Wound healing.

Interesting (if you are into it). The healing around what was a sawn off side branch on this ash tree shows signs of classic  chalara scar above and below the healing part, suggesting the side branch had already died  back from chalara when it was cut off, but the adjacent and subsequent healing was unaffected by the chalara.  To me this adds to the idea that the toxicity of chalara within the tree bark does not carry over from one year to the next and it is  a new infection from the leaf litter cycle each year whose annual effect is offset each year by new growth around the dead part: it is only when the dead parts completely ring a limb or trunk, before the new/healing growth is great enough, that the vascular system in that limb/trunk is completely over come and the limb/trunk dies.