eventos) e Planalto Médio (90 eventos). As regiões da Depressão Central e das Missões também foram bastante atingidas por tais tempestades, porém com uma freqüência ligeiramente menor (83 e 70 eventos). Com relação aos vendavais, as regiões mais afetadas foram as do Alto Uruguai (271 eventos), Planalto Médio (120), Depressão Central (116) e Missões (96 eventos), e o período de maior ocorrência foi a primavera (novembro e outubro). Regiões como o Litoral (24), Encosta do Sudeste (13) e Serra do Sudeste (11) registraram poucos episódios durante os vinte anos estudados, o que caracteriza a porção Sul do estado como a menos preferencial a esses extremos de tempo. Foi mostrado também, que esses eventos adversos não acontecem somente em anos com a presença dos fenômenos climáticos El Niño e La Niña. Houve ocorrências de intensos episódios em anos classificados como neutros (ausência dos fenômenos).This paper aims to carry out a mapping of wind storms and hails natural disasters occurred in Rio Grande do Sul state during the period from 1989 to 2009. Records of the events were obtained at the State Civil Defense Authority to analyze the preferential period for these occurrences and the most affected areas by these events. The results showed that most of the hails occurred in spring (290 events) and in winter (132 events), and the most affected regions were Alto Uruguai (217 events) and Planalto Médio (90 events). The regions of Depressão Central and Missões were also affected, but with a slightly lower frequency (83 and 70 events). Regarding to wind storms, the most affected areas were those located in the northern half of the state: Alto Uruguai (271 events), Planalto Médio (120), Depressão Central (116) and Missões (90), and the highest occurrence were observed in the spring season (preferential period), in the months November and October . In the Sea Shore, Southeast coast and Southeast mountains regions few episodes of hails and wind storms have occurred (24, 13 and 11 events respectively), characterizing the south region of the State as the most improbable region for the occurrence of these extreme events. It was also found that hail and wind storms did not occur only in years with presence of the El Niño and La Niña climatic events. They also occurred in periods without the influence of these phenomena (normal years).

A new method for identifying high impact large-scale wind and precipitation events in the extended Mediterranean region is outlined and applied to the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis dataset ERA-Interim for the years 1979-2012. The method highlights large-scale 10 m gust and precipitation events that classify as extreme if integrated over a spatial scale of 1000 km and a temporal scale of 3 days. The method detects successfully high impact events, and reveals clear seasonal differences among the subregions of the Mediterranean. Western Mediterranean precipitation extremes are more intense, and occur mainly in autumn, while eastern Mediterranean events occur in winter. Composite dynamical analyses of large-scale wind and precipitation extremes, and a combination of them, highlight coherent dynamical flow structures associated with the extremes in the different subregions of the Mediterranean. Precipitation events are preceded by an upper-level trough and strong jet on its western flank, followed by cyclogenesis (mainly in the western Mediterranean), and/or a merging of the polar with the subtropical jet over northeastern Africa (in the eastern Mediterranean). Strong surface wind extremes develop around cyclones that intensify south of a deep parent cyclone near the exit of a strong anticyclonically curved jet, propagate eastwards and create a cold and dry northerly wind anomaly at the surface. Furthermore, combined large-scale wind and precipitation extremes often occur simultaneously near cyclones, either North Atlantic cyclones, which project the wind and precipitation into the western Mediterranean, or Mediterranean cyclones. The latter produce wind extremes over a localized area, which often overlaps entirely with the region that receives extreme precipitation. [ABSTRACT FROM AUTHOR]

