dead organisms are the source of nutrients for decomposers & dead organisms rot ->  rotting organisms are a source of nutrients for decomposers  a mushroom is a kind of fungus & in the food chain process fungi have the role of decomposer ->  in the food chain process mushrooms have the role of decomposer  rotting organisms are a source of nutrients for decomposers & in the food chain process mushrooms have the role of decomposer -> rotting organisms are a source of food for mushrooms