Jock
ArboristSite Operative
Could someone give me a proper explanation as to why you would cable a tree, and would you consider it correct?.....Jock
Tree Cabling
- Thread starter Jock
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John Paul Sanborn
Above average climber
I always phrase it ans reducing the risk of failure. The systems ar not designed to eliminate the risk, but to extend the useful life of a valued specimin.
One must always ensure the client understands that it is not a permenant system and may need replacement down the road, or as stated above removal of the tree at a later date.
It is the clients ulitmate choice as to their risk tolerance, not the consultant/practitioner. We can express our risk tolerance by refusing to perform the instalation though.
One must always ensure the client understands that it is not a permenant system and may need replacement down the road, or as stated above removal of the tree at a later date.
It is the clients ulitmate choice as to their risk tolerance, not the consultant/practitioner. We can express our risk tolerance by refusing to perform the instalation though.
murphy4trees
Addicted to ArboristSite
Cabling is used to "secure" co-dominant stems, with included bark. The tree's growth patterns can cause a weakness at a tight crotch. When there is no more room for the stems' wood to knit in the crotch, as each stem puts on diameter, they begin to push on each other. The build up of pressure in the crotch is evidenced by the included bark, a flat or "sunken" area above crotch.
Cables should be installed as high as possible, and at least 2/3 the hieght from crotch to tips.
God Bless All,
Daniel
Cables should be installed as high as possible, and at least 2/3 the hieght from crotch to tips.
God Bless All,
Daniel
Acer
ArboristSite Operative
This would probably be the most effective use of cabling/bracing. I would have thought a non invasive system like Cobra, installed to restrict movement rather than prevent it, would be the way to go. I've read about systems involving bolts, steel cable etc which is designed to be under tension, or to pull stems together. As we now know that trees will adapt to the forces they experience, wouldn't such a system cause problems in the long run?
tshanefreeman
ArboristSite Operative
Arborists like steel (static) cables because they are tried and true, they last a long time, the materials are reasonably priced, and they work.
At the same time, other arborists like fabric (dynamic) cables because there is no drilling into the tree, no tools are required, installing them is easy to learn, and they work.
Each system is known to work but each system has its downsides that arborists need to consider when deciding which to impliment.
For example, the negative impact of a static system when it comes to restricted movement of the trunk. If a tree is restricted to the point of minimal movement, it cannot develop sufficient 'reaction wood', which is the specialized secondary xylem that develops in response to lean or similar mechanical stress to restore the stem to the vertical. Occurs as compression wood in conifers and tension wood in angiosperms. Therefore, as the crown increases in size, the overall stability of the tree becomes unbalanced and can create new hazardous conditions.
This is why systems like the Cobra are becoming more and more popular. The Cobra system uses a hollow polypropylene rope that stretches when the wind blows. The rope is wrapped around the stem with a splice and the wrap is capable of expanding as the tree grows in diameter. One of the best features of the Cobra system is setting cable tension. With static cables, it can be difficult to decide on proper tension of the cable due to weight of the leaves or different stress loads caused by swirling winds. Because dynamic cables flex in the wind, once the cable is installed properly, the right slack is achieved. Such mobility and flexibility allows a tree to adapt to changing conditions by producing reaction wood down the length of the trunk and in the various branches. Two drawbacks to fabric cables are that after many years the tree may outgrow the cable's ability to meet continued stem expansion or the cable may photo-degrade so much that it loses strength. But the gain may outweigh the costs.
At the same time, other arborists like fabric (dynamic) cables because there is no drilling into the tree, no tools are required, installing them is easy to learn, and they work.
Each system is known to work but each system has its downsides that arborists need to consider when deciding which to impliment.
For example, the negative impact of a static system when it comes to restricted movement of the trunk. If a tree is restricted to the point of minimal movement, it cannot develop sufficient 'reaction wood', which is the specialized secondary xylem that develops in response to lean or similar mechanical stress to restore the stem to the vertical. Occurs as compression wood in conifers and tension wood in angiosperms. Therefore, as the crown increases in size, the overall stability of the tree becomes unbalanced and can create new hazardous conditions.
