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Re: [OM] IMG: Death of an Oak Tree

Subject: Re: [OM] IMG: Death of an Oak Tree
From: "Brian Swale" <bj@xxxxxxxxxxxxxxx>
Date: Thu, 17 Sep 2009 03:20:23 +1200
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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