UKTC Archive

Re: RPA rooting volumes at various radiuses - proof

Subject: Re: RPA rooting volumes at various radiuses - proof
From: Ben Rose
Date: Jan 16 2020 15:54:59
Dear all,

The discussion about how much of the root system BS5837 protects raises an 
interesting question about how much soil volume we design urban tree pits to 
have. Simple calculations over how big a tree pit should be can be made if we 
assume that the tree pit is designed to be 1m deep and we use Table D1 from 
BS5837 (attached). Using this approach it works out that a tree of 30cm DBH 
would require 41 cubic metres of soil, and a tree of 50cm DBH would require a 
soil volume of 113 cubic metres. If you follow this logic a tree has a 
diameter of 1m would require 452 cubic metres of soil........and we have 
prominent members of this forum suggesting that the British Standard guidance 
only protects a fraction of the volume that trees are adapted to use.

Of course BS5737 wasn't designed for calculating tree pit volumes, however 
this exercise suggests that we should be making urban tree pits much larger 
than we are at present. From my experience the standard tree pit has a volume 
of approximately 4 cubic metres, which isn't going to support a sizeable tree.

There is a direct relationship between the volume of below ground growing 
space and how a tree is likely to develop, the greater the soil volume:
- the faster the tree will grow
- the bigger it will become
- the healthier it will be
- the better it will look
- the longer it can be expected to live

I think that we can all agree that large urban trees bring much more benefits 
than smaller trees, and that trees in their mature life-stage need little 
maintenance compared to the same trees in their establishment phase. 
Therefore to get the best return on the investment of planting and 
establishing urban trees we should be designing tree pits that support the 
species planted to reach maturity. I have found that if you think about it 
this way it is quite clear that we should be designing urban tree pits to be 
much larger than we are designing them at present.

Tree planting is high on the political agenda at present and large sums of 
money are being made available for urban tree planting. Surely it is our 
responsibility as landscape professionals to be using this money wisely. I 
think that an important part of the job is to design tree pits to be big 
enough to allow the trees that are planted to reach their mature size.

Ben


Sent: Thursday, January 16, 2020 at 11:26 AM
From: "Julian Morris" <jamorris@xxxxx.com>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Subject: Re: RPA rooting volumes at various radiuses - proof

Furhter to email yesterday, attached is an abridged version of the 
matehematical proof. I don't expect many, or any, to work through it, but 
if you do I am appreciate corrections, but I am giving the proof anyway so 
that no-one thinks I am speculating rater than proving. Expanded workings 
available on request.

And the key outcome is that RPA rooting volume is not proptional to RPA 
rooting radius, but there is a definable mathematical relationship.

When RPA radius is exactly half of total rooting radius, the RPA rooting 
volume is exactly half the total rooting volume.

But when it is one third, the RPA rooting volume is one quarter.

And when it's two, thirds, the RPA rooting volume is three quarters.

In comparison, the ratio between RPA area and total rooting area is (r/R) 
squared.

Half the radius, quarter the area.

Jules




I'm with you most of the way on this Jim, but the elegance falls apart when 
one re-introduces the volume of rooting in place of the area. I've just 
scribbled out a proof and it shows that the volume of rooting in the RPA is 
definitely not half the volume of all rooting. The ratio in fact depends on 
the depth of rooting, i.e. there is no one-size-fits all. I'll check it and 
write it out neatly and post it here tomorrow.

Julian A. Morris - Professional Tree Services
jamtrees.co.uk  and  highhedgesscotland.com
0778 XXX XXXX - 0141 XXX XXXX


Sent: Wednesday, January 15, 2020 at 10:09 AM
From: "Jim Quaife" <jq@xxxxxxxxxxxxxxxxx.co.uk>
To: "UK Tree Care" <uktc@xxxxxx.tree-care.info>
Subject: RE: [EXTERNAL] Tree failure potential assessment study WAS Civil 
cases for nuisance or damage to property

Mike,
Quite a few years ago, prior to writing my article on roots for the AA I 
conducted a straw poll asking how far beyond the radius of an RPA the 
root system would extend.  The principle of the RPA is to protect an area 
(with implied volume - which of course is dependent upon the rooting 
depth profile) of a tree's root system that would sustain it if all roots 
around the circumference were severed.
I make no pretence that the results of the question was in any way 
scientific, but the overwhelming answer was that the root system was 
twice that of the RPA.  Funnily enough, this was much the same as the 
thinking behind the notion of the Root Protection Distance of the 1991 
BS, and the 1980 BS consideration of the crown footprint.
Simple maths makes the RPA a quarter of the root system if the radius is 
half that of the root system.
This is an "alarming" prospect and so I have reduced it to a third as 
this less "scary".   There does not seem to be any research that looks at 
a root system in terms of the RPA, but I am comfortable with the notion 
of it being a third of a tree's root system.
I have argued that when determining what may or may not be acceptable in 
terms of intrusion into an RPA, firstly the intrusion should not 
compromise the assimilative and structural function of the root system, 
bur secondly the intrusion should be considered in terms of the entire 
root system.
As ever, this is a matter of judgement and justification.
Of course there is no mention of this in 5837, but it is not a text book. 
 For instance, there is no justification or research basis for the 20% 
limit on permanent hard surfacing within an RPA!  There are arguments to 
suggest that this needs to be a matter of justification in each instance 
and not a matter for some random benchmark.  Again, this falls within the 
need for justification on page iii, 2nd para under the heading 'Use of 
this document'.
This sentence is an honest recognition of the need for interpretation and 
justification of the BS. I may add that I am a supporter of 5837 and was 
gratified that a few of my insistencies are included, but it does 
necessitate applied interpretation.
Jim

