5837 RPA calc

[kevinjohnsonmbe]

Any opinions on this one?

 

Is it a multi-stem where the combined measurements at DBH provide the total for RPA calc or are they separate trees? I've done the calc's for both and neither present an RPA which would adversely impact the development proposal so it's kind of a mute point but just interested to see how others might approach it.  

 

Short of excavating, and my time / interest / payment doesn't extend that far, and noting the obvious age difference between the main stem and the others, difficult to determine if they are part of the same tree or seedlings that have fallen close by.

 

Any thoughts appreciated! 

 

 

 

[kevinjohnsonmbe]

Would you call it 1 tree or separates Ed? 

 

It doesn’t matter either way in relation to the report, combined or as separates, RPA, distance, gradient and pre-existing natural barriers to root place it firmly out-with the proposed development footprint 

[daltontrees]

Kevin, this is something that I seem to encounter very often. The significance of whether it is one tree affects its (their) categorisation as well as RPA(s).

 

If it's one tree, I'd say it's quality is diminsihed by what is probably maturing epicormics. Furthermore, removal of the subsidiary stems is going to open up the whole tree to infection, and Ash wouldn't stand a chance fighting it off.If that's right, then there is no management recommendation that would restore the tree to the quality of a sinlge stemmed A or B.

 

If it's more than one tree, the subsidiary stems could be removed, and it could be a sound management recommendation that they be removed. When gradign them they could be seen as of "very low quality ... suppressing adjacent trees of better quality", and as such they would be Cat U.

 

Regarding RPAs, there is I recall some published support for the view that where two trees are within each others' RPA the rooting areas are shared, without needing to increase the size of either.   This is irrational except and unless the trees are diminished in development because of their competition for resources. Even then it's a questionable argument, but it is overpowered anyway by the arbitrary nature of the 12x multiplier.

 

To apply 5837 to this situatuon, you have to know or at least settle on an assumption about whther it is one or two or more trees. Then one or multiple RPAs  can be calculated. But if anyone then draws multiple RPAs as circles, they're kidding themselves on. I mean, how would the roots of the smaller stems get under the large stem?

 

Also Duncan Slater published an article a coupel of years ago making a good case that trees are positively hostile to each other, especially if the same species.

 

That's why I investigate and show it's one or multiple failing which state a reasonable assumption of whether it's one or many, and if it's many I skew both RPAS away from each other.

 

And back to my first point, the real significance is in the Categorisation. One tree with multistemmed cna cause downgradde with no managment solution. Multiple treess can result in the subservient ones being downgraded to U, and a valid management solution being their removal.

 

For what it's worth, the body language of your situation is saying to me multiple trees.

[kevinjohnsonmbe]

5 hours ago, EdwardC said:

I'd look at it as a 'worst-case' scenario. I.e. one tree with multiple stems. That way when the layout is being designed taking, into account the tree constraints, there can be no argument around the RPA. 

 

The tree survey and constraints were ascertained at the very start and so could inform the layout, weren't they? Or is it the usual box ticking exercise for planning.

I've done both Ed with exactly that (worst case scenario) premise in mind - worst case scenario doesn't present an RPA which is anywhere near being a barrier to the proposed development - on that basis alone (there are potentially other issues though.)

 

There is quite an entertaining tale behind the sequencing of this one, I may be able to elaborate more soonish....

 

 

 

 

  

[kevinjohnsonmbe]

2 hours ago, daltontrees said:

Kevin, this is something that I seem to encounter very often. The significance of whether it is one tree affects its (their) categorisation as well as RPA(s).

 

If it's one tree, I'd say it's quality is diminsihed by what is probably maturing epicormics. Furthermore, removal of the subsidiary stems is going to open up the whole tree to infection, and Ash wouldn't stand a chance fighting it off.If that's right, then there is no management recommendation that would restore the tree to the quality of a sinlge stemmed A or B.

 

If it's more than one tree, the subsidiary stems could be removed, and it could be a sound management recommendation that they be removed. When gradign them they could be seen as of "very low quality ... suppressing adjacent trees of better quality", and as such they would be Cat U.

 

Regarding RPAs, there is I recall some published support for the view that where two trees are within each others' RPA the rooting areas are shared, without needing to increase the size of either.   This is irrational except and unless the trees are diminished in development because of their competition for resources. Even then it's a questionable argument, but it is overpowered anyway by the arbitrary nature of the 12x multiplier.

