Master of Science (MS)


Biological Sciences

Document Type



Plants often modify microsite conditions important for seedling establishment. Palms may reduce light levels and produce deep leaf litter; both may suppress seedlings, affecting the local abundance, distribution, and species composition of tree seedlings. The abundance and composition of palms were examined along a tropical forest chronosequence at the Barro Colorado Nature Monument, Panama. Palms were sampled along transects in secondary (20, 40, 70, and 100 y in fallow) and old-growth forests. Palm abundance and basal area significantly increased with forest age. Palm distribution was driven by the most abundant palm, Oenocarpus mapora, which accounted for 60% of the total stems. I examined the effects of O. mapora, on seedling distributions on Barro Colorado Island, Panama. I asked: a) what are the effects of O. mapora on light availability and leaf litter accumulations; b) how does O. mapora affect abundances of seedlings; c) does seed size of established seedlings differ between palm and non-palm sites? Seedling composition, light availability, leaf litter, and palm presence were measured in 1-m2 contiguous plots along transects in one late second growth and two old growth forest stands. I conducted a seedling transplant experiment to determine the effect of O. mapora and its leaf litter on growth and mortality rates of Gustavia superba seedlings. Leaf litter depth was higher and light availability was lower in plots where palms were present. There was a lower probability of seedling presence where large palms were present. The probability of seedling presence increased with light availability. Seed size was greater for seedlings in palm plots relative to non-palm plots. Seedling survival was significantly lower for palm and litter treatments relative to controls. I conclude that O. mapora creates poor establishment conditions for seedlings which may affect the local abundance, distribution, and species composition of the seedling pool.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Julie Denslow