Forests a Living Infrastructure: The Role of Tree Diversity in Supporting Epiphytic Orchids

Beyond timber production and carbon storage, forests act as living infrastructure that sustains a wide range of ecological interactions and biodiversity. Among the organisms most dependent on forest integrity are epiphytic orchids, a highly diverse group whose persistence depends strongly on host-tree availability and forest structural integrity. Understanding how changes in forest structure influence orchid communities is increasingly important under ongoing global change.

This study analyzed a decade-long monitoring dataset from four permanent 1-ha plots located in tropical montane forests of southern Ecuador. During surveys conducted between 2015 and 2025, host-tree identity, diameter at breast height (DBH), and plant height were recorded for all mature trees inside plots. For each host tree, orchid abundance and species richness were quantified, and changes in species occupancy between surveys were used to estimate colonization and possible local extinction rates. Relationships between forest structural attributes and orchid community dynamics were evaluated using generalized linear mixed models (GLMMs), alpha diversity estimated using the Shannon index, beta diversity based on Bray–Curtis dissimilarities, and multivariate analyses including non-metric multidimensional scaling (NMDS) and PERMANOVA.

A total of 145 orchid species associated with 17 host-tree species were recorded across the four permanent plots. Orchid richness ranged from 25 to 47 species per plot, whereas the number of host-tree species supporting orchids varied from 8 to 12 among plots. Shannon diversity values ranged from 3.5 to 4.1, reflecting high local diversity. GLMMs revealed a positive relationship between orchid richness and mature-tree density (p < 0.05). Bray–Curtis dissimilarities (0.56–0.71) indicated moderate to high turnover in orchid species composition, a pattern supported by NMDS ordination and PERMANOVA analyses (p < 0.05).

Our findings demonstrate that mature trees and structurally complex forests are critical for maintaining epiphytic orchid diversity and long-term community stability. Incorporating orchid–tree interactions into forest management and restoration strategies may enhance biodiversity conservation and ecosystem resilience.