Dispersal of eastern red cedar (Juniperus virginiana) into pastures: an overview

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Abstract
Seed dispersal, predispersal and postdispersal seed predation, seed dormancy, and germination were followed for four cone-bearing eastern red cedar trees (Juniperus virginiana L.), a predominantly avian-dispersed plant species, in pastures in southwest Virginia from June 1981 through May 1982. Within 12 m from the source trees, 34.7% of the total cone crop was recovered. Recovered material consisted of unripe cones, ripe cones, parasitized cones, and pulpless seeds evacuated by birds, averaging 17.9, 11.6, 1.0, and 4.2%, respectively, of the cone crop. Predispersal avian predation of seeds accounted for 3.1% of the cone crop. After 1 year 0.9% of the cones remained on the trees. The remaining 61.3% of the cone crop was dispersed at least 12 m from the source trees. Less than 3% of the cone crop is likely to germinate within 12 m of the source trees, while about 25% is likely to germinate at greater distances. Red cedar seeds passed unharmed through the digestive tract of avian dispersers and showed greater total germination than manually depulped seeds. Red cedar seed banks were not found under a chronosequence of red cedar stands; seeds generally lost their viability within one growing season. Seed shadows decreased exponentially with distance from cone-bearing trees. A similar distribution function was reflected in the spatial distribution of red cedar cohorts colonizing pastures near source trees. The large cone crop, diverse avian disperser assemblage, physiological adaptation of red cedar to open, xeric sites, and availability of seed sources in fence rows contribute to the successful invasion of pastures by this species.