Estimation of biomass and nutrient capital in stands of old-growth Douglas-fir

Sampling has long been established as an acceptable way of obtainingestimates in circumstances in which, for one reason or another, a completeenumeration or analysis was undesirable or impossible. An extensive theoryand history of application support any effort in this direction, and readyaccess of computers allows routine use of sophisticated methods.
Faced with the formidable task of determining biomass and nutrient con-tent of a 450-year-old Douglas-fir tree, we naturally explored the samplingpossibilities. At about the same time, some of our colleagues, with theassistance of one of us (Overton), developed a sampling methodology forestimation of epiphyte biomass on trees in the same stand (Denison et al.,(1972) and Denison (1973). This methodology had an elaborate procedure fordescribing each "branch system" of the entire tree and a detailed examina-tion of several sample branch systems, such that data from these samplebranches could be expanded to estimates for the entire set of branch systemson the tree. We decided to use the entire sampling system as a base for ourbiomass sampling and to select one of their sample branch systems for destruc-tive sampling. Thus, our sample constituted a second "calibration" phaseimposed on their one-phase, multi-stage sampling procedure.
Root biomass was sampled differently. In conjunction with yet anothergroup of colleagues who were estimating biomass of small trees, shrubs, forbsand grasses, we sampled root cores within the polygon of occupancy of thesample large trees for estimation of small roots. Large roots were studiedin relation to individual trees by examination of the excavated root systemof these trees.