This is why systems like the Cobra are becoming more and more popular. The Cobra system uses a hollow polypropylene rope that stretches when the wind blows. The rope is wrapped around the stem with a splice and the wrap is capable of expanding as the tree grows in diameter. One of the best features of the Cobra system is setting cable tension. With static cables, it can be difficult to decide on proper tension of the cable due to weight of the leaves or different stress loads caused by swirling winds. Because dynamic cables flex in the wind, once the cable is installed properly, the right slack is achieved. Such mobility and flexibility allows a tree to adapt to changing conditions by producing reaction wood down the length of the trunk and in the various branches. Two drawbacks to fabric cables are that after many years the tree may outgrow the cable's ability to meet continued stem expansion or the cable may photo-degrade so much that it loses strength. But the gain may outweigh the costs.
John Paul Sanborn
Above average climber
IMO the rope systems have beedn around long enough to disprove the photodegradation argument as well as one can prove a negative.
With the out-growing argument, no system should be installed into a vigorouse tree and forgotten. any systen can be outgrown and then need parts added or replaced.
I feel that static systems should only now be used for trees with severe defects that should not move, and the client insists on keeping.
With the out-growing argument, no system should be installed into a vigorouse tree and forgotten. any systen can be outgrown and then need parts added or replaced.
I feel that static systems should only now be used for trees with severe defects that should not move, and the client insists on keeping.
Kneejerk Bombas
ArboristSite King
Since a thread about a year ago, where we discussed installing a system with a bolt in the cracked crotch, a steel cable very low in the crotch, and a synthetic rope at about 2/3's of the way up, I have begun installing them.
The system seems to work great. The steel holds and strengthens the defective crotch, and the rope keeps the tree's leverage from ripping the low set steel out, yet allows for movement.
The system seems to work great. The steel holds and strengthens the defective crotch, and the rope keeps the tree's leverage from ripping the low set steel out, yet allows for movement.
Eric E.
ArboristSite Operative
Jock,
To answer your question...This is the best explanation I have found. It comes from the ISA Best Management Practices; Tree Support Systems booklet that is a companion to the ANSI A-300 (part 3).
"Tree Suport Systems are used to provide supplemental support to leaders, individual branches, and/or entire trees. Cables, braces, and guys provide supplemental support by limiting movement of leaders, individual branches, or an entire tree. When a tree has a structural defect or condition that poses a high risk of failure, which may result in injury or property damage, a supplemental support system can often reduce the risk."
Not my definition but a good one.
The 2nd part of your question...it can be correct if done properly. I have seen more poorly installed systems than properly installed systems though.
What a great topic! There is so much info out there...I could go on for hours but I hate typing.
To answer your question...This is the best explanation I have found. It comes from the ISA Best Management Practices; Tree Support Systems booklet that is a companion to the ANSI A-300 (part 3).
"Tree Suport Systems are used to provide supplemental support to leaders, individual branches, and/or entire trees. Cables, braces, and guys provide supplemental support by limiting movement of leaders, individual branches, or an entire tree. When a tree has a structural defect or condition that poses a high risk of failure, which may result in injury or property damage, a supplemental support system can often reduce the risk."
Not my definition but a good one.
The 2nd part of your question...it can be correct if done properly. I have seen more poorly installed systems than properly installed systems though.
What a great topic! There is so much info out there...I could go on for hours but I hate typing.
Tom Dunlap
Addicted to ArboristSite
Jock,
The easiest way to answer your questions would be for you to explain what you know about bracing and cabline b/c and we might be able to fill in the details.
When co-doms grow there isn't any actual pressure exerted between the two stems. The weakness is structural. Don Blair says that "Co-doms are living together but not married"
Trees that have static bracing in them still move and form reaction wood. It's not as if installing cables "freezes" the tree like static guying might do. Dynamic bracing allows more movement.
We now have more cabling tools to use combined with more knowledge about tree physiology. This makes c/b an even more complex issue.
The C/B BMP's that Ercii quoted is a good place to start to learn about c/b.
Happy Holidays!
Tom
The easiest way to answer your questions would be for you to explain what you know about bracing and cabline b/c and we might be able to fill in the details.
When co-doms grow there isn't any actual pressure exerted between the two stems. The weakness is structural. Don Blair says that "Co-doms are living together but not married"
Trees that have static bracing in them still move and form reaction wood. It's not as if installing cables "freezes" the tree like static guying might do. Dynamic bracing allows more movement.
We now have more cabling tools to use combined with more knowledge about tree physiology. This makes c/b an even more complex issue.
The C/B BMP's that Ercii quoted is a good place to start to learn about c/b.
Happy Holidays!
Tom
