large branch split in ash.. ideas why?

[bob]

a well behaved tree turning itself into logs as it nows it,s days are up

[Ben90]

Yeah that's a hazard beam alright. Despite being open to fungus and significantly weaker, the branch shouldn't die back at all because of the direction of the split, very few vascular bundles are actually broken. It could've been caused by the epic snowfall in febuary, or indeed, ash being ash and over-reaching for light.

Edited September 13, 2009 by Ben90

[gmanntpo]

Depending on the target, this hazard beam could be stabilized by reducing the end weight...

 

It looks like a sizeable limb, so pruning back to the main stem would no doubt create a wound that would be colonisied by Inonotus hispidus.

 

Nevertheless, if the target value is high then complete removal is a valid option.. Personally I would reduce and monitor the branches reaction to that pruning..

[Ben90]

2 words: Ratchet strap.