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what exactly is yield class?

Joseph Zorzin redoak at forestmeister.com
Fri Aug 21 01:54:46 EST 1998

Tony Holt wrote:
> I understand that (in the UK at least) yield class is the amount of
> biomass created per annum - eg. YC12 means 12 cubic metres/year/hectare.
> What exactly does this include - is it the total biomass including all
> the foliage and/or branches or does it refer to the economically useful
> timber?

Not sure about how you Brits look at this, but on this side of the big
pond- biomass is the entire tree. The amount of that that is
commercially valuable depends on the site, the mgt. of the forest, and
the markets.

> Ps. How much of a tree is ecomically useable as say sawtimber? I realise
> this is a broad question, but are there any rules of thumb?
> For example, what percentage of an 18 inch white oak might be utilised
> as plank/fencing material? 50 per cent or substantially less?

Depends on the quality of the trees which are extremely variable
depending on site, mgt. of the forest and markets. That 50% probably
isn't too far out of line, plus or minus 50%.

Better mgt. gets you higher yields and higher growth rates.

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