With the growing trend of extreme weather events in the Northeast U.S., a region of dense vegetation, evaluating hazard effects of wind storms on power distribution systems becomes increasingly important for disaster preparedness and fast responses in utilities. In this paper, probabilistic wind storm models for the study region have been built by mining 160-year storm events recorded in the National Oceanic and Atmospheric Administration's Atlantic basin hurricane database (HURDAT). Further, wind storms are classified into six categories according to NOAA criteria and IEEE standard to facilitate the evaluation of distribution system responses under different levels of hazards. The impacts of wind storms in all categories are accurately evaluated through a Sequential Monte Carlo method enhanced by a temporal wind storm sampling strategy. Extensive studies for the selected typical distribution system indicate that our models and methods effectively reveal the hazardous effects of wind storms in the study region, leading to useful insights towards building better system hardening schemes. [ABSTRACT FROM AUTHOR]

An assessment of data on wind storms recorded in Lithuania during the past 48 years is presented. Records of storms with the average wind speeds of at least 30 m/s are compiled into one data set and presented in the paper. Reliability and meteorological homogeneity of wind storm data is assessed. The extreme wind data is estimated in relation to an assessment of damage to the built environment. An exceedance of basic reference wind speeds and design wind speeds specified in Lithuanian loading code by extreme winds (large cyclonic storms) is detected. The annual exceedance frequency was found to be considerably higher than the frequency of once per fifty years declared in the code. The exceedance was also found to be relatively dangerous in terms of magnitude. It is suggested to analyze wind data by a separate treatment of fastest annual winds and hurricane winds. Two hurricane wind regions are proposed for the Lithuanian territory. Basic reference wind speeds for these regions are calculated by applying the approach of partial duration series of extreme wind records. The regionalisation of hurricane-prone parts of Lithuania led to a compilation of two small-size statistical samples of hurricane wind speeds, which can be applied to an assessment of risk posed by hurricanes. Santrauka Nagrinėjami duomenys apie vėjo audras, kilusias Lietuvoje per pastaruosius 48 metus. Pateikiama duomenų apie vėjo audras, kurių vidutinis vėjo greitis buvo ne mažesnis kaip 30 m/s. Įvertinamas duomenų patikimumas ir meteorologinis homogeniškumas. Duomenys apie vėjo audras analizuojami vertinant tokių audrų galią sukelti užstatytos aplinkos pažeidimus. Nustatyta, kad ekstremalūs vėjai (didelės cikloninės audros) daugelį kartų viršijo bazinius atskaitinius ir projektinius vėjo greičius, apibrėžtus anksčiau Lietuvoje galiojusių ir dabar galiojančių projektavimo normų. Atskaitinių ir projektinių vėjo greičių viršijimai daug dažnesni nei normose nustatomas vieno karto per 50 metų dažnis. Atskaitinių ir projektinių vėjo greičių viršijimas taip pat yra gana pavojingas. Siūloma ekstremalius vėjo greičius analizuoti atskirai nagrinėjant metinius vėjo greičio maksimumus ir duomenis apie uraganinius vėjus. Lietuvos teritoriją siūloma dalyti į tris zonas, iš kurių dvi turėtų būti laikomos uraganinių vėjų zonomis. Baziniai atskaitiniai vėjo greičiai šiose zonose skaičiuojami taikant dalinės trukmės sekų metodiką. Uraganinių vėjų zonųįvedimas leido suformuoti dvi mažo dydžio statistines imtis, kurių elementai yra uraganinio vėjo greičio matavimų duomenys. Šias imtis siūloma taikyti vertinant uraganų sukeliamą riziką. Резюме Рассматривается оценка повреждений, которые могут быть причинены природной и застроенной среде экстремальными ветрами. Внимание сосредотачивается на ветровых штормах, наблюдавшихся в Литве за последние 48 лет. В статье представлены данные о штормах со средней скоростью ветра не менее 30 м/с. Оценивается надежность и метеорологическая однородность данных по экстремальным ветрам. Данные анализируются в свете их применения к оценке потенциальных повреждений застроенной среды. Установлено, что экстремальные ветра, создаваемые большими циклонами, во много раз превышали нормативные и расчетные значения скоростей ветра, установленные нормами проектирования, применявшимися в предыдущие годы и применяемыми в Литве в настоящее время. Частота превышения нормативных и расчетных значений значительно превышает декларируемую настоящими нормами одноразовую частоту за 50 лет. Степень превышения нормативных и расчетных значений скорости ветра также является достаточно опасной. Предлагается раздельный анализ данных по годовым максимумам скоростей ветра и данных по ураганам. Вводятся три зоны территории Литвы, две из которых следует рассматривать как зоны возможных ураганов. Нормативные значения скорости ветра в этих зонах определяются при помощи метода последовательностей частичной продолжительности. Введение зон ураганных ветров позволило сформировать две статистические выборки, включающие в себя относительно небольшое количество ураганных скоростей ветра. Предлагается использовать эти выборки для оценки риска, создаваемого ураганами. Reikšminiai žodžiai: vėjo parametrai, štormas, uraganas, dalinės trukmės seka, vėjo apkrova, vėjo zona Ключевые слова: ветровые данные, шторм, ураган, последователъностъ частичной продолжителъности, ветровая нагрузка, ветровая зона

