The Role of Animals in Dispersing a "Wind‐Dispersed" Pine

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Jeffrey pine (Pinus jeffreyi) produces winged seeds typical of many wind—dispersed pines. However, seedlings often occur in clumps, suggesting that many seeds are scatter—hoarded by animals. An experiment is described that examines how the initially wind—dispersed seeds end up in animal caches. Two arrays of 1064 Jeffrey pine seeds were arranged around two "source" trees in a pattern predicted from models of wind dispersal. Seeds were labeled with radioactive scandium—46 and numbered 1—12 with indelible ink to represent the 12 1—m wide annuli centered on the source tree where they were deployed. Within 2 d, between 95 and 99% of the seeds had been removed by rodents. Fifty—four and 35% of the seeds were found stored at the two sites, most of these in shallow surface caches. Seed caches were located 1.3—54.2 m and 6.2—62.9 m from the "source" trees at sites one and two, respectively. Mean distance of the "wind—dispersed" seeds from the source tree was 4.6 m, and rodents moved seeds a mean of 13.0 m farther at site 1 and 24.7 m farther at site 2. Of 375 minimum dispersal measurements, seeds were carried away from the source tree 362 times. Four rodent species may have participated in caching the seeds, but yellow pine chipmunks (Tamias amoenus) appeared to be the species that cached most of the seeds. In a second experiment where rodents were excluded, seeds placed on the soil surface in fall rarely became buried during the winter, and if not buried, they would not germinate. Jeffrey pine seeds appear to be dispersed in two phases; seeds are initially scattered by the wind, and subsequently carried farther and cached in soil by animals.