Paul Melarange

I've just re-read my earlier post and think this paragraph needs further clarification: 'Unless you are cutting large structural branches which have significant heartwood, or the tree is in poor physiological condition, it is unlikely that decay from the cut branches will extend into the main stem.' It is likely that most veteran and ancient trees could be considered to be in poor physiological condition. However, this is where 'functional units' become important. An old tree is likely to comprise a number of functional units I.e a structural branch or stem (and its associated xylem and phloem that link it with it's corresponding roots) that function almost independently from other parts of the tree. So, if the functional unit you are working on demonstrates normal vitality it is unlikely that any decay associated with pruning cuts on lateral branches (depending on their size) will extend into the main trunk. Basically, what I'm trying to say is: if you reduce a functional unit too much and it dies, there is a strong possibility that decay from that section of the tree will affect the main trunk (eventually).

This is probably the perfect opportunity for me to plug our (ancient tree forum) book written/edited by Dr David Lonsdale: Ancient and other veteran trees: further guidance on management. It's available from a number of places including the tree council website: http://treecouncil.org.uk/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=28&category_id=1&vmcchk=1&option=com_virtuemart&Itemid=4 It's a fantastic book. It even has guidance on what to include in a method statement for work on a site where veteran trees are present!

Ty That is a really good question. The use of 'coronet cuts' or 'natural fracture techniques' is to mimic the way branches would tear if they were to fail due to natural events rather than human intervention. The use of these techniques can be for a number of purposes I.e. for aesthetics (looks better than just a stub) and creates crevasses which may provide habitat for invertebrates. I think the key thing is that they allow arborists to make internodal cuts (cuts between points of growth) in a skilled manor, rather than doing (what feels like) substandard work. The thinking behind the use of internodal cuts for retrenchment pruning is to upset the balance of auxins and cytokinins in the branch, potentially initiating epicormic growth and lateral branches lower down in the internal parts of the crown. Unless you are cutting large structural branches which have significant heartwood, or the tree is in poor physiological condition, it is unlikely that decay from the cut branches will extend into the main stem. The retention of dead lateral branches provides habitat and a food source for a whole range of organisms including saproxylic invertebrates (invertebrates that require deadwood to complete their life cycle) and all sorts of fungi, particularly those that are saprophytic. I hope this helps answer your question? Kind regards Paul

Haha, I've been a lurker on Arbtalk for a little while. I think it's a great resource. Doubt I'll bring any sense...just confusion 😕

There will be no benefit in washing out any of invertebrates that might be inhabiting the dysfunctional and/or decaying wood, they will only return. Just stick with the mulching.

Sound advice from 10 Bears. The damage certainly appears to be consistent with that caused by grass cutting equipment. Unfortunately a frequent occurrence :-(

Is there any way you could post a photograph of a branch/twig of the tree? The bud arrangement would really help in its identification?

Good answer from Sloth. Dean is also right in saying that there is a thylakoid lumen, but that is in the chloroplast and as you may already know is site of the light dependant reactions of photosynthesis. Try comparing xylem vessels and tracheids. Also think about how xylem differs in ring porous and diffuse porous. If you're still struggling after that investigate 'cavitation'. 😀

Serpula lacrymans: the fungus that causes dry rot. I don't think it's harmful to human health, see link below: http://www.moldbacteriafacts.com/serpula-lacrymans-health-effects/

