In the context of mushrooms, saprotrophic just means that the fungus uses already dead or dying plant material for sustenance.
This is in contrast to parasitic fungi, which will actually hasten the death of their host plants; for example ganoderma zonatum, or reishi mushroom.
Your trees and landscaping are not really threatened by saprotrophic fungi unless they are already sick or dying, which can happen anywhere. That said, you will find saprotrophic & parasitic fungi of varying types pretty much all over the world.
The possible fungus mentioned in the post you reference (Oyster Mushrooms) are in fact not parasitic, but consume already dead or dying material & are a choice edible!
But, (to the OP's knowledge), not found on non-hardwood species.