Invasion and Ecesis of Bird-Disseminated Woody Plants in a Temperate Forest Sere

Dynamics of bird—dispersed woody species as they take part in succession were examined in a Pinus banksiana stand at Argonne National Laboratory with a focus on the function of small openings in promoting community change. Mathematical models were developed for the three first phases of woody species involvement in succession: input of seeds, germination and 1st—yr survival, and survival to maturity. All species had a 1st—yr survival rate less than 10% of seed input. Each species demonstrated a different degree of dependence on the various factors determining survival to maturity. For example, Prunus serotina balances a fairly low germination rate and a high rate of seed predation with ability to germinate under a wider range of physical conditions (safe sites) than do other species in the study. Vitis riparia, on the other hand, has a high germination rate. Since most seeds of bird—dispersed species are deposited in shade, each species has adapted ways to survive in shade for a limited number of years which is sometimes sufficient to allow for the occurrence of an opening in the forest or for vegetative growth into an existing opening.