Tree Damage Research Articles

Leave No Trace Communication: Effectiveness Based on Assessments of Resource Conditions

The efficacy of different Leave No Trace (LNT) communication interventions designed to persuade forest visitors to practice low-impact camping behaviors were evaluated. Three depreciative campsite behaviors—littering, tree damage, and surface disposal of human waste—were evaluated by before-and-after resource condition assessments. Three LNT communication interventions were evaluated against a control: (1) an LNT brochure and poster display (non-personal), (2) personal LNT communication by a forest naturalist, and (3) a combination of both non-personal and personal methods. The study population was overnight campers using dispersed road-accessed campsites in Western Maryland’s Green Ridge State Forest. LNT communication successfully improved resource conditions for the targeted depreciative behaviors. For litter and human waste, personal communication by a forest naturalist was effective, but the non-personal method was ineffective. In contrast, tree damage was significantly reduced by both non-personal and personal communication methods. Combining personal and non-personal communication efforts did not result in an increased benefit. The core implication of this study is that several camping resource impacts can be measurably reduced when uniformed staff personally communicate the desired low impact practices.

Monitoring Tree-Shrub, and Meadow Vegetation in the Volga-Akhtuba Floodplain Using Remote Sensing Methods (Based on “Krasnyy Buksir” Range)

The article deals with the assessment of the state of tree-shrub and meadow vegetation by remote sensing methods. The author reveals the reasons of degradation and change of floristic richness of vegetation. These include: trampling of grass cover and forest floor (1), mechanical damage of trees (2), increasing the area of fire pits (3), and littering and contamination of the territory (4). In addition, mowing and grazing have a great influence. The development of the path network leads to changes in water-physical properties of the soil. Changes in the species composition of meadow vegetation indicate an increase in the processes of xerophytization and pasture digression. The article considers various methods of decoding forest plantations. Among them, the method of aerospace research is the most effective. This method makes it possible to assess the state of tree-shrub and meadow vegetation in dynamics and to carry out continuous monitoring. For a greater accuracy of the assessment, Earth remote sensing data are confirmed by on-site studies. Projective coverage has been used as a sign of degradation for the assessment. The level of preservation of plantings has been determined by the area of the canopy of the stand, that is the ratio of the canopy area to the entire area of the plantings. Under the area of the canopy a set of pixels that match the tone assigned to the canopy is understood. Using the methodology given in the article, the author has carried out the vegetation analysis at “Krasnyy Buksir” range. The area of land belonging to different environmental levels has been calculated for this purpose. The author draws the conclusion that the studied site is subject to a significant anthropogenic load and environmental protection measures are strongly necessary in this area.

Sofralık zeytinde farklı mekanik hasat sistemlerinin değerlendirilmesi (Olea europaea cv. Gemlik)

The experiments were conducted in Gemlik olive variety (Olea europaea cv. Gemlik)’s orchard to determinate the harvesting performance of different harvesting methods namely hand, branch shaker and trunk shaker at different frequencies and compare the harvesting methods. Trunk shaker with eight different frequencies were operated. In the first and second year of the experiments at the optimum harvest time, fruit volume, fruit detachment force, fruit weight, the ratio of fruit detachment force to fruit weight were found to be 3.9-4.0 cm3, 3.27-3.99 N, 4.23-4.28 g, 0.77-0.94 N g-1 respectively. Best results were obtained by using the trunk shaker with low frequencies as trunk shaker machine (TSM) 22 Hz. Fruit damage, tree damage levels, harvesting efficiency, duration of operation per tree and work productivity of trunk shaker with 22 Hz were found as less than 1.5%, 2.86%-7.24%, 93.93%-92.92%, 2.51-2.81 min tree-1 and 286.22-355.72 kg worker-1 h-1 respectively in two-years (2012 and 2013) trials.

