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The carbon accumulation in forest ecosystems helps to mitigate climate changes, therefore the interest in finding strategies for adapted forest management is a major goal of our time. The artificial plantations of Norway spruce (Picea abies Karst) are part of the Bulgarian project to restore the regulatory functions of forest ecosystems. Due to their low resistance, intensive processes of deposition and degradation take place in them, which emphasizes the need to understand the condition of soils and the amount of accumulated carbon in them. This paper reports results from a study on the thinning in even-aged Norway spruce plantations (Picea abies Karst) and its effect on some soil properties. The study includes two thinned plots and an untinned control: 1) Control – an unmanaged spruce plantation, without any activities in it through the last 20 years; 2) Thinned – managed with regular felling over the years, the last of which was carried out 10 years ago with 25% intensity; and 3) Ice storm – plantation damaged from an ice storm in 2007 (when it was 33 years old), felling followed by removal of all affected trees – over 95%, and afforestation with spruce saplings. The soil was examined by layers from 10 cm to 30 cm depth. The main soil characteristics connected with the carbon stocks in soil are analyzed - bulk density, skel-eton, and carbon content. The results of the experiment show that the performed forestry activities were conducted with abidance of the requirements for habitat protection and the ecosystem’s functionality in the studied sites. No significant changes in coarse fraction content and bulk density of soils were found. There is no statistical difference between the plots in the studied depths, but there is a trend of decrease in the organic carbon content in the managed sites. The differences in the soil carbon stocks are significant for the first two soil layers between the control and the managed trough thinning plot.

The carbon accumulation in forest ecosystems helps to mitigate climate changes, therefore the interest in finding strategies for adapted forest management is a major goal of our time. The artificial plantations of Norway spruce (Picea abies Karst) are part of the Bulgarian project to restore the regulatory functions of forest ecosystems. Due to their low resistance, intensive processes of deposition and degradation take place in them, which emphasizes the need to understand the condition of soils and the amount of accumulated carbon in them. This paper reports results from a study on the thinning in even-aged Norway spruce plantations (Picea abies Karst) and its effect on some soil properties. The study includes two thinned plots and an untinned control: 1) Control – an unmanaged spruce plantation, without any activities in it through the last 20 years; 2) Thinned – managed with regular felling over the years, the last of which was carried out 10 years ago with 25% intensity; and 3) Ice storm – plantation damaged from an ice storm in 2007 (when it was 33 years old), felling followed by removal of all affected trees – over 95%, and afforestation with spruce saplings. The soil was examined by layers from 10 cm to 30 cm depth. The main soil characteristics connected with the carbon stocks in soil are analyzed - bulk density, skeleton, and carbon content. The results of the experiment show that the performed forestry activities were conducted with abidance of the requirements for habitat protection and the ecosystem’s functionality in the studied sites. No significant changes in coarse fraction content and bulk density of soils were found. There is no statistical difference between the plots in the studied depths, but there is a trend of decrease in the organic carbon content in the managed sites. The differences in the soil carbon stocks are significant for the first two soil layers between the control and the managed trough thinning plot. [ABSTRACT FROM AUTHOR]

Ice storms can cause substantial damage to tree crowns and lead to growth reduction. However, in uneven-aged stands, the growth of an individual tree may also increase due to crown release caused by the damage or mortality of neighboring trees. Three years after the devastating ice storm in 2014 in mixed uneven-aged Dinaric forests (Croatia), we cored 156 European beech (Fagus sylvatica) and 85 silver fir (Abies alba) trees across 20 permanent sample plots to study the post-storm growth response as a function of tree, stand, site, spatial arrangement and local competition factors. The ice storm damaged over 84% of trees on the sampled plots. Among the cored trees, 52.7% exhibited growth reduction, which on average amounted to -3.1% relative to the pre-disturbance average. Trees with less than 40% crown damage maintained their pre-disturbance growth rates or experienced only minor growth suppression. While 60% of beech trees suffered a growth reduction at an average rate of -7.2%, the average radial increment of fir after the storm was 14.0% higher compared to the pre-storm rate. A linear mixedeffects model suggests that the growth response can largely be explained by the focal and neighboring tree species identity, tree competition pressure, focal and neighboring tree damage, crown size, slenderness index and stoniness. Growth release was positively associated with fir, inverse distance-weighted crown damage of the nearest neighbor, shorter crowns, slenderness, less stony sites and less damaged trees. The analysis suggests that at the same level of local competition load, trees with a broadleaved and damaged nearest neighbor are more likely to experience growth release than those with a coniferous or undamaged nearest neighbor. This implies that unevenaged stands with a substantial presence and mingling of both conifers and broadleaves are expected to be more resilient to ice storms and are less likely to suffer growth reduction. [ABSTRACT FROM AUTHOR]

Ice storms can cause substantial damage to tree crowns and lead to growth reduction. However, in uneven-aged stands, the growth of an individual tree may also increase due to crown release caused by the damage or mortality of neighboring trees. Three years after the devastating ice storm in 2014 in mixed uneven-aged Dinaric forests (Croatia), we cored 156 European beech (Fagus sylvatica) and 85 silver fir (Abies alba) trees across 20 permanent sample plots to study the post-storm growth response as a function of tree, stand, site, spatial arrangement and local competition factors. The ice storm damaged over 84% of trees on the sampled plots. Among the cored trees, 52.7% exhibited growth reduction, which on average amounted to −3.1% relative to the pre-disturbance average. Trees with less than 40% crown damage maintained their pre-disturbance growth rates or experienced only minor growth suppression. While 60% of beech trees suffered a growth reduction at an average rate of −7.2%, the average radial increment of fir after the storm was 14.0% higher compared to the pre-storm rate. A linear mixed-effects model suggests that the growth response can largely be explained by the focal and neighboring tree species identity, tree competition pressure, focal and neighboring tree damage, crown size, slenderness index and stoniness. Growth release was positively associated with fir, inverse distance-weighted crown damage of the nearest neighbor, shorter crowns, slenderness, less stony sites and less damaged trees. The analysis suggests that at the same level of local competition load, trees with a broadleaved and damaged nearest neighbor are more likely to experience growth release than those with a coniferous or undamaged nearest neighbor. This implies that uneven-aged stands with a substantial presence and mingling of both conifers and broadleaves are expected to be more resilient to ice storms and are less likely to suffer growth reduction.

