Productivity and cost estimates for whole-tree timber harvesting systems in the US South

Accurate machine productivity estimates are necessary for timber harvesting cost estimates. Research from the 1980s and 1990s on whole-tree harvesting system productivity may not reflect current equipment performance, while recent research may be too narrowly focused for broader applicability. The objective of this study was to estimate the productivity and cost of whole-tree harvesting machinery operating in the Piedmont and Coastal Plain of the US South. Elemental time studies were conducted on wheeled feller-bunchers, grapple skidders, and trailer-mounted knuckleboom loaders operating in seven clearcuts, two first thinnings, and two second thinnings in pine (Pinus spp.) stands, and two hardwood harvests. Machine rate estimates were combined with productivity data to estimate harvesting costs per tonne (t). Regression models were developed to predict cycle time using independent variables such as machine power and skidding distance. Machine productivity on pine clearcuts averaged 82.4, 27.1, and 36.7 t per productive machine hour for the feller-buncher, skidder, and loader, respectively. Onboard truck costs averaged $13.67 t-1 (USD) on pine clearcuts and ranged from $10.99 t-1 on pine second thinnings to $17.42 t-1 on hardwood harvests. Study results can be used to improve the accuracy of harvesting cost estimates and identify opportunities to increase harvesting productivity.