In order to recognize the wind erosion situation of a region, the survey of its windiness is not sufficient and the physical characteristics of earth are of importance too. In fact, the outbreak of dust storms in a region is due to the sensitivity of earth and domination of wind in that region. In this investigation we have tried to find a way for determining the regions in which a dust storm is generated. In addition to wind rose that determines the windiness of a region, we have used another graph with the name of storm rose. With this new graph we have tried to find a relationship between the earth surface situations (threshold erosion velocity) and windiness of a region, so that we can reach a more suitable analysis for wind erosion. Studies made in the region show that where the threshold velocity less than 8 m/s (16 knots) is, the land is susceptible for erosion and thus has an important role in generation of dust storms. With the Storm roses drawn, it was also distinguished that most of the dust storms evolved in the region have the directions between west and northwest. So if we want to lessen the damages of flying dust and particles on Yazd city, we should stabilize the dust in the above-mentioned direction and bring them under control. [ABSTRACT FROM AUTHOR]

Abstract: Insect outbreaks and wind storms are the most common natural disturbances affecting the northern slopes of montane Norway spruce (Picea abies (L.) H. Karst.) forests in the European Alps. The combined effects on stand dynamics, including tree regeneration, of these natural disturbances and an anthropogenic (i.e., salvage logging) disturbance were studied to assess the role of post-disturbance management practices. The study areas were in two adjacent inner valleys of the Aosta Valley Autonomous Region (western Italian Alps). Les Combes study area experienced an insect (Lymantria monacha L.) outbreak that affected 91ha in 1984–1990, while a wind storm impacted 70ha in the other valley (Parriod study area) in 1990. Salvage logging took place in both study areas 2years after the natural disturbance occurrence (i.e., in 1991–1992 in Les Combes, and in 1992–1993 in Parriod), and only dead trees were salvaged. Site characteristics, overstory and understory trees, and coarse woody debris (CWD) data were collected during the summer of 2010 in 90plots randomly distributed within disturbed portions and in control stands of the two study areas. The variability of natural regeneration structure and composition in relation to environment, forest structure, type of disturbance, and salvage logging were analyzed by univariate (i.e., ANOVA and correlations) and multivariate (i.e., MRPP, PCA, and RDA) analyses. Regeneration structure and composition were clearly different for the two disturbance types. Individuals originated mainly from seed after the insect outbreak, while an important role was played by advance regeneration in the windthrow area. Regeneration was more abundant and rich in shade tolerant species (i.e., Abies alba Mill.) after the insect outbreak, while Larix decidua Mill. and light demanding broadleaves were dominant after the windthrow. The two major factors influencing post-disturbance regeneration were the amount of the residual overstory and the amount and distribution of CWD. The presence of residual forest patches facilitated regeneration establishment by reducing herb and shrub competition, and regulating the light that penetrates to the ground. Woodpiles had a negative influence on regeneration in terms of abundance and also influenced composition. On the contrary, scattered CWD facilitated the establishment of new individuals by reducing competition with herbs and shrubs, reducing the impact of browsing, and improving substrate moisture, especially for Norway spruce. [Copyright &y& Elsevier]