Norway spruce (Picea abies [L.] Karst.) has been at the centre of controversy for many decades. Recent evidence of its profound disturbance-induced damage and consequent stock depletions across forest landscapes in Europe has reinforced doubts regarding the sustainability and prospects of this tree species in the future. Like many other European countries, Slovenia has experienced significant Norway spruce mortality and a decrease in growing stock primarily as the result of several disturbance agents (bark beetle outbreaks, an ice storm, windthrows). We investigated a countrywide spruce growing stock decline based on data between 2010 and 2018. Particular focus was placed on identifying the main ecological drivers of this decline, namely geological conditions, climatic parameters, soil attributes, topographic factors and forest stand characteristics. The effects of potential predictors on the relative change (%) in spruce volume (m3 ha-1) during the period 2010-2018 were analysed with Generalized Additive Models. Based on a national dataset including forest compartments (n = 6355) with a spruce growing stock decline > 10%, we found mixed support for ecology-based hypotheses. While spruce decline responded to bedrock type as predicted (i.e., greater relative decline in carbonate compared to silicate compartments), higher forest naturalness (preservation of tree species composition) was not associated with a lower decline. Spruce decline was amplified by higher potential evapotranspiration and soil clay content but showed a strong negative relationship with spruce proportion in the year 2010. General trends along the gradients of other selected predictors (stoniness/rockiness and heat load index) were less pronounced. The results suggest that most of these ecological predictors interact with geology and forest naturalness in affecting Norway spruce decline. Our analysis reveals that bedrock type can play an important role due to its mitigating effects. However, forest naturalness is of secondary significance as intensified large-scale forest disturbances likely override its buffering potential.

Winter storms occur in the Gulf of Mexico (GoM) every few years, but there are not many studies on oceanic responses to severe winter storms. Although usually considered less destructive than hurricanes, they can result in cumulative damages. Winter Storm Outbreak of February 2021 (WSO21), the most intense winter storm to impact Texas and the GoM in 30 years, passed over the western GoM and brought severe cold to the GoM coastal regions, which caused a sudden cooling of the ocean surface, resulting in an extensive loss of marine life. In this study, we analyze multiple datasets from both in situ and satellite observations to examine the oceanic changes due to WSO21 in order to improve our understanding of oceanic responses to winter storms. Although the pre-storm sea surface temperature (SST) was 1–2 °C warmer than normal, severe coastal cold spells caused a significant cooling of the order of −3 °C to −5 °C during WSO21 and a −1 °C average cooling in the mixed layer (ML) over the western GoM. Net surface heat loss played a primary role in the upper ocean cooling during WSO21 and explained more than 50% of the cooling that occurred. Convective mixing due to surface cooling and turbulent mixing induced by enhanced wind speeds significantly increase the surface ML in the western GoM. Apart from rapid changes in SST and heat fluxes due to air-sea interactions, persistent upwelling brings nutrients to the surface and can produce coastal "winter" blooms along the Texas and Mexico coast. Prominent salinity increases along the coastal regions during and after WSO21 were another indicator of wind-induced coastal upwelling. Our study demonstrates the utility of publicly-available datasets for studying the impact of winter storms on the ocean surface. [ABSTRACT FROM AUTHOR]

Introduction: Natural disturbances modify forest structure by affecting regeneration dynamics and can change main ecosystem functions. An ice storm unusually took place in southern China in early 2008, which caused huge damage to forests. Resprouting of woody plants in a subtropical forest has received little attention. The role of survival time and mortality has been assessed for newsprouts after an ice storm. Methods: In this study, damage types, in addition to the annual number and mortality rates of sprouts for all tagged and sampled resprouted Chinese gugertree (Schima superba Gardner & Champ.) individuals more than or equal to 4 cm in basal diameter (BD), were monitored. A total of six plots (20m × 20 m) wererecorded in a subtropical secondary forest dominated by S. superba in Jianglang Mountain, China. This investigation had been conducted for six consecutive years. Results: The results showed that the survival rates of the sprouts were dependent on the year they sprouted. The earlier the year they boomed, the lower the mortality. The sprouts produced in 2008 were of the highest vitality and survival rates. Sprouts of the decapitated trees exhibited a better survival rate than those of uprooted or leaning trees. Sprouting position also plays a role in regeneration. Sprouts at the basal trunks of uprooted trees and the sprouts at the upper trunksof the decapitated trees exhibited the lowest mortality. The relationship between the accumulative mortality rate and the average diameter of new sprouts isaffected by damage types. Discussion: We reported the mortality dynamics of sproutsin a subtropical forest after a rare natural disaster. This information could serve asa reference for the construction of a branch sprout dynamic model ormanagement of forest restoration after ice storms. [ABSTRACT FROM AUTHOR]

Ice storms, as important sources of frequent and injurious disturbances, drive forest dynamics in the Northern Hemisphere. However, stand-level differential vulnerability to ice storms and the associated factors that predispose forest stands remain unclear. This is particularly concerning in the subtropics where the frequency of ice storms is predicted to increase with global warming. Here we assessed how the impact on three forest stands (early and late secondary-growth forests, and old-growth forests) differed after an extreme ice storm during 20-21 March 2022, and identified the abiotic and biotic factors that determine the damage intensity in the Shennongjia World Natural Heritage Site, a biodiversity conservation hotspot in central China. We found a stand-specific 'middomain effect' where the late secondary-growth forest sustained the most severe damage, the early secondarygrowth forest sustained the least, and the old-growth forest suffered an intermediate amount. 'Crown broken' was the most severe damage type across all three forest stands, although the proportion of 'branch broken' was also high in the old-growth forest. Topography played a significant role in determining the vulnerability of the early secondary-growth forest to severe ice storms whereas the forest structure and composition were important factors in explaining the damage rates in the old-growth forest, although they differed among the damage categories. In contrast, topography, forest structure and composition generally explain the intensity of damage in the late secondary-growth forests. Our results highlight that, in subtropical forests, the intensity of damage caused by severe ice storms and related determining factors are stand-level dependent. We also suggest exploring potential management strategies (e.g., slow-growing hardwood species that can resist storms should be the main species for reforestation in early secondary-growth forests) to mitigate the risk of future severe ice storms, as well as other wind-related climatic extremes. [ABSTRACT FROM AUTHOR]

