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Tree damage is one of the destructive behaviors of the Asiatic black bear (Ursus thibetanus G. (Baron) Cuvier, 1823), and this type of damage causes great economic loss to the forest. A survey about Himalayan white pine (Pinus wallichiana (A. B) Jacks, 1836) damages was conducted at Kaghan Valley, District Mansehra, Khyber Pakhtunkhwa, Pakistan. Field surveys were carried out within five major sites of Kaghan Valley, including Manshi reserve forest, Kamal Bann reserve forest, Malkandi reserve forest, Noori Bichla reserve forest, and some Guzara forests. Line transects and diameter at breast height (DBH) methods were selected for data collection. Eighteen transects were placed in different sites of the valley. A total of (n = 201) affected trees were observed from eighteen transects, along with a total population of 1081 trees with the encounter rate (ER: 0.657) and the mean DBH is x¯ = 71.97 cm. Among total damages, the most severe (n = 39: 19.4%) were fully damaged with a greater encounter rate. Bark stripping was made during the late winter season and used as foodstuff when natural food is limited in the area. In severe cases, the bear-stripped bark encircles from the entire tree trunk, which results in the drying of trees and, finally, falls. Among all five sites, Manshi reserve forest was greatly affected, where the highest number (n = 76) of tree damage, and (n = 21) the entire diameter of trunks were damaged. People of the study area claimed that the black bear causes great forest damage, as well as crop destruction that leads to high economic loss.

Cut-to-length harvesting is a cost-efficient method of the wood supply chain. However, it risks causing stem damage in the mechanized process of thinning forest stands, thereby reducing the growth and technical quality of the remaining trees, which would then be exposed on the increased vulnerability to fungal diseases. For these reasons, it is critical to support quality monitoring of harvesting machines. One way to support quality monitoring is through the application of machine vision solutions. In this study, the damaged stems were photographed systematically from a strip road. The success of the stem-damage detection was analyzed to determine the relationships between successful detection, stand condition, and the image-processing technique. Statistically meaningful relationships were identified via logistic regression analysis, which can be used in selection of tailored image processing technique. The study indicated that the quality-monitoring system of mechanized harvesting could be improved by an increased focus on developing the multi-view photogrammetry of stem damages according to different stand conditions. Further, refining the machine learning system would support the need to determine accurate image-processing thresholds of the texture of stem damages. Then, the overall proportion of successful stem-damage detections will be 89%. These improvements of the quality monitoring system will provide the efficient thinning process in the sustainable wood supply from forests to forest industry. The implementation of such a system could be much broader, initially under Nordic conditions and then in other countries as well, given that its development takes into considerations the significant calibration factors of local conditions.

• The relative importance of tree mortality risk factors remains unknown, especially in diverse tropical forests where species may vary widely in their responses to particular conditions. • We present a new framework for quantifying the importance of mortality risk factors and apply it to compare 19 risks on 31 203 trees (1977 species) in 14 one-year periods in six tropical forests. We defined a condition as a risk factor for a species if it was associated with at least a doubling of mortality rate in univariate analyses. For each risk, we estimated prevalence (frequency), lethality (difference in mortality between trees with and without the risk) and impact (‘excess mortality’ associated with the risk, relative to stand-level mortality). • The most impactful risk factors were light limitation and crown/trunk loss; the most prevalent were light limitation and small size; the most lethal were leaf damage and wounds. Modes of death (standing, broken and uprooted) had limited links with previous conditions and mortality risk factors. • We provide the first ranking of importance of tree-level mortality risk factors in tropical forests. Future research should focus on the links between these risks, their climatic drivers and the physiological processes to enable mechanistic predictions of future tree mortality.

