Limits of Temperature on Branch Strength

[Frax]

How do you seasoned veterans factor in reduction in branch strength when you need to stand on, tie into or rig onto branches in very cold weather. Is there much strength loss, or only in certain species?
It's obvious that at least small branches are extremely brittle at cold Temp (was minus 20 deg C, or around minus 5 deg F today). It's hard not to kniock off bits even with casual contact.
I was wondering about this today while working in a willow. I have trust issues with willows even on nice days.

 

[rfwoodvt]

not much thought on branch strength but we have seen a tendency of our felling hinges to not be as flexible as we need and to have them pull out with moderate side leaners.

We had 3 felling cuts in a row go awry on the same cold day. One Acer, one Abies and one Pinus, three different sawyers. All trees had a slight side lean and all the hinges pulled out of the stump.

 

[simplyarbor]

I notice some pretty significant differences around here. Not some much when felling, but when limbing pines and juniper, they become very 'snappy' at low temps. Juniper will usually just peel, but recently it's popping off when cut. I don't trust willows either, but I think as long is you have a solid TIP (say bigger than about 6 inches), that branch strength at the point of attachment is not so much of a concern.

 

[tophopper]

Honestly, if I questioned a limb's ability to support me during extreme cold temps, I would question the same limb at any other time.

Short answer- no difference 95 degrees or -10 degrees its all the same.

As mentioned above, hinge characteristics are another story.

 

[Tom Dunlap]

When I was working in Minneapolis during the winter I would notice a difference in hinging from morning to afternoon. After having some tense moments I learned what to expect and adjusted my technique or at least I was ready for what might happen.

the branches that would break in the cold were so small that I would never trust them in the warmth either. Kinda like what Top said.

 

[guymayor]

Brittle wood is noticeably more brittle; can be quite a difference ime. Short of actual breaking, avoid cracking, which can be quiet and less visible but definitely ungood for the tree.

Cold days the pole tools are handy to keep a good tip and still reach the right cuts.

 

[RopeShield]

Into minus 15 to 25 degrees celsius and on occcasion 30 climbing and pruning/removals for over twenty years in Southern Ontario I have found that fast growing species like willow, some maples,cedar, fir etc are slightly less or equally as brittle as in the warm season and for me what is the most noticeable is the amount of pressure or flexing/bending a limb will endure before it breaks. Take a branch and see how it breaks in the cold and then try it after it has a warmed up. It definitly take more bending before it snaps. They both will break with the same effort but one breaks sooner with less bend.
With Strong wooded trees I haven't noticed any marked difference.
I have great respect for Willow and white Pine ffrom first hand and second hand experience the two tree I fear the most.Cold or warm.I would guess willows have harmed more arborists than any other tree in Canada.
Most likely has to do with the moisture being stored out of the cells and wood structure.
Hope that helps.

 

[Frax]

Thanks all for sharing your experience and observations. I had not considered differences in hinge behavior probably because I've never done any big cutting in extreme cold. But now when I do I will think about it and maybe modify tactics before cutting.

 

[dylanclimbs]

Absolutely there is strength loss in cold wood. I must say I have tied in lower in trees due to temperature where I would have tied in higher in the summer (not out here though ). Its all about your comfort level.

For a straight up and down loading (compression), sure there may be no difference, but I would imagine there would be a substantial difference when sideloaded. Hey, this sure would be a good research project, wouldn't it?

 

[Adkpk]

[ QUOTE ]
Hey, this sure would be a good research project, wouldn't it?

[/ QUOTE ]

If there isn't any scientific data on this subject I would certainly say this would be a worthy project. Something insurance companies might want some of.
Not a scientist here but I slab wood in the winter and I have seen that a 24" thick piece of wood does freeze through like broccoli in the freezer. It's more like ice than wood when frozen.
Live trees could be different. Does the movement of the water in the tree keep it from freezing? At what temperature does a 24" thick trunk freeze through?
I'm thinking along the lines of; frozen wood loses strength as well as gains strength when frozen. Think of a tree as an ice structure, I mean, no wood just ice. It would take a chainsaw to cut it down. You could probably get it down with a few cracks with a sledge hammer too. But add saw dust and it would give it some strength. Now if the wood was all connected as in cells even more strength.
I instinctively use larger diameter tips when climbing in cold weather.

 

[lumberjackson]

that would be a fun science project. has anyone seen the Mythbusters episode where they make a boat out of frozen soggy newspaper? it was really cool, and adkpk's post reminded me of that...