[Greenbuilding] rot resistance

[RT]

On Tue, 17 Jul 2012 06:13:13 -0400, Grace Annam <grace.annam at gmail.com>  
wrote:

> On 2012/07/14 17:16 PM, Clarke Olsen wrote:
>
>> Heartwood will always perform better then sap wood.
>
>  And yet, here in New England,it seems like the maple trees always rot  
> from the ground up, in the heartwood.

There are a number of huge, old, still-living maples in the woods around  
my home where two or three people and their pets can walk into the hollow  
centre portion at the base of the tree and a then jump out and scare the  
bejeepers out of unsuspecting passersby.

There are also a few old Eastern White cedars (a species which is used  
extensively for fence posts) where you will see the hearts rotted out but  
the trees will continue to live for centuries.

The short answer to your question is that while tree is still alive, the  
sapwoood, living part of the tree, is capable of of an active response to  
rot-causing fungal invasion (due to the still-flowing sap) whereas the  
heartwood, the non-living part, does not.

A possible clue as to why maple seems to be more prone to such heart-rot  
might be given by observing what happens when you swing a splitting maul  
at a large chunk of still-green maple during non-freezing weather.

It'd likely that that maul will bounce back and hit you smack in the head  
rather than make a dent in the end of the maple block. We call it "rubbery  
maple". (ie Maple is tight-grained and holds a lot of moisture and takes a  
lot longer to dry than other more porous-grained woods like oak or ash.)

One notes that it's usually trees where limbs have broken off and the  
wound never healed properly, that you'll find rotted-out hearts in the  
still-living tree.

But for a better explanation, one would probably do well to Google  
"heartwood rot in living trees" or somesuch.

Me ? I'm going for a bike ride.

In the meantime y'all may enjoy this video that Habib John Gonzales  
http://www.sustainableworks.ca/ sent along the other day on the subject of  
"Starlings' murmurations".

http://vimeo.com/31158841





-- 
=== * ===
Rob Tom					AOD257
Kanata, Ontario, Canada

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