Vegetation dynamics in lands degraded by gold mining in the southeastern Peruvian Amazon

In the southeastern Peruvian Amazon, small-scale and artisanal gold mining has become a common activity and represents one of the greatest threats to forests. The study evaluated the natural regeneration of vegetation and the physicochemical properties of the soil for a chronosequence in Madre de Dios (Peru). Fourteen plots of 250 m2 were installed, distributed across areas with abandonment times varying from 2 to 19 years. All stems with a diameter at breast height ≥ 1 cm in each plot were recorded and classified according to size categories (saplings, poles, and trees). We recorded 1023 individuals distributed in 80 species and 27 families. The most abundant families were Fabaceae, Annonaceae and Euphorbiaceae. Inga thibaudiana, Ochroma pyramidale, and Cecropia membranacea were present in all three size categories. The plots exhibited high heterogeneity, with medium diversity and very low species dominance. The dominant dispersal syndrome was zoochory (>60%). Pioneer species dominated initial and secondary succession with a higher abundance and species richness, decreasing considerably in late secondary succession. The soils exhibited a sandy loam texture, moderate to strongly acidic pH, poor nutrients, and limited organic matter. Soil alterations due to mining will therefore lead to slow natural regeneration.