1. Widespread degradation of tropical forests is caused by a variety of disturbances that interact in ways that are not well understood. 2. To explore potential synergies between edge effects, fire and windstorm damage as causes of Amazonian forest degradation, we quantified vegetation responses to a 30-min, high-intensity windstorm that in 2012, swept through a large-scale fire experiment that borders an agricultural field. Our pre- and postwindstorm measurements include tree mortality rates and modes of death, above-ground biomass, and airborne LiDAR-based estimates of tree heights and canopy disturbance (i.e., number and size of gaps). The experimental area in the southeastern Amazonia includes three 50-ha plots established in 2004 that were unbumed (Control), burned annually (Blyr), or burned at 3-year intervals (B3yr). 3. The windstorm caused greater damage to trees (>10 cm DBH) in the burned plots (B1yr: 13 ± 9% of 785 trees; B3yr 17 ± 13% of 433) than in the Control plot (8 ± 4% of 2,300; ± CI). It substantially reduced vegetation height by 14% in B1yr, 20% in B3yr and 12% in the Control plots, while it reduced above-ground biomass by 18% of 77.7 Mg/ha (B1yr), 31% of 56.6 (B3yr), and 15% of 120 (Control). Tree damage was greatest near the agricultural field edge in all three plots, especially among large trees and in B3yr. Trunk snapping (70%) and uprooting (20%) were the most common modes of tree damage and mortality, with the height of trunk failure on the burned plots often corresponding with the height of historical fire scars. Of the windstorm-damaged trees, 80% (B1yr), 90% and s57% (Control) were dead 4 years later. Trees that had crown damage experienced the least mortality (22%-60%), followed by those that were snapped (55%-94%) and uprooted (88%-94%). 4. Synthesis. We demonstrate the synergistic effects of three kinds of disturbances on a tropical forest. Our results show that the effects of windstorms are exacerbated by prior degradation by fire and fragmentation. We highlight that understorey fires can produce long-lasting effects on tropical forests not only by directly killing trees but also by increasing tree vulnerability to wind damage due to fire scars and a more open canopy.

We studied the damage caused to unfelled trees during skidding operations in four beech stands of northern and central Greece that were managed under differing harvesting systems.After timber was harvested we recorded and analyzed all damage to a width of 2 m along both sides of the skid trails.The percentage of damaged residual trees was 17–28 %.Higher numbers of saplings were uprooted or destroyed in parts of the stands with high natural regeneration.Most damaged trees suffered 1.33–1.90 wounds that were inflicted up to a height of 1 m above ground level.At all sites mean wound sizes were large,89–1190 cm2,and caused elevated risk of future fungal infection.The damage caused by skidding during timber harvesting can be minimized by better planning the harvest operations,and training forest workers in reduced impact logging.

Tree mortality is an important outcome of many forest fires. Extensive tree injuries from fire may lead directly to mortality, but environmental and biological stressors may also contribute to tree death. However, there is little evidence showing how the combined effects of two common stressors, drought and competition, influence post-fire mortality. Geographically broad observations of three common western coniferous trees subjected to prescribed fire showed the likelihood of post-fire mortality was related to intermediate-term (10 yr) pre-fire average radial growth, an important component of tree vigor. Path analysis showed that indices of competition and drought stress prior to fire can be described in terms of joint effects on growth, indirectly affecting post-fire mortality. Our results suggest that the conditions that govern the relationship between growth and mortality in unburned stands may also apply to post-fire environments. Thus, biotic and abiotic changes that affect growth negatively (e.g., drought stress) or positively (e.g., growth releases following thinning treatments) prior to fire may influence expressed fire severity, independent of fire intensity (e.g., heat flux, residence time). These relationships suggest that tree mortality may increase under stressful climatic or stand conditions even if fire behavior remains constant.

Context Global change is leading to more frequent and intense tree damage and mortality events. Drought-induced tree mortality is occurring worldwide leading to broad-scale events, but the spatial patterns of tree damage and mortality, their underlying drivers and their variation over time is largely unknown. Objectives We investigated the spatial patterns of tree damage and mortality across Mediterranean forests of the Iberian Peninsula, the underlying effects of stand structure and climate, and how the spatial patterns and relationships with underlying drivers changed over time. Methods We used the Spanish Forest Inventory to analyse the autocorrelation in tree damage and mortality across forest types, hurdle-gamma models to quantify the effect of stand structure and climate on tree damage and mortality, and cross-correlograms to assess their spatial dependence and its change over time. Results We observed a greater magnitude and a stronger autocorrelation in tree damage than mortality, with positive aggregation up to 20 kms. There was a spatial dependence between tree damage and mortality with their drivers, with spatial aggregation increasing with water availability, drought intensity and stand structure. The spatial dependence of tree damage and mortality with the underlying drivers increased over time, particularly for drought intensity. Conclusions Our results suggest that the combined effect of intense competition and drought could favour more extensive die-off and tree mortality events, providing key information for identifying vulnerable areas and the planning of adaptation measures.