This study examines the impacts that an emergency had on people’s preparedness levels, using the December 2013 Ice Storm in the Greater Toronto Area (GTA) as a case. A questionnaire consisting of three sections was developed to measure the associated impacts, people’s reactions/opinions, as well as their preparedness levels before and after the ice storm. The goal of the research is not only to discuss the factors that influenced people’s ability to prepare, respond to and recover from the ice storm but also to generate useful insights for future disasters that are similar in nature. Our analysis includes various aspects such as the effectiveness of advance warnings and their ability to disseminate information to mass audiences. The findings show that, most of the respondents believe that they learned a lot about ice storms and their impacts because of their prior experience; a significant majority believe that it is the city’s/municipality’s responsibility to prepare for emergencies like ice storms; home ownership was significantly associated with the previous ice storm preparedness; and, power outage experience was significantly associated with the next ice storm preparedness.

In February 2021, a widespread cold-air outbreak, with two associated winter storm systems, impacted the South-Central United States. After a comprehensive summary of the synoptic setup and a day-by-day analysis of the event, we assess the significance of the storm from a climatological perspective. Concerning winter precipitation, there were isolated instances of record snowfall accumulations. While freezing rain and freezing drizzle both occurred, total freezing precipitation accumulations did not exceed a one-in-50 year event. The duration of the cold was notable — many stations across the region broke records for the highest number of consecutive days below freezing. When analyzing hourly temperature observations, we found that the February 2021 event was the record longest duration of hours below freezing for 12 stations. Nearly 6,000 daily temperature records were broken by this event. We next summarize significant impacts of this event. While we find that this event was extreme, most aspects of this storm were not unprecedented. Even in the context of a warming climate, cold events such as this should be considered when assessing risk and hazard mitigation planning. The magnitude of impacts associated with this event suggests a lack of preparedness that needs to be addressed. We discuss the importance of using climate services in planning for future extreme events. While there are documented benefits to users engaging with climate service providers and integrating climate information into their decision-making, the February 2021 event serves as an example of the failures that can occur when climate services have not been integrated into planning. We recommend the use of climate services when assessing risk and planning for future climate and weather extremes.

Leaf abundance of trees plays a dominant role in energy, water and nutrient flux of forest ecosystems, in defining the habitat structure of entrained biota and in mediating interspecific competition among tree species. We quantified leaf abundance of three dominant tree species (Acer saccharum Marsh.; Fagus grandifolia Ehrh.; Betula alleghaniensis Britt.) for 27 years in mature northern hardwood forest at the Hubbard Brook Experimental Forest, New Hampshire, USA using annual counts of leaves of each species collected in 117 litter traps (0.1 m2, each). We hypothesized that variation in leaf abundance would reflect known disturbance events and canopy dieback episodes. No significant trend in leaf abundance of the three species over 27 years (1993–2019) was observed in seven reference stands despite known canopy dieback of sugar maple and American beech in these stands, indicating that 1) maple decline preceded our sampling interval and 2) expansion of beech understory compensated for canopy dieback caused by beech bark disease. Leaf abundance temporarily declined significantly in response to known disturbances (ice storm, 34 to 47%; late-spring frost, 13 to 16%). Increased leaf abundance, especially for sugar maple (30%), on a watershed where calcium addition restored acidified soils, was probably associated with increased soil pH, Ca availability and decreased Al. The temporal sequence of decline of paper birch at higher elevations following a severe drought in 2002 also was apparent. Leaf abundance based on leaf litterfall in deciduous forests provides a useful indicator of forest ecosystem function and forest health.

Forest decline, in course of climate change, has become a frequently observed phenomenon. Much of the observed decline has been associated with an increasing frequency of climate change induced hotter droughts while decline induced by flooding, late-frost, and storms also play an important role. As a consequence, tree mortality rates have increased across the globe. Despite numerous studies that have assessed forest decline and predisposing factors for tree mortality, we still lack an in-depth understanding of (I) underlying eco-physiological mechanisms, (II) the influence of varying environmental conditions related to soil, competition, and micro-climate, and (III) species-specific strategies to cope with prolonged environmental stress. To deepen our knowledge within this context, studying tree performance within larger networks seems a promising research avenue. Ideally such networks are already established during the actual period of environmental stress. One approach for identifying stressed forests suitable for such monitoring networks is to assess measures related to tree vitality in near real-time across large regions by means of satellite-borne remote sensing. Within this context, we introduce the European Forest Condition monitor (EFCM)—a remote-sensing based, freely available, interactive web information tool. The EFCM depicts forest greenness (as approximated using NDVI from MODIS at a spatial resolution of roughly 5.3 hectares) for the pixel-specific growing season across Europe and consequently allows for guiding research within the context of concurrent forest performance. To allow for inter-temporal comparability and account for pixel-specific features, all observations are set in relation to normalized difference vegetation index (NDVI) records over the monitoring period beginning in 2001. The EFCM provides both a quantile-based and a proportion-based product, thereby allowing for both relative and absolute comparison of forest greenness over the observational record. Based on six specific examples related to spring phenology, drought, late-frost, tree die-back on water-logged soils, an ice storm, and windthrow we exemplify how the EFCM may help identifying hotspots of extraordinary forest greenness. We discuss advantages and limitations when monitoring forest condition at large scales on the basis of moderate resolution remote sensing products to guide users toward an appropriate interpretation. [ABSTRACT FROM AUTHOR]

