When a Volcano erupts the lava destroys basically everything in it's path, that includes indigenous plants and animals.
Most animals manage to fly away or out run the burning lava.
Plants can't run away so they are burned badly or completely covered by lava. The lucky trees are turned into tree molds or lava trees. A lava tree is formed when lava surrounds a tree, cools around the trunk and the remained flows away. Some of the tree is left. Sometimes parts of the environment are spared.