Spatial scaling of plant and bird diversity from 50 to 10,000 ha in a lowland tropical rainforest

While there are numerous studies of diversity patterns both within local communities and at regional scales, the intermediate scale of tens to thousands of km(2) is often neglected. Here we present detailed local data on plant communities (using 20 x 20 m plots) and bird communities (using point counts) for a 50 ha ForestGEO plot in lowland rainforest at Wanang, Papua New Guinea. We compare these local diversity patterns with those documented in the surrounding 10,000 ha of lowland rainforest. Woody plant species richness was lower within 50 ha (88% of 10,000 ha richness), even when both were surveyed with identical sampling effort. In contrast, bird communities exhibited identical species accumulation patterns at both spatial scales. Similarity in species composition (Chao-Jaccard) remained constant while similarity in dominance structure (Bray-Curtis) decreased with increased distance between samples across the range from < 1 to 13.8 km for both plant and bird communities. The similarity decay was more rapid in plants, but in both cases was slow. The results indicate low to zero beta-diversity at the spatial scale represented here, particularly for birds but also for woody plants. A 50 ha plot provided a highly accurate representation of broader-scale diversity and community composition within 10,000 ha for birds, and a relatively good representation for woody plants. This suggests potential for wider generalization of data from ForestGEO plots which are almost always locally unreplicated, at least for those in lowland tropical forest.

Automated summary

The study compared diversity patterns of plant and bird communities at both local and regional scales in a lowland rainforest in Papua New Guinea. It found that bird communities exhibited similar species accumulation patterns at different spatial scales, while plant species richness was lower in smaller plots. With increased distance between samples, similarity in species composition remained constant but similarity in dominance structure decreased gradually. This suggests that a 50 ha plot can provide an accurate representation of broader-scale diversity for birds, and a relatively good representation for woody plants.