Forest decline, in course of climate change, has become a frequently observed phenomenon. Much of the observed decline has been associated with an increasing frequency of climate change induced hotter droughts while decline induced by flooding, late-frost, and storms also play an important role. As a consequence, tree mortality rates have increased across the globe. Despite numerous studies that have assessed forest decline and predisposing factors for tree mortality, we still lack an in-depth understanding of (I) underlying eco-physiological mechanisms, (II) the influence of varying environmental conditions related to soil, competition, and micro-climate, and (III) species-specific strategies to cope with prolonged environmental stress. To deepen our knowledge within this context, studying tree performance within larger networks seems a promising research avenue. Ideally such networks are already established during the actual period of environmental stress. One approach for identifying stressed forests suitable for such monitoring networks is to assess measures related to tree vitality in near real-time across large regions by means of satellite-borne remote sensing. Within this context, we introduce the European Forest Condition monitor (EFCM)—a remote-sensing based, freely available, interactive web information tool. The EFCM depicts forest greenness (as approximated using NDVI from MODIS at a spatial resolution of roughly 5.3 hectares) for the pixel-specific growing season across Europe and consequently allows for guiding research within the context of concurrent forest performance. To allow for inter-temporal comparability and account for pixel-specific features, all observations are set in relation to normalized difference vegetation index (NDVI) records over the monitoring period beginning in 2001. The EFCM provides both a quantile-based and a proportion-based product, thereby allowing for both relative and absolute comparison of forest greenness over the observational record. Based on six specific examples related to spring phenology, drought, late-frost, tree die-back on water-logged soils, an ice storm, and windthrow we exemplify how the EFCM may help identifying hotspots of extraordinary forest greenness. We discuss advantages and limitations when monitoring forest condition at large scales on the basis of moderate resolution remote sensing products to guide users toward an appropriate interpretation.

It is expected that climate change as well as abiotic and anthropogenic disturbances will strongly influence temperate forests. Besides changes in the main climate variables, various disturbance factors may significantly worsen conditions for mesic Slovenian forests (SE Europe) dominated by European beech (Fagus sylvatica), Norway spruce (Picea abies) and European silver fir (Abies alba). In Slovenia, the climate has warmed in recent decades, with an average annual rate of increase of about 0.4°C per decade or even more than 0.5°C per decade in summer. In addition, disturbances have caused considerable damage to trees in the most extensive forest types in Slovenia, starting with a widespread ice storm in 2014, followed by bark beetle outbreaks, windthrows and salvage logging interventions. After 2014, salvage logging increased from about one third to two thirds of the total annual felling. Over the last two decades, we have observed a decline in Norway spruce growing stock, with the highest rate of decrease in areas below 500 m a.s.l., and an increasing trend for European beech. Overall, the three dominant species (beech, spruce, silver fir), which together account for more than 70% of the total growing stock, have shown a declining trend over the last 20 years. The patterns observed are broadly consistent with earlier predictions developed for different climate change scenarios and with those reported in many other European countries. Adaptive forest management, which implements close-to-nature silviculture, has been traditionally practised in the region under study and has the potential to play an important role in reducing the risks associated with the impacts of climate change and disturbances in the future. [ABSTRACT FROM AUTHOR]

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This article proposes a robust resilience enhancement method for a power distribution network in ice storms by the optimal routing of mobile de-icing devices (MDIDs) on congested transportation roads. We consider MDIDs as emergency vehicles, as other vehicles yield the right-of-way to MDIDs, and propose a de-icing schedule (DIS) to illustrate how MDIDs are routed on congested transportation roads. We further coordinate the DIS and MDID routing, which mitigate transportation routing congestions, with power distribution system operation, which considers distribution network reconfiguration and distributed energy resource dispatch. A two-stage robust model is proposed to manage the effects of ice storms forecast errors on both power distribution and urban transportation networks. The proposed model is reformulated as a mixed-integer second-order cone programming problem. The Benders decomposition and column-and-constraint generation algorithms are further utilized to solve the proposed MISOCP. Numerical results for the modified IEEE 33-bus 12-node, IEEE 123-bus 25-node, and 252-bus 80-node electricity-transportation systems show the effectiveness of the proposed model and solution technique for enhancing the power system resilience. [ABSTRACT FROM AUTHOR]

Between January and February 2008, a severe ice storm occurred in southern China. The storm damaged nearly 21 million hectares of forest lands with broken branch, trunk breakage, and stem bending of many trees. This natural disturbance provides a unique opportunity to study impacts of extreme climatic event on forest birds. Using hierarchical multi‐species occupancy model (species richness; 27 species) and N‐mixture model (abundance; 3 species), we investigated how the storm affected resident bird species in subtropical forest in southern China. We sampled birds at Chebaling National Nature Reserve in Guangdong Province, monthly for 1 year each before and after the storm by mist nets. To take into account variations in temperature between years and between months, we incorporated monthly mean temperature into the models as an additional covariate. Observed species richness was greater before the storm. Estimated species richness (from the hierarchical model) also tended to be greater before than after the storm although 95% Bayesian credible intervals of these estimates were overlapped. Temperature showed a negative effect on estimated species richness, indicating greater species richness during winter. Among three species captured the most, abundance of Chestnut Bulbul (Hemixos castanonotus) significantly decreased after the storm. Other two species, Grey Treepie (Dendrocitta formosae) and Huet's Fulvetta (Alcippe hueti) showed insignificant responses to the storm. Our study indicates that the 2008 ice storm may not have a significant impact on species richness of resident birds in subtropical forest; however, the effect can be species‐specific and negative to some species' population. [ABSTRACT FROM AUTHOR]

