Understanding forks a bit more

Today I attended an Arboricultural Association workshop presented by Dr. Duncan Slater entitled Assessment of Tree Forks.

I thought I should share my take on it as I find it very important for people in my industry to consider these things.

The workshop is based on research by the above doctor and his associates. There were many points raised, but what I found most relevant to myself and I believe to anyone inspecting and/climbing trees in a commercial manner, are the uses of terms such as compression forks and tight unions to denote high risk of failure unions. It was proven that there is no compressive force pushing forks with included bark apart and that a fork with an acute angle does not necessarily mean that it is weak or without a branch bark ridge/with bark inclusion. Weak forks are most often formed when little or no pressure is exerted on their apex/top but this is usually because they are supported higher up in the canopy by crossing/rubbing branches or/and actually fused branches. A weak fork will not fail if it is supported.

What this means in practical terms is that one should think twice about crown cleaning crossing branches despite the commonly accepted practice to remove crossing branches because they can lead to branch failure.

This also means that if supporting branches decay, the fork must build sufficient reaction wood before it is subjected to a force strong enough to make it fail. The period before it has done this is when such forks are at the highest risk of failing. Some forks with included bark will never be able to reinforce themselves sufficiently, but these types of forks can be identified.

It is important to know your forks when working with trees and this has helped me be more confidant in my tree assessments.

For all the references, you will need to attend the workshop as there are too many for me to site here at this time

Where was today's? I went Tuesday to myerscough.

Cool, How did you find it?

It was at Askham Bryan, York

Interesting but I had already read a lot of his papers and heard Duncan at last years conference, so not too much new.

I'm still in two minds about the 'new model of Branch attachment'. I'm not sure that Alex Shigos model hasn't been taken too literally, then been condemned as being wrong. Duncan really didn't expand on his his model and the workshop notes provide no real answers- to my mind.

Guess I'm going to have to do some reading to get my head around it.

I found the fork formation quite interesting, though provoking and logical however, i think there is a difference between branch attachment and fork formation and im not sure that was explained very well or maybe i didnt grasp it so well.

Overall im definitely glad i made the effort to go and i agree with Duncan that things move on and maybe now due to advances in technology we are able to improve on research that was done many years ago as in years to come we will progress further.

Hopefully:001_huh:

MM

But, to be fair, it was a fork workshop and forks were well explained.

I'm just a layman at this and am not setting out to discredit the work done and might be missing the points completely.

My experience. Up in and around woody plants is....Acute angle forks are rarely sound in their loading ability in conifers and broad leafs. If they are ok because they are supported it's still negative for the plant, if the support dies or is damaged it doubles the death or damage potentially miss shaping and damaging, could create a heavy lean

Few trees actually graft naturally to really inter support themselves.

When forked tissue is exerted upon it nearly always causes far more and deeper wounding. Something else that does this is trilobata type growth where a pair of opposite buds normal for some genetic reason have 3. Acers and malus 2 species that this occurs in.

Fastigate forms (upright narrow) poplars etc the wound of a branch torn away is often deep due to the acute angle of growth and the tissue along with leverage exerted upon it.

I often see young forks in tree and despite the temporary misshape that would result am inclined to remove it for long term development.

Size for size a wider angled branch is much stronger to stand on when in the tree. A crotch that would snap out with a foot close to the main stem.Would bear the same weight without failure upto 30cm away from the main stem. As an example.Species dependant.

With the freak winds we sometimes get, even if someone never climbs the tree, surely it's better to engineer in flexibility to resist damage with wider angled stronger wood.

In many cases it's too late.

Yeah, I definitely have more questions and I need to read through the notes and I need to make observations.

Goaty, what do you mean by "could create a heavy lean"?

Yes, I don't know many trees that actually fuse and if those stabilizing branches go then the system is compromised, but, apparently, maybe only temporarily.

I would have always pruned out small branches with inclusions before but now I would like to observe if they reinforce themselves as they are exposed to more stress.

There are definitely some trees that have genetic tendencies to make poor forks.

Some forks with tight unions have a branch bark ridge but it is indeed rare. I really don't think a wider angle makes a stronger branch if that branch has a well formed branch bark ridge and bulging at the fork base, but I will be keeping an eye out and doing some tests with trees we take down.

Sounds like this talk left its attendees more puzzled than informed. Not sure I will attend now.

Heavy lean explained better. It wasn't perhaps the best nor most accurate terminology. Unbalanced maybe a better phrase.

If a tree has a fork that breaks out, the remaining tree can be lop sided in its balance of weight and volume, should strong wind come or even the growth stay dominant at than side. It is biased to go one way when it does fail. Depending on fungal attack, wind, old age or young growth, species and soil structure/anchorage.

My heavy lean expression was just to sum up the above stresses exacerbated by fork failure possibly leading to plant failure.

Although I have done a lot of tree climbing. Most of my experience is the training and manipulating of growth in nursery stock production. Built on that I have Sussed angles of flex and yield and it's only my opinion that it carries through in larger specimens. I've never climbed with harness or rope, so I have a blooming good idea of branch yield failure point.

Yes when you start to research something like this which is a variable question. It's not suprising you end up with more questions instead.