Oak VTA - Professional Tree Inspection

[jacquemontii]

I’m currently studying Visual Tree Assessment, with a view to eventually taking the Professional Tree Inspection. I have a theoretical question based on an oak (please see photos).

 

Considering the overall form and balance of the tree, the trunk and leader has developed a natural lean and curve to the south. At the base of the trunk there is a pronounced root flare on the tension side, (in the opposite direction to the curve) which I would interpret as being an important component in stabilizing the tree. A decay hollow is forming within this root flare. At the opposite side of the trunk (compression side) there is another wound (possibly impact by machinery?) with a small Ganoderma bracket (indicating white rot in either trunk or roots).

 

With the format of the professional Tree Inspection course in mind, what conclusions/recommendations would be expected of this tree? Is this the type of tree likely to be encountered in the exam? Having weighed up the risks of potential targets, would this be a straight forward decision to fell for safety reasons, or am I jumping the gun slightly?

 

I know it’s difficult to form an assessment based on a few photos, but any helpful advice would be appreciated.

[Dean O]

what are the targets?

[Dean O]

sorry I should say - I haven't done the PTI so could be talking nonsense - but would the overall condition/ vitality of the tree and likely life expectancy not also contribute to the final recommendation where targets/lack of would allow a reduction in height to retain?

 

is there any other structural issues in the canopy - tight forks old pruning wounds.

is the decayed hollow and the gano on the opposite side a result of coalescence?

[Chris at eden]

I’m currently studying Visual Tree Assessment, with a view to eventually taking the Professional Tree Inspection. I have a theoretical question based on an oak (please see photos).

 

Considering the overall form and balance of the tree, the trunk and leader has developed a natural lean and curve to the south. At the base of the trunk there is a pronounced root flare on the tension side, (in the opposite direction to the curve) which I would interpret as being an important component in stabilizing the tree. A decay hollow is forming within this root flare. At the opposite side of the trunk (compression side) there is another wound (possibly impact by machinery?) with a small Ganoderma bracket (indicating white rot in either trunk or roots).

 

With the format of the professional Tree Inspection course in mind, what conclusions/recommendations would be expected of this tree? Is this the type of tree likely to be encountered in the exam? Having weighed up the risks of potential targets, would this be a straight forward decision to fell for safety reasons, or am I jumping the gun slightly?

 

I know it’s difficult to form an assessment based on a few photos, but any helpful advice would be appreciated.

 

 

Possibly jumping the gun slightly. Sounds like you have completed stage 1 of the VTA process (visual check for defect symptoms) but you would need to go on to 2 and 3. i.e. quantify and evaluate against the failure criteria.

 

There may be several options when it comes to recommendations but you would just need to justify them. If you are saying fell then you would need to give good reasons. e.g. t/R evaluation, target, etc.

 

You could equally come back with crown reduce (but how much by would need to be shown) or conduct a more detailed investigation. e.g. Picus or resi-PD drill to quantify. As long as its reasonable and you can defend it. If you had a partial root plate failure and you recommended crown reduce you would probably struggle to justify that but there is some flexibility with lesser defects.

 

In terms of type of trees. I did mine in 2006 but at that time we had to inspect 10 trees all of varying condition. I don't think I recommended felling for any of them from what I remember.

 

Hope this helps

 

Cheers and good luck

[10 Bears]

Initially I agree with Dean. It appears there are no targets, so little to worry about in the real sense.

 

I would also note that in the second image (buttress with hollow), the tree is doing a good job of laying down additional wood either side of the cavity in an attempt to minimise the impact of the structural loss. Can you see what appears to be woody ridges that are tieing down the buttress like a couple of ropes?

 

From the image, any damage from the Gan. doesn't appear to be well advanced/significant decay, therefore there remains a lot of structural strength in the remaining wood.

 

I would simply note the lean as a feature of the tree. As this is a mature tree it is well adapted to its size shape and condition.

 

So all in, I would simply put this on an annual monitoring - but only if there is a current target or there is a change in site use and a target gets placed in the potential failure zone eg new site for a car port or similar.

 

FYI - Ive not done the PTI either, but I have applied VTA methodology to your images in as reasonable a way as I can.

[daltontrees]

A good wqy to think of the decision is assessing separately how likely the tree is to fail, how likely something or something will be there directly beneat in nthe conditions under which it would fail, and how serious the harm or damage would be. So the VTA part is only the first of three factors.

 

The Ganoderma could co-exist with an Oak for decades. If ther is good vitality, no evidence of rootplate movement, there is evidence of adaptive growth I'd saay there is nonly a slightly elevated likelihood of failure compared with a normal oak of the same size.

 

How serious would the harm be? Wold the whole tree snapo at the base? Probably not, it's rare and the tree would have to be really really and obviously goosed. Would ti shed a branch instead? Unlikely if it is of good vigour.

 

What's it going to land on? Shrubs in an unused area of a garden?

 

All in all, it looks likie a low risk. I daresay in a PTI assessment you'd be jsstified in recommending it be left alone ansd re-assessed in 2 or 3 years.

 

As others have said, state the evidence and relate the decision to it and you can't be criticised if it is a reasonable decision. There's no right answer, although you'll get failed for arriving at a wrong one and/or not explaining why or not basing it on what you have recorded about the tree and the situation.

[jacquemontii]

Thanks very much to everyone for the responses. Some useful pointers regarding the decision making process, much appreciated.

[jacquemontii]

I also found this ash tree nearby, with a bark deformity, which I suspect could be target canker (nectria). The affected area occurs at about 4m high, and from the ground I observed peeling cracking bark, with what looks like the concentric annual rings of target canker beneath?

It’s a fairly large tree and I am concerned this could be a potential area of weakness and in a critical position, below the fork of a large ascending stem.

Does anyone else recognise the cause of this deformity? And if so is structural failure known to occur?

[10 Bears]

Thats a good spot as the canker is mostly covered. Its best seen in the lower left of the first image I believe, and I would agree likely to be Nectria (without seeing anything further)

 

Its not a great position admittedly, and I have seen this in similar locations before. At a couple of RFS meetings I have heard long discussions on similar situations as this, and differing views on the extent that structural strength would be compromised.

 

So, I'm just going to sit back a little on this one and see what others think...

[sloth]

Looks more like necrosis from Innonotus hispidus to me - check the ground below for old black brackets...