Background: Freezing rain, also known as gelicidium, glaze, or ice storm, is an unpredictable and rare meteorological event with an impact on millions of citizens and which can affect the healthcare system of large areas. It occurs if rain hits the ground when surface temperatures are below 0 °C. Objective: To report what occurred on January 13th 2017 in Lombardy, a northern Italy region with Milan as capital, when a freezing rain caused an overload of the emergency system. Methods: We obtained data on emergency vehicles calls and missions from the emergency reports (four Lombardy areas covered by Azienda Regionale Emergenza e Urgenza-AREU-and encompassing 117 emergency departments). Emergency examinations data included overall visits, diagnosis, severity degrees and workload of emergency departments. Results: The Milan area emergency calls had an increase unseen in the previous four years of service (from 1369 to 2700 p < 0.001). A total of 1913 trauma cases were managed versus a daily average of 484 during January 2017 (p < 0.001). Road accidents and injuries at work increased while non-traumatic causes did not. More than 70% of the 38 emergency departments in the Metropolitan Area around the city of Milan were overloaded. Conclusion: We presented the first European report on the impact of an ice storm on a healthcare system, suggesting that early recognition, communication between meteorologists and health authorities, and an alert of ambulance services and healthcare professionals (orthopaedics above all) is mandatory, jointly with warnings to the population by public authorities. [ABSTRACT FROM AUTHOR]

We estimated canopy structure and transmitted radiation using hemispherical photography in four monitoring years (2008–2010, 2016) following the 2008 huge ice storm in a subtropical forest in south China, so as to assess changes in canopy biophysical parameters during forest recovery from natural disturbance. Significant decrease in canopy openness (CO), transmitted direct radiation (TransDir), and transmitted diffuse radiation (TransDif), as well as significant increase in leaf area index (LAI), were found in the disturbed forest stand in the subsequent years following the ice storm, indicating rapid canopy recovery. In contrast, these biophysical parameters of the undisturbed forest stand were quite stable during the monitoring years. The strength of relationships between CO and other canopy biophysical parameters decreased in the disturbed stand along the monitoring years. The disturbed stand had common slopes for the CO-TransDir and CO-TransDif models in the first two monitoring years, but different slopes for the CO-LAI model between the first and the subsequent monitoring years, while the undisturbed stand had common slopes for all the regression models in the first three monitoring years following the huge ice storm. These results showed that stronger correlations of LAI or TransDir with CO were characteristic of less complex canopies, such as those damaged by disturbance; the sensitivity of transmitted radiation in response to CO decreased with canopy recovery. Our findings demonstrated that forests with different canopy structure varied in biophysical parameters, which can be quantified by hemispherical photography. [ABSTRACT FROM AUTHOR]

Abstract Background Ice, or freezing rain storms have the potential to affect human health and disrupt normal functioning of a community. The purpose of this study was to assess acute health impacts of an ice storm that occurred in December 2013 in Toronto, Ontario, Canada. Methods Data on emergency department visits were obtained from the National Ambulatory Care Reporting System. Rates of visits in Toronto during the storm period (December 21, 2013 – January 1, 2014) were compared to rates occurring on the same dates in the previous five years (historical comparison) and compared to those in a major unaffected city, Ottawa, Ontario (geographic comparison). Overall visits and rates for three categories of interest (cardiac conditions, environmental causes and injuries) were assessed. Rate ratios were calculated using Poisson regression with population counts as an offset. Absolute counts of carbon monoxide poisoning were compared descriptively in a sub-analysis. Results During the 2013 storm period, there were 34 549 visits to EDs in Toronto (12.46 per 1000 population) compared with 10 794 visits in Ottawa (11.55 per 1000 population). When considering year and geography separately, rates of several types of ED visits were higher in the storm year than in previous years in both Toronto and Ottawa. Considering year and geography together, rates in the storm year were higher for overall ED visits (RR: 1.10, 95 % CI: 1.09-1.11) and for visits due to environmental causes (RR: 2.52, 95 % CI: 2.21-2.87) compared to previous years regardless of city. For injuries, visit rates were higher in the storm year in both Toronto and Ottawa, but the increase in Toronto was significantly greater than the increase in Ottawa, indicating a significant interaction between geography and year (RR: 1.23, 95 % CI: 1.16-1.30). Conclusions This suggests that the main health impact of the 2013 Ice Storm was an increase in ED visits for injuries, while other increases could have been due to severe weather across Ontario at that time. This study is one of the first to use a population-level database and regression modeling of emergency visit codes to identify acute impacts resulting from ice storms.

Abstract: Evergreen broad‐leaved forests are widely distributed in eastern Asia with evergreen broad‐leaved (EBL) and deciduous broad‐leaved (DBL) tree species coexisting under the same climatic regime, raising questions as to the underlying mechanisms. Since EBL and DBL species differ in leaf life span, a key component of resource economic strategies, their coexistence might be attributed to regeneration niche partitioning across habitats varying in resource supply. We investigated the effects of variation in insolation and topography on regeneration of EBL and DBL species in a subtropical EBL forest of eastern China after an ice storm that caused severe canopy disturbance. Using a mixed‐effects modelling framework and census data from 2011 to 2014 on 8,548 wild seedlings of 123 species, we quantified habitat preferences of EBL and DBL species during post‐disturbance regeneration and how their survival and height relative growth rates varied among habitats. The relative density of DBL seedlings (proportional to all seedlings) was greater in habitats with greater (canopy gaps) compared to habitats with lesser (understorey) insolation and increased with canopy gap size. However, DBL seedlings were not more frequent in higher (valleys) compared to lower (ridges) fertility habitats. Although DBL seedlings exhibited larger differences in growth between higher and lower resource habitats than EBL seedlings, their growth rates did not increase with canopy gap size. Seedlings of EBL species had high survival in all habitats, but larger DBL seedlings survived equally well on ridges. Consequently, the relative density of DBL seedlings declined in valleys, so that by 2014 it became more similar in valley and ridge habitats, whereas it remained higher in gaps than in the understorey, and especially in larger gaps. Synthesis. Specialization on contrasting topographic habitats is considered the primary mechanism mediating coexistence between deciduous broad‐leaved and evergreen broad‐leaved species. Our results, however, suggest this may not always be true, since seedlings of deciduous broad‐leaved and evergreen broad‐leaved species partitioned regeneration niches based on light more so than topography. We propose that coexistence of deciduous broad‐leaved and evergreen broad‐leaved species can strongly depend upon canopy disturbance to create a mosaic of habitat patches, including high light gaps favouring regeneration of deciduous broad‐leaved species. [ABSTRACT FROM AUTHOR]

