EFFECTS OF LITTER, DISTANCE, DENSITY AND VEGETATION PATCH TYPE ON POSTDISPERSAL TREE SEED PREDATION IN OLD FIELDS

Because the fate of seed rain is critical to understanding the invasion of old fields by trees, we investigated spatial and temporal variation and difference among six tree species in seed predation. Very few Juniperus virginiana seeds were lost to predation but predation for all other test species was reduced by additions of Quercus litter and Solidago litter. Carya tomentosa seed predation was also reduced by increasing distance from the forest edge. In addition to litter and distance effects, differing starting densities of Acer rubrum seeds significantly affected predation rates but Fraxinus americana rates were not affected. Also, predation was greater under patches of woody vegetation compared to herbaceous patches. All results show spatial variation. Temporal variation was implied when, with increasing age of old field (from 7 to 17 years since abandonment), seed predation increased and the order of decreasing seed preference changed from Acer, Cornus florida, Carya, Quercus rubra, Fraxinus and Juniperus to Quercus, Acer, Fraxinus and Carya. Overall, for tree seeds in old fields. litter, distance to forest edge and starting density affect predation rates, there is less predation in herbaceous patches compared to woody patches and the amount of predation increases and the order of seed preference changes with increasing old field structure.