Fomes (horses hoof) grows where it's wet.
Chaga grows really cold.
Razerstrop grows damp and like fomes can be found on other species.
Razerstrop and fomes are bracket fungus, they are fruiting bodies, chaga isn't.
cheers,
Toddy
I have been harvesting brackets in one form or another for donkeys years and the difference between damp and wet environments, in my experience, is indistinguishable one from the other, I have always found woodland to be both wet and damp. As for Chaga only growing where it is cold, I have it on good authority, i.e. from someone I dealt with a few years back, whose parent works for the Forestry Commission, that he could collect Chaga and Fomes from the same local in Scotland, which I presume was therefore both cold and wet enough to sustain both species. Anyhow, being a soft southerner, I always believed that Scotland was wet, cold and damp all year round at least it was when I went there with the Royal Artillery, so I always presumed that these fungi grew all over Scotland.
In my experience although many of the woodland, down south, have a variety of brackets growing on a variety of trees only the Birch Polypore grows on Silver Birch hence its name, I will qualify this by saying that I have never found it growing on anything else other than Silver Birch in the parts of the world that I usually frequent. The Horses Hoof fungus, I can say I have never seen growing on Silver Birch down south, but I have seen it growing on other trees.
Cheers,