Bifurcation or Co-dominant Stems

becmate

What is the defining difference with co-dom stems Vs bifurcation? I thought it might be the cell structure in the union of the stems but I can't find the technical terms for it. Has anyone got a good description and maybe a pic of some cross sections to show the difference?

Darrell Mcleod

I thought essentially they were the same thing but thought interesting question
Maybe off topic a little but ........

Discovered this tree report online with a reference to Shigo re Co-dominant Stems Definition on page 9

http://bit.ly/iemTPB

becmate

Thanks cruisin! It appears it does have something to do with the union however I can't find an explanaintion of bifurcation.

The Shigo description of co-dom is really helpful... it states no collar and no built in protection zone so is bifurcation where branch and trunk collar still exist to form a barrier?

Is it even a term arborists continue to use?

Eric Frei

Hmmm, I don't like that report. I have uploaded to here.

The author writes:-

On P11 to question S179(a)(iv)

He wrote:-

What a load of bull. Through bolting both stems above the defect would significantly reduce the probability of failure. Then as you progress into the crown dynamic cabling would allow natural movement with dampening. The tree has survived this long, it is mature, I think it was an option but not thought through enough. There could be more than one through bolt.

Through bolting above the defect creates a fulcrum effect where the stems are actually pushed together not pulled apart.

Plenty of documents here on cabling and bolting:-

Tree Cabling| Bracing| Dynamic| Static





The author makes comment of water pooling at the crotch. So what? If there is no cavity or bark removed then it is most likely that no decay is present, he has failed to determine if there is decay present. But water pooling alone is seldom an issue for trees providing the bark is there, the old fashioned idea of draining them by drilling is what helped invite then spread decay.

In addition the tree is a ripe candidate for growth control treatment, although back when the report was written there was no label and even today there is no label for that species I would apply to go off label (yes, even off the label I already got). The benefit is increased drought resistance and decay preventative propensities in addition to slower growth and denser timber. It has been shown that the growth control treatment also slows trunk growth.

The author spoke of maintenance. with stainless steel through bolts it's pretty much set and forget. The dynamic cable in the crown .... 2 years to 5 years.

You can still have your own recommendation but decent advice on the options should have been provided not discarded in a negative biased way. The author spoke of failures above the bracing and even drastic crown reductions of 30% ... what nonsense!

Selective thinning wont result in epicormic regrowth, dynamic cabling wont result in karate effect breakages, brace rods above the co-dominant union will not have karate effects either.

That's why I do not like that report.

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1DFeb08.pdf (534.3 KB, 52 views)

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Eric Frei

Personally I think the term bifurcation is used when the main trunk is co-dominant into the ground and not used say when there's a division of a tree trunk or branch to co-dominants.

So in that report which was put up I would use the term co-dominant. I would write that the main trunk divides into two co-dominant leaders (or stems) at approximately 6m high, both stems are approximately the same diameter of Xcm.

Now in another report I see this author presenting what I am saying a little better but still not the best. In this case the tree is co-dominant at ground level.

He writes on P8 for Tree 5:-

He wrote, "that it is developing from codominant stems" .... so we know it is two stems/trunks that must be one stem lower down .... but he wrote, "that bifurcate at ground level." .... So there should be 4 stems at ground level according to that description because they bifurcated again.

It would have been clearer to write:- The tree has a decurrent, symmetrical canopy that is developing from a bifurcation at ground level.

Sadly in the same paragraph he continues to write:-

I'm sceptical of a bifurcated tree being structurally sound.

In Jayd's post he had a picture of what I called a trifurcated tree.

And in my post I put up this pic of a bifurcated scribbly gum that failed. To say bifurcated trees are structurally sound is erroneous IMHO.

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Garry Brockley

I would have said that the tree in the picture was more than likely two trees at the sapling stage that have grown together then had the failure, rather than one tree bifuricated at ground level

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Jeff Darby

As defined in The Dictionary for Managing Trees in Urban Environment Drapper,Richards (2009).

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becmate

hmm, or is bifurcation the term used for the union at co-dom stems? coz then the "developing from codominant stems that bifurcate at ground level" would make some sense.. but it doesn't sound right to me either.

If the codominant starts at ground level and this would be then called a bifurcation, what is the need to call it a bifurcation? Wouldn't you just say codominant stems from ground level? I think I'm confusing myself!

Also, I can't work out how the TPZs were calculated in that report. The methods of calculation are given as per AS4970 however the two trees with codom stems don't fit those methods and the combined stem DBH calculation doesn't work either... am I doing something wrong here?

Eric Frei

Personally I find the older or more "old school" the person/author the more likely they are to use the term bifurcation.

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becmate

Sweet, thanks JayD.. so essentially they could mean the same thing if the bifurcation happened on the main stem / trunk. But a bifurcation can also happen on a branch which is not a main leader and therefore codominance does not apply.

That makes sense right?

Eric Frei

Why doesn't codominance apply on 2nd order branches? who made that rule?

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becmate

haha what do you call it when a codominant stem codominates again? I have seen it in a Spotted Gum where the trunk spilt into two stems and both of those stems split into two stems, so four leaders are prevelant.

