Why does standing dead Ash become so brittle

[devon TWiG]

Wet wood is always more "pliable " than dry wood , see steam bending , or just compare a dead stick from any tree to a live one ...hazel is an easy one to try .  Bigger Ash are ok as the butt is thick and will take some time to lose its moisture content , but the limbs up in the air could be well dry by then , also Ash is a fairly dry wood any way , and it has fairly large pores so moisture escapes quite readily  , personally I have found Sycamore the worst for trying to fell against the way it wants to go , and the hinge just snapping after very little movement .

[monkeybusiness]

5 minutes ago, EdwardC said:

Fungi can be latent in trees. Propogules, be it yeast type cells, fragments of hyphae, or something else can survive in trees for decades without germinating. Once conditions become suitable for the fungus, usually a reduction in moisture content, the fungus can become active and spread quite rapidly.

 

Also, if a fungus is active in a tree and the tree is resisting it, should something happen to the tree to reduce its vitality, the fungus may be able to breach the trees barriers and enter new substrate.

 

In ash one of the main decay fungi is Inonotus hispidus. This fungus can weaken the structure of the wood by selective delignification of the tips of the medullary rays. This significantly reduces the strength of the wood making it brittle and much less able to withstand sudden impact by up to 90%, and do it without any evidence of decay being visible in the wood. 

 

If an ash tree is weakened by Chalara, I. hispidus may get a hold in either of the above ways making the tree brittle. This is then observed when the tree is felled. 

 

Daldinia concentrica also affects the strength of the wood. Again, it can colonise quickly once conditions become suitable.

 

In summary. Whether its by emerald ash borer, or Chalara, the tree is weakened. I. hispidus becomes active making the timber brittle.

That makes sense and is brilliantly described. 

How come these issues don’t tend to present themselves on/in harvested timber though?