Measuring lean

[Daniël Bos]

I'm working on a place with some fun trees at the moment, two of which (both Scots pine) have significant lean.

For one, the target in the lean direction is just fencing etc so no need to worry, the other has the potential to do damage.

 

The one that has the building built up to it has either grown well over 5cm in thickness in the last two years or is slowly falling.

I reckon the way half of its root system is deprived of water may be an issue?

If it falls I imagine the root plate will do some damage to the building.

Soil is sandy.

So, for the building tree, I've made solid measuring points (screws) on both tree and building to monitor it's movement.

The field tree has a baler twine pendulum with a marker point (cable tie) on a fixed ground point. Disadvantage of this is that I can only really measure it on still days.

 

I've no previous experience with actually measuring lean, and am just doing what springs to mind. Advice would be appreciated.

 

Building tree:

 

 

Field tree:

[openspaceman]

 

The one that has the building built up to it has either grown well over 5cm in thickness in the last two years or is slowly falling.

 

I don't understand this; if the tree is growing the measurement would decrease, if it is leaning more it will increase

[Daniël Bos]

I don't understand this; if the tree is growing the measurement would decrease, if it is leaning more it will increase

Yes, it just appears to have grown so quickly, at the Base of the tree, the floor goes right up to the bark, where there was a gap left before.

Or, because it's leaning more, the flaring of the trunk is what filled the gap.

 

Not knowing the expected increase in girth annually makes for hard guessing.

 

My measuring screws are at the roofline, as the higher the measuring point, the larger the change.

[openspaceman]

Yes, it just appears to have grown so quickly, at the Base of the tree, the floor goes right up to the bark, where there was a gap left before.

Or, because it's leaning more, the flaring of the trunk is what filled the gap.

 

Not knowing the expected increase in girth annually makes for hard guessing.

 

My measuring screws are at the roofline, as the higher the measuring point, the larger the change.

 

OK I see now, you were referring to the buttress and floor rather than the stem at the measurement point.

 

If the building has value then the tree will need to be removed either way unless the floor is very solid.

[Daniël Bos]

The floor is suspended about a foot above soil level, with beams resting on points away from the rootplate, so unless it becomes a more pronounced lean retention is preferred.

[David Humphries]

Paul Barton shared this little useful tip for measuring leans a few years ago

we continue to use it to good effect on a couple of leaning trees were monitoring.

 

http://arbtalk.co.uk/forum/general-chat/40740-guying-leaning-trees-4.html?nojs=1#links

 

[Daniël Bos]

Paul Barton shared this little useful tip for measuring leans a few years ago

we continue to use it to good effect on a couple of leaning trees were monitoring.

 

http://arbtalk.co.uk/forum/general-chat/40740-guying-leaning-trees-4.html?nojs=1#links

 

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Handy!

How do you mark the measuring point to ensure any subsequent measuring occurs in exactly the same spot?

[daltontrees]

I've monitored a Cedar using a pendulum and also recording the angle. Putting a clinometer against the bark is not something you can replicate the next year. What I have done is get 2 very long nails and hammer them in to the stem along the axis of lean. Top or underside is equally as good. Get the nails nearly a foot apart. Make sure they're into the wood (just) so they don't get pushed out by subsequent growth, and leave enough nail showing to accommodate years worth of annual increments. Use galvanised nails, and don't do this trick on broadleaves. Then the angle can be measured again and again by putting a rigid stick or ruler along the heads of the nails and then the clinometer along that. The wider apart the nails, the more precise the measurement.

 

I have toyed with the idea of making up a semi-permanent in-situ clinometer, I know how to do it but haven't got round to it yet. If anyone's interested I can post a sketch.

 

The problem of windy days is traditionally surmounted by putting the base of the pendulum in a dish of liquid. High precision plumblines were made of stiff wire and the liquid was oil. Baling twine has got to be the worst sort of string for catching the wind. Maybe replace it with a bit of throwline and a fishing weight? A dish of water should do for such a short drop.

[David Humphries]

Handy!

How do you mark the measuring point to ensure any subsequent measuring occurs in exactly the same spot?

 

 

We've scored the bark as a data measuring point on that old pine and have also nailed a flat board with scored measuring points on an oak.

 

.

[Daniël Bos]

I did consider making a scaffold tube L shaped bracket, ratchetstrapped to the tree.

The long side of the L sticking out horizontally away from the direction of lean and extending past the rootplate circle.

Then putting a stake (quite deep) into the ground to be the reference.

The longer the horizontal, the higher the accuracy.

 

But, I'm not here as a tree professional on this job, so it seemed an excessively involved method.

 

 

Pendulum in liquid would help with the wind, but wouldn't it mean the measurement would vary with the levels of wind loading as the tree flexes with the wind?

For that reason I thought I'd want to only measure on still days. Also, there is a large weight on the pendulum (5kg of steel) which should help with accuracy.