Spatial patterns in the distribution of tropical tree species

Fully mapped tree census plots of large area, 25 to 52 hectares, have now b een completed at six different sites in tropical forests, including dry dec iduous to wet evergreen forest on two continents. One of the main goals of these plots has been to evaluate spatial patterns in tropical tree populati ons. Here the degree of aggregation in the distribution of 1768 tree specie s is examined based on the average density of conspecific trees in circular neighborhoods around each tree. When all individuals larger than 1 centime ter in stem diameter were included, nearly every species was more aggregate d than a random distribution. Considering only larger trees (greater than o r equal to 10 centimeters in diameter), the pattern persisted, with most sp ecies being more aggregated than random. Rare species were more aggregated than common species. All six forests were very similar in all the particula rs of these results.