Vander Wall 9708155 The objective of this research is to determine the relative contributions of primary (wind) and secondary (animal scatter hoarding) dispersal to the reproductive success of four species of pines with winged seeds that vary in seed mass: lodgepole pine (Pinus contorta; 7 mg/seed), ponderosa pine (Pinus ponderosa; 55 mg), Jeffrey pine (Pinus jeffreyi; 146 mg), and sugar pine (Pinus lambertiana; 288 mg). Scatter-hoarding animals provide several important benefits to the seeds, including dispersal that often carries the seed away from the source plant, burial of the seeds in soil, and caching the seed in microhabitats that often favor seedling establishment. The variation in seed size is expected to influence the aerodynamic behavior of the seed and the attractiveness of the seed to vertebrate foragers (i.e., both primary and secondary dispersal). As seed size increases, the relative effectiveness of wind dispersal should decrease and the relative effectiveness of animal-mediated dispersal should increase. This research will make fundamental contributions to our understanding of seed dispersal and reproductive success in plants, especially with regard to the role of secondary dispersal, which has received little study. Further, this study will also provide information that will help foresters more effectively manage these economically valuable trees. The critical steps of seed dispersal and seedling establishment are poorly understood for these pines. The current assumption, based on seed morphology and cone phenology, is that these pines are wind dispersed and that animals act almost exclusively as seed predators. The results of this research will fill this gap in our knowledge and provide scientifically sound data on which to base management decisions.
