From Rob Prebble:
“I have had a recent enquiry regarding acceptable stump heights for manual and mechanical tree felling. While there does not appear to be any specific criteria around what is acceptable, there are physical reasons why stump heights tend to creep up in some situations, (excluding of course, stumps that may be used for anchors).
One is the butt flare on trees. When carrying out mechanical felling, if the felling head cannot be clamped snuggly against the bole of the tree because of butt flare, operator’s tend to lift the head up to avoid cutting into the ground. Some manufacturers have experimented with recessed saw boxes but I am not sure how successful that has been. Similarly when manual felling, fallers tend to put their cuts in above the flare because it is easier to get the cuts right and requires less cutting.
Another reason for higher than normal stumps can be the amount of slash around the base of the tree. This sometimes occurs when manual felling follows mechanical felling.
For manual felling, bar length can also influence stump height, there is a tendency for fallers to lift their stump heights up to avoid having to put the scarf in from both sides of the tree.
The steepness of the slope will also have a significant influence over stump height, particularly with mechanical felling. There may also be regional differences such as sand embedded in the bark of trees or rocky ground conditions that might result in stumps being higher than normal
If you have specific requirements for stump heights in your operations, I would be keen to get a bit of feedback. Obviously I would keep the sources of the information confidential, but I could summarise the results and tell you what the average is and the upper and lower limits are. That way, you will be able to see where your operations are in relation to the “average” and look for reasons why your expectations might differ from others.
Appreciate your feedback.”
Feedback to go direct to Rob Prebble: firstname.lastname@example.org