Even the mightiest of trees have to fall at some point. Once they die they become food for countless species of fungi. Here are couple examples of such process with colorful mushrooms.
Fallen tree. Moisture collects in the bark. Moss starts to grow on it and initiates production of the soil on top of wood. Then mushrooms come in growing from the moss.
Wąwóz Lipy - here.
Next comes orange jelly. It might be sort of Tremella but I'm not even sure these are the same species on each picture. First one was from Wąwóz Lipy, next are two speciments from different parts of Mokrznia Forest near my garden.
Young jelly drops on fallen beech.
Coral spots painting dead branches.
Multiple different polypores on a single tree.
Most of them are probably Stereaceae