Прогнозування постпірогенного відпаду в сосняках, пошкоджених літніми низовими пожежами, у Лівобережному Лісостепу України

Пожежі є одними із найнебезпечніших чинників дестабілізації лісів. У зв’язку зі зростанням посушливості клімату ризик збільшення частоти й масштабів лісових пожеж залишається високим, тому актуальним є розроблення науково обґрунтованих заходів із пом’якшення екологічних, економічних та соціальних наслідків лісових пожеж. Удосконалено та уточнено показники, що характеризують візуальні прояви пошкодження дерев після низових пожеж, та показники вогнестійкості середньовікових дерев сосни звичайної (Pinus sylvestris L.). Виявлено, що в міру збільшення середньої висоти нагару на стовбурах зростає частка відпаду в досліджуваних групах дерев (r = 0,87, tф = 5,80, t0,01 = 3,17). Встановлено, що вогнестійкість дерев збільшується зі збільшенням природного ступеня товщини дерева в насадженні (виявлено обернений достовірний кореляційний зв’язок між природним ступенем товщини (ПСТ) і категорією санітарного стану пошкоджених дерев: (r = -0,54; р = 0,05). Розроблено прогностичну модель для встановлення ймовірності відпаду дерев, пошкоджених низовими стійкими літніми пожежами, яка як предиктори включає середню висоту нагару на стовбурах та ПСТ (точність прогностичної моделі становить понад 78 %).

Sapwood-inhabiting mycobiota and Nothofagus tree mortality in Patagonia: Diversity patterns according to tree species, plant compartment and health condition

Temperate forests ecosystems are threatened by declines and diseases worldwide. Causes have been investigated during the last decades allowing, in some cases, to relate such deterioration to climate change or pathogens but, in many cases, causes have not yet been elucidated. In recent decades, a phenomenon of grouped mortality, whose etiology remains unknown, has been observed in the two most distributed Nothofagus species of North Patagonian forests. This study aimed to assess sapwood-inhabiting fungal diversity of N. dombeyi and N. pumilio trees in healthy and affected stands in order to determine whether health condition shape these fungal communities, to characterize such patterns and, to seek for the likely pathogens associated with tree damage. Seven sites in Los Alerces National Park (Chubut, Argentina), were sampled seasonally for two years. Eighty-eight fungal taxa were recovered and identified. Spatial heterogeneity across plant compartments was found, involving community composition and structure, with stem harbouring greater diversity than root. It was found that the sapwood in both Nothofagus species was inhabited by different fungal species, in high richness and showing different patterns according to health condition and plant compartment. Health condition was a stronger driver of N. dombeyi sapwood-inhabiting fungal community than it was for N. pumilio; the latter evidenced plant compartment as a stronger driver of such community. Nothofagus pumilio presented higher frequency of decomposition agents in both affected and healthy trees than it was in N. dombeyi, indicating a greater wood deterioration of its stands. More decomposition agents and potential pathogens have been found in symptomatic stands of N. dombeyi than in healthy stands, although their frequency patterns do not allow the inference of conclusions about the primary fungal agent causing tree mortality. Our findings suggest a secondary role of living-wood-inhabiting mycobiota in tree damage processes as an expression of tree stress caused by climatic factors.

Predicting trunk flare diameter to prevent tree damage to infrastructure

Tree roots often come in conflict with elements of the built environment, particularly when planted in limited soil locations. For street trees located between roadways and sidewalks, minimum planting width requirements can be calculated to prevent large supporting roots from lifting or growing over paved surfaces. In this study, we used diameter at breast height (DBH) to predict trunk flare diameter for common shade tree species from four different communities in the United States (Milwaukee, Minneapolis, Saint Paul, and Tampa). These predictive models were then used to calculate minimum width requirements to reduce infrastructure damage given the maximum expected DBH measurements for each species based on existing urban forest inventory data in the communities studied. For all ten taxa tested, DBH was a significant predictor of trunk flare diameter (minimum R2 = 0.81), indicating that this commonly used urban forestry measurement can be used to design minimum growing space based on selected species to potentially prevent root and infrastructure conflicts. The methods employed in this paper can be easily replicated by other researchers in order to create guidelines for species and environments not captured in our data set. Alternatively, broader functions for estimating trunk flare based on DBH are provided for species based on natural habitat type (i.e., upland, wetland, variable).

