Abstract
Two ground-based timber harvesting methods have been commonly used for beetle-kill salvage treatments after a bark beetle epidemic in northern Colorado. A “lop and scatter” method uses a mobilized stroke delimber to delimb and buck trees at the stump, leaving tree tops and limbs on the forest floor, while a whole-tree harvesting method brings the entire tree to the landing where it is delimbed and bucked, and thus produces logging residue piles at the landing as a byproduct. We conducted a detailed comparative time study of the two harvesting methods to develop productivity and cost models and compared the performance of the two methods under various site conditions. We applied the productivity and cost models to lodgepole pine forest stands totaling 3400 hectares of the Colorado State Forest State Park to estimate salvage harvesting costs for each forest stand and identify the least costly harvesting options. The results show that the estimated stump-to-truck timber production costs were $30.00 per oven dry ton (odt) for lop and scatter and $23.88 odt−1 for the whole-tree method in our study harvest unit. At the forest level, the estimated average stump-to-truck costs were $54.67 odt−1 and $56.95 odt−1 for lop and scatter and whole-tree harvesting, respectively. Skidding distance and downed trees affect the harvesting costs of both methods, but their influence appears to be more significant on the whole-tree method.
Highlights
Since 1996, approximately 1.37 million hectares of coniferous forests in Colorado have been affected by eruptive populations of bark beetles [1]
Our analysis shows that whole-tree harvesting (WT) remains a less expensive harvesting option for more than 50% of the study area when the downed tree proportion is less than 30%
Our results suggest the following: (1) downed trees significantly and negatively affect feller-buncher productivity; (2) the efficiency of the delimber more significantly affects the productivity of lop and scatter harvesting; and (3) the productivity of whole-tree harvesting is more sensitive to skidding distance than lop and scatter
Summary
Since 1996, approximately 1.37 million hectares of coniferous forests in Colorado have been affected by eruptive populations of bark beetles [1]. The dead trees resulting from the pine beetle epidemic represent a vast, high-density biomass resource for wood products, bioenergy and bio-based products, there exist many economic and environmental uncertainties with respect to the harvesting of beetle-killed stands, as well as downstream logistics and product markets. These uncertainties become especially apparent when one attempts to market and utilize low-value, less-merchantable woody biomass, including logging residues and logs from severely damaged trees [2,3]. There are a number of past studies that investigated forest biomass utilization to improve the efficiency of biomass production and associated supply chain logistics.
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