The tree felling process will either set you up for efficient extraction, processing and best forest value recovery, or it will be a first step toward stem breakage, slower extraction, waste and lost value which you can’t get back.
Unless you plan, train, monitor and communicate well about the tree felling process – it will most likely be the latter.
Poor felling leads to significant waste. Felling direction determines losses from breakage when the tree lands across terrain features or other stems, and when it is extracted. Harvest planning and landing position, your tree fallers’ skill their decisions will either determine your early losses, or improve your fortunes.
Mechanised felling can allow accurate directional felling, and depending on system, can lay each tree down more slowly. This can minimize breakage and allow for better value recovery.
Use of a mechanised harvester/processor can also result in poorer quality log making decisions, especially if the operator has been selected for machine skills and production rather than log making ability. Losses can also occur due to the limitations of visibility of the stem in a grapple processor at a distance from the operator. Later articles address these issues.
Excessive stump height can result from poor felling technique, whether mechanized or manual. Any excess wood left on the stump can add up to thousands of dollars left on an acre, but it is only the beginning of value loss. That wasted wood means lost stem length, which also contributes to reduced value recovery up the stem. Less overall stem length means fewer valuable log lengths and combinations are available to be cut from the stand.
Wing cuts are designed to ensure that the hinge wood breaks cleanly without tearing the sides of the buttlog, when manual felling. They can be seen when checking the stump, as shallow angled cuts on each side of the hinge wood, and on the sides of the sloven (the end of the log incorporating felling cuts, which is removed to leave the butt end flush).
The top face of a conventional scarf (the wedge of wood removed on the side of the tree facing the intended direction of fall) should still be visible on the end of the log after the sloven is removed. It is too common to see valuable buttlogs on trucks with no scarf face remaining. A Humboldt scarf has the angled cut at the bottom, with a flush topcut which can save wood.
Know your scarf face tolerances (the length of the scarf face allowed at the large end when checked at the sawmill). Make sure that scarf faces are left on, as far as allowable, otherwise you are over trimming the biggest and most valuable part of the tree and leaving it in the forest as waste or firewood.
If you don’t have scarf face tolerances in your sawlog specs, negotiate some, and make them generous. Most of the scarf face is removed when the log is squared up in the sawmill, so there is little or no disadvantage to your customer, even if it looks odd on stack or truck.
Note that a plywood mill is different, they won’t want scarf faces left on to show on the edge of the veneer at every turn of the lathe. But you can educate fallers to use only the smallest scarf required, keep their stumps low and remove the sloven accurately with least waste.
Make sure that scarf face, sloven thickness and stump height are measured during log making and tree felling audits. Recording this data, publicly comparing operators (once you have a reasonable level of performance in your crews) and feeding back results quickly, will signal its importance and can be used to build professionalism in your workforce. Signal importance correctly and people will pay more attention, putting more money in your bank. And theirs, if you choose to share some wins.
Remember that the oldest, densest, most stable, and most valuable wood in your trees is in the bottom few centimeters. Keep stumps and felling waste to a minimum and send all possible volume and quality over the weighbridge to the sawmill or port.
James Powrie B.For.Sc (Hons)
James Powrie is a Freelance Forester and has worked in all aspects of forestry since starting with the NZ Forest Service in 1984.
He offers Education, Planning Assistance and Coaching for Forest Owners, Directors, Investors and others wanting to Maximise Forest Value Recovery at Harvest.
He is also available for conference sessions and workshops by arrangement.
firstname.lastname@example.org | +64 272 757757 | www.forestvaluerecovery.com