Local and regional dominance of woody plants along an elevational gradient in a tropical montane forest of northwestern Bolivia

Abstract

The aim of this study was to investigate the dominance patterns of woody plants in a tropical montane forest of northwestern Bolivia and to understand underlying processes at the local and regional scales. We inventoried three elevation ranges: lower (1,200–1,500 m), intermediate (2,000–2,300 m), and upper montane forests (2,800–3,100 m). At each elevation, we inventoried two sites that were ~100 km apart. Specifically, we asked the following questions: (1) are dominant taxa distributed locally, or are they also dominant at larger scales? And (2) is the local importance of shared taxa congruent among sites at the same elevation range? We inventoried 18,876 woody plant individuals with a diameter at breast height ≥2.5 cm belonging to 877 species, 286 genera, and 100 families in 54 0.1-ha plots. A strong floristic congruence was found at the family and genus levels within and across elevations, but not at the species level. The pattern of species dominance for the whole study regions was similar to that reported for similar scales in the Amazonia (10–15 % of species accounted for 50–75 % of individuals), although dominant species were not oligarchic across the whole elevational gradient due to the high environmental heterogeneity. Dominant taxa were shared to a larger degree between sites at the same elevational range than non-dominant taxa, indicating that oligarchy does not mean uniformity. Finally, the shared taxa exhibited similar importance between sites at the lower elevation range but dissimilar importance at the higher elevation range, reflecting an increase in the relative importance of local processes versus regional processes with increasing elevation.