Tree Diversity, Floristic Composition, and Forest Structure in Three Permanent Montane Forest Plots in Northern Peru

Tropical montane forests provide essential ecosystem services and are of considerable ecological importance. However, knowledge gaps remain regarding how tree diversity, floristic composition, and forest structure vary among permanent plots across the sampled elevational range (2169-2519 m a.s.l.). We established three independent 1 ha permanent forest plots, with a single plot representing each sampled elevation (2169, 2347, and 2519 m a.s.l.). Because each sampled elevation was represented by a single plot, this design does not provide replication for formal statistical testing of elevational trends; therefore, differences among the three plots were interpreted descriptively. All trees with DBH ≥ 10 cm were inventoried to characterize tree diversity, floristic composition, and forest structure. Diversity was estimated using Hill numbers, and floristic differentiation was assessed using non-metric multidimensional scaling (NMDS). A total of 2336 individuals belonging to 46 families, 75 genera, and 147 species were recorded. Alpha diversity differed among plots, with values ranging from 49 to 67 species (q = 0), 17.2 to 24.6 (q = 1), and 10.7 to 13.6 (q = 2). P-OC1 showed the highest observed species richness and floristic diversity among the three plots. Lauraceae was the most diverse family, while the ecological importance of dominant families, as indicated by FIVI, varied among plots. Comparison with nine additional permanent plots from montane forests of northern, central, and southern Peru revealed floristic differentiation among plots in the NMDS ordination (stress = 0.068). Neither elevation (R² = 0.280, p = 0.223) nor species richness (R² = 0.044, p = 0.826) was significantly associated with the ordination. This study establishes an ecological baseline for the three permanent plots evaluated and expands the available information on the diversity, composition, and structure of montane forests in northern Peru.