Re: Jim Nichols' oak tree,
I am a forestry professional by training with a Masters degree in the field,
and for a good part of my paid employment I had significant responsibilities
in the area of forest pathology, though in the field of forest pathology on a
forest scale rather than on an individual tree scale..
In my opinion, while a reading of stem density (we never had such clever
devices in 'my' day) can give an indication of decay or other solid wood loss
in the zones assessed, the important indicator that Jim also mentioned is
leaf health during the growing season. For oak leaves to curl at the edges
and become prematurely brown indicates to me that there is at least one
pathogen of some sort (be it fungal, bacterial, viral nematodes; or insects; or
even a high level of soil water (drowned roots)) seriously interfering with
either the cambium layer in the lower stem / roots, or the roots themselves,
so that the tree is being starved of water and/or nutrient supply. Yes, trees
with hollow centres can be very strong, if a slow wood rot fungus is the only
pathogen at work, but clearly in the case of Jim's tree something else was at
work too.
There are many people in the USA who are skilled in assessing what are
called "hazard trees" in parks and other areas of high human use, and there
is a substantial literature on the topic.
I reckon that Jim had little other option than keeping ahead of the game as
he did in this instance.
Brian Swale.
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