Lightning strikes, Canberra, Australia © Flickr/Prescott
Severe thunderstorms give rise to sudden electrical discharges in the form of lightning and thunder. They often bring heavy rain or hail, strong winds and occasionally snow and in some parts of the world they trigger tornadoes. In areas where lightning is not accompanied by rain, so-called dry lightning, it may also be a source of ignition for forest fires as noted in some remote areas of Canada and the Russian Federation. However it is generally recognized that the majority of forest fires are caused by humans and not by lightning.
Tall trees tend to be the most vulnerable to lightning strikes, especially those growing singly in open areas such as on hills, in fields, near water or in urban environments. Lightning can impact a tree’s biological functions and structural integrity. Along the path of the strike, sap boils, steam is generated and cells explode in the wood, resulting in strips of wood and bark peeling or being blown off the tree. Trees may survive if only one side of the tree shows evidence of a lightning strike; however when the strike completely passes through the trunk, trees are usually killed. Many trees can suffer severe internal or below-ground injury despite the absence of visible, external symptoms when the lightning passes through the tree and dissipates in the ground. Major root damage may cause the tree to decline and die.
Abiotic disturbances and their influence on forest health
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