arb culture

Keep trying Andy. It took about 5 or 6 serious attempts (as well as many half hearted ones)for me to finally give up about five years ago. If you keep trying you'll get there.

I manage to keep myself (and my colleagues) busy, but I wouldn't know how much work the rest of the sector has. I hear that some are going through hard times at the moment. I've found that it can be difficult to find people who know what they are doing who can also maintain client focus. Prices sound about right, but it will depend on what the client wants - a quick VTA, or detailed Picus etc. Good luck with it whatever you're trying to do.

It would be funny if it wasn't so bloomin frutsrating and counter productive. If someone doesn't have the intellectual ability to change a light bulb, are they really going to read and comprehend this? You have to ask what the real point of all this excessive risk assessment documentation is, it can't seriously be about a reasonable approach to risk.

I know its difficult to tell from photos, but I'd be very surprised if this tree was hazardous in its current form. Also, once its been pollarded you will have removed the sail area, so the chances of the stems falling over (I would guess) are almost zero. Hope this helps

I'm not sure if this is counted as a veteran, but I was really impressed by its survival. Almost all of the base has rotted through - causing the whole left hand stem to fall over. Although having just a thin strip of live cambium (approximately 5cm across) acting as a bridge between the roots and the 60cm diameter stem, the tree appears to be putting on good extension growth and has a reasonable amount of foliage. Added to that the tree is a shade intolerant ash, and is now growing in the partial shade of an oak woodland. Despite its history this tree really wants to live.

Not going to give us a worked example then?

"The road structure itself is not the target, rather the vehicles and the occupants travelling along it...so strictly speaking no a "busy" road does not represent a constant target value." Fair enough, but the level and type of road use is constant isn't it?

Sean, perhaps you could provide a worked example showing us how you have worked out the accurate target value and impact potential in a QTRA assessment?

Wow! Fantastic pictures

Tony, I don't understand why the idea of a constant target does not reflect reality. Isn't a busy road a constant target?

Thanks everyone for your anwers everyone. Reading between the lines, it seems I'm getting some people's backs up. So I thought I'd better explain myself a bit more clearly. I'm not trying to say that QTRA is without value, it does seem to be a sensible method of prioritising works to trees and tree inspections. However, I am questioning its accuracy, and also the way in which some practitioners seem to accept the resultant numbers as an absolute truth rather than just as an indicator. If the risks really are accurately quantified using QTRA, then it would be simple to take the risks posed by each individual tree from a population, combine them and then work out the total combined risks from a population of trees. Using the several QTRA assessments I have seen over the years, then the combined risks from trees would be huge, and obviously incorrect. The method desribed by Arborist Sites is similar to the method I would use if I were to use QTRA. However, I accept QTRA as a rough reckoner, and nothing more. So far, and over several years, no-one has been able to show me otherwise. I would really love to see a worked example which shows me to be wrong though. I like working with numbers and probability, so the idea of a quantified risk assessment for trees is so very tempting. Sorry for using the 'brave' comment Tony, I was being provocative.

Hello all, Buried in another thread somewhere I asked if any QTRA users would be so kind as to explain how they would quantify the risks from many trees at once. For example, on a large estate with many vistors and many trees. With a little help from Tony we discovered the proper mathematical method for working out culmulative probability, but as this gives some crazy answers it can't be the method used by QTRA. So I'm still waiting to hear how QTRA users work it out. Any QTRA users brave enough to tell us?

"I ve done PTI and it aint [nothing] with respect depth of knowledge of decay technology...... " I thought it was pretty good for a surveying level assessment. What's your problem with it Bundle?

Mesterh - that's what I meant when I said it depends on who's asking and why. As D Mc says these are not hard rules. 30% reduction to you may mean something very different to a non arb client, or even to an enforcing tree officer. It's important to be specific and precise, and to consider why the reduction is being perfomed in the first place. Is it for sail effect reduction, overall shade alleviation, to clear a nice view...?

The LANTRA PTI course includes a consideration of the various types of decay detection equipment. I've not done the tech cert, but I'd be surprised if they didn't teach/assess it as well.

It depends on who is asking and why.

:thumbup:Very nice pics Hama.

An example of sods law Earlier in this thread I confidently said that in the last three years I haven't needed anything other than a hammer and a probe and my own experience/knowledge to asses trees. No sooner had I said that than I visited a site with some very high value beech in a frequently visited area with slightly thin crowns and minor die-back. One or two also have decay fungi at the base (Kretschmaria and Ganoderma sp. - not sure which) and all have been subject to compaction from landscaping/development. Hammer not revealing any signs of decay and there's no holes to probe. Trouble is, I need to know if the thin crown is due to compaction (ie the trees probably won't fall over for a while yet) or whether it's due to massive root decay (ie trees might very well fall over). I know what I've recommended, but what would others suggest for assessing the decay on these things?

If I was in charge of many trees (ie a local authority parks department) I would want to know total risk from trees to allow me to make budget decisions. Ie should I spend more on preventing deaths from people drowning in the ponds, or on people tripping over uneven paths, or on undertaking tree work? A quantified system should allow this to be straightforward. eg if the total risks from trees is more than 1/10,000 then I must deal with that. If the total risk is between 1/10,000 and 1/1,000,000 then I have to do what is reasonable. If the total risks from the uneven paths is greater than the total risks from trees then it would be reasonable to prioritise the work to the paths etc... Anyway, it's time for wine and rubbish tv I think.

Thanks Tim, but perhaps you could just let us know how you as a qtra user would calculate the total risk from many trees. I've trawled through most of the links, but I couldn't find an answer.

Nice one, thanks Tony:001_smile: Firstly, let's get the higher and lower risk sorted out. A 1/2 risk is higher than a 1/10 risk (ie 0.5 is greater than 0.1) therefore a 1/10,000 risk is greater than a 1/1,000,000 risk. Now, if you rely on the same sources as the authors of QTRA (the 'living with risk' book I mention earlier) the 1/10,000 threshold is just one of two thresholds. The other being 1/1,000,000. According to this research on which QTRA is based, any risk below 1/1,000,000 is not worth bothering with and anything between 1/1,000,000 and 1/10,000 should be reduced as far as is reasonable. Anything greater than 1/10,000 should immediately be dealt with irrespective of reasonableness. So I understand why trees with a greater than 1/10,000 risk are considered dangerous under the QTRA system. However, I don't understand why trees between 1/10,000 and 1/1,000,000 are deemed acceptable. This seems contrary to the research on which QTRA is based. My main query though is that I don't understand how QTRA deals with a situation where there are lots of trees. How is the total risk from all trees on an estate or a highways network worked out?

To the client, HSE, law courts, the family of the people affected, the local authority who decides on whether to provide an extra lollypop person or to prune loads of trees. How do QTRA users suggest the threshold is set, assuming the client is a non arb with no specialist knowledge of risk management?

Pretty bloomin close though Tony. Bear with me and you'll see why I ask these geeky questions, there is something I really want to know.

Bundle, no disrespect, but if you follow the link below to the relevent GCSE bitesize page, I think you will find that 0.9 is the same 9/10. BBC - GCSE Bitesize: Fractions and decimals Unless I've missed something

Now, what is the threshold at which the risk from a tree is deemed unacceptable?