Eucalyptus blamed for Subsidence

[Albedo]

According to the research posted by Ben, which is very well carried out and states all its methods etc.

 

For managed reduction etc to be effective in stabilising soil moisture content, as Ben pointed out the initial reduction has to be significantly greater than 50% i.e the 70 to 90% quoted - much more than I would have thought - then it goes on to say

 

'To ensure a continued decrease in canopy leaf area and maximise the period of soil moisture conservation, crown reductions should be repeated on a regular managed cycle with an interval based on monitoring re-growth'.

 

So reduction and management appears to be acceptable, but the initial reduction is pretty heavy.

 

Just add here that knowing how tricky it is to judge tone and intent by the written word, my tone is just enquiring and learning is my intent. I am very happy to be wrong and have no axe to grind.

 

The report says a lot of other stuff too and others may interpret its findings differently to me:001_smile:

[Bundle 2]

"The cost of repairing the damage caused by the failure of domestic house foundations, due to subsidence, was during the years preceding this project of the order of £300-£400 million annually. Not all of this can be attributed to the presence of tree roots. However, most of the subsidence incidents in the UK are found to occur in areas with clay soils and in these areas, tree roots are claimed to have an effect on subsidence incidents in 73% of cases (Loss Prevention Council, 1995). Hence the potential for saving on remedial costs, by reducing the need for rectification work, may be around £200 million per annum. Currently, no methods exist that reliably predict which trees may cause damage and not all trees near buildings are implicated.-

" There are approximately 100 million trees in the urban environment. Of these, a large, but undefined, proportion is in sufficient proximity to a building to pose a perceived risk of damage. However, even in a drought year, the number of actual cases of subsidence is only about 50,000. The risk of a tree causing subsidence damage which is related to species, foundation depth and soil type may therefore be less than 1%. If one could identify this 1% with any reasonable accuracy, they could be pruned accordingly.-

"If trees that pose a risk cannot be identified, then one alternative is to treat all trees, regardless of the risk they pose. The environmental consequences of this would be catastrophic; nor could there be economic justification for any such policy as the cost of recurrent pruning would far outweigh alternative methods of remediation. For example, even pruning 1% of the tree population could cost any where between £50-100 million."

I guess its a question of perspective and the degree to which resources are being subverted ,disproportionately, to subsidence claims....?

 

It also says....

"• More information is needed on the effect of repeated pruning to determine the impact on the

root system and soil moisture conservation at the periphery of the root system.

• Root restriction within geotextile membrane lined pits may be used as an effective method for controlling shoot growth, but more knowledge is needed on the long-term integrity of the membrane, the stability and the performance of the tree...."

The LTOA would seem to have a significant data base aswell as the march on any other body likely to accrue meaningful statistics..?

[Albedo]

After the big bit that you quoted Bundle which sort of says ... for the 1% that might be a problem, which we have no way of telling anyway... blah blah

 

It goes on to say...

 

"The aim of this project was to improve the understanding of how isolated amenity trees use water,and to determine whether reduction in canopy leaf area and root-restriction are sustainable ways to control growth and reduce water uptake from soil".

 

This thread has some of the arbtalk big guns in it and I'm cackking it here:001_smile: but isn't the whole point of this research an attempt to address the statistics and problems etc outlined in its own preamble?

 

Whether it has suceeded in this or not, I'm not sure, but it is without doubt a bloody good effort.

 

edit: the last bit of this post is not a challenge or anything, more of a what do you think question type thing

Edited December 1, 2010 by Albedo

[Bundle 2]

Kinda thought this bit was pretty relevant....(included above)

 

"• More information is needed on the effect of repeated pruning to determine the impact on the

root system and soil moisture conservation at the periphery of the root system."

It's not insignificant that LTOA have a risk limitation strategy that utilises this technique, coupled with a cyclic regime of pruning...Its equally relevant ( all i was trying to point out) that nowhere else sees the need/benefit (as you like). It is of limited occurrence.

I am not making any comment, as far as I am aware, as to how effectively the research has succeeded in answering its own remit.

The implications are obvious......Lets have trees that are all mullered to within an inch of their lives..(every year) at some cost because it is the only solution we have for a very specific issue relating to 1% of trees? Or is there a better way?

Plastic trees anyone?

[Albedo]

I get your point now Bundle.

 

It says somewhere in the credits that this research has guided the new British Standard. If it - the standard - ever appears (or has appeared) it will be interesting to see the advice that ends up in there.