Effects of Palatability and Dispersal Mode on Spatial Patterns of Trees in Oldfields

MYSTER, R. W. (Terrestrial Ecology Division, University of Puerto Rico, San Juan, PR 00936), AND S. T. A. PicyErr (Institute of Ecosystem Studies, Mary Flagler Cary Arboretum, Millbrook, NY 12545). Effects of palatability and dispersal mode on spatial patterns of trees in oldfields. Bull. Torrey Bot. Club 119: 145-151. 1992.-The spatial patterns of tree stems in 480 plots were examined on a series of ten experimental oldfields adjacent to an old growth forest over a 31 -year period. Tree stem density decreased exponentially with distance from the forest edge early in succession. Later in succession the predictive power of the negative exponential model decreased, suggesting that processes such as animal seed dispersal within a field become important. Species palatable to herbivores were denser than unpalatable species close to the forest edge which implies that consumer pressure originates in the field rather than in the forest. Stems of all species were clumped on the scale of the 1 m2 plots. However, stems of bird-dispersed species showed the highest degree of clumping as expected if perches serve as recruitment foci. Results suggest that spatial patterns of tree seedlings in oldfields are significantly influenced by successional age, herbivory, dispersal vector and proximity to forest edge.