Mycorrhiza

This symbiotic relationship is called mycorrhiza. The roots and the mycelium exchange substances like nitrogen (mushroom to tree) and carbohydrates (tree to mushroom). The birch bolete, for example, is a mycorrhizal fungus on birch trees.

Parasitic mushrooms attack the tree. The cauliflower mushroom is a good example of this. Eventually a cauliflower mushroom will bring down a pine tree.

Saprophytic mushrooms digest dead organic matter and thus decompose dead leafs and wood.