Tropical foothill forests are heterogeneous transition zones, yet field inventories remain sparse in the Andean–Amazonian region. We compared four forest stands to establish a local biodiversity baseline and determine whether tree diversity, floristic differentiation, and stand structure showed similar descriptive patterns. Four 0.25-ha plots located between 239 and 487 m a.s.l. in Madre de Dios, Peru, were inventoried for trees with diameter at breast height ≥ 10 cm. Diversity was characterized using Hill numbers, floristic differentiation using coverage-standardized beta diversity, and forest structure and soil properties descriptively. We recorded 532 trees representing 163 species, 97 genera, and 34 families. Observed richness ranged from 56 to 68 species, whereas abundance-weighted diversity varied more markedly. At 84% sample coverage, richness-based Sørensen-type and Jaccard-type dissimilarities ranged from 0.251 to 0.602 and from 0.401 to 0.752, respectively. Structural attributes varied among plots but did not follow the same ordering as diversity or floristic differentiation. Soil properties were treated solely as environmental context because each plot had one composite sample. The findings document heterogeneity among the four sampled stands and provide a sampling-standardized baseline for this poorly documented foothill sector, without establishing regional patterns or environmental causes.

Alluvial gold mining can alter Amazonian tree communities, but its association with medicinal tree diversity, structure, and carbon stocks remains poorly documented. We compared four 1-ha forest plots in Boca Colorado, Madre de Dios, Peru: two with greater evidence of mining intervention and two less-impacted plots. All medicinal trees with DBH ≥ 10 cm were inventoried, and taxon richness, Hill diversity, rarefaction, floristic dissimilarity, dominance, structural attributes, and biomass carbon were evaluated. A total of 1344 individuals representing 203 taxa were recorded. Mean plot-level richness was higher in less-impacted forests than in impacted forests (135.5 vs. 95.5 taxa), as were diversity of orders q = 1 (79.9 vs. 48.1) and q = 2 (38.7 vs. 23.6). Richness therefore showed a scale-dependent pattern: less-impacted plots were richer individually, whereas impacted forests accumulated more taxa when plots were pooled (172 vs. 143), reflecting greater among-plot differentiation. Turnover accounted for 79.5% of Jaccard dissimilarity. Less-impacted forests also had 16.1% higher stem density and 47.1% higher total biomass carbon, with the carbon contrast supported by the hierarchical bootstrap analysis (p = 0.043). These findings indicate that mining intervention was associated with differences in abundance distribution, floristic composition, forest structure, and carbon stocks that were not captured by pooled richness alone.