Forest stand susceptibility mapping during harvesting using logistic regression and boosted regression tree machine learning models

Economic and environmental consequences of harvesting operations are important in forestry because of the damages caused by tree felling and timber transportation. In this research, we analyzed forest stand damage susceptibility using GIS-based logistic regression (LR) and boosted regression tree (BRT) machine learning models for the Shourab Forests. These forests contain valuable stands of Hyrcanian forests in northern Iran that represent many of the plant covers, geographical, and forest management features of this ancient ecosystem. To this end, we applied traversed transect to cover the forest unit. This allowed us to sample any damaged residual tree intersected by the transect resulting in a dataset of 152 damaged trees in the study area. Of this dataset, we utilized 106 damaged trees for training purposes, while the remaining instances (46 damage locations) served as the verification dataset. We utilized eight input factors as stand damage conditioning variables to model damage susceptibility, including distance from the skid trails, distance from the road, forest density, type of forest, topographic position index (TPI), length of slope (LS), altitude, slope aspect, and slope degree. Using these predictive variables, we calculated damage susceptibility using LR and BRT machine learning models, and, subsequently, devised the outputs in ArcGIS to produce the final stand damage susceptibility maps. As the statistical evaluative criteria, we calculated the area under the curve (AUC) and Akaike Information Criterion (AIC) for the validation and training data sets. According to the validation results, the BRT model (AIC = −109.04; AUC = 0.91) strongly outperformed the LR model (AIC = 96.14; AUC = 0.77). According to the results, among the explanatory variables, the slope degree and slope length had more significant impact on the stand damage. Moreover, the susceptibility maps depicted that more than one-third of the forest area were surveyed in high and very high damage susceptibility classes. According to the results mentioned above, using machine learning technique is an inevitable approach in controlling and mitigating the damages caused by human interferences in natural ecosystems especially in mountain forests. Our findings revealed that the susceptibility maps produced by BRT are highly relevant and beneficial for planning forest harvest operations.

Olive knot damages in ten olive cultivars after late-winter frost in central Italy

Olive knot is among the most relevant diseases affecting olive cultivation. Pseudomonas savastanoi pv. savastanoi (Pss) is recognized as the causative agent of this disease. Its penetration in the plant occurs through wounds in all the aerial plant tissues. Frost, or hailstorm damages to the bark of shoots, branches and trunk might expose plants to higher risks of infection. In the coldest regions where freezing events may occur regularly, an employment of tolerant varieties to cold, or to Pss infection represents a valuable approach for limiting tree damages. However, the relationship between the tolerance to different frost types and the susceptibility to Pss disease in different organs (trunk, branches of different age) might be not univocal and rather change among olive tree varieties. In the Marche region of central Italy, the damages occurring during late winter frosts (end of February) and caused by olive knot disease were investigated. Our work considered 10 locally, nationally and internationally known cultivars that were studied under field conditions in 6 different groves in Marche region. In all the groves, olive knot incidence and severity were positively correlated with frost damaged organs. All the varieties were damaged by the late winter frost and showed olive knot disease symptoms after 6 months. ‘Piantone di Mogliano’, ‘FS-17’ and ‘Frantoio’ were the most affected cultivars. ‘Carboncella’, ‘Maurino’ and ‘Arbequina’ showed an intermediate susceptibility, whereas ‘Ascolana Tenera’ ‘Leccino’, ‘Piantone di Falerone’, ‘Rosciola Colli Esini’ resulted tolerant to this peculiar late frost and olive knot infection. The >3-year-old branches were generally more damaged in comparison to younger branches.

