My lovely Cotoneaster horizontalis has suffered a significant set back. I collected this tree myself eight years ago, and you can see something of its history here. By 2011 there were already some signs of it loosing vigor on one side and this gradually progressed. My guess is that the carving disrupted sap flow and that the remaining foliage was not sufficient to support the cambium and root mass in that part of the tree, trees are segmented organisms in this way and the remaining branches are very vigorous. I will allow free growth this year, to ensure maximum health, and then radically restyle in 2017.
From old ends come new beginnings, and it is common to see old oaks, formerly giants, reduced to a single live branch that becomes a new canopy.