What's a 30% reduction to you?

[paradise]

So here's a question for a Monday afternoon when I have no work on. Is a 30% reduction:

 

(a) The removal of 30% of the leaf area

 

(b) The removal of branches to reduce the profile by 30% (more or less cutting branches back to two thirds their previous length)

 

© Something else.

[Czlowiek Drzewo]

reduction of canopy.

[Dean Lofthouse]

Leaf area

[pmtree]

leaf area

[Yorkshireman]

In the main I would tend to agree that a reasonable perception would be of the canopy as a whole of functional wood leaf bearing or not , within the form that would be expected of that genus so not 30% wolloped off one side, but as an overall to leave the specimen within its normal form ,

this may however depend on whether or not the specification listed other works

ie crown thinning, crown lifting or crown cleaning

[paradise]

reduction of canopy.

You mean a reduction in the size of the canopy by 30%? Are you measuring that by profile, as in (b), or by volume of canopy? Thinking about it, they wouldn't be the same. Volume of canopy should maybe have been the © option.

[arb culture]

It depends on who is asking and why.

[paradise]

I don't know if it seems like I'm splitting hairs, but it's one of the most widely quoted figures - no more than 30% for a healthy reduction - and I always took it to mean leaf area, but I see people reducing the height and width of the canopy by 30% (option b) and calling it a 30% reduction and I suddenly doubted that everyone is meaning the same thing when they talk about reduction percentages.

 

I reckon a 30% reduction using option (b) often results in, say, a 50% or more reduction in leaf area, because of the distribution of leaves within the tree (more on the ends of branches). Is this ok in terms of the tree's health?

[D Mc]

This is a good question and should be clarified.

 

When referring to a maximum amount to be taken from a tree, it is generally regarded as live mass. This includes storage tissues as well as leaf area but does not include deadwood. Thirty percent removal of live mass can be achieved through either reduction or thinning. It can also be achieved by removing one single live leader.

 

As either reduction, thinning, raising or lowering could result in the maximum amount of live tissue being removed, it is important to clarify which method will be used to achieve the goal as the results would be quite different.

 

Dave

[paradise]

Hmm, so it's meant to be live mass? Does anyone have any scientific sources btw? I've seen the 30% figure used so much and not sure where it comes from - which is one reason I'm not sure what it means. Is it Shigo?

 

If it is live mass, does it really make no difference at all to the tree whether most of the mass is removed as leaf area or more of it is removed as wood? What about winter/summer differences on deciduous trees? And how do you weigh leaves compared to wood? Damn, this is even more complicated than I thought.