Foliar endophytic fungi: diversity in species and functions in forest ecosystems

As mycorrhizal fungi, endophytic fungi are ubiquitous in natural forest ecosystems. A great number of foliar endophytic fungi (FEFs) have been isolated from leaves of forest trees, and some metabolites are also isolated and characterized from the FEFs. These metabolites show strong potential to inhibit or kill insects and pathogenic fungi, especially those causing decline or damage of forest trees. In addition, FEFs can inhabit in leaf litter for a short or long period depending on endophytic species, thus they affect decomposition rate of leaf litter. Some FEFs can colonize in plant roots and promote plant growth. In the review, we provide an overview of the ecological roles of FEFs and hope the resources of FEFs can be developed and be used in forestry and agriculture to reduce use of insectcides and fungicides and in pharmacology to maintain human health.

Occurrence of European Mistletoe (Viscum album L.) on Forest Trees in Poland and Its Dynamics of Spread in the Period 2008–2018

As recently reported, European mistletoe has become an important agent of damage to forest trees in Central Europe. To document the extent of its impact, host and environmental preferences, as well as spatial and temporal dynamics, we have analyzed the results of 10 years of annual assessments of tree damage in level 1 plots of country-wide national forest monitoring. Mistletoe was found on 12 forest tree species, most frequently on silver fir and Scots pine, much less often on birches and deciduous admixture species. Common beech, pedunculate, and sessile oaks, as well as coniferous admixture species, were found to be free from the parasite. Mistletoe was more common on larger trees, mainly those in the 1st and 2nd Kraft classes, characterized by a higher DBH value than trees without V. album. Infestation was also age-dependent with low numbers of infested trees in young age classes and a much higher proportion of infested trees being over 80–100 years in age. Defoliation of trees colonized by mistletoe was found to be significantly higher than in trees free from the parasite, confirming the adverse effect of infestation on tree health. The increase of relative incidence of tree infestation by mistletoe in forests in Poland was high throughout the entire period 2008–2018 and significant for the most threatened host species: silver fir, Scots pine, and birches. It was also found that spread direction was from west to east and that the occurrence of V. album shows clear regionalization. The most endangered forests were located within a 200 km wide zone ranging through lowland Central Poland from the border with Germany down to the border with Ukraine and Belarus. The highest concentration occurred in the Western part of the country. Outside this zone (to the north and south) the mistletoe was much less abundant as expressed by the amount of injuries caused by the parasite or infested trees per plot.

Long-term effects of thinning and woody control on longleaf pine plantation development, understory abundance, and tree damage from an ice storm

Longleaf pine (Pinus palustris) plantations have been established across the southeastern United States as the first step in restoring the declining savanna ecosystem, yet their long-term stability and development to open canopied woodlands may depend on early density and vegetation management treatments. Commercial thinning (CT) was applied in 2012 (year 18) to a long-term study of longleaf pine community restoration at the Savannah River Site near Aiken, SC to increase abundance of herb species. Although precommercial thinning (PCT) and woody vegetation control increased herb species cover during the first five years of the study, measurements from years 17 to 22 indicated a continuing decline in their cover since year 9 despite application of CT in year 18. Herb species richness, however, increased from 21 to 43 species per 100 m2 area during the last six years of the study, likely a result of disturbances associated with CT and an ice storm in year 20. Application of PCT in 1994, when the plantations were 8–11 years old, reduced their susceptibility to stem bending and breakage from the ice storm, which occurred 20 years later in 2014. Measured 5 months before the storm, pine height: dbh ratio (HD) averaged 78 and 90 for trees growing with and without PCT, respectively, and stem breakage (% of trees) from the ice storm increased linearly (r2 = 0.53) with HD. Pine mortality from the combined effects of glaze ice and wind differed with (28%) versus without (45%) PCT, indicating that long-term stability of longleaf pine plantations depends on early density management.

