Are Western Juniper Seeds Dispersed Through Diplochory?

Abstract

Abstract Western juniper (Juniperus occidentalis) “berries ” are consumed by frugivorous birds, which then defecate and disperse the seeds. However, rodents also consume western juniper seeds, and seedlings can establish from rodent scatterhoards. To explore relative roles of potential seed dispersal agents, we experimentally quantified removal rates by birds and rodents of intact western juniper berries versus seeds cleaned either manually or by passage through bird guts at two northeastern California sites (Likely and Shinn Peak). We also conducted seedling emergence experiments with berries, hand-cleaned, and bird-passed seeds placed on the soil surface or buried at a depth typical of rodent caches. Birds removed juniper berries from plots and left seeds undisturbed at Likely, but bird activity was negligible at Shinn Peak. Rodent removal of seeds versus berries was similar at Likely, but at Shinn Peak rodents removed significantly more seeds. In the seedling emergence experiment, juniper seeds or berr...