Biomass and Stand Characteristics of a Highly Productive Mixed Douglas-Fir and Western Hemlock Plantation in Coastal Washington

Abstract

Aboveground biomass predictive equations were developed for a highly productive 47-year-old mixed Douglas-fir and western hemlock stand in southwest Washington State to characterize the preharvest stand attributes for the Fall River Long-Term Site Productivity Study. The equations were developed using detailed biomass data taken from 31 Douglas-fir and 11 western hemlock trees within the original stand. The stand had an average of 615 live trees per hectare, with an average dbh of 35.6 cm (39.1 cm for Douglas-fir and 33.3 cm for western hemlock) and an average total tree height of 31.6 m (32.8 m for Douglas-fir and 30.2 m for western hemlock). Equations developed were of the form ln Y = b1 + b2 ln dbh, where Y = biomass in kg, dbh = diameter in cm at 1.3 m height, b1 = intercept, and b2 = slope of equation. Each tree part was estimated separately and also combined into total aboveground biomass. The total aboveground biomass estimation equations were ln Y = −0.9950 + 2.0765 ln dbh for Douglas-fir, and ln Y = −1.6612 + 2.2321 ln dbh for western hemlock. The estimate of the aboveground live-tree biomass was of 395 Mg ha−1 (235 Mg ha−1 for Douglas-fir and 160 Mg ha−1 for western hemlock), with 9.5, 29.3, 12.9, 308, and 32.7 Mg ha−1 in the foliage, live branches, dead branches, stem wood, and stem bark, respectively. When compared with biomass estimates from six other studies, ranging in age from 22 to 110 years and from 96.3 to 636 Mg ha−1, the biomass of the Fall River site was relatively high for its age, indicating very high productivity.

Methods for estimating aboveground biomass and its components for Douglas-fir and lodgepole pine trees

“…Beaucham andOlson 1973, Flewelling andPienaar 1981) and the effects of adjustment might be negligible (e.g. Harrison et al 2009). Therefore, we did not use the correction factor in this study.…”

Predicting the spatial and temporal dynamics of species interactions in Fagus sylvatica and Pinus sylvestris forests across Europe

“…Equations 3 to 5 were fitted for each species as mixed models, with plot nested within site as the random structure, using the nlme package for fitting the mixed models (Harrison et al, 2009) with R 3.2.1 (R Core Team, 2016). To correct for the bias when back-transforming the response variables, a correction factor was calculated as the sum of the measured values divided by the sum of the (back-transformed) predicted values (Snowden, 1991).…”

“…The scale, shape and location parameters were then fitted to Equations B1 to B6 where they are described as functions of mean diameter (B, cm), relative height (rh, height of the target species divided by the mean height of all species in the plot), age (A, years) and competition, which as calculated using Equation 6. Equations B1 to B6 were fitted as mixed models with site as the random variable using the nlme package for fitting the mixed models (Harrison et al, 2009) with R 3.2.1 (R Core Team, 2015). where locBx, scBx and shBx are fitted parameters for the B distributions, and locwx, scwx and shwx are fitted parameters for the ws distributions.…”

Douglas-Fir Biomass Allocation and Net Nutrient Pools 15–20 Years after Organic Matter Removal and Vegetation Control

“…Douglas-fir biomass has been previously sampled on all sites (Table 2). Prior to harvest at Fall River, biomass components of 47-year-old second-growth Douglas-fir were sampled [20]. After five growing seasons planted Douglas-fir biomass was sampled at all three sites [18].…”

“…Forest nutrient pool sizes are typically calculated by combining predictions of vegetation biomass with estimates of nutrient concentration for each biomass component [17][18][19][20]. In a comparison of the three PNW LTSP affiliate sites in year 5, total aboveground N stored in conifer, shrub, and herbaceous vegetation had a positive linear relationship with total soil N to a depth of 60 cm [18].…”