Pete, Thanks so much for posting. You are absolutely right and you make some really interesting points. Apologies for the delay in responding. I have discussed your post with my colleague Paul Muir of Treework Environmental Practice (the Uk's leading expert in tree statics) and he has written the following response: Pete Bannister is correct. A safety factor of 1.5 is what engineers would be likely to use when designing an aircraft, and higher safety factors are incorporated during the design of buildings, for example. While there is more information and a higher degree of certainty regarding the material properties applicable to aircraft construction, I would suggest that accepting a safety factor of 1.5 is more to do with cost considerations whilst also requiring the aircraft to be light enough to actually leave the ground. The engineers would prefer higher safety factors, but this would require more expensive materials, a heavier plane and greater running costs. The aviation comparison is actually appropriate. Tree statics developed from a university study in Germany (Lothar Wessolly) that looked at lightweight structures in nature. Remember trees have to balance competitive height growth with available resources (costs), so there is an evolutionary advantage to not over-investing in safety margins. Trees only start to achieve high safety factors during the mature phase (because they can’t stop producing annual increment). Even then lower order branching will have lower safety factors – twigs break on an annual basis. In terms of the static load test a safety factor of 1.5 is a desired minimum. I am comfortable that this is (generally) acceptable. There are a lot of margins for error within each element of the model. Most importantly, I suspect that the design wind load that the tree is required to carry is almost always an over-estimate in our calculations. There is a further important consideration. Trees are structures that change. When considering a measured safety factor an appropriate interpretation will involve considering how much the safety factor is different from what would be expected. A safety factor of close to 1.5 for an early mature tree might be the best one can expect, even if defect free. For a late mature tree with a large stem diameter a safety factor of up to 10 or more, might be expected, so a result of 1.5 would perhaps be cause for concern. All balanced against the vigour of the tree. What potential is there for the situation to improve rather than deteriorate. My experience is that trees with large stem diameters, like the cedar at Kingston Lacey, have very high (theoretical) safety factors (i.e. the safety factor one would expect if they were defect free), and that even though these might be extensively reduced through decay (say from a safety factor of 10, to one of 3 or 4), the residual safety factor is still higher than one might expect for an early mature defect free tree. In other words these old trees are less likely to fail. The implication is that strength loss formulae are fundamentally flawed in terms of being appropriate failure criteria. Which is stronger - a rope with a 10 ton breaking strength with half the fibres cut or a rope with a 1 ton breaking strength?

Hi Tony I think we may well have a difference of opinion as to what constitutes an empirical test let alone 'objective'! But I have no intention of getting into semantics. You ask 'how was the 1.5 safety factor determined?'. I assume you mean why is it 1.5 rather than 1 or 2? Below is a quote from Andreas Detter's paper 'Static load tests in arboriculture'. He explains it perfectly: 'If the resistance against failure matches exactly the expected wind load, the factor of safety of the tree would be 1. But according to engineering standards any structure must have sufficient strength reserves beyond the expected loads. Due to the level of uncertainty involved in any numeric approach, a factor of safety of 1.5 is required in the static load test'. I hope this answers your question?

Hi Tony Static load tests enable an objective assessment of tree stability to be made. The tests result in the calculation of a factor of safety. A tree with a factor of safety of 1.5 (one and a half times stronger than it needs to be) or more would be considered as safe enough to be retained without further work. A tree with a safety factor of less than 1.5 would require either crown reduction (to lessen the wind load) or felling depending on the circumstances. A static load test consists of three stages: stage one involves pulling the tree with a winch. During this procedure sensors positioned on the stem measure changes in the length of the wood fibres both in tension and compression. ‘The degree of compression or extension in the marginal fibres by the applied load is used as an indicator of the resistance to fracture’ (Detter, 2012) Tilting of the root plate is also measured. The second stage involves wind load analysis. Details of expected wind speed and wind characteristics, for the area in which the tree is located, are obtained using published weather data. The trees resistance to streaming i.e. it’s surface area, porosity etc (the crown acting as a sail) is calculated. The third stage involves the evaluation of the previous two stages using specialist software to produce a factor of safety. The use of decay detection equipment such as Picus and Resistograph, although potentially very accurate, only enable a subjective management decision to be made. This is because the main criterion on which assessment of tree stability is based, using this equipment, is hollowness and the application of Mattheck’s rule: t/R ratio <0.3, which, as we know applies (loosely) only to trees with a full crown. So what about trees that have been reduced or that are retrenching? Difficult to know isn’t it? Just because a tree is hollow doesn’t necessarily mean it will fail. Furthermore, recent research indicates trees with a large diameter may be able to get away with having a residual wall that is significantly less than t/R ratio 0.3. I didn’t have the opportunity to inspect the cedar at Kingston Lacy. However, based on Jeremy’s video, which included extracts from Mick Boddy’s report, I think that it is quite likely that a static load test would have provided the evidence necessary to justify the retention of the tree.

It is circumstances such as this where a 'static load test' aka 'tree pulling test' is likely to have enabled a more objective management decision to be made. Although the tests are expensive, the cost is certainly justifiable when dealing with heritage trees of such high cultural and historical value. http://thinktrees.co.uk/portfolio/tree-stability-testing/

Just to clarify, the role would only involve 'grounding' for the person carrying out the climbing inspections, they would not be expected to carry out any tree inspection themselves. So a nice easy job for someone!

Arborist/Groundperson required to assist an arboricultural consultant in undertaking climbing inspections. Candidate must be self-employed, available to work on an ad-hoc basis and NPTC CS38 (climb trees and perform aerial rescue) is essential. Please PM me if interested.