Girth and Crown Spread

Girth and Crown Spread

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TOPIC: Girth and crown spread
http://groups.google.com/group/entstrees/browse_thread/thread/4249e6a7f78dde47?hl=en
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== 1 of 3 ==
Date: Mon, Dec 17 2007 6:29 pm
From: "Edward Frank"

ENTS,

I have been wondering if the width of cambium in a tree limits the maximum growth of a tree? What I am thinking is that all of the sap flowing between the roots and the canopy of the tree must flow through a band aroundthe tree that is equal in length to the girth of the tree. As the tree grows the girth increases arithmetically Girth = (pi) x (diameter). the canopy on the other had increases its volume geometrically. It gets taller and broader over time. The leaf mass increases dramatically, so the production of sugars and the like through photosynthesis increases at a much faster rate (I am guessing) than the width of the path - the cambium layer - increases in length. So over time, as the tree gets bigger, does there come a crunch time whereby the size of the tube carrying the sap become overwhelmed by the need to transport fluids along the trunk of the tree?

If ypou look at trees some are tall, skinny, with small crowns, others are short and squat with wide crowns, and others are tall, and fat with big crowns. Is there some factor - say a ratio between the width of the flow path (girth) and the volume of the crown that represents this balance between the two?

Is there some critical ration that represent the max size for a particular tree species based upon the efficiency of the transport system? Are there some species more efficient than others, so that it allows them to grow bigger than other species?

These are just ideas for brainstorming if anyone wants to take a shot. As for where to measure girth for examining this idea - I would say anywhere so long as you are consistent - therefore the standard girth at 4.5 feet is as good as any other. (Really it would be better for larger trees to measure above basal flair).

How does the sap flow through the cambium? It must be able to move laterally in many species because I have seen lightning paths spiral down a tree. If it went straight up and down all of the vertical paths would be interupted by the lightning path. Also the massive fallen cucumber at Cook Forest had a spiral crack that ran around the tree, along with a pressure ridge- So again if the flow was completely verticle it also would have been blocked. long vertical lightning scar similarly do not seem to kill the trees, so a simple spiral pattern is also not viable. I am sure this is something that people know - It is just that I don't, and it relates to the questions I posed above. So if you know, please respond.

Ed Frank

== 2 of 3 ==
Date: Mon, Dec 17 2007 9:32 pm
From: James Parton

Ed,

This is a very good question. I would like to hear this one answered
myself.....

James P.

== 3 of 3 ==
Date: Tues, Dec 18 2007 2:50 am
From: Beth Koebel

Ed,

I don't know the answers but you have proposed very
interesting questions.

Beth

== 2 of 4 ==
Date: Tues, Dec 18 2007 6:13 am
From: "William Morse"

Hi Ed,

You may be interested in these older, yet relevant, articles:

Murmanis, L. and M. Chudnoff. 1979. Lateral flow in beech and birch as
revealed by the electron microscope. Wood Science and Technology
13(2):79-97.

Snow, R. 1942. On the causes of regeneration after longitudinal splits. New
Phytologist 41(2):101-107.
*
*I attached a copy of Snow's paper to this message. I can PDF a copy of the
'79 paper to if you would like.

Travis Morse

== 3 of 4 ==
Date: Tues, Dec 18 2007 7:10 am
From: "Lee E. Frelich"

Gary, Ed:

Not much is known about this topic. Ed-I believe that cross-sectional area
and width of of sapwood actively involved with transporting sap is the
variable of interest, rather than cambium width or area, although the
activity in the cambium does ultimately determine the widths of the sapwood
and the phloem. Gary--it will be interesting to see if you find any other
points of view besides that I give below.

Here is what I think about the subject:
A number of studies have been done on ratio of leaf area to sapwood area,
which generally have found a decrease in this ratio as trees get taller,
possibly representing a homeostatic mechanism that compensates for
decreased hydraulic conductance as trees get taller. In other words, it
takes more sapwood to supply water to the same amount of foliage in a tall
or old tree as in a shorter or younger tree, and the tree keeps adjusting
this ratio as it ages to reflect the fact that it is harder to get water to
the highest foliage as the tree grows taller. I believe there would be a
crunch time at which the tree can no longer make rings wide enough to
conduct enough water, probably due to accumulated injuries and cavitations
so that not enough water is fed to the leaves to make enough photosynthate
to produce new rings of adequate width, thus initiating what has been
called the death spiral in older trees.

The problems with these analyses are that sapwood area is not a very
accurate measure (the few outermost rings probably conduct water much
faster than those a little further in, so that measures of total sapwood
are probably not adequate to explain water conducting capacity, instead the
capacity of each ring should be quantified and its basal area measured;
there are methods for doing this, but they require more tree climbing than
most tree physiologists have been willing to do, since they require real
time measurements of sap flow in individual rings at different heights in
the tree).

Another factor is tracheid or vessel diameter, which as predicted by theory
would have to get progressively narrower with height in the tree to
maintain water conductance that is independent of height. The limitation
there is that vessels at the base of the tree must be larger in diameter in
a taller tree to accommodate the decreasing vessel diameter with increasing
height, which could reach a threshold minimum diameter at a certain height
such that water could not be conducted any higher. In an old tree that
could not produce sufficiently wide rings at the base of the tree, due to
the fact that the circumference of the tree was so large and it is
impossible to produce enough raw materials to create a wide ring around
such a large trunk, the vessel diameter may decrease as the tree ages, thus
limiting the ability of the tree to conduct water to the height that
already exists, initiating dieback or death of the tree.

Lee

== 4 of 4 ==
Date: Tues, Dec 18 2007 7:19 am
From: "Gary A. Beluzo"

Thanks Lee, I'll throw out a wide net and see what I catch.

BTW, I have discovered that I have free access to JSTOR (and other
academic indices) at home through the Boston Public Library.

Gary

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