increasingly here in aust. local councils are requesting an accurate determination of the location of roots prior to granting development applications which may impact on a nearby trees health. at present use an air knife to expose the roots along the line of the intended cut/disturbance as it seems to be the most tree friendly approach. my question is does any one know of alternatives to this approach (apart from water excavation which tends to sever too many roots). is there anything like a sonar/xray probe that maps roots without soil disturbance?? or is that wishful thinking on my part? thanks for your consideration
mark lutherborrow

Reply to post by mark lutherborrow, on August 06, 1999 at 15:36:09:

Iv'e seen pictures of achiologists using a "sonar sled" that is draged across the ground at a set pace.

Maybe you could contact a local university to see what types of images they get of root systems?

Reply to post by mark lutherborrow, on August 06, 1999 at 15:36:09:

Mark,

Ground penetrating sonar has been used successfully to map
roots on a tree in Texas. The tecnology is understandably
expensive but reliable and unfortunately not available in Australia
at this stage.

I am not sure however that knowing the location of structural
roots is as impotant as we may be led to believe. It seems to
me that understanding the function and physiology of woody roots,
absorbing roots and root organs is more important. It is great to
know the root is there. It is more important to know what impact
damaging this root will have on the tree system and how to minimise
the impact of such damage.

Mark

Reply to post by Mark Hartley, on August 06, 1999 at 15:36:09:

Mark, I think the point in knowing where the roots are is at the start of the problem. You're right, we have to know what the effects of damage will be, but by knowing location, and hence the severity of damage (number of roots cut, size, etc.) we will have a much better idea of the impact overall.

Reply to post by mark lutherborrow, on August 06, 1999 at 15:36:09:

1. I'm not sure if the archaeological survey tools are sonar or radar, I'll have to look to see if I can find an article that I saw about it. In any case maybe that stuff could be rented or time shared from the universities that have it.

2. a) I get the sense that in environments like Texas and parts of Australia (arid??) trees tend to be less abundant and more valued, hence more effort to save than places like New England where we have trees, trees and more trees and "those leaves are a pain in the neck to rake up anyway." I haven't encountered any requirements for actual root location hereabouts. The rule (where there is one) seems to focus on typical, critical root zones (dripline, some multiple of trunk size, etc.). b) that said, given the typical existence of groups of trees rather than isolated specimens, I'd anticipate either trench excavation or sonar/radar probe to reveal a maze of roots from an array of plants and often underground structures, utilities and debris as well (is that an old phone line or traffic signal cable or a root on the sonar image?). Either way interpretation is not dead simple.

Reply to post by mark lutherborrow, on August 06, 1999 at 15:36:09:

thank you all for your responses. i will do some research into ground radar/or sonar and see what the state of the technology is. mark i agree that knowledge of the functions of the root system is imperative but as russ points out unlees you know how many and what type of roots you are affecting your appraisal is less than accurate. the local council where i am has seized on the fact that the extent and location of the root system of a tree cannot be predicted with any great certainty and therefore root probes are necessary for accurate location and categorisation of root type. scott as you mention it will be interesting to see if the available technology is able to distinguish between roots and other objects in the soil i will let you know what i find out in due course

Reply to post by mark lutherborrow, on August 06, 1999 at 15:36:09:

I did a search on the Subj and contacted three pages and pasted the replies below:
---------------------------------------------------------------
Paula Turner

We have located tree roots that were causing problems
around swimming pools and other structures. GPR images
of tree roots resemble those of buried pipes. A general
rule of thumb for GPR is that a tree root 1-inch in diameter
can be seen at one-foot depth; a 2-inch tree root at two-foot
depth; etc.. For smaller tree roots at depth, the GPR image
(soil) usually looks disturbed or bumpy.

If you need more information, please contact us again.

Paula Turner

John Paul Sanborn wrote:

> AT this site http://tree-tech.com/board/?topic=topic11 some one was
> asking about non invasive techniques for finding root systems of trees.
>
> What are your on the use of GPR for this purpose? what types of images
> do you get of woody material?

---------------------------------------------------------------
Marvin Speece

The best radar reflections are generated by objects with high electrical
conductivity such as metal barrels. I often observe side scatter from
trees that show up in my data as noise. I have not tried to look for tree
roots per se but wooden objects are not good targets in general. As long
as the roots have significantly different electrical property contrasts
from surrounding soil they would cause reflections. Whether or not you
would see the roots would depend on local soil conditions. My hunch is
that you would have success in sandy soils. I hope this helps. Marv
---------------------------------------------------------------

If the third message is replied to I'll post theat also.

Reply to post by Russ Carlson, on August 07, 1999 at 20:28:34:

Russ, I guess I come at it from a transplanting point of view.
It is all very well to know where the roots are but how do I do what I
want to do. Do I need to cut further out or do I need to stimulate and
benefit absorbing roots.

I agree whole heartedly that when we cut woody roots we cut absorbing roots.
There is a big difference between these two. Certainly our knowledge of canopy
pruning has improved but I seriously doubt that our understanding of roots
is up to scratch yet.

Lastly so now we know that there is a large root from the live oak 20 feet
from it's trunk. What action should I take? Perhaps I can move the building.
If I can't (and that's too often) then what should I do?

Reply to post by Mark hartley, on August 08, 1999 at 20:44:27:

I think the process is set forth in a number of sources in the literature, but I can't cite specifically at the moment.

Taking your question as rhetorical, some plain common sense needs to be applied early in the process. You do an initial study or survey of site resources (trees or whatever). The decision makers (owners, architects, engineers) decide what resources are desireable and then of those which can be accomodated at all in the overall site design (including building, paving and utility placement). Somewhere along the line the arborist advises which are worth saving or if worth saving can survive unavoidable impact.

If a tree is in an unavoidable impact area it may just have to go. There's no need for an expensive root survey. If a tree has to have its roots cut at a particular point and the arborist says it's worth the risk, there's no purpose in an expensive root survey. If decisions need to be made about where disturbance can be made, then maybe a root survey is worthwhile.

This has come up before in various threads here and it's sort of coming up lately on the UKTC List: Arborists tend to be tool junkies, they like big impressive stuff and they like gadgety stuff. And some of these gadgety investigative models too. But just because the tool is available or you know how to use it doesn't mean it makes sense.

It's unethical to suggest that all these measures are always required. It's not in our professional interest to create "standard" approaches or protocals which are excessive because then more senisible approaches get characterized as sub-standard.