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ABSTRACT Lightning frequency in tropical forests has been increasing for decades and lightning is a major agent of forest biomass mortality, but the implications of increased lightning frequency are unclear. Here, we provide a species‐ and spatially explicit implementation of lightning in a mechanistic forest dynamics model. We evaluated the model's ability to reproduce current‐day observations in a Panamanian tropical forest, and the sensitivity of model outputs to plausible changes in lightning frequency. The lightning‐enabled model simulated aboveground biomass (AGB), carbon flux, and stem densities that were consistent with observations. As expected, AGB declined with increasing lightning frequency. However, the magnitude of AGB decline was greatly reduced when trees were assigned empirically derived, species‐specific lightning tolerances. Changes in species composition weakened the sensitivity of AGB to increasing lightning: the AGB of a small number of large‐statured, lightning‐tolerant species increased with increasing lightning frequency. In addition, the effect of lightning on AGB tended to saturate at high lightning frequencies because of the combined effect of changes in size structure and composition. Specifically, the number of large, lightning‐susceptible trees was relatively small at high lightning frequencies. Overall, this study shows that an empirically informed representation of lightning captures the contemporary effects of lightning on forests, indicates that changes in lightning frequency will change forest AGB, species composition, and size structure, and shows that forests can partially acclimate to higher lightning frequency through changes in composition. Thus, more widespread inclusion of the lightning into global ecosystem models would be an important step toward improving simulations of forest responses to global change. 

ABSTRACT Falling to the ground is hazardous for arboreal ants. Workers of six ant species dropped onto leaves had the lowest landing success on inclined and wet leaves; epiphyll presence and ant body size had no effect. Consequently, landing on leaves in wet forests apparently is challenging for arboreal ants. 

Summary Lightning strikes kill hundreds of millions of trees annually, but their role in shaping tree life history and diversity is largely unknown.Here, we use data from a unique lightning location system to show that some individual trees counterintuitively benefit from being struck by lightning.Lightning killed 56% of 93 directly struck trees and caused an average of 41% crown dieback among the survivors. However, among these struck trees, 10 direct strikes caused negligible damage toDipteryx oleiferatrees while killing 78% of their lianas and 2.1 Mg of competitor tree biomass. Nine trees of other long‐lived taxa survived lightning with similar benefits. On average, aD. oleiferatree > 60 cm in diameter is struck by lightning at least five times during its lifetime, conferring these benefits repeatedly. We estimate that the ability to survive lightning increases lifetime fecundity 14‐fold, largely because of reduced competition from lianas and neighboring trees. Moreover, the unusual heights and wide crowns ofD. oleiferaincrease the probability of a direct strike by 49–68% relative to trees of the same diameter with average allometries.These patterns suggest that lightning plays an underappreciated role in tree competition, life history strategies, and species coexistence. 

ABSTRACT Lightning is an important agent of tree mortality and gap formation. Here we quantified spatial and temporal patterns of lightning‐caused canopy disturbance in a 50‐ha plot in Panama using monthly drone imagery, and compared these patterns with field measurements of disturbance severity and spatial extent. Of 22 lightning strikes that we tracked, the impacts of 18 were monitored for at least 12 months (range of 17–50 months), and 67% of these 18 strikes led to canopy disturbances. The mean time for the first and last canopy disturbance to appear post‐strike was 8.2 months (range: 0.8–14 months) and 14.6 months (range: 0.8–23.9 months), respectively. Canopy disturbances were generally highly irregular in shape (i.e., not circular), and clustered around the rooting point of the directly struck tree. A mean of 43% (± 19%) of the total lightning‐associated canopy disturbance area was within 10 m of the rooting point, whereas only 3% (± 5%) occurred 30–40 m from this point. Drone‐based measurements of canopy disturbance area and volume were good predictors of variation in ground‐estimated dead biomass (r² = 0.48 and 0.46, respectively), reflecting their strong association with overstory dead biomass (r² = 0.42 and 0.41, respectively). The total drone‐estimated canopy disturbance area was 49% of the ground‐estimated canopy disturbance area. Thus, lightning typically causes canopy disturbances that are detectable with drone imagery despite their irregular shape, and drone‐detected gap formation lags 8–15 months poststrike, potentially disconnecting drone‐detected disturbances from their ultimate cause. 

