Medicinal Tree Diversity, Floristic Turnover, and Forest Structure in Gold-Mining-Disturbed and Reference Forests of the Peruvian Amazon

Gold mining alters tropical forests, but its association with medicinal tree assemblages remains poorly documented in the Peruvian Amazon. We compared taxonomic diversity, floristic composition, and forest structure between three gold-mining-disturbed plots and their corresponding reference forests in San Juan, Huacamayo-Pacal, and Boca Amigo, Manu Province. Six permanent 1 ha plots contained 1878 non-palm medicinal trees representing 182 species and 46 families. Diversity was assessed using Hill numbers, rarefaction and extrapolation, sample coverage, beta diversity, NMDS, PERMANOVA, and structural attributes. Species richness and effective diversity were consistently lower in disturbed plots. Relative to their paired reference forests, species richness was lower by 52.3%, 18.5%, and 22.5%; q = 1 diversity was lower by 69.3%, 35.7%, and 25.2%, and q = 2 diversity was lower by 77.5%, 59.6%, and 26.6%. Basal area was also lower by 43.0%, 33.2%, and 31.2%, respectively. Floristic differentiation was strongest in San Juan, while multivariate composition differed among the six sampled plots (PERMANOVA: pseudo-F = 4.156, R2 = 0.278). These results show consistent differences in medicinal tree diversity between disturbed and reference plots, although the magnitude of floristic and structural contrasts varied among communities.