If a tree grows against a taut wire then the tree will grow around it, eventually enveloping the entire wire. This often scars the tree, and if the wire is thick enough, it will interrupt nutrient flow and cause more significant damage.
But if the tree grows against a larger obstacle, such as a wide board, the tree displaces the obstacle as it grows.
As a real-life example of this, I have a large pine tree on my property next to an old wooden building. The tree, as it grew, pushed hard enough against the building's eaves to bend a 2x4 piece of lumber five inches out of the way. When that 2x4 finally met the rest of the building, the tree could no longer move the board and started growing around it.
Where is this threshold? I assume it can be described as a simple pressure (force over area), and that it is dependent on the specific type of tree. Is this tabulated somewhere?
Specifically, I wish to hang a 40lb (18kg) weight, permanently, from a branch of an ~80ft (~25m) lodgepole pine. I intend to use some sort of wider material in between the cord and the branch. It would be great if I could simply run the cord through a larger-diameter pipe and position this pipe over the top of the branch. But if this wouldn't be sufficient then I'll use boards (or similar) to distribute the weight. I won't be constricting the entire circumference of the branch.
I know that mounting a bolt into the tree would be better, but that isn't an option for me in this case.
I don't want to do this: (!)