If one has a multi-trunk tree, and we measured the circumference for each trunk (cbh), one can calculate dph using the circle equations (circumference = 2 π r) and dph = 2r if the tree has one trunk, but in our case the tree has multi-trunk what is the right method for measuring a tree dph?
There are two condition when a tree has two or more than two stem if a tree has two stem than it is called the forked stem and if it has more than two than it is candelabra. Know if the above two condition is exist, we will measure the dbh of each trunk if the forked or the candelabra condition found below the BH point, in this case we will consider each trunk a separate tree but if the forked or the candelabra condition found above the BH point so we will consider it one tree and will measure the dbh at BP of the main stem
Dear Dr. Adnan Ahmad,
Thanks a lot for your answer! Our tree is the second type, sometimes at BH has one stem, and sometimes has more than stem (3 to 8 stems).
kind regards,
Mohamed
If the lower division of the trunk at a height of 1.3 m height ,They can find two trees.
If this separation occurs at higher elevations, They are a tree.
Here are commonly-accepted methods used in the United States:
If the tree forks below DBH or near DBH, the measurement is recorded at the narrowest part of the main stem below the fork. The height of the DBH measurement and the fork should be noted (eg. 3 ft diameter @ 2 ft [forks @ 4 ft]).
If the tree splits into several trunks close to ground level, measure the DBH of each trunk separately. The DBH for the whole tree is then found by taking the square root of the sum of all squared trunk stem DBHs.
Hope this helps!
The practice rule for ecological surveys in Victoria, Australia aims for a simple, repeatable method. That is, the tree is always measured at BH (even if the fork occurs there) and if it has multiple stems at breast height, the stem with the largest diameter is recorded to represent the tree.
If the tree forks below DBH or near DBH, we too record the narrowest part of the main stem below the fork.
However, if the tree divides close to the ground we take the DBH of each trunk and then create a sort of virtual DBH by taking the square root of the sum of the squares of the individual stem DBHs (as described by Melanie earlier).
So, if the tree has divided close to the ground into two stems which have a DBH of say 20 cm and 15 cm, then the virtual or effective diameter is (20^2 +15^2)^0.5 - the root of 400+225 or 25 cm. If there are 3 stems of say 3, 4 and 5 cm DBH then we would take it as 7.1 cm [square root of 9+16+25 ] and so on.
All the best
Rajesh
I think the above mentioned answers of Mr. Rajesh, Harley, Ahmed are welcomed. It could be the useful way to measure the diameter of multi-trunk tree.
Hi Mohamed,
I agree with Melanie. The german national forest inventory uses exactly that method. See link below:
http://wiki.awf.forst.uni-goettingen.de/wiki/index.php/Diameter_at_breast_height
It is obvious if the trunks are jointed below the soil surface, you can measure dbh individually and if at bh the main stem id divided into many stems, still the individual diameters of each stem are measured.But if the main stem segregates into many stems above your bh, then take it as on stem becoz you are supposed to measure the diameter at breast height.
I had exactly the same problem. I used DBH as a proxy for total leaf area at one tree site. That's why I needed forked trees as one datapoint, so I took the squareroot of the sum of the trunk stem 'crosssections', as Melanie wrote. Only, I don't find any source I could cite in my work. Do you know any papers or books on this particular problem?
I'm sorry to revisit this question but I am in the same situation that Alexander. Where I have a dataset and I comprehend how the DBH of an individual with multi-stems is obtained but I can't find this in any of the vegetation analyses articles or books I've searched.
Neither have I found the method that Harley mentions, where the largest DBH stem is taken as representative.
A source would not only help in the citation but in the comprehension of why this is done like this instead of what I've seen in many situations which is adding DBH of all stems and then calculating Basal Area.
Any updates on this front?
Thanks in advance for your direction and for your support.
Hi everyone,
Melanie L. Truan and Rajesh Thadani do you have a reference for the method you mentioned above?
I would appreciate if you can share it :)
Thanks,
Romina
Romina Daiana Fernandez see this link: http://wiki.awf.forst.uni-goettingen.de/wiki/index.php/Diameter_at_breast_height
Also posted above.
In this recent work the authors use the formula mentioned above:
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