Framework for assessing the windthrow risk to Norway spruce forests in Switzerland

If forests are to satisfy all our demands in the long term, then they must be managed purposefully. Disturbances that could jeopardise the provision of ecosystem services occur repeatedly. To better deal with these disturbances, knowing what damage and consequences can occur is important. In Switzerland, storms are the biggest large-scale disturbances in forests. No simple framework exists to characterise storm risk to forests. In this work, an extreme value statistic was used to generate a frequency–intensity distribution of storms. In addition, a correlation between gust peaks, i.e. intensity, and quantitative damage, i.e. consequence, for different tree heights of Norway spruce was constructed based on a relationship between tree height and damage percentage found by Schmidt et al. (Can J For Res 40:1636–1652, 2010). The combination of the two resulted in a frequency–consequence distribution. Although many uncertainties still exist due to sparse loss data and lack of long measurement series, this study provides a framework that can be used for risk assessment. The resulting expected damage can be used to study the effects on forest development and to optimise forest management accordingly.

Morphological and molecular analyses of a Meloidogyne mali population with high intragenomic rRNA polymorphism.

Root-knot nematode, Meloidogyne mali can cause damage in trees, shrubs, and herbaceous plants, and was placed on the EPPO Alert List in 2014. In the present study, we report a population isolated from Japanese maple. The recovered population is described by detailed morphological and molecular approaches. The molecular phylogentic analysis based on 28S rRNA, ITS, and mitochondrial COI genes places the population in the clade together with other M. mali sequences available in GenBank. The cloned sequences of the 28S rRNA gene revealed a high intragenomic rRNA polymorphism where the polymorphic copies are spread across M. mali clade. Similarly, we also found high variation in the mitochondrial COI gene. Among four haplotypes in M. mali, three occur in the newly found population. Our study provides the first report of intragenomic polymorphism in M. mali, and the results suggest that intragenomic polymorphism maybe widespread in Meloidogyne.

Performance evaluation of lateral canopy shakers with catch frame for continuous harvesting of oranges for juice industry

Citrus is mainly oriented to fresh consumption, and harvesting is usually performed manually. However, the high cost of harvesting and the low availability of labour can compromise the profitability of the crop when it is destined to juice industry. The development of citrus mechanical harvesting for industrial processing is conditioned to reach a high fruit removal efficiency, with a reduced damage to both fruit and trees. The current machines available are very large, requiring extensive plantations with long rows of trees to be efficient. In this study, two lateral canopy shakers equipped with a catch frame were evaluated to harvest independently both sides of the hedge on intensive citrus plantations with the main objective of determining their performance and feasibility. The lateral canopy shakers tested were three tractor-drawn machines, one commercial machine and two prototypes. The tested machines reached a mean value of 78% of fruit removal. Besides, the prototypes, equipped with a catch frame, were able to recover a mean value of 70% of yield. Although the results were promising, for achieving an efficient result, the application of this harvesting technology still requires a process of improvement, and the adaptation of both the machine and the plantation. The machines should reduce the amount of post-harvest ground fruit (5.9%-10.4%). Tree damages generated by the contact of the catch frame with the trunk and the metal rods with main branches were the most relevant. Therefore, it is still necessary to increase the ground speed of the machinery and improving the design of the rods, regulating the rod penetrating deep in the canopy to improve the fruit recovery and limit the damage caused to the trees. Keywords: harvester, mechanical harvesting, fruit removal, tree damage, Citrus sinensis L. Osbeck DOI: 10.25165/j.ijabe.20201303.4998 Citation: Sola-Guirado R R, Castro-Garcia S, Blanco-Roldán G L, Gil-Ribes J A, González-Sánchez E J. Performance evaluation of lateral canopy shakers with catch frame for continuous harvesting of oranges for juice industry. Int J Agric & Biol Eng, 2020; 13(3): 88–93.

