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Why do "old growth" trees produce better lumber?

Started by Mongo, June 11, 2003, 01:06:14 PM

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Mongo

Hi all,

I feel kind of guilty, I don't really contribute much to this community, but do pop in every few months when I have a question. So, first let me thank you all for the advice I've gotten (and hopefully will get :)  )

I just posted this msg on rec.woodworking, and as soon as I hit send I thought of this place and realized it'd be a much more appropriate place to ask.

I'm wondering what makes old growth lumber better then the stuff being cut today. I know that it's because of the tighter growth rings, and hence denser wood, but what causes that? Why did the stuff a couple hundred years ago grow so much denser/slower then it does today?

I can almost understand this phenomenon in plantations where the trees are planted with ideal spacing etc for fast growth rate, but what about in natural enviroments?

Thanks again!

--
"Mainiacs away from Maine are truly displaced persons, only half alive, only half aware of their immediate surroundings. Their inner attention is always preoccupied and pre-empted by the tiny pinpoint on the face of the globe called Down East. They try to live not in such a manner that they will
eventually be welcomed into Paradise, but only so that someday they can go home to Maine."

-- Louise Dickinson Rich

woodmills1

I am pretty sure it has to do with the spacing.  given enough time the trees will fill up the celestory space, limiting the sunlight falling on each tree so slowing the growth.  at the same time they will self prune those branches that are in shade for a shade intolerant species.  If I remember correctly the the climax species is usually intolerant, thou I am not sure of that.  given the amount of time for growth a large tree with considerable clear wood on the bole will be produced.  my red oak forest is untouched for 100 years following a fire and shows very close rings though the trees are not real large.  In the summer you can not see the sky through the leaves.
James Mills,Lovely wife,collect old tools,vacuuming fool,36 bdft/hr,oak paper cutter,ebonic yooper rapper nauga seller, Blue Ox? its not fast, 2 cat family, LT70,edger, 375 bd ft/hr, we like Bob,free heat,no oil 12 years,big splitter, baked stuffed lobster, still cuttin the logs dere IAM

Ron Wenrich

There is only one way to get growth on the bole of the tree, and that is through crown expansion.  All trees keep growing taller, but it really slows down after awhile.

The square footage of wood is measured as basal area.  That's the cross section of a tree at dbh.  You add them up on an acre and you get the stocking.

If there is a clear cut, then the stocking is 0.  Let the trees grow a few years, and you'll start getting stocking pretty quick.  At some point, the stand will be fully stocked.  That is where you get the best growth and the best site utilization.

Let it go too long, and you'll have an overstocked stand.  Growth will start to slow, and will eventually reverse as some trees give it up and die.  Slow growing stands are often called stagnant..

Periodic thinnings can keep a stand fully stocked and growing at an acceptable rate.  Thin too hard and you under utilize the stand and usually lower the quality of the remaining wood.  No thinning will cause a stand to become overstocked and to slow down growth.

The other problem you have is that plantation trees are often grown too fast.  Young trees have a lot of juvenille wood and it isn't very stable.  Timber companies and landowners are pushing to get trees from seedling to marketplace a whole lot faster.  In some places, trees never get past the juvenille stage before cut.

Those trees in a climax stand are called tolerant.  That means they are very tolerant to shade.  Typical climax species are white oak, beech, sugar maple and hemlock.

Hardwood species that are in the most demand tend to be intermediate in tolerance.  
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Tom

In Southern forest where pine and cypress are the two main lumber producing trees,  fire and inaccessibility are the two main reasons that old trees produce better wood.

The Cypress stands could not be reached until the great effort was made in the late 1800's to harvest them.  Cypress had stood for eons in swamps and their growth was not only slow but they inhibited other trees from competing.  They owned the swamp and the rings were very tight.  Heart wood compromised the majority of the tree and it became a large tall beast with no limbs for considerable distance.

