Graduation Date

Fall 2022

Document Type



Master of Science degree with a major in Natural Resources, option Forestry, Watershed, & Wildland Sciences

Committee Chair Name

Hunter Harrill

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Susan Edinger Marshall

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Andrew Stubblefield

Third Committee Member Affiliation

HSU Faculty or Staff

Fourth Committee Member Name

Han-Sup Han

Fourth Committee Member Affiliation

Community Member or Outside Professional

Subject Categories



The implementation of tethered harvesting allows for the expansion of mechanized logging onto steeper slopes. Recent updates to the California Forest Practice Rules have explicitly removed the slope limitation for logging equipment, provided it’s tethered. California is now witnessing the reintroduction of ground-based logging equipment on steep slopes. Previously, operating equipment on steep slopes was considered detrimental due to the potential for soil disturbance. However, tethered equipment interacts with the soil in a new way due to the use of a winch. Relatively few studies have attempted to quantify soil disturbance with this new practice. The goal of this study was to quantify the severity and extent of soil disturbance from two different tethered harvesting operations on steep slopes in Northern California: a whole-tree operation and a cut-to-length operation. Extent of visual soil disturbance was assessed through visual classifications of soil disturbance based on a relative scale considering rutting, mounding, and mineral soil exposure. The severity of compaction was determined by measuring the change in bulk density along machine trails. Soil samples were collected along the machine trail at equally spaced intervals from between tracks, under track treads, and undisturbed soil adjacent to the machine trail, at three different depths: 10 cm, 20 cm, and 30 cm. The whole-tree operation did not see any statistically significant changes in bulk density while the cut-to-length operation saw a statistically significant increase of 12.8% at the 10 cm depth under the track tread. Of all the collected soil samples in both sites, 60% had some degree of compaction while 40% had some degree of loosening. The visual disturbance was highest in the whole-tree operation, with 15% of the corridor showing the highest class of visual disturbance. The most detrimental visual disturbance was found near the top and bottom of the trail, where there was an abrupt change in grade, while the cut-to-length operation had fewer areas of concerning visual disturbance. Statistical analysis suggests that the soil and site characteristics such as slope, rock volume, and organic matter influence how susceptible a site is to soil compaction and the extent to which soils are visually disturbed.

Citation Style



Thesis/Project Location