АЛЬТЕРНАРИОЗ СЕМЕЧКОВЫХ КУЛЬТУР

The research was carried out on the premises of the experimental study farm of Russian State Agrarian University – Moscow Timiryazev Agricultural Academy in Moscow in 2018–2019. Over two years, the authors collected and microscoped samples of affected plants of different families to determine the causative agents of fungal diseases. The identification of the fungi species of the Alternaria genus was carried out by morphological features of conidia and the habitus of sporulation. It was found that the damage of apple and pear trees is caused by two non-specialized fungus species of Alternaria tenuissima and Alternaria infectoria. It was found that 73% of 110 apple varieties and 47.2% of 53 pear varieties studied were affected to varying degrees by the fungi of the Alternaria genus. The paper describes apple varieties that have been damaged by Alternaria. There has been detected a high malware of Alternaria blight on the young seedlings of pome crops. The species of A. tenuissima and A. infectoria pathogens have been determined to affect dicotyledonous weed plants widely distributed in fruit gardens, as well as a number of garden-protective and ornamental crops. Also, their possible role as infection reservoirs and vectors for fruit crops has been established. The authors considered grade vulnerability to Alternaria blight lesion of different pome and stone fruit varieties. The most Alternaria blight-resistant varieties of pome crops have been identified. The authors have stated the relationship between the degree of Alternaria blight progression and factors such as pest damage and the location of plantings. They also describe some differences in the manifestation of Alternaria blight symptoms on apple and pear trees during the initial period of disease progression. As a result of the studies, recommendations are given on the implementation of protective measures aimed at reducing the spread of Alternaria blight of pome crops in fruit gardens.

Self-healing of electrical damage in thermoset polymers via anionic polymerization

The self-healing of large scale electrical tree damage in a bulk thermoset polymer is achieved through an anionic polymerization-based microcapsule approach.

Challenges on the conservation of traditional orchards: Tree damage as an indicator of sustainable grazing

Traditional orchard meadows are among the most valuable cultural and agricultural systems for nature conservation in Europe. They comprise scattered fruit trees over a highly diverse herbaceous layer and provide a wide range of ecosystem services. However, they are strongly endangered due to farmland intensification and abandonment. Livestock grazing is known to promote grassland diversity but it may also cause tree damage through debarking. In this study, we evaluated the effect of different grazers (cattle, horse and sheep) on fruit trees in 42 traditional orchards of the Rhenish uplands (Germany). Overall, we found that 70% of the study trees showed debarking damage, although most of them (40%) were slightly damaged (1–10% of the trunk debarked). Most debarked trees showed accumulated damage over time, and only 8% of the study trees were damaged during the last year. The probability of strong debarking (>50% of the trunk damaged) was higher in orchards grazed by cattle and horses than on those grazed by sheep (5.3 and 3.7-fold difference, respectively). Importantly, unsustainable levels of cumulative debarking caused a decay of crown development, which may strongly affect fruit production. Additionally, lower tree densities favored higher levels of debarking intensity but did not affect the probability of occurrence. Individual tree-protection was an effective practice in decreasing trunk debarking (95% reduction in tree damage occurrence). The impact of grazing animals on trees might represent a useful indicator to assess the sustainability of each grazing system and should be taken into account in future agriculture and conservation policies.

Sanitary state of water-protection pine plantations in the interfluve of Dnieper and Desna

