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Tree dispersal modes reflect many different trade-offs. Some trees rely on animals to eat the fruit containing their seeds and expel them far from the tree; others rely on wind to blow their seeds to other parts of the forest. Seeds face many risks to their survival, and these risks may vary with dispersal model. Some seeds will be consumed by insects; others may become diseased. There is a chance, however, that the seed finds the perfect spot and grows into a healthy tree. Why don’t all tree species invest in protection against seed enemies and simply drop their seeds directly underneath them, rather than invest energy in dispersal?
Simply, seedling survival is lower underneath parent trees, or even under trees of the same species. Janzen (1970) and Connell (1971) proposed that species-specific enemies such as insects and other pathogens accumulate near parent trees, decreasing survival for nearby seedlings of the same species as the parent (“Janzen-Connell effect”). What is little understood, however, is the degree to which tree species (with differing dispersal methods) vary the strength of Janzen-Connell effect.
I investigated the impact of tree seed dispersal mode on the strength of the Janzen-Connell effect on tree seedlings. By observing enemy damage on seedlings and density of seedlings both near and far from adult tree species with differing dispersal methods, I quantified the strength of the Janzen-Connell effect as modified by dispersal mode.
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Jones, Isabella Pistello, "Effect of seed dispersal mode on the strength of the Janzen-Connell effect in secondary-growth temperate forests" (2020). Senior Projects Fall 2020. 8.
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