Prediction of aboveground component biomass for coastal Douglas-fir (Pseudotsuga menziesii var. menziesii)

Abstract

Contemporary forests are being managed for more uses simultaneously than ever before. Alongside historically important forest products such as timber and game, forests are often concurrently managed for a multitude of diverse anthropogenic goals such as wildlife habitat, biodiversity, recreation, ecosystem services, and bioenergy. The effective balancing of these varied goals requires more precise and accurate tools than previously. This study developed one such set of tools for measuring components of above ground biomass for the coastal Douglas-fir, Pseudotsuga menziesii var. menziesii. Many current methods for estimating above ground component biomass for coastal Douglas-fir may be insufficient for landscape, stand, and individual tree-level estimations, due to their disuse of important environmental variables. This study generated and utilized an extensive dataset of 32 destructively sampled Douglas-fir trees throughout maritime Oregon and Washington State. The study employed a balanced orthogonal experimental design considering age, stand density, crown position, elevation, and latitude. These samples came from both planted and naturally regenerated stands on public and private forestlands from a range of landowners. All stands were primarily composed of Douglas-fir, with the majority of stands having a single cohort, and the remainder having two cohorts. This dataset was combined with a similar dataset of 30 trees sampled at a single location in southwestern Washington State. The following were the component biomass equations produced in this study: 1.) Total Aboveground Biomass, 2.) Slash, 3.) Foliage, 4.) Live Branch Bark & Wood, 5.) Dead Branch Bark & Wood, 6.) Stem Bark, and 7.) Stem Wood. An eighth set of component equations for the 5 biomass components was developed using the ratio method, but its usefulness was limited. All response variables were analyzed and reported in terms of dry pounds (lbs).