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Natural disturbances play a key role in ecosystem dynamics and are important factors for sustainable forest ecosystem management. Quantitative models are frequently employed to tackle the complexities associated with disturbance processes. Here we review the wide variety of approaches to modelling natural disturbances in forest ecosystems, addressing the full spectrum of disturbance modelling from single events to integrated disturbance regimes. We applied a general, process-based framework founded in disturbance ecology to analyze modelling approaches for drought, wind, forest fires, insect pests and ungulate browsing. Modelling approaches were reviewed by disturbance agent and mechanism, and a set of general disturbance modelling concepts was deduced. We found that although the number of disturbance modelling approaches emerging over the last 15 years has increased strongly, statistical concepts for descriptive modelling are still largely prevalent over mechanistic concepts for explanatory and predictive applications. Yet, considering the increasing importance of disturbances for forest dynamics and ecosystem stewardship under anthropogenic climate change, the latter concepts are crucial tool for understanding and coping with change in forest ecosystems. Current challenges for disturbance modelling in forest ecosystems are thus (i) to overcome remaining limits in process understanding, (ii) to further a mechanistic foundation in disturbance modelling, (iii) to integrate multiple disturbance processes in dynamic ecosystem models for decision support in forest management, and (iv) to bring together scaling capabilities across several levels of organization with a representation of system complexity that captures the emergent behaviour of disturbance regimes. [Copyright &y& Elsevier]

This article discusses marine meteorology and the effects of powerful windstorms that form at sea. Specific attention is given to the presence of this phenomena in North-West Europe. It examines the scientific progress in the prediction of such storms as well as the problems that continue to persist.

The article identifies the factors contributing to the return period of windstorms in Europe. Assessment of the magnitude and frequency of extreme wind speed plays a fundamental role in safety, engineering and reinsurance applications and preparations for extreme weather. It is evident that windstorms and strong winds represent a major loss for reinsurance companies. Factors contributing to the occurrence of wind storms include unstable surface wind field and the continued changes in the global climate.

Local policies can play an important role in establishing a context that shapes vulnerability and influences subsequent recovery of lifelines under the natural hazards of extreme wind and seismic events. External factors, such as access availability, have long been known to influence the rate of restoration of utility systems following blackouts. Thus, since system performance takes place within a socio-technical-political context, it can be anticipated that selected local policies may also influence either the geographic extent of damage or the rate of restoration or both. This project empirically validates the assumption that selected local non-design policies establish a context that significantly (measurably) influences system functionality in terms of spatial extent and duration of outage. [ABSTRACT FROM AUTHOR]

Windstorms are forest disturbances which generate canopy gaps. However, their effects on Mediterranean forests are understudied. To fill that research gap, changes in tree, cover, growth and soil features in Pinus halepensis and Pinus sylvestris plantations affected by windthrows were quantified. In each plantation, trees and soils in closed-canopy stands and gaps created by the windthrow were sampled. Changes in tree cover and radial growth were assessed by using the Normalized Difference Vegetation Index (NDVI) and dendrochronology, respectively. Soil features including texture, nutrients concentration and soil microbial community structure were also analyzed. Windthrows reduced tree cover and enhanced growth, particularly in the P. halepensis site, which was probably more severely impacted. Soil characteristics were also more altered by the windthrow in this site: the clay percentage increased in gaps, whereas K and Mg concentrations decreased. The biomass of Gram positive bacteria and actinomycetes increased in gaps, but the biomass of Gram negative bacteria and fungi decreased. Soil gaps became less fertile and dominated by bacteria after the windthrow in the P. halepensis site. We emphasize the relevance of considering post-disturbance time recovery and disturbance intensity to assess forest resilience within a multi-scale approach. [ABSTRACT FROM AUTHOR]

