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Abstract In lowland tropical forests, “arthropod rain” (i.e., arthropods falling from the canopy to the understory), represents a potentially important terrestrial nutrient flux.We investigated the composition, abundance, biomass and environmental drivers of arthropod rain on Barro Colorado Island, Panama. Pairs of traps (pan traps and pole traps) placed 1 m above the ground, respectively, collected fallen arthropods and arthropods potentially climbing to the canopy.Average (±SE) arthropod biomass in pan traps was dominated by Hymenoptera (primarily ants; 0.501 ± 0.023 mg dry mass m⁻² day⁻¹) and Lepidoptera larvae (0.228 ± 0.001 mg m⁻² day⁻¹). Total dry biomass in pan traps was 0.891 ± 0.033 mg m⁻² day⁻¹; thus, ca. 27 kg of arthropod biomass rains into the understory per km²per month during the wet season in this forest. This equates to ca. 3 million mid‐sized ants falling from the canopy per day on BCI as a whole.Arthropod abundance in pan traps, especially ants and spiders, increased marginally with the increasing number of high‐wind events. By contrast, arthropod biomass showed no relationship with wind or rain.Arthropod abundance was higher in pole traps than in pan traps and was dominated by Collembola and Acari. Compositional overlap between pan and pole trap contents suggests that some fallen arboreal arthropods regularly return to the canopy.These findings illustrate an understudied pathway linking canopy and understory food webs within tropical forests, and the complex interactions between environmental conditions and arthropod rain. 

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. 

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 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. 

Abstract Lightning strikes are a common source of disturbance in tropical forests, and a typical strike generates large quantities of dead wood. Lightning‐damaged trees are a consistent resource for tropical saproxylic (i.e., dead wood‐dependent) organisms, but patterns of consumer colonization and succession following lightning strikes are not known. Here, we documented the occurrence of four common consumer taxa spanning multiple trophic levels—beetles,Aztecaants, termites, and fungi—in lightning strike sites and nearby undamaged control sites over time in a lowland forest of Panama. Beetle abundance was 10 times higher in lightning strike sites than in paired control sites, and beetle assemblages were compositionally distinct. Those in strike sites were initially dominated by bark and ambrosia beetles (Curculionidae: Platypodinae, Scolytinae); bark and ambrosia beetles, and predaceous taxa increased in abundance relatively synchronously. Beetle activity and fungal fruiting bodies, respectively, were 3.8 and 12.2 times more likely to be observed in lightning‐damaged trees in strike sites versus undamaged trees in paired control sites, whereas the occurrence probabilities ofAztecaants and termites were similar between damaged trees in lightning strike sites and undamaged trees in control sites. Tree size also was important; larger dead trees in strike sites were more likely to support beetles, termites, and fungal fruiting bodies, and larger trees—regardless of mortality status—were more likely to hostAzteca. Beetle presence was associated with higher rates of subsequent fungal presence, providing some evidence of beetle‐associated priority effects on colonization patterns. These results suggest that lightning plays a key role in supporting tropical insect and fungal consumers by providing localized patches of suitable habitat. Any climate‐driven changes in lightning frequency in tropical forests will likely affect a broad suite of consumer organisms, potentially altering ecosystem‐level processes. 

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 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. 

Abstract Temperature is a key abiotic condition that limits the distributions of organisms, and forest insects are particularly sensitive to thermal extremes. Whereas winged adult insects generally are able to escape unfavorable temperatures, other less-vagile insects (e.g., larvae) must withstand local microclimatic conditions to survive. Here, we measured the thermal tolerance of the larvae of three saproxylic beetle species that are common inhabitants of coarse woody debris (CWD) in temperate forests of eastern North America: Lucanus elaphus Fabricius (Lucanidae), Dendroides canadensis Latreille (Pyrochroidae), and Odontotaenius disjunctus Illiger (Passalidae). We determined how their critical thermal maxima (CTmax) vary with body size (mass), and measured the thermal profiles of CWD representing the range of microhabitats occupied by these species. Average CTmax differed among the three species and increased with mass intraspecifically. However, mass was not a good predictor of thermal tolerance among species. Temperature ramp rate and time in captivity also influenced larval CTmax, but only for D. canadensis and L. elaphus respectively. Heating profiles within relatively dry CWD sometimes exceeded the CTmax of the beetle larvae, and deeper portions of CWD were generally cooler. Interspecific differences in CTmax were not fully explained by microhabitat association, but the results suggest that the distribution of some species within a forest can be affected by local thermal extremes. Understanding the responses of saproxylic beetle larvae to warming habitats will help predict shifts in community structure and ecosystem functioning in light of climate change and increasing habitat fragmentation.