Pollen Content of Moss Polsters in Relation to Forest Composition

Abstract

A comparison of the composition of a Douglas fir-white oak community in the McDonald forest in the eastern foothills of the Oregon Coast Range, near Corvallis, with modern pollen deposition, as detd. by pollen analysis of moss polsters, reveals the degree of over- and under-representation of the principal forest trees. Frequency, abundance, basal area, and size classes of the trees were detd. from 100, 25-ft.-square quadrats. On the basis of trees 1 inch and over DBH, Pseudotsuga taxifolia constitutes 42% abundance and is represented by 76% of the pollen. Quercus garrvana comprises almost 47% abundance but is represented by only 4% of the total pollen. With respect to trees 10 inches and over DBH, Pseudotsuga comprises 80% while Quercus constitutes 12%. In the pollen statistics, Pseudotsuga is under-represented by 4% and Quercus by about 7%. When basal area is considered, Pseudotsuga constitutes 68% and Quercus 23%, resulting in over-representation of oak by 19%. Abies grandis with a basal area of 2.4 sq. ft., of trees 10 inches and over DBH and a pollen avg. of 2.8%, is most accurately represented. Acer macro-phvllum is under-represented on all bases of comparison, probably because it is entomophilous. At least 13 spp. of trees are represented by pollen in the polsters, 9 of which occur in the sample plots, while 8 woody spp. occurring in the plots are not represented by pollen. Arborescent spp. not in the sampling area are represented by about 16% of the total pollen, most of which can be accounted for by their occurrence in the higher Coast Range to the west.