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of AV Arboriculture
Sent: 15 January 2020 09:07
To: UK Tree Care
Subject: Re: [EXTERNAL] Tree failure potential assessment study WAS Civil 
cases for nuisance or damage to property

Jim,

I was a bit startled at your comment: "BS5837 advocates the removal of 
perhaps two-thirds of a tree's root system." I am not aware of this in 
the BS, but perhaps I have misunderstood you?

Wayne, there has been a lack of research into the effects of root 
pruning. Andrew Benson from NZ has been doing his PhD work on this, and 
was speaking at the AA conference last year. His Research Gate page is [ 
https://www.researchgate.net/profile/Andrew_Benson9 | here ] .

Mike Charkow
[ https://www.researchgate.net/profile/Andrew_Benson9 ]

From: "Wayne Tyson" <wt750mv@xxxxxx.com>
To: "uktc" <uktc@xxxxxx.tree-care.info>
Sent: Wednesday, 15 January, 2020 01:32:21
Subject: Re: [EXTERNAL] Tree failure potential assessment study WAS Civil 
cases for nuisance or damage to property

Dave (if that's your real name), I quite agree about the importance of
specifics with respect to cases, provided individuals are left out. I
believe that the Moderator is correct to eschew personal exchanges like ad
hominem attacks. When discussing matters in the abstract, I believe that 
it
is the responsibility of the discussants to be directly responsive to the
points made by the other correspondent, and quoting same in the "reply"
otherwise it is not *responsive*, by definition. This includes avoiding
restatements that distort or misrepresent the other's statement. That is,
one should quote the statement to be discussed, discuss it, wait for a 
like
response, then reconcile the issue(s) if not resolve them. I consider it
poor form to "bait" the other discussant(s).

For example, to your statement: "Precise, reasoned and easily repliable
[sic] are the way to go" I would add *relevant*. [*Je ne parl pa 
Francias*]

If you would like to discuss a specific issue about arboricultural
practice, please discuss the merits and validity of the practices, for
example, of "lion-tailing," "top-hatting," and "lacing" (all US terms; 
they
may be used in the UK too, for all I know).

Cheers,
Wayne

On Tue, Jan 14, 2020 at 4:07 PM oldoaktree@xxxxxxxxx.net <
uktc@xxxxxx.tree-care.info> wrote:



Wayne, I appreciate what you say, and I am very much interested in the
mechanics of argument.

I imagine that your 'expert' dismissal is down to the Dunning-Kruger
effect where people of little knowledge on a subject think themselves as
massive experts because they talk about it a lot.

(on the other hand, people being immensely knowledgeable, tend to avoid
giving comment because they know of the lack of DATA to ensure a reliable
answer).

We are beginning to get well Batman philosophical here, but my point would
be that on a moderately technical and ethical forum such as this, we need
to post fairly direct comments and make our questions or criticisms very
pointed.

Precise, reasoned and easily repliable are the way to go.

Cheers

Dave

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
<uktc-request@xxxxxx.tree-care.info>
On Behalf Of Wayne Tyson
Sent: 14 January 2020 23:33
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: [EXTERNAL] Tree failure potential assessment study WAS Civil
cases for nuisance or damage to property

Perhaps, Dave, you misunderstood. My remark was not aimed at any
particular person, only a category--that, by the way, covers every 
"expert,"
regardless of what field the individual might be out standing in. If you
read my remarks carefully, I hope you will find that this is clearly so.
Henry Wheeler Shaw put it this way: "The worst kind of ignerance ain't so
much not knowin' as 'tis knowin' so much that ain't so."

Apparently I was wrong, but I presumed that every tree professional would
agree with the statement, since (I presumed they would all believe) none
of us knows everything. As Margaret Mead once put it: "The most important
thing to know is what you don't know."

So my statement was not aimed at those, while perhaps possessing a lot of
knowledge in a particular field, do not consider themselves omniscient 
(the
fools to which I was referring), but continuing scholars advancing
knowledge and exchanging ideas through forums such as this one. I'm
certain, Dave, that you know many things that I do not. I would hope that
we could continue to discuss principles without interpreting each others
remarks as a personal offense, and thus gain in the exchange.

Wayne

On Tue, Jan 14, 2020 at 2:14 PM oldoaktree@xxxxxxxxx.net <
uktc@xxxxxx.tree-care.info> wrote:

Nicely shot from the hip there Wayne, but you rub a lot of peoples
noses in the dirt there.

