The scenario immediately reminds me of the MR James story The Ash Tree where a tree plays host to some particularly nasty denizens which plague the local lord of the manor. Indeed, trees and death have a long association. The wold over they are used as improvised gibbets, and in certain cultures "Burial Trees" support corpses or coffins. The idea that trees can grow from seeds nourished by corpses links them to re-birth and the cycle of life. Jesus was, of course, nailed to one, albeit dismembered into the constituent parts of a crucifix.
The comedian Steve Punt recorded an investigative radio programme on the Bella case and it is well worth a listen. Though light-hearted, he uncovers some interesting facts about the case and potential links to local covens, war time spies and even conspiracies. It is now unlikely that we'll ever know the full facts surrounding this mysterious corpse, but I am sure it will continue to shape the psychogeography of the region.
Props to the excellent Hedge Row Devil tumblr for putting me onto this horrible bit of folk history, and for being the source of the images above.