Urbanization tends to increase local lightning frequency (i.e. the ‘lightning enhancement’ effect). Despite many urban areas showing lightning enhancement, the prevalence of these effects is unknown and the drivers underlying these patterns are poorly quantified. We conducted a global assessment of cloud-to-ground lightning flashes (lightning strikes) across 349 cities to evaluate how the likelihood and magnitude of lightning enhancement vary with geography, climate, air pollution, topography and urban development. The likelihood of exhibiting lightning enhancement increased with higher temperature and precipitation in urban areas relative to their natural surroundings (i.e. urban heat islands and elevated urban precipitation), higher regional lightning strike frequency, greater distance to water bodies and lower elevations. Lightning enhancement was stronger in cities with conspicuous heat islands and elevated urban precipitation effects, higher lightning strike frequency, larger urban areas and lower latitudes. The particularly strong effects of elevated urban temperature and precipitation indicate that these are dominant mechanisms by which cities cause local lightning enhancement. 

Abstract Temperature extremes often limit animal distributions. Whereas some poikilotherms (e.g., winged insects) can escape local thermal extremes, many less vagile organisms (e.g., insect larvae and arthropods with limited dispersal ability) are at the mercy of local microenvironmental conditions. Here, we quantified the thermal tolerance of an abundant, endemic, Nearctic millipede (Euryurus leachii), and explored the effects of seasonality, mass, and sex on its critical thermal maxima (CTmax). We also measured the thermal microenvironments of dead wood representing different decay classes. Overall, the mean CTmax for this species was ca. 40.5°C. Mass and sex had no effect on millipede CTmax. However, the mean CTmax for millipedes collected in the fall was 0.6°C higher than for individuals collected in the spring. An exposed dry log representing one common microhabitat for E. leachii readily warmed to temperatures exceeding its CTmax. The results suggest that CTmax is a seasonally plastic trait in E. leachii and that microclimatic conditions potentially limit the local distribution of this species. With habitat fragmentation and climate change contributing to warmer temperatures in forested systems, understanding the responses of detritivores like E. leachii can help predict potential shifts in community composition and ecosystem processes. 

Synopsis Arboreal ants must navigate variably sized and inclined linear structures across a range of substrate roughness when foraging tens of meters above the ground. To achieve this, arboreal ants use specialized adhesive pads and claws to maintain effective attachment to canopy substrates. Here, we explored the effect of substrate structure, including small and large-scale substrate roughness, substrate diameter, and substrate orientation (inclination), on adhesion and running speed of workers of one common, intermediately-sized, arboreal ant species. Normal (orthogonal) and shear (parallel) adhesive performance varied on sandpaper and natural leaf substrates, particularly at small size scales, but running speed on these substrates remained relatively constant. Running speed also varied minimally when running up and down inclined substrates, except when the substrate was positioned completely vertical. On vertical surfaces, ants ran significantly faster down than up. Ant running speed was slower on relatively narrow substrates. The results of this study show that variation in the physical properties of tree surfaces differentially affects arboreal ant adhesive and locomotor performance. Specifically, locomotor performance was much more robust to surface roughness than was adhesive performance. The results provide a basis for understanding how performance correlates of functional morphology contribute to determining local ant distributions and foraging decisions in the tropical rainforest canopy. 

Abstract Lightning is a common agent of disturbance in many forest ecosystems. Lightning-damaged trees are a potentially important resource for beetles, but most evidence for this association is limited to temperate pine forests. Here, we evaluated the relationship between lightning damage and beetle colonization of tropical trees. We recorded the number of beetle holes on the trunks of trees from 10 strike sites (n = 173 lightning-damaged trees) and 10 matching control sites (n = 137 control trees) in Panama. The trunks of lightning-struck trees had 370% more beetle holes than control trees. The abundance of beetle holes increased with increasing total crown dieback among both control and lightning-damaged trees, and with larger tree diameter among lightning-struck trees. Beetle holes also were more abundant in trunk sections of lightning-damaged trees located directly below a damaged section of the crown. The results of this study suggest that lightning damage facilitates beetle colonization in tropical forest trees and provide a basis for investigations of the effects of lightning-caused disturbance on beetle population dynamics and assemblage structure.