Is that a bifurcation of codominance?

might give up on this one and never use the term bifurcation coz I don't know exactly what it means.

Eric Frei

You call it exactly what it is ... it's you who is putting limitations on the use of the term.

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TrevMcRev

I'd agree, i think bifurcation is just old-school terminology for co-dominant stems. Same/same.

Eric Frei

Today we cabled this tallowwood.

Maybe 500mm DBH, co-dominant at around 5m height, total tree height maybe 25m.

Pronounced elephant ears, no signs of crack making it to external, no signs of sap oozing, no signs of decay in crotch with bark in tact.

Tree age is estimated at 40 years.

Tree has withstood all storms and punishment to this day.

Customer does not want to cut this tree down.

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serialtreekiller

Every body gets to cable except for me your going down gay bee

Bowani Siam

As I know it, they are both relevant although they do not mean exactly the same thing. Bifurcation is essentially just another word for forking into two (or sometimes three!) more or less equal parts. eg. the main branch has bifurcated, forming two co-dominant stems. It basically describes the action of forking/splitting. The term co-dominant stems describes the result (of said split)

I think that "co-dom stems that bifurcate at ground level' does make sense, as it defines the location of the fork.

What I would like to know is if there are any cases of co-dominant stems in trees resulting from pseudodichotomy? If so, how would you determine it? Is it possible?

Time for another beer!

Eric Frei

Well it defines something at ground level but exactly what? To bifurcate means to divide not join.

"co-dom stems that originated from a bifurcation at ground level" would be more appropriate ...yes/no? I think yes.

So maybe this:-

Should be something like this:-

"The tree has a decurrent, symmetrical canopy that is developing from codominant stems that originated from a bifurcation at ground level."

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Bowani Siam

sorry, that should read NOT resulting from pseudodichotomy. Can co-dom stems be from the same growing point? I am intrigued!!

Maybe "co-dom stems forming from ground level bifurcation."

"The tree has a decurrent, symmetrical canopy that is developing from codominant stems that originated from a bifurcation at ground level."

hahahah yeah yeah..

Or how about.....

"Bifurcation at ground level has resulted in codominant stems that are forming a decurrent, symmetrical canopy."

Man you could go on all day!

Eric Frei

Yep, but I think we've nailed this one.

I do not use the term much.

Many ironbarks here will have the trait throughout the canopy on most unions, co-dominants with included bark that is. Like a genetic condition.... culled a few.

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Apocalypsse

Got this from TAFE yesterday.

Bifurcation has included bark where as co-dominant has a more sound union where the apical bud has split off into 2 leaders.

Eric Frei

That's the worst yet!

Is that in text or some-ones personal version?

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Apocalypsse

Possibly the latter where it was taught by someone else. There was one where it was just using co-dominant, completely ignoring the term bifurcation and just describing the union (ie: included bark, etc).

Eric Frei

So is this two trees or a bifurcation (co-dominant at base) Garry?

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Garry Brockley

mmmm thats an interesting one after seeing the Aussie plantsmens attempts at producing decent stock
I would personally say its probably two trees as ive found that at seedling stage they don't pluck out any poor stock or thin out over planted plugs, however there are certain species that have bifurcation naturally and knowing this is the best way to differentiate them i.e. Jacarandas are renowned for bifurcation/ co-dominance at ground level.
well thats my 0.02 cents worth

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Eric Frei

The only real 100% conclusive way is DNA test each side and see if they match.... I reckon.

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Garry Brockley

true but who is going to pay to have a dna test on one/two trees just to see if they are related an expensive past time better to find the original planter and ask.......

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Eric Frei

Some-one who wants to either win or lose a decent bet.

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TrevMcRev

http://www.google.com.au/search?client=safari&rls=en&q=bifurcation+definition&ie=UTF-8&oe=UTF-8&redir_esc=&ei=qkp9TcDQBs74cZK3vLgG
No shortage of definitions of bifurcation out there.

Doesn't neccesarily have anything to do with trees (or included bark), but essentially describes the point at which something forks or divides into two "branches" - again that is not neccesarily meaning a tree branch. Could be anything from an artery to an investment portfolio.


http://www.google.com.au/search?client=safari&rls=en&q=bifurcation+definition&ie=UTF-8&oe=UTF-8&redir_esc=&ei=qkp9TcDQBs74cZK3vLgG#hl=en&sugexp=gsih&pq=bifurcation%20definition&xhr=t&q=codominant+definition&cp=10&pf=p&sclient=psy&client=safari&rls=en&aq=0&aqi=&aql=f&oq=codominant+definition&pbx=1&fp=dc0057adb156f860
Also plenty of definitions for codominance.

The common denominator in codominance definitions is that the two things being compared are equal.

So I say when it relates to trees:
Bifurcated: A trunk/stem divides into two (not equal) trunks/stems, with or without included bark.
Bifurcation: The point at where trunk/stem divides into two (not equal) trunks/stems.
codominant: A stem dividing into two equal (or very close to) stems, with or without included bark.