UKTC Archive

rooting volumes/tree pits

Subject: rooting volumes/tree pits
From: Hare, Gareth
Date: Jan 16 2020 16:37:04
Hi Jim (and all of uktc of course). Your hope regarding tree pits being 
surrounded by suitable soil conditions to enable root growth is seldom 
realised on development sites. (I know you know this but thought it worth 
making the point). Where designed tree pits are necessary, the soil 
conditions surrounding the pit are invariably dire with foreign material, 
contaminants, high bulk density, root barriers and barriers to roots, 
waterlogging etc.

It is very unusual to provide a tree pit of a size capable of sustaining a 
tree to maturity. We should be pushing other professionals to take the above 
into account and where the soil conditions are hostile to root growth, tree 
pits should be the 'right' size for the job.

This may inadvertently push developers into protecting soils where 
landscaping is going rather than undertaking costly remediation or 
engineering operations. 

This document: 
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/716510/pb13298-code-of-practice-090910.pdf
 although not perfect, is lamentably underused/unknown and could do with 
being updated and 'pushed'.

Where there is money to be made/saved, so the developers will follow.


Kind regards

Gareth


Gareth D Hare
Arboricultural Officer
Lichfield District Council 

District Council House, Frog Lane, Lichfield, Staffordshire WS13 6YZ
T: 01543 XXXXXX
E: gareth.hare@xxxxxxxxxxxx.gov.uk





-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Jim Quaife
Sent: 16 January 2020 16:13
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Subject: RE: RPA rooting volumes at various radiuses - proof

Hi Ben,
There is an inversion here in that the RPA is to protect a sufficient rooting 
mass where there is to be a curtailment of root spread.  Planting pits are 
surrounded by soil, which (one hopes!) roots will grow out of into the soil.  
 If there are existing limitations to root growth then species choice comes 
to the fore. 
I suggest that it is very unusual to provide a tree pit of a size 
commensurate with a projection of root growth in maturity for a new tree.
Jim



-----Original Message-----
From: uktc-request@xxxxxx.tree-care.info 
[mailto:uktc-request@xxxxxx.tree-care.info] On Behalf Of Ben Rose
Sent: 16 January 2020 15:55
To: UK Tree Care
Subject: Re: RPA rooting volumes at various radiuses - proof

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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