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short and fat tall and skinny

Started by woodtroll, April 29, 2009, 11:33:21 PM

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woodtroll

I was asked this question and gave an answer, but my answer was not convincing. Or the ask-er just likes to ask. So I will ask you.

Why do open grown trees grow short and fat, while forest grown trees grow tall and skinny?

Gary_C

Lack of competition, and competition.
Never take life seriously. Nobody gets out alive anyway.

madhatte

Oh man, I could go on for hours.  A lot of the land I work on is prairie-colonization forests, and we get some WILD shaped trees.  The above is mostly correct (<90%) but omits the important effect of seral processes. That is, an open-grown tree is at a disadvantage to a tree which is part of a canopy, due to wind and other effects, and is therefore duty-bound to reproduce.  The full crown often throws stress cones annually instead of every few years, and the tree, as a result, grows broader and shorter, with more branches and more taper.  Each branch continues to contribute to the photosynthetic capitol, and is therefore not self-pruned.  A generation or two later, the progeny of these prairie colonizers crowd their parent and force self-pruning.  Trees are notoriously miserly with their energy. 

If you want to know more, PM me.  This is a big chunk of what I do and I have lots of pictures. 

ID4ster

Competition or the lack of competition is the main reason. In a forest setting the stems are competing for light. To do that they will try and grow taller than their competition. They will sacrifice diameter growth for height growth in order to grow taller than the surrounding stems. Once they out grow the competing trees their crowns will spread out and they'll begin to put wood on the stem (increase their diameter) and won't put on as much height growth.  Depending on what products you want out of a tree you can manipulate the stocking and density levels to develop those products. If you want clear stems for high value lumber and veneer than you may grow the stems closer and thicker for a period of time to develop a straight clean bole that will (hopefully) develop into a high quality tree at harvest. If you want to produce maple syrup than you want more open grown trees with lots of crown so that they will move more sap through their systems during the sugar season. Both open grown and closed canopy grown trees have their uses. Its up to the landowner to decide which uses they want.
Bob Hassoldt
Seven Ridges Forestry
Kendrick, Idaho
Want to improve your woodlot the fastest way? Start thinning, believe me it needs it.

Gary_C

Quote from: madhatte on April 30, 2009, 12:59:23 AM
and is therefore duty-bound to reproduce.  The full crown often throws stress cones annually instead of every few years, and the tree, as a result, grows broader and shorter, with more branches and more taper.

Are you saying that too much reproduction activity causes things to become broader and shorter?   :o :o

I'm getting out of here.   :D :D :D
Never take life seriously. Nobody gets out alive anyway.

woodtroll

it will need to be more scientific.

Gary_C

It's not the scientific implications that makes me nervous, it's the gender ones.     ;D
Never take life seriously. Nobody gets out alive anyway.

Riles

Statistical studies consistently show that height is much less sensitive to stand density than diameter, so the short vs tall question is more an issue of genetics and site conditions. In other words, an open grown tree will be dramatically fatter than the forest grown one, but it won't be dramatically shorter. The fatter part makes sense when you consider a tree puts on volume through photosynthesis, which you get more of when you have more branches.
Knowledge is good -- Faber College

madhatte

Open-grown vs closed-canopy trees of the same height:  the open-grown trees will almost always have greater taper and a crown that reaches the ground. 

woodtroll

Riles, so are you saying it just looks shorter because it is fatter. The taller trees in a forest is slimmer with a less crown making it look taller, and likely more merchantable height.

So if I could take the a tree, and it grows to 120 in the forest (with slight-moderate competition), and start it over in a clear cut with no competition, it will grow 120 feet but also be fatter and likely hold its branches. And this is based on increased photosynthesis?

Dodgy Loner

Riles, you are only partially correct with that statement.  The studies that show that tree height is not strongly correlated with stand density only apply to forested situations, not to open-grown trees.  What that means is that a plantation that has a stocking of, say, 400 trees per acre will not be significantly shorter than a plantation that has a stocking of 1200 trees per acre, even though the denser stand has more competition.  However, if a tree grows in the open, with no competition, then it will most certainly be shorter than if it grows in a forested situation.
"There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey." -John Ruskin

Any idiot can write a woodworking blog. Here's mine.

woodtroll

O.K. Dodgy, why? They should be getting plenty of light to grow. They are still phototorphic (sp? light loving). Growing towards the light. Is there some chemical/plant growth hormone that is increased for diameter?

VTLogSlayer

i have always been told in school that for say, a white pine that grows ina  field to have almost a full crown bottom to top is due to the fact that there is no competition and that sunlight can reach all sides....could be wrong  :D :P but that what i always have thought
ms361 20" 
044 20"
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Dodgy Loner

I don't think I could improve upon madhatte's explanation.
"There is hardly anything in the world that some man cannot make a little worse and sell a little cheaper, and the people who consider price only are this man's lawful prey." -John Ruskin

Any idiot can write a woodworking blog. Here's mine.

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