A Comparison of Spatial Patterns of Trees in Some Tropical and Temperate Forests

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Abstract
We compared spatial patterns of tree species (> 10 cm DBH) from two north-temperate (Bryn Athyn, southeastern Pennsylvania, and Smoky Mountains, Tennessee, U.S.A.), two south-temperate (Abtao and Huillinco, Chiloe, Chile), one subtropical (Berenty, Madagascar), and three tropical forests (Guanacaste, Costa Rica; St. John, U.S. Virgin Islands; and Saul, French Guiana). An index of dispersion based on distances to nearest conspecifics (DNC) was used to infer tree spatial patterns. Clumped spatial patterns were predominant in all tropical forests (75-100% of species) and in one north-temperate forest (Smoky Mountains). In the two south-temperate forests and in Bryn Athyn, Pennsylvania, random spatial patterns were more common (50-58% of species). Uniform distributions were rare in all forests. Examination of the overall distributions of DNCs revealed a marked and unexpected similarity between some tropical and north-temperate localities. South-temperate forests exhibited the highest densities of trees and the smallest average DNCs. The differences in the proportions of random vs clumped spatial patterns among forests seem to be related to different histories of disturbance in the forests compared. We postulate that forests which are subjected to frequent, catastrophic disturbances should exhibit a predominance of random spatial patterns, whereas clumping should predominate in forests where canopy gaps are the major cause of structural change.