A model to estimate noble fir bough weight.

Abstract

The harvesting of noble fir (Abies procera) for the production of Christmas wreaths and related products has been a mainstay of the nontimber forest products industry in the Pacific Northwest (PNW) for decades. Although noble fir is the single most important bough product harvested in the PNW, little or no work has been published concerning the estimation of the weight of harvestable boughs from standing trees. The model presented in this article was designed specifically for use in predicting the weight of harvestable boughs from standing trees. A total of 322 noble fir were selected on the west side of the Cascades of Washington and Oregon. The stands and sites for sampling were chosen to represent a wide range of environmental and stand conditions. Sample trees were selected at fixed distances along systematical located lines at each selected site. Circular plots with a 20-ft radius centered at each sample tree were established to provide data on competition. Regression analysis was used to estimate the final model. Variables included in the final model were total tree height, merchantable bough height, dbh², age at dbh, whorl age for each merchantable whorl, and the associated number of boughs for each whorl as well as the total number of trees within a 20-foot radius of the plot tree. In addition, an intercept shifter (0,1) to designate noble fir stands located north and South of the Marion/Clackamas County line in Oregon (South = 0, North = 1) was included in the model. The overall model was significant at the 0.0001 level with an adjusted R² of 0.77.

Citation

Blatner, Keith A.; Fight, Roger D.; Vance, Nan; Savage, Mark; Chapman, Roger. 2005. A model to estimate noble fir bough weight. WJAF. 20(1): 44-49