Dispersal Patterns of One-Seed Juniper Seeds Contained in Mammal Scats and Bird Pellets

Abstract

We conducted a two-year study in New Mexico, USA, to determine the role of birds, lagomorphs, mesocarnivores, and porcupines in one-seed juniper (J. monosperma (Englem.) Sarg.) seed dispersal. We established random plots: (1) around cone-bearing juniper trees in the woodland; (2) around non-cone-bearing juniper trees in the woodland; (3) in woodland/grassland transition zones; and in (4) grassland habitats near juniper woodlands. We estimated seed density and tallied the number of plots with seeds deposited by each disperser group. Birds deposited the highest number of seeds/ha under the canopy of cone-bearing trees. Mesocarnivores were responsible for the highest average seed deposition in all other habitats. In juniper cone-bearing tree habitats, birds deposited seeds in 100% of plots under-canopy and 93% of plots outside-canopy. Seeds deposited by lagomorphs were observed in plots across all sampled habitats. Overall, seed deposition was greatest around cone-bearing juniper trees, followed by non-cone-bearing juniper trees, woodland-grassland transition zones, and grassland habitats. Birds deposited seeds primarily under cone-bearing tree perch sites. Lagomorphs deposited seeds widely in relatively high numbers across all habitats and are likely responsible for the greatest number of one-seed juniper seeds deposited on the soil surface at our research site.