Crown Ratio  
  Jan 05, 2004 15:13 PST 

The current Dictionary of Forestry has:

live crown ratio (crown length ratio) the ratio of crown length to total tree
length - see crown length

crown length (live crown) of a standing tree the vertical distance from the
tip of the leader to the base of the crown, measured to the lowest live whorl
(upper crown length) or to the lowest live branch, excluding epicormics (lower
crown length) or to a point halfway between (mean crown length) - see live
crown ratio

whorl a circle of leaves, flowers, branches, or other organs developed from
one node

Since epicormics can be difficult to determine after they become large, maybe
epicormic branches should be included (after all, the top could be
blown-out), while adventitious sprouts (5 years or less?) excluded?

Randy (Jan 07, 2004)
RE: height champions, corn and white pine   Lee E. Frelich
  Jan 05, 2004 12:40 PST 

Randy and Will:

I think we could grow 400-500 foot white pines in an artificial
environment. The reason we won't find such trees, or even a whole bunch of
200 footers, in a tightly packed stand in the forest is that the crowns
will not be deep enough (i.e. ratio of live crown as proportion of total
tree height will be too low) to produce enough photosynthates to extend
wide enough rings all the way down to the base, so the outer rings that
conduct water to the top of the tree would be constricted at the base, thus
stopping water flow and limiting height growth at under 200 feet, since the
top twigs would not get sufficient water to keep going up. This is a
second limitation in addition to the need for trees in a real forest to
stay at 40% or less of the buckling height that would occur in a completely
calm artificial environment, because of wind that rocks trees even in the
densest stands.

Remember that topographic shelter from wind is important for two reasons:
(1) trees can get closer to their buckling height if everyday winds that
rock the tree are lower in velocity (although the water effect mentioned
above in many cases will negate most advantage from this effect); and
(2) there is a lower probability of being hit by extreme winds and
lightning that damage the crown, thus allowing a larger proportion of trees
to reach unusual heights before they are set back by injuries.


RE: height champions, corn and white pine   edward coyle
  Jan 05, 2004 14:25 PST 

Hi Lee,

Forgive my ignorance, but I am trying to understand why, if the root
constriction idea is true then how is it we have several species(3-4) in
stands in the west which far exceed 200'. My understanding is that the
redwoods obtain a good deal of their moisture from roots within moss mats in
the canopy negating the need to pump it up 360' or so. I don't believe that
is the case for the other tall ones.

As a second part to this, why don't we have 260' white pines in the
Smokies? It is wet and rich, and there are valleys. Genetics?

I dare to have a third part, With the water need filled, why don't we have
400' redwoods? Do they grow above the upper limit for moss, or the fog

Sorry to ask so much, but you got me thinking.
RE: height champions, corn and white pine    lef
   Jan 05, 2004 16:43 PST 


The west has different species and different climate. They especially have
species more long-lived than most of ours, and have very little lightning
and high winds compared to the east. So, it pays to get tall, and the
trees out there have adapted to get tall.

Also, The trees out west can photosynthesize over quite a long growing
season, which allows more time to store up enough energy to put rings down
a long trunk. Also, most of their species do maintain a fairly high live
crown ratio.


RE: height champions, corn and white pine (The Boogerman)   Will Blozan
  Jan 05, 2004 15:13 PST 

At its peak height, the Boogerman Pine had 52% live crown ratio. Any idea
what may be needed as a minimum for a 200 foot tree?

RE: height champions, corn and white pine (The Boogerman)   lef
  Jan 05, 2004 16:50 PST 


My field experience with white pines indicates that they can rarely support
more than 100 to 110 feet of trunk with no branches. They could have a
range of live crown ratios as long as the branch free trunk doesn't get
longer than that. They will need (my educated guess) at least 45% live
crown to attain 200 feet, which would yield a 110 foot clear trunk.   So...
we ENTS need to start measuring live crown ratio and see if the data
confirm my guess.


RE: height champions, corn and white pine
  Jan 06, 2004 07:32 PST 

Let me answer two of your questions.

It is true that canopy soils and leaf absorbtion of water are two methods to reduce water stress but there are always times during drought when the trees must use their full height to get their water. This is often when tops die back a few meters. The current limit of height is not a genetic one, it is an environmental one. During the mid 90s we saw many tall trees die back or grow slowly. The last few years have been kind, however, and we have seen some of these tall trees growing 20-30 cm in a year. The tallest trees are in Rockefeller Forest (86 trees over 107 m) which is an inland site that receives very little fog during the summer. The environment at the tops of these trees is very similar to the oak savannas growing on the nearby hills - HOT!


RE: height champions, corn and white pine (The Boogerman)   Robert Leverett
  Jan 06, 2004 09:56 PST 


Measuring live crown height and clear trunk length needs a few rules
of the road. Do you start at the first branch that has live foliage on
it and go to the top?

RE: height champions, corn and white pine (The Boogerman)   Lee E. Frelich
  Jan 06, 2004 10:19 PST 


Not always. Sometimes a hemlock will have a small live branch a few feet
from the ground, even though the main part of the crown doesn't start until
70 feet above the ground.

In most cases the first live branch is OK, because it is close to the
crown, but you have to use a little judgment as to where the base of the
crown is.

The worst trees I have ever seen for determining live crown ratio are white
pine growing on rock in northern MN. Some of them have one branch every 10
feet, starting from near the ground, and a little tuft at the top. Two
reasonable people could perceive the crown as being the whole tree, while
the other perceived only the top few feet as being the crown. Fortunately,
trees that confusing (although as beautiful as they are confusing) are rare
in dense forests where most of us work.


