How do you calculate percentage of canopy

vl2007

The standard is don't remove more than 25% of canopy, but how do you calculate canopy percentage? Diameter of trunk?

Pro Nemus

Are you asking just out of curiosity, or do you have a specific project in mind?

I have very rarely, if ever, had a job where we had to be significantly concerned with approaching the 25% point. I think that the true moral of this story is that less is more. If you develop a solid plan with objectives before starting to prune, and develop a course of action which accomplishes your objectives with the smallest possible quantity of cuts and volume of debris, you will seldom even have to think about the "25% Question".

However, if I had to estimate the pruning limits of a specific tree, I would most likely try to divide the canopy into "zones", and not go over 25% in any one zone.

Hope this helps.

arborjockey

I think that it dpends on the species. Certain vigerous types can be "Hard Pruned" taking off more then 25%. It also depends on the age of the tree and over all health. If you take a tree that has been slowly getting by ( from being in the wrong hardiness zone or poor soil conditions ect..). Then you come along and over prune it the tree may have a hard time recovering. It is good question though. To bad for us were not here long enough to see some of the results we have on trees. When you prune a 80 year old tree it would be nice to see it again when its 180yrs.old. Butchers beware!!!!!!! You will be brought out into the light. Time will show your work as fraud. The trees dont lie.

quercus

Don't forget that dead limbs and rubbing or other problematic branches are not to be included in the 25% maximum.

Therrin

I can't see how the diameter of the trunk would have much to do in direct relation to the amount of canopy. (but maybe I'm wrong...)

I've worked on stuff that had very little canopy towards the bottom, where the trunk is thicker, and had tons towards the top, where it is thinner. Also worked stuff that was pretty similar in DBH from there to 70', and stuff that was huge in diameter, but had very little in the way of canopy (some oaks)....
As well as some pines which are so thin...4" or so, that are just bursting with canopy...

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Ekka

Great question.

Often you'll here terms like ...

20% thin, 20% reduction, 25% of canopy etc.

In my opinion I consider it foliage, in absence of foliage I consider it SURFACE AREA at the tips as that is what leaves are all about.

This attached link to a pic will also help you.

http://www.treeworld.info/attachment...davidevans.jpg

Lets say you have a 100' tall tree and some-one tells you to do a 25% reduction.

Do you simply make the tree 75' tall? I hope not.

Here's another, with a 20% thin do you remove 20% of the branches? I hope not.

Trees use leaves and for the greater part it's the leaves surface area that photosynthesize and make food, provide shade, transpire, and make that wind resistant sail.

Imagine a tree with the traditional apple on a stick canopy. Lets say the canopy is 40' diameter like a big ball.

Lets say we want a 25% reduction. So now do we just make it a 30' diameter ball?

Lets look at this.

The formula for calculating surface area of a sphere is 4πr2, however I found an online calculator here

Volume and Surface Area of a Sphere - Geometry Calculator

40' tree canopy surface area is 5027'2

30' tree canopy surface area is 2827'2

So in the two answers above you see that using the "linear" method of reduction actually resulted in a 44% loss of canopy surface area (leaves and sail).

Now, we want a 25% reduction in canopy surface area.

The answer is 25% x 5027'2=1257'2 or leave the tree with a 3770'2 canopy surface area.

To achieve that we need a 34.64' big ball canopy.

Hope this made sense.

PS: This thread may be destined to the facts area if enough research is done.

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Sean Freeman

Lets not forget about the mistaken tendancy to lump all branches into the tree model, with larger tree species each large developed limb needs to be treated as an autonimous unit...ie I would not be very happy removing more than 25% of live foliage from any single limb structure (without good cause and sound reasoning) knowing that to do so will dramatically impact on the apical control operating within that limb.

For me this is where experience and knowing the species you are working on comes to the fore. A very great many Euc species have very sparse live foliage held far out on the ends of the limbs, almost naturally lions taiiled! Reduction/thinning etc is a real art with these trees...if you remove too much live foliage from the limb you will predispose that section of the tree to epicormic flushes, weakened chemical and physical defences...great care and consideration is needed...know why you are cutting and what the likely consequences will be.

One more oint try always to impress on clients the inportance of improving the soil root environment...yes they might be focussed soley on the leaves branches the stuff they can see...but we all know (I hope) that the real deal is in the ground. Keep the soil and roots healthy and thriving and you can have greater fllexibility up top with reductions/thinning etc...

BTW branch autonomy is kind of fascinating Coder has a little bit about it in his papers on chemical messaging in tree systems.

Growth control systems.pdf

Tree growth response systems.pdf

Control of shoot root balance.pdf

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Sean

Trees are poems that earth writes upon the sky,
We fell them down and turn them into paper,
That we may record our emptiness.
- Kahlil Gibran

Pro Nemus

Nice approach. What is your opinion on this?:

What you described is an "apple on a stick", but your surface-area calculation is more like a "balloon on a stick", with all of the mass on the outside, and nothing but air in the middle.

Because the leaf structure of the tree is spread throughout the canopy, would it better to calculate volume than surface area?

Ekka

Depends on the tree of course, like a mango tree here seldom has much in the middle and all leaves on the outside with 100% coverage.

Gums here are often open and sparse etc.

So for sure, what's appropriate, thinking canopy volume rather than linear is what it's all about.

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vl2007

Okey, found one formula that Dr. Gilman used in his study on how pruning affects tree movement under hurricane winds. the study is outline in the Arvboriculture and Urban forestry, volume 34 for January2008. After e-mail exchanges he informed me that this formula may not work for larger trees. Additionally, I found it unusable because they had to weight the folage.