Some months ago I was exploring a large country park and came across an open field, in which there two oak trees and a mound that housed a couple of ash. One oak was particularly intriguing, for in its retrenchment it has remained in existence with only one strip of sapwood on one of its sides – the remainder of the structure is simply exposed heartwood, which is colonised by Laetiporus sulphureus at least in part.
The below images, which show the tree from all four sides, really do speak for themselves, though we can see that a small ‘crown’ has formed from the only functional sapwood that remains. This oak, assuming the sapwood connection is not drastically damaged, may remain living for many decades.
For more information on veteran and ancient trees, the Ancient Tree Forum has released three publications in PDF format. These are: (1) Ancient and other veteran trees: further guidance on management; (2) Veteran Trees: a guide to good management; and (3) Veteran Trees: a guide to risk and responsibility. The latter two can be found on Natural England’s website split into chapters, though here they are found as entire PDFs. The first book is new (as of 2013), and was written by David Lonsdale. I advise that you purchase a hard copy from the ATF, if you can.