Pollen deposition and vegetation in the southern Rocky Mountains and southwest Plains, USA

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Abstract
A 2-year study of pollen influx in 37 Tauber traps along a 320-km transect extending from 1–224 to 3642 m elevation indicates that pollen dispersal occurs both upslope and down-slope in the southern Rocky Mountains. The dispersal pattern is related to both westerly airflow over the mountain crest and south and southwest summer winds. Tree taxa exhibit a greater variability in pollen production, from one year to another, than shrubs and grasses. Higher pollen percentages generally correspond to greater influx values. Abies, Picea, and Pinus pollen influx correlate with tree absolute density (trees per hectare). Montane species of Abies and Picea are under-represented in pollen percentages, while Pinus species are over-represented, as in eastern North America. Aspen trees dominate several forest stands, but Populus is a minor component of pollen trap assemblages. Between 20 and 60% of the pollen grains deposited in the traps has originated by medium- or long-distance transport.