What is this damage?

So we're working on an analysis of structural damages for university and im having problems figuring out what this is supposed to be. It's obviously mold that grew because of the water dripping down on it since it's outside. So far we're about to plan alternatives in construction to protect the soon to be installed new wooden beams but before that happens we will have to describe the damage in the most scientific way. Google doesnt help me aß much aß i thought it would, maybe some of you have a clue and can help out?