Yellow Birch trees, (this isn't one of them), in particular, are known around here for living on even when knocked down by other falling trees or by wind storms, as long as some part of the roots are still in the ground. You will see new branches leading vertically from a fallen tree and starting new life in that position. Also, when the trunk begins to rot out in the centre the upper part of the tree will send down new roots, bypassing the rotten area and continuing to feed the upper part of the tree.