Ash

This is the stump of an ash tree, felled years ago. Ash rots at the base a long time before there is any damage to the rest of the tree. If you leave it, it will fall in a strong wind, tearing out all the useful nooks and crannies formed where it is rotting. So often we fell as soon as there is substantial decay, and the wood has many of these useful structures, moss covered and full of creatures.