Where is the top of a tree?

Native Tree Society Tree Measuring Guidelines and related materials.

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#1)  Where is the top of a tree?

Postby a_blooming_botanist » Wed May 11, 2016 6:25 pm

The other day as I was returning home from big tree hunting I stopped to notice a young green ash sapling. I’ve spent so much time studying and measuring the big guys that I took a moment to crouch down and appreciate a tree that is only now about a foot tall.

Here’s a picture of Junior:

               
                       
Green ash sapling.jpg
                                       
               

Looking at this picture got me thinking…is this a 10-inch green ash or a 13-inch green ash? If the top of the tree is defined as the highest apical meristem, then I would call this a 10-incher. If, however, the top of the tree is more broadly defined as the highest cell belonging to that organism, then I would call this, rounding to the nearest inch, a 13-inch green ash.

This may seem pedantic in this example, and in most cases I think the difference would be negligible, but I can also imagine that a similar question might come up when measuring a palm or other such plant with large leaves that project at an upward angle from the stem and rise noticeably above their point of attachment.

So, what do you consider to be the top of a tree?

Jared
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#2)  Re: Where is the top of a tree?

Postby MarkGraham » Wed May 11, 2016 7:34 pm

I think the highest stem makes the most sense.  If an upward projecting leaf falls off an oak tree in November, that event should not make the tree shorter.  Similarly when it comes into leaf in May, that event should not in and of itself increase the tree's height.
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#3)  Re: Where is the top of a tree?

Postby a_blooming_botanist » Wed May 11, 2016 9:59 pm

MarkGraham wrote:I think the highest stem makes the most sense.  If an upward projecting leaf falls off an oak tree in November, that event should not make the tree shorter.  Similarly when it comes into leaf in May, that event should not in and of itself increase the tree's height.


I agree, especially in the case of oaks and most other deciduous trees whose leaves do not typically add substantial height above the point from which they emerge.

Though not North American, there is a palm species in Africa (Raphia regalis) that is reported to grow to heights of 16 meters with upward-projecting leaves up to 25 meters long. I’m just curious if there is a consensus on where to call the top of a tree whose leaves constitute such a large portion of the apparent size of the plant.

Jared
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#4)  Re: Where is the top of a tree?

Postby Matt Markworth » Wed May 11, 2016 10:24 pm

Jared,

Good topic for discussion!

In a strict and theoretical sense, I think that the leaf adds to the tree's current height.

In a practical sense, I agree that the tree's listed height will depend on what definition is being used, which in turn is determined by what the data will be used for. For many species the added height would be within the margin of error for most height measuring methods, but for those that add significant height a rule would need to exist so that the measurers are consistent.

Matt

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#5)  Re: Where is the top of a tree?

Postby Don » Wed May 11, 2016 11:09 pm

Good question, Jared!
At one level, you can measure anyway you want, define your system of measurement, and seek agreement with those you encounter.
At the national champion tree register level, you imagine you're lowering a completely horizontal plane until it first contacts the tree being measured.
Simlarly, you establish a horizontal plane at the base of the subject tree, and then you measure the vertical distance between the two horizontal planes, which is by American Forests definition of the height of the tree. Leaning, bent, it doesn't matter...two horizontal planes at tip top, and tree's bottom (defined as the root collar, or point where it was apparent that the original seed level was (point where tree bole turns into root system)).
Mark brings up a good point...you may lose a couple of tenths (of a foot) measuring winter's height leaf off, versus spring/summer's height with leaf on...but that probably can be obfuscated by the seasonal growth that trees can be capable of.
For the really picky...I maintain that the tree's respiration/transpiration during diurnal and seasonal variations can easily vary in the tenths of a foot realm.
Don Bertolette - President/Moderator, WNTS BBS
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#6)  Re: Where is the top of a tree?

Postby bbeduhn » Thu May 12, 2016 9:22 am

Spring growth can increase the height or decrease the height. Often, the tallest sprig, especially on multileaf trees, leans from the weight of the leaves, I can see a metasequoia at work that grew a nice, tall, narrow sprig that leaned over in new leaf, taking a couple of feet off the height. It strengthened over the summer and topped its previous height.

The height of a tree is the highest that can be attained when measured. The height can vary a bit throughout the year.

Brian

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