Seed and Seedling Ecology of Carapa Guianesis Aubl.
McHargue, Laurie A.
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Carapa guianensis is a common swamp and riparian species of the wet Atlantic coastal forests of Costa Rica where research on several aspects of its seed and seedling ecology was conducted. Dispersal of the large seeds is by water and the activities of mammals, primarily the scatter hoarding behavior of the agouti (Dasyprocta). Seeds show good germination but are very susceptible to drying. The most serious restrictive site factor for seedling establishment is soil moisture content. Low nutrient availability or imbalance may prevent successful establishment in some soils. Up to 90% of the total seed crop falling beneath a tree is destroyed or removed by deer, agouti, pacas, spiny rats (Oryzosys) and larvae of the shoot-borer moth (Hypsipyla grandella Zell.) and other insect predators. The large seed size of c. guianensis may allow the seed to sustain some loss of its food reserves and still survive. Seed weights experimentally reduced from 50 to about 90% germinated but survived only a short while, attaining a final height dictated by the amount of material left in the seed. Damage of less than 50% may not be fatal. c. guianensis provides an example of a tree species with density-responsive predators. A population recruitment curve for the tree, empirically constructed from the seed shadow and the location of juveniles around an isolated adult, supports D. H. Janzen's theoretical population recruitment curve for a species with density-responsive predators, where the destruction of seeds and seedlings is greatest in areas of high seed/seedling density.