Hurricane winds can have large impacts on forest structure and dynamics. To date, most evaluations of hurricane impacts have focused on short-term responses after a hurricane, often lacked pre-hurricane measurements, and missed responses occurring over longer time scales. Here, we use a long-term data set (1974-2009, 35 years) of tree stems (>3 cm in diameter at 1.3 m aboveground) in four sites (0.35 ha in total) in montane rain forest (∼1600 m elevation) in Jamaica to investigate the patterns of crown damage in individual stems by Hurricane Gilbert in 1988, and how subsequent growth and mortality were affected by hurricane damage, sprouting, and the incidence of multiple stems. Topographical position on a mountain ridge was the best predictor of crown damage, followed by crown size and species identity. The average diameter growth rate of stems that survived the hurricane was greater than that pre-hurricane for the whole 21-yr post-hurricane period. Growth rates of stems with damaged crowns increased less than those with undamaged crowns; differences in growth rate between damaged and undamaged trees disappeared after 11 years. Hurricane-damaged stems had two to eight times higher mortality than undamaged stems for 19 years post hurricane. Many stems sprouted shortly after the hurricane, but few sprouts managed to establish (grow to >3 cm diameter at breast height). However, sprouting and multi-stemming were associated with reduced mortality rate, particularly in damaged trees. From an initial population of 1670 stems in 1974, 54% were still alive in 2009 (21 years after the hurricane). We conclude that despite the high frequency of hurricane damage to tree crowns and the subsequent increased mortality rate in this hurricane-prone tropical montane forest, many stems will be hit and recover from several hurricanes in their lifetime.

The ability of tree stems to recover from damage is critical for tree survival and may explain species distributions across disturbance regimes. Two primary responses to stem damage, decay compartmentalization and wound closure, act in concert to limit decay and pathogen spread. A previous study demonstrated a tradeoff between wound responses that varied with anatomical traits, but its wide taxonomic range made it hard to analyze responses in an evolutionary context. Here, we tested the stem wound responses of 13 species of Quercus inhabiting three habitats across a gradient of fire intensity. We also quantified anatomical and structural traits and phylogenetic position, in order to assess the relative contributions of ecological adaptation and phylogenetic history in determining traits. Xylem anatomical traits were phylogenetically constrained, while phloem traits and damage responses varied with habitat. Across habitats, hammock and sandhill species closed bark wounds effectively, whereas scrub species limited the spread of xylem decay. There was a tradeoff between wound closure and decay compartmentalization within the white+live oaks. The fact that some wound response traits are phylogenetically constrained while others respond to ecological pressures suggests that damage responses integrate mechanisms operating at several levels within plants.

ContextThe southeastern U.S. experiences tornadoes and severe thunderstorms that can economic and ecological damages to forest stands resulting in loss of timber, reduction in short-term carbon sequestration, and increased susceptibility to forest pests and pathogens.ObjectivesThis project sought to determine landscape-scale patterns of recurring wind damages and their relationships to topographic attributes, overall climatic patterns and soil characteristics in southeastern forests.MethodsWe assembled post-damage assessment data collected since 2012 by the National Oceanic and Atmospheric Administration (NOAA). We utilized a regularized Generalized Additive Model (GAM) framework to identify and select influencing topographic, soil and climate variables and to discriminate between damage levels (broken branches, uprooting, or trunk breakage). Further, we applied a multinomial GAM utilizing the identified variables to generate predictions and interpolated the results to create predictive maps for tree damage.ResultsTerrain characteristics of slope and valley depth, soil characteristics including erodibility factor and bedrock depth, and climatic variables including temperatures and precipitation levels contributed to damage severity for pine trees. In contrast, valley depth and soil pH, along with climactic variables of isothermality and temperature contributed to damage severity for hardwood trees. Areas in the mid-south from Mississippi to Alabama, and portions of central Arkansas and Oklahoma showed increased probabilities of more severe levels of tree damage.ConclusionsOur project identified important soil and climatic predictors of tree damage levels, and areas in the southeastern U.S. that are at greater risk of severe wind damage, with management implications under continuing climate change.