Development of additional revenue streams for timber products with relatively low profitability is an important step in securing future economic success for the forestry sector in Humboldt county. Utilization of California Sitka spruce (Picea sitchensis) for use in domestic acoustic steel-string guitar manufacturing may provide exactly that. Determining the quality and quantity of California Sitka spruce is the logical first step in achieving this.

Quality was determined from tree core samples gathered at sites on Green Diamond Resource Company’s (GDRco) California timberlands and the Arcata Community Forest (ACF) with high basal area of Sitka spruce. Rings Per Inch (RPI) is the most significant indicator in quality for guitar manufacturing (Pedgley et al., 2009) and was used as the anchor for tree core analysis. Cores were analyzed for the mean annual RPI of the stem and other physiological measurements. A minimum mean RPI of 10 was used to determine acceptability for manufacturing use (Stephens, 2015). Statistical tests determined significant differences in mean RPIs between GDRco and the ACF as well as between individual GDRco sample sites. Age was the most significant quantitative predictor of RPIs. The analyses indicated that Sitka spruce in this region is capable of producing the desired RPIs at an optimal age. Quantity requirements were calculated from several sources and results indicated that the region’s inventory is sufficient for domestic manufacturing needs.

Management objectives and site-specific silvicultural prescriptions may be key in achieving the desired results in accelerated time frames to meet GDRco management goals (GDRco FMP, 2023).


Spring 2024


Forestry, Fire, & Rangeland Management


Forest Operations


Hunter Harrill

Citation Style



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