Distribution Patterns of Tree Species in a Lowland Rainforest at Nanjen Lake, Southern Taiwan

Spatial patterns of trees in a lowland rainforest at Nanjen Lake, southern Taiwan were evaluated. Among the 91 species with more than 15 individuals in the 1.61-ha plot, 90.1% species showed an aggregated distribution pattern, and 8.8% species were randomly distributed at the 4 m scale. Along the distance scales, 71.4% species kept aggregated distribution pattern, and only one species remained randomly distributed at all distance scales. Rare species tended to be more aggregated than the common species. As for trees in different size classes, 40.9% highly aggregated species became less aggregated or even randomly distributed with the increase of tree size, while 9.1% species had an inverse pattern. As for trees in the size class ≥ 8 cm diameter, 68.2% species were randomly distributed and only 29.6% species were aggregated. No species displayed a regular pattern in any size class. There were four major habitat types in the study plot, including ridge, mid-slope, valley and streamside types. Our results suggested that the distribution patterns of most species within the Nanjen Lake plot were related to habitat heterogeneity, such that some species were only distributed along the streamside and some species could only be found on the ridge top. Other factors, such as dispersal limitation, might also play a role in determining the distribution patterns of trees