Breaking compatible trees with an axe will cause connected valid blocks to be destroyed, creating a "tree feller" effect. Each block destroyed uses one durability on the axe, regardless of the unbreaking enchantment.
Valid Blocks
Additionally, Wart Blocks, Shroomlights, and Mangrove Roots connected to logs are broken.
Technical Details
The connected blocks are broken in a width-first manner and the process can be terminated either
naturally: When the algorithm runs out of connected valid blocks, or
forcefully: When either 256 blocks have been destroyed, or 32 recursion layers have been exceeded.