The TWI researchers that are looking into this can’t totally explain the wood welding phenomenon, actually. They think the cellular structure melts and forms an unknown matrix which cools into a stable joint, now actually a feature of a single fused object. During the fusing process, charred wood is ejected in tight shavings, meaning that some portion of the wood is actually burned away as the friction process begins.
Wer seinen Kindern beibringt, dass man Holz nicht schweißen kann, muss sich eines besseren belehren lassen.