DISPERSAL OF SOREDIA FROM INDIVIDUAL SORALIA OF THE LICHEN HYPOGYMNIA-PHYSODES (L) NYL IN A SIMPLE WIND-TUNNEL

Dispersal of soredia from individual soralia of the lichen Hylogymnia physodes (L.) Nyl. was studied using a simple wind tunnel constructed in the field. Individual lobes with terminal soralia were placed in the wind tunnel on the adhesive surface of dust particle collectors. Air currents produced by a fan were directed over the surface of the lobes. The majority of soredia were deposited within 5 cm of the source soralium but some soredia were dispersed to at least 80 cm at a wind speed of 6 m s(-1). Variation in wind speed had no statistically significant effect on the total number of soredial clusters deposited averaged over soralia but the mean size of cluster and the distance dispersed were greater at higher wind speeds. The number of soredia deposited was dependent on the orientation of the soralium to the air currents. More soredia were deposited with the soralium orientated away from the fan at a wind speed of 4 m s(-1); more were deposited with the soralium facing the fan at a wind speed of 9 m s(-1). Moisture in the form of a fine mist reduced substantially the number of soredia deposited at a wind speed of 6 m s but had no effect on the mean number of soredia per cluster or on the mean distance dispersed. The data suggest: (1) that wind dispersal from an individual soralium is influenced by wind speed, the location of the soralium on the thallus and the level of moisture and (2) that air currents directed over the surfaces of thalli located on the upper branches of trees would effectively disperse soredia of H. physodes vertically and horizontally within a tree canopy.