Modern Forest Pollen Spectra from Eastern Washington and Northern Idaho

Abstract

The modern pollen spectra from 55 climax or near-climax forest stands in Washington and Idaho reveal diagnostic differences among the major vegetation groups, but generally not among different associations with the same overstory dominant(s). Pinus ponderosa stands with grass understory display spectra with characteristically high percentages of grass pollen and may produce Arceuthobium pollen as opposed to stands with a shrubby understory. Larix/Pseudotsuga-type pollen is prominent (>5%) only in stands with high coverage of Pseudotsuga. Tsuga heterophylla and Thuja plicata pollen in percentages greater than 1% may be used to identify associations in which these conifers have high canopy coverage. Occurrence of what is believed to be T. plicata pollen plus abundant spores of Athyrium filix-femina is diagnostic for the T. plicata-A. filix-femina association. Pollen spectra from the floristically distinct Abies (either A. grandis or A. lasiocarpa) associations cannot be distinguished reliably. Spectra from the Pinus albicaulis-A. lasiocarpa association are unique among these climax forests by having a substantial haploxylon pine pollen component. Spectra from the grass-dominated xerophytic parks within the subalpine zone contain much arboreal pollen from nearby stands plus grass and Liguliflorae pollen. Stands of the microphanerophyte-dominated Crataegus douglasii-Symphoricarpos albus and C. douglasii-Heracleum lanatum associations produce high Rosaceae and low Pinus pollen percentages plus generally high nonarboreal pollen. The prominence of Heracleum-type pollen is distinctive of spectra from the C. douglasii-H. lanatum association.