In recent years, forests are exposed to various meteorological disasters. The climate change and warming of atmosphere cause more intensive and frequent occurrences in the atmosphere. This is also reflected in Slovenian forests - in particular in the form of windthrow, snow-damage, landslides and avalanches, and in 2014 a catastrophic ice storm. Some forecasts indicate that the future will bring more of this kind of disasters. The ice storm in the last year stroke the land the most in history, in particular in terms of damaged trees and areas. According to the available data, the damaged quantities of trees represent more than a two years planned annual cut in Slovenian forests, while about a half of the country was affected. The majority of the damaged wood comes from private forests. The remedying of such extensive meteorological disasters is demanding, dangerous and prolonged - it is also hindered by the specific ownership structure of the forest land in Slovenia and its average size. 75% of all forest have private owners, and this land is fragmented with a large number of forest holders. An average forest land is only 2.3 ha per individual owner. In these conditions, the following questions have to be answered: who, how and in what time is it possible to remedy the caused damage? What is the current quality of wood which was damaged in many ways in the meteorological disaster? Is it possible to use more modern felling technologies and wood transports from the forest in so fragmented private land?

Ice storms greatly affect the structure, dynamics, and functioning of forest ecosystems. Studies on the impact of such disasters, as well as the post-disaster recovery of forests, are important contents in forest biology, ecology, and geography. Remote-sensing technology provides data and methods that can support the study of disasters at the large-to-medium scale and over long time periods. This study took Chebaling National Nature Reserve in Guangdong Province, China, as the study area. First, field-survey data and remote-sensing data were comprehensively analyzed to demonstrate the feasibility of replacing the forest stock volume with the mean annual value of the Enhanced Vegetation Index (EVI), to study forest growth and change. We then used the EVI from 2007 to 2017, together with a variety of other remote-sensing and forest sub-compartment data, to analyze the impact of the 2008 ice storm and the subsequent post-disaster recovery of the forest. Finally, we drew the following conclusions: (1) Topography had a considerable effect on disaster impact and forest recovery in Chebaling. The forest at high altitudes (700−1000 m) and on steep slopes (25−40°) was seriously affected by this disaster but had a stronger post-disaster recovery ability. Meanwhile, the hardest-hit area for coniferous forest was higher and steeper than that for broad-leaved forest. (2) In the same terrain conditions, coniferous forests were less affected by the disaster than broad-leaved forests and showed less variation during the post-disaster recovery process. Nevertheless, broad-leaved forests had faster recovery rates and higher recovery degrees; (3) Under the influence of human activities, the recovery and fluctuation degree for planted forest in the post-disaster recovery process was significantly higher than that for natural forest. The study suggests that forest has high disaster resistance and self-recovery ability after the ice storm, and this ability has a strong correlation with the type of forest and the topographic factors such as elevation and slope. At the same time, human intervention can speed up the recovery of forests after disasters.

A comparative study of young European beech, silver fir and Norway spruce in the Slovenian mixed forest stands was made at four locations, exposed to the rapid canopy disintegration after the severe ice storm in 2014. Nitrogen amount (N tot ), Leaf mass per area (LMA), maximal Assimilation response to light (A max ) and Quantum yield (Φ) were measured in three categories of different light intensities under closed canopy with Indirect Site Factor (ISF) < 15%, at the forest edge (15% < ISF < 25%) and in the open (ISF > 25%). Tree responses were compared between damaged plots – rapidly exposed to light and undamaged sites, where young trees gradually adapted to the light environment during two years (2015 and 2016) after the disturbance event. Nitrogen content of all three species was within optimal range values, highest in the open and lowest under canopy conditions on every plot. Rapid exposure to increased light levels affected most directly fir in the category of forest edge and under open canopies. Contrary to fir, beech responded in a favourable way, while no differences in response were evident in spruce. Assimilation efficiency, where both fir and beech were equal shifted towards the shade in both years. [ABSTRACT FROM AUTHOR]

Natural and anthropogenic forest canopy disturbances significantly alter forest dynamics and lead to multi-dimensional shifts in the forest understorey. An understorey plant's ability to exploit alterations to the light environment caused by canopy disturbance leads to changes in population dynamics. The purpose of this work was to determine if population growth of a species adapted to low light increases in response to additional light inputs caused by canopy disturbance, or alternatively, declines due to long-term selection under low light conditions., To address this question, we quantified the demographic response of an understorey herb to three contrasting forest canopy disturbances (ice storms, tent caterpillar defoliation and lightning strikes) that encompass a broad range of disturbance severity. We used a model shade-adapted understorey species, Panax quinquefolius, to parameterize stage-based matrix models. Asymptotic growth rates, stochastic growth rates and simulations of transient dynamics were used to quantify the population-level response to canopy disturbance. Life table response experiments were used to partition the underlying controls over differences in population growth rates., Population growth rates at all three disturbed sites increased in the transition period immediately after the canopy disturbance relative to the transition period prior to disturbance. Stochastic population models revealed that growth rates increased significantly in simulations that included disturbance matrices relative to those simulations that excluded disturbance. Additionally, transient models indicated that population size ( n) was larger for all three populations when the respective disturbance matrix was included in the model., Synthesis. Obligate shade species are most likely to be pre-adapted to take advantage of canopy gaps and light influx to a degree, and this pre-adaptation may be due to long-term selection under dynamic old growth forest canopies. We propose a model whereby population performance is represented by a parabolic curve where performance is maximized under intermediate levels of canopy disturbance. This study provides new evidence to aid our understanding of the population-level response of understorey herbs to disturbances whose frequency and intensity are predicted to increase as global climates continue to shift. [ABSTRACT FROM AUTHOR]