Re: height champions, corn and white pine (The Boogerman)
  Jan 06, 2004 11:11 PST 
In a message dated 1/6/2004 1:20:12 PM Eastern Standard Time, writes:

The worst trees I have ever seen for determining live crown ratio are white
pine growing on rock in northern MN. Some of them have one branch every 10

I've seen the same thing in NE Maine with white pines that grow along open
areas (like streams). The live crown ratio could be defined as the "relative
green crown proportion", which would exclude dead tops. If crown is defined as
the "branch-bearing portion of a tree", live crown ration could include small
epicormic branches, but exclude some adventitious sprouts. If we really
wanted to cover all green growth, we could include suckers (that grow from the
surface roots). In my own urban arboriculture practice, I am mostly concerned
with 2 measurements;

(1) The distance from the ground to the lowest scaffold (primary structural
branch, usually directly attached to the main stem).

(2) The distance from the lowest scaffold to the highest point.

Some species that do not develop a spreading crown, if exposed to light after
maturity, may go on to develop a 100% live crown ratio. Unfortunately, many
urban trees' crowns are limited to the upper 1/3 of the tree or less. But
palms don't seem to mind!


Re: height champions, corn and white pine (The Boogerman)
  Jan 06, 2004 11:26 PST 

In my experience, even in the most dense hardwood stands, the largest and
most dominant trees generally have about 1/3 live crown. In extremely tight and
stagnant stands trees may get by with as little as 22-25% live crown but with
anything less than 25% an older tree is often living on a vigor related razor
blade of instability that can be disrupted by even most modest severe weather

Russ Richardson
RE: height champions, corn and white pine "Q-tip Pine"   Will Blozan
  Jan 06, 2004 15:18 PST 


The "Q-tip Pine" in Cataloochee has a 15% LCR (with a few low straggler
limbs), while maintaining it's height at 165'. The "Dale's Demise" white
pine likely has 25% or less, and is now ~183' tall and growing. I'll measure
more LCR in the Smokies to help with your theory. The "Mountain Mama" white
pine (170') in Cataloochee has about a 70% LCR but has a tweaked top
(probably from hurricane Opal '95) but should keep growing up.

RE: height champions, corn and white pine "Q-tip Pine"   Lee E. Frelich
  Jan 07, 2004 05:53 PST 


I wonder if any of these trees find themselves with a low LCR now because
of injury from lightning, wind or ice storm, where some of the lower
branches were knocked off. If so, these trees are likely to decline in
health in the next few decades even if they are putting on some growth. It
is also possible that they can go through a period of low LCR and recover
to a higher LCR later on by adding new crown on top. If we both live to be
90 years old we will find out.

RE: height champions, corn and white pine "Q-tip Pine"   Paul Jost
  Jan 07, 2004 07:00 PST 


If not "pruned" directly from storm damage, could they have been pruned by
adjacent trees or branches being felled during a storm event during their
lifetimes? If so, there should be evidence in the form of CWD near the

RE: height champions, corn and white pine (The Boogerman)   Dale J. Luthringer
  Jan 07, 2004 16:25 PST 

Is tree length the same as tree height in this case?

Re: height champions, corn and white pine (The Boogerman)
  Jan 07, 2004 17:12 PST 
In a message dated 1/7/2004 7:25:55 PM Eastern Standard Time, writes:
Is tree length the same as tree height in this case?

That's a good question. I guess, in the absence of this dictionary's
definition of tree length, length, tree height & height, we can but assume that.
Though both forestry & arboriculture saw their birth in this Country about the
same time, and most arboricultural terms have been taken from forestry, I've
been told that not a single practicing arborist was included in the editorial
committee of this dictionary. Since the original question may not have even come
up, if not for foresters turned arborists (like Will), that are given to
climbing tall trees. I guess that's part of what makes ENTS so unique; it
combines researchers, foresters and arborists. With that broad a base, you're bond
to eventually come up with the best answer. Especially, if one believes the
recent SAF Journal article that "Urban Forestry; (is) The Final Frontier".

RE: height champions, corn and white pine (The Boogerman)   Lee E. Frelich
  Jan 08, 2004 06:07 PST 


To actually measure this in the field, I would take an extra distance and
angle measurement to the point on the trunk where you think the base of the
crown is, and then calculate base of tree to base of crown the same way you
would calculate total tree height. We don't need to worry about tree
length, which would be too difficult for routine measurement.

Note that the base of the crown may or may not be the same as a major
branch point. Sometimes live foliage starts well above the main branch
point. Also, sometimes the main branches bend downwards and foliage is
lower than the point where the main branches meet the trunk.

Many trees have a straightforward easy to recognize crown base, although
not all, especially in old growth. It may help to envision the tree as a
ball and stick model and visually estimate where the base of the ball would
be. Sometimes it also helps to envision the tree as if you were going to
wrap all the green part of the crown in cellophane, and where would the
base of that odd-shaped cellophane mass be?

It a little bit of an art, and there is no analog to finding the highest
twig when measuring height. If you always took the lowest live trig on a
species like red maple, then most would all have 100% live grown ratio,
since most older red maples have a few little basal sprouts with a
few leaves near ground level. As the definition Randy posted says, small
sprouts on the trunk should be ignored.