Talk like "show me an expert and I'll show you a fool" doesn't really
gell very well with any of us who might have some expertise in certain
areas.

If you want to make a criticism, then please make it clear, specific
and recognisable. Scattergun approaches do not help your position.

Ta

Dave

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info
<uktc-request@xxxxxx.tree-care.info>
On Behalf Of Wayne Tyson
Sent: 14 January 2020 20:30
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: Re: [EXTERNAL] Tree failure potential assessment study WAS
Civil cases for nuisance or damage to property

Then "arbs" have a long way to go. "They" haven't scratched the
surface of science, and if by "judgment" you mean "experience," they
are settling for far too little. There are WAGs and SWAGs, but show me
some DATA! That is, *discipline*! Where are the actual studies that
can back up "judgment?" I can't find 'em. The tree professions *can*
get better and better, if the individuals in it want to. Show me an
"expert" and I'll show you a fool. At the very least, the profession
can move from "imminent" to recognizing unstoppable trends.

On Tue, Jan 14, 2020 at 11:42 AM Jim Quaife
<jq@xxxxxxxxxxxxxxxxx.co.uk>
wrote:

Nice idea Wayne, but no chance of enactment. By and large root
systems are over-designed in nature, and root severance is a matter
of judgement and not law. BS5837 advocates the removal of perhaps
two-thirds of a tree's root system. There are any number of
instances where roots have been severed to an extent that raises
eyebrows and yet the tree doesn't miss a beat.
Of course there are converse examples, but I have been in situations
where a single root is deemed to be important and when one looks at
what else is sustaining the tree, that notion is frankly ridiculous.
Like everything else to do with trees, root severance is a matter of
judgement and justification. This is an arb's stock in trade!
Jim

-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info [mailto:
uktc-request@xxxxxx.tree-care.info] On Behalf Of Wayne Tyson
Sent: 14 January 2020 18:38
To: UK Tree Care
Subject: Re: [EXTERNAL] Tree failure potential assessment study WAS
Civil cases for nuisance or damage to property

The main "practical" point is that there should be a law prohibiting
the severance of tree roots. Of course, we all know that's not going
to happen, but it should be done with full knowledge of the
consequences, and under permit that requires real data on the
potential consequences (including
liability) derived from sound scientific procedures (e.g., tritium
tracing or approved equal [For the record, I have not performed this
procedure, only read about it.]). What is not well understood is the
complex nature of the radial root system development in all
directions from the stem/trunk in relation to tree health and
structural stability. What really provides resistance to
toppling/uprooting is the fine-root matrix that extends to and
beyond the "drip-line" of the tree and whether or not meristematic
tissue is present to facilitate "recovery" of the severed roots, which
is limited to fine roots.
Anchoring roots tend, in many if not most species, to lack such
tissue, and their severance kills the attached finer roots that
actually provide the resistance. Big roots lacking the capacity to
recover do not, by themselves, provide much resistance--root "pruners,"
listen up! Loss of resistance is essentially permanent, and the load
continues to increase as the tree grows. At the very least, such a
practice does not increase resistance (root-system "strength").

Here is a link of relevance I recently discovered by one of our (US)
best arborists. It should be noted that while it may be an absurdly
extreme case, tree failure potential can be significantly induced by
far
less.
https://www.youtube.com/watch?v=xFqU2kBlxkI

WT

On Tue, Jan 14, 2020 at 4:33 AM Harrison, Sean <
Sean.Harrison@xxxxxxxxxxx.gov.uk> wrote:

Nice one Wayne;
I shall use that next time an insurance company wants a 200 year
old tree removed because roots are damaging the foundations of a
70 year old
house.
Sean



-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info <
uktc-request@xxxxxx.tree-care.info>
On Behalf Of Wayne Tyson
Sent: 11 January 2020 22:40
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: [EXTERNAL] Tree failure potential assessment study WAS
Civil cases for nuisance or damage to property

Warning: email from outside of MVDC - if in any doubt do not open
links
or
attachments, or carry out requested actions
________________________________


Mike Charkow,

Somewhat tongue-in-cheek but (contrarily and seriously), I might
suggest that the construction of the fence and slab might have
caused damage and
to
the root system and compromised its integrity, possibly
compromising the tree's well-being and shortening the tree's life,
not to mention
weakening
the tree's ability to support itself constitutionally and
physically, as well as the slab depriving the root system of air
and water, thus causing the root system to favor the part of the
soil profile nearest the
surface,
i.e., the slab as well as possible or probable damage to the root
system
by
the digging of fencepost pits, not to mention the installation of
underground facilities such as foundations, utility facilities, etc.

On the other hand, the planting of a large-growing tree in a
location close to a property line by someone who knew or should
have known that it would encroach upon an adjacent property might
also be questioned. If the tree was natural, both owner and
neighbor might be guilty (as if there
were
any justice for Nature's voiceless) of compromising the tree's
rights to the quiet enjoyment of its home and sustenance, as well
as expectations
of
freedom from injury.

I'll be interested to know (and get links to) any cases and
judgments. Do tree's have standing?

Wayne



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