Introduction: Natural disturbances modify forest structure by affecting regeneration dynamics and can change main ecosystem functions. An ice storm unusually took place in southern China in early 2008, which caused huge damage to forests. Resprouting of woody plants in a subtropical forest has received little attention. The role of survival time and mortality has been assessed for newsprouts after an ice storm., Methods: In this study, damage types, in addition to the annual number and mortality rates of sprouts for all tagged and sampled resprouted Chinese gugertree ( Schima superba Gardner & Champ.) individuals more than or equal to 4 cm in basal diameter (BD), were monitored. A total of six plots (20 m × 20 m) wererecorded in a subtropical secondary forest dominated by S. superba in Jianglang Mountain, China. This investigation had been conducted for six consecutive years., Results: The results showed that the survival rates of the sprouts were dependent on the year they sprouted. The earlier the year they boomed, the lower the mortality. The sprouts produced in 2008 were of the highest vitality and survival rates. Sprouts of the decapitated trees exhibited a better survival rate than those of uprooted or leaning trees. Sprouting position also plays a role in regeneration. Sprouts at the basal trunks of uprooted trees and the sprouts at the upper trunksof the decapitated trees exhibited the lowest mortality. The relationship between the accumulative mortality rate and the average diameter of new sprouts isaffected by damage types., Discussion: We reported the mortality dynamics of sproutsin a subtropical forest after a rare natural disaster. This information could serve asa reference for the construction of a branch sprout dynamic model ormanagement of forest restoration after ice storms., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Cao, Zhou and Wang.)

Due to the severe damages to transmission systems caused by ice storms, reasonable de‐icing work becomes pressingly significant for power systems. This study proposes a transmission line de‐icing outage optimal scheduling framework based on DC de‐icing method. First, an ice thickness prediction model and a time‐varying forced outage rate model are introduced to delineate the ice accretion and the reliability of lines. Then, a multi‐objective de‐icing outage optimal problem is formulated to minimise the ice thickness peak value of icing lines and the expected energy not supplied of the system during the decision period. Finally, non‐dominated sorting genetic algorithm‐II optimisation approach is used to determine the Pareto optimal solutions, and a decision making method is utilised to choose the final de‐icing scheme. Simulation results on IEEE 24‐bus reliability tests system show the effectiveness of the proposed de‐icing strategy. [ABSTRACT FROM AUTHOR]

Ecosystem services associated with urban forests have received significant consideration in the last decade, but less attention has been given to disservices. In the urban forest, examples of common disservices include air pollution, allergens and physical damage to property. The way perceived and experienced urban forest disservices influence residents' tree management is unclear yet important to understand when developing management goals and strategies. This study's objective is to examine residents' experiences, attitudes, and actions related to an ice storm, which created a set of urban forest disservices, to better understand the role of disservices in residential tree management. To address the objective, residents from the Greater Toronto Area were surveyed six month after the December 2013 ice storm. The survey responses indicated that the majority of participants had multiple small and large branches fall on their property as a result of the storm, although few lost trees. As a result of their ice storm experiences, many survey participants altered their tree plans, including deciding to remove healthy trees on their property to reduce future risks. Most respondents want their municipality to continue street tree plantings, but utilize more structurally sound trees and take better care of existing trees. The case study highlights the ways disservices can influence the attitudes and actions of residents, thus, illustrating the importance of documenting disservices, along with ecosystem services, in order to develop successful management strategies and better understand socio-ecological interactions in the urban forest. [ABSTRACT FROM AUTHOR]

Background: Ice, or freezing rain storms have the potential to affect human health and disrupt normal functioning of a community. The purpose of this study was to assess acute health impacts of an ice storm that occurred in December 2013 in Toronto, Ontario, Canada.Methods: Data on emergency department visits were obtained from the National Ambulatory Care Reporting System. Rates of visits in Toronto during the storm period (December 21, 2013 - January 1, 2014) were compared to rates occurring on the same dates in the previous five years (historical comparison) and compared to those in a major unaffected city, Ottawa, Ontario (geographic comparison). Overall visits and rates for three categories of interest (cardiac conditions, environmental causes and injuries) were assessed. Rate ratios were calculated using Poisson regression with population counts as an offset. Absolute counts of carbon monoxide poisoning were compared descriptively in a sub-analysis.Results: During the 2013 storm period, there were 34 549 visits to EDs in Toronto (12.46 per 1000 population) compared with 10 794 visits in Ottawa (11.55 per 1000 population). When considering year and geography separately, rates of several types of ED visits were higher in the storm year than in previous years in both Toronto and Ottawa. Considering year and geography together, rates in the storm year were higher for overall ED visits (RR: 1.10, 95 % CI: 1.09-1.11) and for visits due to environmental causes (RR: 2.52, 95 % CI: 2.21-2.87) compared to previous years regardless of city. For injuries, visit rates were higher in the storm year in both Toronto and Ottawa, but the increase in Toronto was significantly greater than the increase in Ottawa, indicating a significant interaction between geography and year (RR: 1.23, 95 % CI: 1.16-1.30).Conclusions: This suggests that the main health impact of the 2013 Ice Storm was an increase in ED visits for injuries, while other increases could have been due to severe weather across Ontario at that time. This study is one of the first to use a population-level database and regression modeling of emergency visit codes to identify acute impacts resulting from ice storms. [ABSTRACT FROM AUTHOR]

ABSTRACT Ice storms, defined by the US National Weather Service as freezing rain accumulations over 0.635 cm (0.25 inch), are often costly and destructive. Formation processes include the classic 'melting' process and supercooled warm rain process. Freezing rain is most commonly found ahead of a warm front or occlusion, where warm air is lifted over a cold shallow layer near the surface. Other synoptic patterns conducive to freezing rain include arctic fronts, isentropic lift over an arctic air mass, and cold air damming. Causes of spatial and temporal variations in freezing rain include, but are not limited to, terrain and proximity to water. Areas with the most occurrences of freezing rain in the United States include the Pacific Northwest, Upper Midwest, and Northeast/Appalachian regions. Empirical forecasting methods and numerical weather prediction are currently used to predict freezing rain. Successful forecasting of ice storm events requires evaluation of the thermodynamic profile of the atmosphere. Local effects such as proximity to water and topography must be taken into account, and non-linear processes such as latent heating and cooling must not be ignored. Ice accumulation can cause tree damage, which, in addition to breakage of electrical cables, can lead to power outages. Deposition of ice also impacts road, rail, and air travel, with associated economic costs due to lost hours as workers are unable to travel. Ice storms also provide a significant risk to human health and life, with falling debris and slippery surfaces being primary threats. [ABSTRACT FROM AUTHOR]

