Trunk Taper    Rory Nichols
   Mar 11, 2004 22:03 PST 


ENTS:

Looking at conifers itís easy to notice that the trunk doesnít taper the same amount from tree to tree. What actually dictates a treeís thickness as you move up the trunk? I assume a variety of reasons, but Iíve noticed trees that are about the same girth and height growing not too far from one another with noticeably different volumes of the main trunk.

Rory
RE: Trunk Taper    Joseph Zorzin
   Mar 14, 2004 04:15 PST 


Rory,

Lots of reasons. First, in an unthinned stand of conifers, there will be
less taper- as the shape "naturally" adjusts to the amount of wind that
the tree "feels". In a dense stand, the trees support each other, so
they'll grow with less taper. This is why thinning such a dense stand in
mid age might result in a lot of "blow down". If the stand had been
thinned from an early age and kept thinned, most trees would develop
taper.

As to why individual trees vary in the amount of taper in a particular
stand- could be lots of reasons. A more vigorous tree will have a larger
volume- it might be more vigorous because it's a superior genetically,
or just had better luck on where it got started- that is a better
micro-environment.

JZ

Re: Trunk Taper    greentreedoctor
   Mar 14, 2004 21:46 PST 
While maybe the largest contributor, I wouldn't limit loading to wind. Snow & ice can cause loading and stimulate reaction wood.   Conifers can develop compression wood on the leeward side, while broadleafs can develop tension wood on the windward side.   Also, tree growth is stimulated by the sun (phototropism) and gravity (geotropism).   While a southern coastal pine plantation may have like bole taper, once you move towards the mountains, taper can and does differ.   Tight stand trees do share the load, but let a tree emerge to fill an opening or dominate above the canopy, and both loading and reaction wood is increased.   Also, wounding, erosion and even compaction can effect taper.

I would think that forest management is not limited to juvenile thinning; that mature stands can be successfully thinned without widespread failure.   Highgrading is an unfortunate forestry practice contrary to present day agriculture.   But so is preventing the harvesting of overmature old growth.   I suspect that some of the same people that vilify highgrade harvesting are also old growth protectionists.   Don't get me wrong-I am for the preservation of old growth and believe in preserving champions, notable specimens and dwindling old growth remnants.   I just perceive a conflict.   On the one hand, we should only harvest the more inferior trees, on the other, we should protect aged giants that are nigh returning to the forest floor from which they ascended.    Not every greenhorn forester may be able to start their own private consulting firm.   They may have to actually have their employer's interest at heart and treat trees as marketable crops for a number of years before they're able to eke out a living on their own.    Though they rarely find their way into our discussions, arborists are mostly about preservation, while foresters are mostly about harvesting.   We look at trees differently...       

An observance from a layperson,

Randy