SECONDARY DISPERSAL BY THE WIND OF WINGED PINE SEEDS ACROSS THE GROUND SURFACE

It has been assumed that secondary dispersal of winged pine seeds acro ss the ground occurs, but the process has been little studied. We moni tored the fates of 287 inedible pine seeds that differed in size (lodg epole pine, Pinus contorta, mean fresh seed mass with wing 9 +/- 2 mg; ponderosa pine, P. ponderosa, 62 +/- 11 mg; and Jeffrey pine, P. jeff reyi, 185 +/- 23 mg) to determine the effects of wind and gravity on s econdary dispersal across the ground. Animals largely ignored the seed s. Most seeds moved <1 m during the 37-day observation period. Only se ven seeds were known to have moved >1 m. Nineteen seeds disappeared, b ut rodents and birds probably took many of these. Seeds placed on mine ral soil moved significantly farther than those placed on pine needle litter, and, on needle litter, large seeds moved significantly farther than small seeds. Except during an initial windy period, most seeds m oved <5 cm/day. Most seeds became immobile after about 8 days because they became entrapped in plant litter. By the end of the study, only t wo lodgepole pine seeds had become completely buried in soil. Wind and gravity appear to be relatively ineffective at moving pine seeds long distances across the ground surface. For large pine seeds (e.g., thos e of ponderosa and Jeffrey pine), rodents and birds serve as an altern ative means of secondary dispersal by scatter hoarding seeds in soil, whereas small pine seeds (e.g., those of lodgepole pine) are more like ly to be overlooked by foragers as they are gradually buried in plant litter and soil.