For those who are concerned about people cutting their ground-anchored climblines, what about just setting your anchor higher off the ground? If you are using a running bowline, you can probably adjust it up the trunk high enough that someone would have to be cutting right next to the tree, at head height to cut it. A high-vis climbline would make this even less likely to have happen.
If you are using a POW anchor point, choke the sling over head height.
Question about POW anchor for SRT: When the rope is tensioned by the climbers weight, then slacked if not weighting the climbline, does the POW tend to bob up and down? I imagine not.
How many incidents do people know of where a groundman cut a rigging line between the lowering device and the block/ crotch (sorry can't think of the proper rope terminology)? I am sure that there are a few.