Graduate Thesis Or Dissertation


Tires, Tracks, and Tethering: Idaho Steep Slope Harvesting Öffentlichkeit Deposited

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  • Steep slope timber harvesting often falls under scrutiny of labor, safety, and operational challenges, but is beginning to advance past these barriers through substantial technological progression. Across previous decades, large advancements of technology have occurred in ground-based timber harvesting systems, giving mechanized options to every phase of timber harvesting. These progressions have created outcomes including, but not limited to, improved worker safety and reduced risk, increased productivity and reduced harvest cost, while also increasing consistent harvest output through seasonal conditions. Timber harvesting methods on steep slopes historically involved motor-manual tree felling and labor-intensive extraction, but are now giving way to mechanization in steep slope harvesting. Tether-assist technology is now bringing the decades of progression from groundbased harvesting systems onto steep slopes. With the ability of ground-based harvesting systems to now traverse slopes steeper than previously possible, there is much to learn of their impacts and relationships with the landscape. Previously developed state and federal government policies in the Pacific Northwest (PNW), within the United States of America (USA), limit ground-based harvesting equipment on steep slopes. Different levels of regulation come into application by means of restriction for traditional ground based harvesting equipment above specified slope thresholds, in addition to extra requirements and some restrictions for tether-assist technology. This research is a case study showcasing soil impacts of traditional steep slope cable harvesting systems alongside developing tether-assist ground-based harvesting systems in similar terrain and timber conditions. Felling methods vary from motor-manual to mechanized directional felling head, while extraction methods incorporate grapple skidder, shovel, and cable logging, each exhibiting a different interaction with the site. Pre-harvest and post-harvest observations were collected of bulk density and penetrometer resistance for impact characterization and comparison. Bulk density measures work to capture differences in top-soil disturbance, while penetrometer resistance captures soil profile differences at increased depths. Sampling consisted of pre-operation and post-operation measurements taken at repeated locations on an established grid, allowing for paired testing of observations. The results from this study have shown differences in harvest system and operational area impacts, with each configuration contributing a unique distribution of soil impact to the harvest area. Through a variety of cable, tracked, and rubber tire equipment, this is to be expected due to the differing contact relationships and payload interactions with the soils in the harvest area. Machine passes and spatial distribution of machine activity was also found to be variable between harvest system configurations. These differing outcomes led to support traditional trends found in ground-based harvesting soil disturbance studies, with grapple skidding exhibiting the greatest impacts followed by shovel, and cable logging. Although trends in the data led to this comparative conclusion, significant differences were not found between either of the tether-assisted skidder or shovel systems. Further development of tethered logging system research is necessary, as trends may be similar to flat ground, yet additional forces via tether tension and extra payload may be entering new magnitudes.
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