Lightning is an important agent of tree mortality in many forests. Despite its extremely powerful and often lethal effects, lightning damage is highly variable and factors that influence tree response to lightning remain unquantified. Circumstantial evidence suggests that differences in tree electrical properties are the proximate mechanism underlying these patterns. We compared electrical resistivity among species of trees and lianas (woody vines) in a seasonal rainforest in central Panama. We combined these results with similar data from temperate forests to test the hypothesis that plant characteristics affect how they dissipate the energy of lightning strikes. Specifically, we used a modeling approach to determine how lightning energy dissipation differs among tree species and size classes. To test the previous hypothesis that lianas protect trees from lightning, we also modeled lightning energy dissipation by trees supporting lianas. We further examined such patterns in the context of lightning strikes that differ in total power.
Results/Conclusions
The results of the model supported our predictions. Specifically, lightning energy dissipation differed among tree species by up to ca. 300%, with the lowest predicted energy dissipation by Jacaranda copaia and the highest by Pinus resinosa. Estimated energy dissipation by tropical trees tended to be lower than by temperate trees. Within a species, predicted energy dissipation density by small trees was substantially greater than by large trees, such that energy dissipation density by a 10 m tall individual of A. blackiana was ca. 5000% greater than by a 30 m individual. Likewise, the energy dissipation density by Dipteryx panamensis differed ca. 4000% between 10 m and 30 m tall individuals. Estimated energy dissipation was lower in lianas than trees, and the model suggests that trees infested with multiple lianas are largely spared the damaging effects of lightning strikes. These patterns have implications for future forest structure in an altered climate that likely will include higher lightning frequency.