Time to thin?

[rcanderson1968]

I have a friend who has about 500 acres of timber in the coast range in northwest Oregon.  Most of it is managed for the production of saw timber, but on one 5 acre piece that was planted with Douglas fir in 1988, he wants to grow very high quality clear wood.  So the trees have been pruned up to over 20 feet and the density is about 330 trees per acre.  He recently took some samples with an increment borer and the outer most inch average about 7 to 8 growth rings.  The next inch closer to the center averaged about 4 to 5 growth rings. I haven't made any measurements, but I estimate the average DBH is about 7 to 8 inches.  Is it time to thin?

[beenthere]

Is he aiming for high quality dimension, or a board market?

For the high quality wood, he needs to keep from growing his trees too fast. More than 6 rings per inch and as little earlywood as possible to help keep the wood in the "dense" grading category.

Interesting project.

[WDH]

If the crown ration falls below 40%, it is time to thin.  Needles grow wood.  You need healthy crowns with good needle density. 

Crown ratio is the height (length) of the live crown (green needles) divided by the total height of the tree.  98% (just my estimate) of people thin too late, and then, do not thin heavily enough.

[rcanderson1968]

Beenthere, He's definitely thinking these trees will produce wood that's suited for a higher value use than dimension lumber.    He will have a lot of clear, tight grain Douglas fir.  The question is finding the balance between growing the trees fast, but not so fast that you get few growth rings per inch.  Your comment about the early wood vs. late wood ratio is interesting. Has anyone figured out for sure how foresters can manage for more late wood?

WDH, right now the crowns are about 50% of the tree height.

[WDH]

The % of latewood is directly correlated to the amount of summer and late summer rainfall for many species. 

[Clark]

From what I recall of my time out there, the typical industrial rotation called for the first thinning somewhere between 25-30 years old, depending on site conditions but he should know that if he has 495 other acres in timber production!  It's a tough call as to what should be done to meet his management goals, few people have trod where he is going.

WDH mentions % live crown ratio which is a good thing to keep in mind, the other is that if you let them go too long at 330 trees/acre, they will get too tall and spindly and have a hard time staying upright if you thin them too late.  I'd be inclined to thin them in the next several years but not as heavy as a "normal" first thinning.  Maybe do several thinnings but never taking that much in one operation?

Clark

[rcanderson1968]

UPDATE:  I talked to my friend and I had the growth rings per inch wrong.  The trees now have about 11 growth rings in the outer inch instead of 7 to 8.

[SwampDonkey]

Earlywood width is pretty much constant by species and site, it's the latewood that is more variable. This is easiest to demonstrate in ring porous hardwoods as you see the big pores in the earlywood, then the pores are smaller and more spaced out in the latewood and form a pattern in some species like elm. Better growing conditions and more crown gives wider latewood. Bigger crown means more knot wood to.

[petefrom bearswamp]

Why not contact the U of Oregon Forestry staff with your question
I'm sure they have done lots of research on this subject.
Pete







why

[BaldBob]

Why not contact the U of Oregon Forestry staff with your question
I'm sure they have done lots of research on this subject.
Pete
OSU NOT U of O.






why