 "In vitro" mycorrhizal associations formed with non-pine species include Pacific madrone, bearberry, western larch, Sitka spruce, and coast Douglas-fir.Fungal growth is inhibited by the presence of high levels of the heavy metals cadmium (350 ppm), lead (200 ppm), and nickel (20 ppm).During the regrowth of pine trees after disturbance like clearcutting or wildfire, there appears an orderly sequence of mycorrhizal fungi as one species is replaced by another.