Methods have been developed to yield total tree estimates of biomass for various components of a tree (trunk, axes, twigs, and needles) and its community of epiphytes (microorganisms, lichens, and bryophytes). Trees were sampled with the help of climbing techniques modified from mountain climbing. Two stages of sampling were involved. First, all units of the population were described so that their weights could be predicted. Second, several units were chosen with probability of selection dependent upon predicted weight and sampled in detail. Biomass estimates from the sampled units were expanded to tree totals with information gathered during the first sampling stage. Internal structure of the crown (tree components and epiphytes) is illustrated by maps of trunk and branch systems and by diagrams of horizontal and vertical distributions. This internal structure was also derived from the first sampling stage.These methods have been applied to nine old-growth Douglas fir trees (Pseudotsugamenziesii (Mirb.) Franco). Data from a single 400-year-old tree (1.46 m dbh, 77 m in height) in the H. J. Andrews Experimental Forest in the western Cascade Mountains of Oregon are presented. Biomass and surface area estimates are as follows: trunk, 26 870 kg, 223 m 2 ; axes (>4 cm), 1530 kg, 81 m 2 ; living twigs (<4 cm), 480 kg, 373 m 2 ; dead twigs, 78 kg, 104 m 2 ; needles, 198 kg, 2860 m 2 ; lichens, 13.1 kg; and bryophytes, 4.7 kg. Total cell volume of microepiphytes on twigs was estimated to have been 300 cm 3 and total cover by microepiphytes on needles was estimated to have been 191 m 2 .
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