COS 123-4 - Lianas amplify the severity of lightning-caused disturbance in a neotropical forest

Abstract: Lightning is an important agent of plant mortality and disturbance in tropical forests. Lightning-caused disturbance (hereafter lightning disturbance) is highly variable in terms of its area of effect and disturbance severity (i.e., tree damage and death), but we do not know how this variation is influenced by forest structure and plant composition. We hypothesized that lianas increase the severity and area of lightning disturbance by providing electrical connections among trees. We used a novel lightning detection system to quantify how lianas influenced the severity and spatial extent (i.e., area) of lightning disturbance using 78 lightning strikes in central Panama.

The local density of lianas (measured as liana basal area) was positively associated with the number of trees killed and damaged by lightning, and patterns of plant damage indicated that this occurred because lianas facilitated more electrical connections from large to small trees. Liana presence, however, did not increase the area of the disturbance. Thus, lianas increased the severity of lightning disturbance by facilitating damage to additional trees without influencing the footprint of the disturbance. These findings indicate that lianas spread electricity to damage and kill understory trees that otherwise would survive a strike. As liana abundance increases in tropical forests, their negative effects on tree survival with respect to the severity of lightning-related tree damage and death is likely to increase.