Hi All
Re: Rotation ages.
Rotation ages varies with forest growth capacity. On a poor or slow-growing site (ie northern forests) we may have a rotation age of 120 years. ON the coast, we may do a spacing at year 20, a commercial thinning at year 40 and a final harvest at year 100, depending on when the crown closes and the growth rates slow down dramatically.
It makes no sense to harvest early unless there is an economic incentive to do so — by increasing growth of remaining trees while using the spaced / thinned products for fibre, chips, lumber.
Longer stands may produce finer grained wood, which is often more valuable, but that added value has to be juxtaposed agains market values as we go along. For example, are two 60 year old trees more valuable for lumber at than one larger 120 year log. The easy answer is — ‘It depends’.
Likewise, since trees slow down growth rates (even if the forest has higher capacity ) one has to look at volume accumulation. Do five 100-year old trees have as much wood/value as one 500 year-old tree? From a volume perspective — no. From a value perspective — That depends.
And the factors in that ‘what depend’ response include — current market conditions, value of stored carbon in the forest or built environment, value of potential products (lumber or furniture), and a whole other list.
And before anyone raises the question of the value of Old Growth wood (and my favourites are OG Yellow Cypress and Douglas fir which I collect for ‘future’ projects to be determined, much to my wife’s chagrin), the big trees are not typically cut down and converted to conventional lumber products. They are greed in the mill and sorted for clear and VG. The clear, fine grain is certainly worth more. However, a good chunk of those trees does get used for lumber, including lam stock, but the outer clear boards are sold for higher value.
One other thing about Old Growth — it is often NOT the best structural wood. It is entirely based on physical properties. (I know, I know — not what you expected to hear, but I am happy to have a phone chat with why that is often the case.)
Peter