The aim of this study is to identify the main mesoscale features and mechanisms responsible for the generation of a very intense precipitation and wind storm event, named "Vaia", that affected the eastern Italian Alps on 27–29 October 2018. The event was characterized by extreme accumulated precipitation (up to 850 mm in three days) and exceptionally strong winds, causing severe and widespread impacts, such as floods, landslides, and extensive damages to forests and growing stock. The synoptic situation was characterized by a trough, which deepened over the eastern Atlantic, extending to France and Spain, driving a strong moist flow towards the Alpine region. At the surface, a wide cyclonic area developed over the western Mediterranean, east of the trough axis, and moved, deepening, towards northwestern Italy. The storm is investigated using a comprehensive dataset composed of both observations and numerical simulations by means of two models, namely WRF and MOLOCH, at convection-permitting resolution. The analysis highlights that the storm was characterized by two consecutive phases with strong precipitations, both fed by an intense moist southerly flow. In particular, the second phase was also marked by strong wind gusts in the Alpine area, exceeding 50 m s−1 at some weather stations. It is found that these extreme wind gusts were connected to the presence of an intense southerly low-level jet immediately ahead of a cold front, displaying an average wind speed of 35 m s−1 at 1500 m MSL. The comparison between observations and numerical results shows that the main characteristics of the storm are well simulated by both models, confirming the high predictability of this kind of events, typically associated with well-defined large-scale forcing. Also local scale features are reasonably captured by the simulations, despite the high complexity of the Alpine orography. However, WRF significantly underestimates total precipitation amounts over the most affected areas, while wind speed is overestimated by both models in the inner Alpine sectors. • The Vaia storm is analyzed with observations and convection-resolving simulations. • WRF and MOLOCH reasonably reproduce precipitation and wind gusts over the Alps. • A strong low-level jet ahead of the cold front is detected by both observations and simulations. • The variability in the numerical results induced by different global analyses is small. [ABSTRACT FROM AUTHOR]

Storms and wind damage are the main cause of biomass loss in forests of Northern Europe, as well as they are synergic with the disturbances causing intense water and temperature stress. This highlights the necessity for climate-smart management at landscape level coupling ecological demands of forestry species with their wind resistance. Silver birch (Betula pendula Roth.), which is highly plastic species, appears to be promising for a wider application under such conditions, as it is believed to tolerate wide range of weather conditions. Though silver birch can be sensitive to water deficit and windthrow, local information on its wind tolerance in sites with different moisture regimes is advantageous. Mechanical stability of 71 mid-aged silver birches (Betula pendula Roth.) growing in seven dry (Hylocomiosa) and five periodically waterlogged (Myrtilloso-sphagnosa) sites with mineral soils in Latvia (hemiboreal lowland conditions) were assessed by the destructive static pulling tests. Site type had a significant, yet intermediate effect on the stability of silver birch. As expected, trees under periodically waterlogged conditions were more prone to collapse under static loading, however, they showed a better resistance to primary failure (beginning of wood structure deformation). Uprooting was the most common form of tree collapse. Surprisingly, considering similar root depths, stem breakage was more frequent in the periodically waterlogged than dry sites (21.9 vs. 5.1%, respectively), indicating high loading resistance of roots, supporting high plasticity and wind resistance of the studied metapopulation of silver birch. Nevertheless, in the periodically waterlogged sites, the difference between forces needed to cause primary and secondary (collapse) failures of stem decreased with age/size, implying necessity for optimization of rotation length. Accordingly, quantification of wind resistance can aid climate-smart selection of species for forest regeneration depending on landscape, suggesting birch as wind resistant option under periodically waterlogged conditions. [ABSTRACT FROM AUTHOR]