The Electrical Pathway and Instantaneous Effects
When lightning strikes a tree, the immense electrical current seeks the path of least resistance to the ground. This path is often found just beneath the bark, where the tree’s sapwood and cambium layers are rich in water and sap. These fluids act as conductors, allowing the current to surge through the tree’s internal structure. The instantaneous passage of this current causes the water and sap within the tree’s cells to heat rapidly and vaporize.
This rapid heating converts the moisture into superheated steam within milliseconds. The sudden expansion of this steam generates explosive pressure inside the tree. This internal pressure can cause the tree’s tissues to rupture, leading to immediate physical effects.
Visible Damage and Structural Impact
The explosive pressure generated by the vaporizing sap often results in immediate, visible damage to the tree’s external structure. A common outcome is the stripping of bark, as the steam forcefully expands and tears away the outer protective layers. This can create long, vertical grooves or channels along the trunk. The intense heat can also cause charring or scorching on the bark and underlying wood, leaving distinct burn marks.
Beyond bark damage, the internal pressure can lead to the splitting or shattering of the trunk and branches. This mechanical damage can range from minor cracks to large sections of the tree. The severity of this structural impact depends on factors such as the tree species, its moisture content, and the intensity of the lightning strike.
Subtle and Delayed Consequences
Even if a tree appears to withstand a lightning strike with minimal visible damage, it can suffer from internal injuries with delayed effects. The cambium layer, located just beneath the bark and responsible for growth, can be severely damaged or destroyed by the electrical current and heat. This injury can disrupt the tree’s ability to transport water and nutrients, leading to a gradual decline. Root damage can also occur, as the current may spread into the surrounding soil.
This hidden damage compromises the tree’s overall health. A lightning-struck tree often becomes more susceptible to secondary issues, such as fungal infections, insect infestations, and diseases. These organisms can exploit the weakened tissues and compromised immune system, leading to decay and eventual death, sometimes months or even years after the initial strike. The long-term prognosis for a lightning-struck tree is often uncertain, regardless of its initial appearance.