Background and Aims Despite a longstanding interest in variation in tree species vulnerability to ice storm damage, quantitative analyses of the influence of crown structure on within-crown variation in ice accretion are rare. In particular, the effect of prior interception by higher branches on lower branch accumulation remains unstudied. The aim of this study was to test the hypothesis that intra-crown ice accretion can be predicted by a measure of the degree of sheltering by neighbouring branches. Methods Freezing rain was artificially applied to Acer platanoides L., and in situ branch-ice thickness was measured directly and from LiDAR point clouds. Two models of freezing rain interception were developed: 'IceCube', which uses point clouds to relate ice accretion to a voxel-based index (sheltering factor; SF) of the sheltering effect of branch elements above a measurement point; and 'IceTree', a simulation model for in silico evaluation of the interception pattern of freezing rain in virtual tree crowns. Key Results Intra-crown radial ice accretion varied strongly, declining from the tips to the bases of branches and from the top to the base of the crown. SF for branches varied strongly within the crown, and differences among branches were consistent for a range of model parameters. Intra-crown variation in ice accretion on branches was related to SF (R² = 0·46), with in silico results from IceTree supporting empirical relationships from IceCube. Conclusions Empirical results and simulations confirmed a key role for crown architecture in determining intra-crown patterns of ice accretion. As suspected, the concentration of freezing rain droplets is attenuated by passage through the upper crown, and thus higher branches accumulate more ice than lower branches. This is the first step in developing a model that can provide a quantitative basis for investigating intra-crown and inter-specific variation in freezing rain damage. [ABSTRACT FROM AUTHOR]

Suburban protected areas may soon become extremely important in conservation as suburban-style development is increasing and known to reduce biodiversity through habitat loss and fragmentation. However, their long term ability to preserve plant diversity despite increasing disturbances remains to be tested. In 2013, we resurveyed 133 plots in forest stands of a Canadian suburban park first sampled in 1977. Since the initial survey, invasive species have expanded in surrounding areas, a major ice storm hit the region, and white-tailed deer have become abundant. We evaluated changes in alpha, gamma, beta and functional diversity, as well as in the forest structure and composition, using a set of univariate and multivariate analyses. We also used a species-traits indicator approach to identify drivers of changes. We found a major increase in alpha and gamma diversity, accompanied by a 30% decrease in beta diversity. These changes were associated with an increase in native plant frequency and abundance. Moreover, we found no loss in functional diversity (higher functional richness, dispersion and evenness in 2013 than in 1977). These changes likely resulted from the combination of stand maturation (more shade-tolerant species), forest regeneration following the ice storm (densification of the sapling layer), deer browsing (increased frequency and abundance of ferns, sedges and grasses, and of species with a storage organ) as well as post-disturbance recovery (alpha and gamma diversity increase). Our findings highlight the ability of suburban parks to preserve native flora, despite natural and anthropogenic disturbances as well as overall biotic homogenization. [ABSTRACT FROM AUTHOR]

Each year severe winter storms (≈ice storms) damage trees throughout the southern USA. Arkansas and Oklahoma have a history of severe winter storms. To extend that history back beyond the reach of written records, a distinctive tree ring pattern or signature is needed. Storm-caused breakage, branch loss and bending stress provide that signature. We found a severe storm signature in shortleaf pine ( Pinus echinata ). We used three published site chronologies, a set of five new site chronologies from a growth-and-yield study conducted by Oklahoma State University and the unpublished Shortleaf Canyon chronology from a master’s thesis at the University of Arkansas. Our method is based on two ring width values for the first and second growing seasons after the storm standardized to the ring widths of the seven growing seasons after the storm. Concordance between storm years predicted by tree ring patterns and actual storm years was tested using Cohen’s Kappa. Concern about confounding of ice storm signals by droughts led us to test concordance between severe storms and drought in July, August and September; results were inconclusive but stand as a warning that these two phenomena cannot be distinguished with certainty in the tree ring record. Damaging severe storms occurred in about 2.8% of all years. Two out of three storms identified as “severe” produced glaze icing. [ABSTRACT FROM AUTHOR]

An increase in the frequency and magnitude of extreme weather events, such as major ice storms, can have severe impacts on southern forests. We investigated the damage inflicted by a severe ice storm that occurred in February 2014 on two loblolly pine ( Pinus taeda L.) ideotypes in Cross, South Carolina located in the southeastern coastal plain. The “narrow crown” ideotype allocates more resources to stem growth while the “broad crown” ideotype allocates more of its resources to leaf area. We sampled each clone in August of 2014 and assessed damage based on four mutually exclusive damage categories: crown damage (visual estimation of percent damage); bent bole (bending shape and angle); snapped bole (distance from ground to snapped height); and uprooted. Damage category was statistically different between clones ( χ 2 = 120.36; p = 0.001); 67% of the individuals of the narrow crown ideotype suffered crown damage compared to 94% of the broad crown ideotype; 27% of the individuals of narrow crown ideotype suffered immediate mortality after the bole snapped, compared to only 3% for the broad crown. Of the individuals that incurred crown damage, the degree of damage sustained was statistically different by clonal type ( F = 8.73; p < 0.01). The broad crown ideotype incurred greater crown damage than the narrow crown (38.0 ± 1.34 and 31.8 ± 1.6, respectively). Damage that resulted in a bent bole was minimal, with 4% for the narrow crown ideotype and 3% for the broad crown. The observed clonal differences in response to damage that incurred from an extreme ice storm may be attributed to differences in morphology and carbon allocation strategies between the two ideotypes. These differences are important to carbon sequestration projects and ideotype development in regions that are prone to extreme glazing events. [ABSTRACT FROM AUTHOR]

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