Lianas increase lightning-caused disturbance severity in a tropical forest

Area of Science:

• Tropical ecology
• Forest disturbance dynamics
• Plant-environment interactions

Background:

• Lightning is a significant driver of tree mortality and forest disturbance.
• The variability in lightning disturbance severity and spatial extent is not fully understood in relation to forest structure and composition.
• Lianas are increasingly abundant in tropical forests, but their role in mediating lightning impacts is unknown.

Purpose of the Study:

• To quantify the influence of lianas on the severity and spatial extent of lightning disturbance.
• To investigate the mechanisms by which lianas affect lightning-induced tree damage and mortality.
• To assess the implications of increasing liana abundance for forest resilience to lightning strikes.

Main Methods:

• Utilized a novel lightning detection system to record 78 lightning strikes in central Panama.
• Measured liana density using liana basal area in the vicinity of lightning strikes.
• Assessed the spatial extent and severity (tree damage and mortality) of lightning disturbance.

Main Results:

• Local liana density was positively associated with the number of trees killed and damaged by lightning.
• Evidence suggests lianas facilitate electrical connections, spreading damage from large to smaller understory trees.
• Liana presence did not significantly increase the spatial area (footprint) of the lightning disturbance.

Conclusions:

• Lianas enhance the severity of lightning disturbance by increasing tree mortality beyond the immediate strike zone.
• Understory trees that might otherwise survive a lightning strike are killed due to electrical spread facilitated by lianas.
• Increasing liana abundance in tropical forests is likely to exacerbate tree mortality and alter forest dynamics in response to lightning events.