 

To apply 5837 to this situatuon, you have to know or at least settle on an assumption about whther it is one or two or more trees. Then one or multiple RPAs  can be calculated. But if anyone then draws multiple RPAs as circles, they're kidding themselves on. I mean, how would the roots of the smaller stems get under the large stem?

 

Also Duncan Slater published an article a coupel of years ago making a good case that trees are positively hostile to each other, especially if the same species.

 

That's why I investigate and show it's one or multiple failing which state a reasonable assumption of whether it's one or many, and if it's many I skew both RPAS away from each other.

 

And back to my first point, the real significance is in the Categorisation. One tree with multistemmed cna cause downgradde with no managment solution. Multiple treess can result in the subservient ones being downgraded to U, and a valid management solution being their removal.

 

For what it's worth, the body language of your situation is saying to me multiple trees.

The categorisation element is an interesting one Jules.

 

Difficult to justify "U" since it is caveated by the "in the context of the current land use" phrase.  The current land use doesn't impose a "less than 10 years" implication.  The current land use could see them continue until failure - which would likely be greater than 10 years (notwithstanding pathogens.)

 

C1 would probably be the closest in a less than optimum choice of categories.  

 

Then one or multiple RPAs  can be calculated. But if anyone then draws multiple RPAs as circles, they're kidding themselves on. I mean, how would the roots of the smaller stems get under the large stem?

 

This opens a question for me...

 

Leaving aside the (less than ideal) issue of RPA 'circles' as an unrealistic but perhaps workable (unless obvious obstructions exist) compromise for presenting likely or anticipated extent of the rooting presence, wouldn't it be the case that the result of combining the multiple stem DBHs to provide the 'big circle' takes account of the reality that some of the smaller diameter stems will not reach the outer extremities of the big circle (uniformly) but that having this method allows for a kind of over estimation which 'should' accommodate the lesser or off-set root areas of the smaller diameter trees?

 

I'm hoping this whole situation will arrive at a conclusion before too long, then I might be able to share some more of the details.

 

 

[kevinjohnsonmbe]

5 hours ago, EdwardC said:

Am I missing something here. Trees don't share their rooting environments? What about woodlands, or groups of trees. What size would an RPA for these  be if each tree has to have it's own seperate RPA. Not to mention how do such features survive due to all that competition. And it's worth noting that the RPA is woefully short of the true extent of root spread.

I thought it would have been this part that raised the question:

 

“...Also Duncan Slater published an article a coupel of years ago making a good case that trees are positively hostile to each other, especially if the same species...”

 

Gonna have to try and look that up. 

[daltontrees]

On 03/11/2018 at 16:43, EdwardC said:

Am I missing something here. Trees don't share their rooting environments?

You are missing something. I didn't say that trees don't share their rooting environments. I said that not having to increase the collective rooting area or see diminished growth was an irrrational assumption.

Does nature allow a highly evolved species the luxury of not maximising its use of available resources? I really don't think so. So, introduce comeptition from a similar individual of that species into those limited resources and something has to give and/or synergies have to arise to benefit one or both.

We aren't discussing the rooting area, we are restricting ourselves to the defined constraints or RPA per BS5837.

[daltontrees]

On 03/11/2018 at 21:51, kevinjohnsonmbe said:

I thought it would have been this part that raised the question:

 

“...Also Duncan Slater published an article a coupel of years ago making a good case that trees are positively hostile to each other, especially if the same species...”

 

Gonna have to try and look that up. 

I'll try and find it. I think it was in the AA mag.

[daltontrees]

On 03/11/2018 at 15:34, kevinjohnsonmbe said:

Leaving aside the (less than ideal) issue of RPA 'circles' as an unrealistic but perhaps workable (unless obvious obstructions exist) compromise for presenting likely or anticipated extent of the rooting presence, wouldn't it be the case that the result of combining the multiple stem DBHs to provide the 'big circle' takes account of the reality that some of the smaller diameter stems will not reach the outer extremities of the big circle (uniformly) but that having this method allows for a kind of over estimation which 'should' accommodate the lesser or off-set root areas of the smaller diameter trees?

 

Thoroughly impressive and careful sentence construction there.

 

No. But...

 

A plausible starting point for analogy with ring porous species perhaps.

[daltontrees]

It's a 4 dimensional problem, but to reduce it to 3 dimensions, I was on a site today doing a 5837 survey where I know all the trees were planted at the same time. I found a tree that sat within all of the slightly overlapping RPAS of 4 other trees. It was the only tree on the site that was dead.