Pollen dispersal by Artemisia tridentata (Asteraceae).

While the biophysics of anemophilous pollen dispersal is understood in principle, empirical studies for testing such principles are rare, particularly in native ecosystems. This paper describes mechanisms underlying the dispersal of Artemisia pollen in a Wyoming sagebrush steppe. The relationships between meteorological variables and pollen flux were defined during the 1999 Artemisia flowering season, and detailed processes at the individual plant level were experimentally tested in the field in 2000. Results indicated that Artemisia pollen presentation is continuous but with early morning maxima. Atmospheric pollen concentrations and potential dispersal rates are controlled at diurnal time scales by individual flower development together with characteristic changes in temperature/humidity and wind speeds, at multi-day scales by frontal weather patterns, and at week-long scales by flowering phenology.