In the Pine Barrens fire was used to keep the under story down so that the Indians and later the settlers could hunt and farm. This regular burning got rid of most of the scrubby hardwoods and killed the pines that were not fire resistant.  Long Leaf was one of the most fire resistant species and became the dominant forest tree.  It just so happened that its slow growth and greater percentage of heart wood  made it the prime lumber tree.  

Since heart wood is the most rot resistant and bug resistant part of the tree then these combinations created trees that everyone was after. They were not only used locally but prized well into the north for huge timbers to build the big industrial plants.   Those are the same beams that are being salvaged today, re-manufactured and presented to the market again.

Ron Scott

Old Growth is not necessarly "good lumber", but rather a key component of biological diversity. Forest old-growth areas are ecosystems dominated by various trees which are old and uisually quite large. Though they can produce good lumber they also provide many other co valued components for a sustainable ecosysrtem.

Old-growth is a stand of trees older than normal rotation age for the timber type. Such stands provide important habitat conditions not normally found in younger stands.

Old growth stands have distinctive structural features. These structural features include large, live, old trees; large snags; and large fallen logs.

The large old trees have irregular, course branch systems, broken tops, and often vertical crowns. The structure of these stands is more heterogenous than that of young forests.

Old growth forests are very complex and are often the subject of debate between environmentalists and forest users.

~Ron

Bibbyman

Oak and other hardwoods are dominant in my area.  Our farm has a verity of forest types.  

About half is covered with what I would call "sustained" forest.  It had been forest before the first settlers and still is forest.  But it has undergone harvest of some degree and type for the past 175 years.  

About 1/4 is covered with "re-growth" forest.  These areas were once forest but were completely clear-cut and probably cultivated or at least pastured until the land was "used up".  Abandoned from farm use, "invasion" tree types took over followed by a more permanent stand of oak and other hardwoods.

There are a few isolated pockets of "old growth",  as I would call them.  These exist only in locations were it was too difficult to harvest them.  While some trees are large and old,  I would not say they are part of a virgin stand of timber as there are no very large, very old trees left - apparently being harvested very early in the settlement of the area.  But they were probably understory trees to the virgin stand.

We've owned the farm for the past 25 years and have been working at upgrading the stand by removing lower value and damaged trees.  

We have recovered some of the "old growth" that have fell victim to bugs, lighting strikes, or other damage.  While some produce very good lumber, others are too damaged by wind shake, fire burns, or what ever killed them.  

The larger "re-growth" trees are large enough to make lumber but even the best produce low quality lumber.  Growing without competition and upper canopy cover, they have developed hundreds of little grown over knots from lower limbs that have since died and fallen off.  These knots often also contain pockets of rot and bug holes.  Trees of the red oak family (mostly black oak in our stand) are dying of the red oak beetle.  We've been trying to recover some value from these trees by making blocking or firewood out of them.  Among the stand is trees with more potential (mostly white oak) we are hopping will benefit from the removal of the low value trees.

Our best lumber comes from trees in the "sustained" forest area.  Having not had a hard harvest in 25 years,  many are now reaching the lower end of good commercial value.  Each year we remove a few of these trees that are damaged or have died.  The logs generally produce very good lumber as the tree trunk is void of knots almost down to the heart because they grew tall under competition of full-grown trees.  About every 10-20 years,  this area was "cut over" and many of the largest trees removed - allowing room for these tall but young trees a faster growth rate.  

You can read the history in the growth rings.  In the "sustained" forest, the heart area of 3-6" of the trees the growth rings are so close together you can hardly count them - showing they started out with almost overwhelming competition.  From there to present date,  you can see the growth rings widen from 1/8" to as much as 3/8" a year - indicating when other competing trees were removed from around them.  In the "old growth" area,  the growth rings are about uniform throughout of about 1/16".  In the "re-growth" area,  the growth rings are about 1/4" to 1/2" a year throughout.

Not having any formal training in forestry,  these are my own labels and definitions I have used to describe the hardwood forest types on our farm.
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