The purpose of the study was to establish the sanitary state of pine plantations, identify the causes of the development and spread of diseases and pathogens, develop recommendations for improving the condition and increase the biological stability of pine plantations between the Dnieper and Desna rivers. The studies were carried out in middle-aged, mature and over-mature pine plantations of the Ukrainian interfluve of Dnieper and Desna. The sanitary state of the stands was determined on 52 circular trial plots laid in the forest growing conditions of fresh poor site and fresh rich site. On each trial plot, the index of the sanitary state was calculated according to the generally methodology accepted in forestry. Calculations of the sanitary state index showed that middle-aged plantations are more resistant to biotic and abiotic factors, the dominant number of trees is classified as weakened. In general, the sanitary state index of middle-aged pine forests of fresh poor site and fresh rich site is 2.04 and 1.79, respectively. The mature plantings of fresh poor site with sanitary state index 2.86 are highly weakened, and fresh rich site are weakened, due to the more fertile rich site soil conditions enriched by the biodiversity of the living ground cover. Pine plantations of ІХ and XI age classes, in which the sanitary state index varies between 2.30–2.33, and the percentage of drying and dead trees reaches 10 %, are weakened. It has been established that the most influential factors of a significant deterioration in the sanitary state of mature and over-mature water-protection pine plantations are changes in the hydrological regime of floodplain territories, which leads to tree damage by the mistletoe Austrian and root sponge. In order to prevent the development of these pathogens, it is recommended to create mixed plantations of Scots pine with the introduction of 20–40 % deciduous species, which will simultaneously serve as a fire barrier to the spread of ground fires. Key words: biological stability, state categories, indicator of sanitary state, Austrian mistletoe, roots sponge, dry wood.

Ice-storm damage to trees in mixed Central European forests: damage patterns, predictors and susceptibility of tree species

AbstractIn northern temperate forests, ice storms are a common disturbance agent, though climate change may alter their occurrence patterns. Their impact on forest ecosystems is complex, as they influence both structure and processes. In 2014, an ice storm of high intensity and large spatial extent occurred in Slovenia, Central Europe, which enabled a detailed study of ice damage to individual trees across a broader spatial scale. Pre- and post-ice storm measurement data on 11 414 trees on 960 permanent plots were used to examine ice damage patterns on trees in the disturbed forest area (~8700 km2) to determine the predictors of ice damage to trees and to investigate the relative susceptibility of eight groups of tree species in mixed Central European forests. We used a novel approach to modelling ice-storm intensity across the region based on measured data on air temperature, precipitation amount and duration, precipitation intensity and wind speed. The ice storm damaged 31 percent of the analysed trees; high variability in the damage rate was observed across the disturbed area. For the tree species, a susceptibility to ice damage index (SI) ranging between 0 (no damage) and 1 (complete damage) was calculated based on terrestrial assessment of trees. Tree species differed significantly in susceptibility to ice damage: Abies alba (SI = 0.14) and Quercus sp. (SI = 0.11) were rather resistant; Picea abies, Fagus sylvatica and Acer sp. (SI = 0.23–0.28) were moderately to very susceptible; and Pinus sp. (SI = 0.62) was extremely susceptible to ice damage. Eight predictors and three interactions were included in an ordinal logistic regression model of tree damage: ice damage on trees depends mainly on ice-storm intensity, elevation and tree species, whilst tree dbh and social status, tree size and tree species diversity indices and slope were relatively less important. Our study illustrates the complexity of damage patterns on trees due to ice storms and the significance of ice-storm intensity and tree species as predictors when modelling ice damage on individual trees.

Autonomous Self-Healing of Electrical Degradation in Dielectric Polymers Using In Situ Electroluminescence

Summary Dielectric polymers are ubiquitous as electrical insulation in electrical power systems and electronic devices. Electrical treeing is typically regarded as an irreversible degradation process of dielectric polymers subjected to high electric stresses, which significantly limits their lifespan and endangers the reliability of electronics and electrical power systems. Here, we report self-healing polymers consisting of microcapsules that are capable of completely restoring the dielectric properties as a direct response to electrical tree degradation. We design the microcapsules with a relatively higher dielectric constant than polymer matrix to guide the propagation of electrical trees. The electroluminescence generated in situ during electrical treeing of polymers triggers crosslinking of the healing agents released from the capsules to repair the electrically damaged areas under ambient conditions. Notably, the breakdown strength of the mended region is largely enhanced upon healing, which was initiated at different locations. The integration of autonomous healing capability into dielectric materials opens new avenues to smart polymers for electronics and energy applications.