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From Wikipedia Site: (https://en.wikipedia.org/wiki/Ganoderma_applanatum)
“This fungus grows as a mycelium within the wood of living and dead trees. It forms fruiting bodies that are up to 30–100 centimetres (12–39 in) across, hard as leather, woody-textured, and inedible in raw form. They are white at first but soon turn dark red-brown. Brown spores are released from the pores on the underside of the fruiting body. The fruiting bodies are perennial, and may persist for multiple years, increasing in size and forming new layers of pores as they grow.
Ganoderma applanatum is a wood-decay fungus, causing a rot of heartwood in a variety of trees. It can also grow as a pathogen of live sapwood, particularly on older trees that are sufficiently wet. It is a common cause of decay and death of beech and poplar, and less often of several other tree genera, including alder, apple, elm, buckeye and horse chestnut, maple, oak, walnut, willow, western hemlock, Douglas Fir, old or sick Olive tree and Spruce.”