Pollen dispersal and representation on an isolated, forested plateau

Modern pollen assemblages from 18 small ponds and wetlands on the spatially isolated and forested Kaibab Plateau were studied to determine how the pollen assemblages recorded vegetation patterns. Vegetation of the Plateau consists of an inner core of subalpine Picca/Abies forests, surrounded by mixed Abies/Picea/ Pseudotsuga/Pinus ponderosa forests, which are in turn surrounded by extensive Pinus ponderosa forests. The flanks of the Plateau are vegetated by Pinus edulis/Juniperus woodlands, with scattered Quercus populations. Arboreal pollen assemblages were dominated by Pinus (70-98 %), which was most abundant in the P. ponderosa forests. Picea, Abies, Pseudotsuga and Populus pollen were abundant only at sites in the mixed and subalpine conifer forests, where their combined abundance never exceeded 16% except at the site deepest in the subalpine forest (22%). Pollen percentages of Cupressaceae and Pinus Subsection Cembroides were highest in the outermost P. ponderosa forests (nearest the P. edulis/Juniperus woodlands) and in the mixed and subalpine conifer forests, where Quercus pollen was also highest. Percentage representation of the well-dispersed pollen of Quercus, Cupressaceae and Pinus Subsect. Cembroides was amplified at these latter sites by the poor pollen representation of the dominant Picca, Abies and Pseudotsuga trees. This effect is similar to that recorded in many pollen assemblages from arctic and alpine tundra regions.