Few studies describe the factors that influence the natural regeneration in abandoned gold mining areas in the Amazon. Here we focus on the influence of the distance to the forest edge and abandonment time in a spontaneous succession of degraded areas by gold mining in the southeastern Peruvian Amazon. We assessed woody species composition (DBH ≥ 1 cm) and forest stand structure across a chronosequence (2–23 years). A total of 79 species belonging to 30 families were identified. The natural regeneration was dominated by Fabaceae, Malvaceae, and Urticaceae. Together, they represented 60% of the importance index. Cecropia membranacea and Ochroma pyramidale were the dominant pioneer species at the initial successional stage. The basal area and species diversity were directly related to time after abandonment and inversely related to the distance to forest edges. The distance-based redundancy analysis showed that more of the variation in species composition was explained by distance to the forest edge than the abandonment time. Our study revealed that regeneration was relatively slow and provided evidence that the distance to the forest edge is important for natural regeneration in areas degraded by gold mining.

Amazon rainforests are critical for providing a wide range of ecosystem services. In the Southeastern Peruvian Amazon; however, goldmining activities are causing severe soil degradation and forest loss. We analyzed aboveground biomass (AGB), forest structure, and species diversity recovery during secondary succession in 179 forest plots. Our study provides the first field-based quantification of AGB recovery following the abandonment by two types of goldmining (heavy machinery and suction pumping) in Madre de Dios (Peru). We found that successional secondary forests in areas subjected to suction pumping were more resilient than those in areas subjected to heavy machinery. After 20 years, mean AGB in suction pumping mining areas had reached 56% of reference forest AGB, while in areas of heavy machinery mining it was only 18%. Mining type, stand age, and distance from the forest edge had a significant effect on AGB. The influence of the distance from the forest edge on AGB varies according to mining type because the effects of species diversity on AGB are mediated by the distance from the forest edge. Our results clearly showed the dynamics of AGB recovery across a secondary succession after goldmining, and the contrasting responses of AGB between the two mining types. Our study disentangles the importance of key factors in forest recovery after mining and improves understanding of the resilience of biomass accumulation in these highly degraded ecosystems.

In the Peruvian Amazon, large area of primary forest have been deforested by Artisanal and small-scale gold mining (ASGM). Vetiveria zizanioides (Poaceae) is considered an excellent plant for the ecological restoration of degraded lands. The present study aimed to analyze the growth and survivorship of V. zizanioides in degraded soils by gold-mining in the Peruvian Amazon (Madre de Dios). The experiment was conducted under greenhouse conditions, and it followed a randomized complete block design with four treatments (substrates). The substrates were sand (mining), sand+pebbles (mining), forest soil, and amended soil. We evaluated the survivorship, shoot, tiller, and biomass production of V. zizanioides for two months. Univariate analysis of variance was used to detect differences among treatments. Fifteen days after experiment establishment, V. zizanioides survivorship was significantly higher in ASGM substrate 2 (sand+pebbles) than in other substrates, following the order of ASGM substrate 1 (sand) > forest soil > amended soil. However, at the end of the experiment, we did not find a significant difference on survivorship in subsequent assessments, and the total biomass per plant was lower in mining substrates than in non-mining substrates. The total biomass was significantly higher in amended soil than in other substrates, with yields between 1.7 and 3.6 times more biomass in amended substrate than in mine substrates. The soil substrate type significantly affected the survivorship, number of shoots, and biomass of V. zizanioides. The research results can provide a reference for remediation of degraded soils by gold-mining in the Peruvian Amazon.

Gold mining has been causing the most severe impacts on the soils of the Peruvian Amazon. It has created challenges for their recovery. In this context, soil amendments could play a crucial role in plant establishment in post-mining soils. The study aimed to analyze the effects of two amendments on the early plant survival and growth of seven species in the reclamation of severely degraded lands by gold mining in the Southeastern Peruvian Amazon. The study was based on a completely randomized block design, including 2-amendment treatments (T1: sawdust + island guano manure and T2: T1 + organic soil + hydrogel) and a control. The plant survivorship, height growth, diameter growth, and biomass accumulation were measured. This study found that amendments may be effective at increasing survivorship and plant growth in degraded lands by gold mining in the Peruvian Amazon. The amendments increased the survival, diameter, height, and biomass of most plant species in the study. In general, survivorship and plant growth in T2 were high compared to T1. At the end of the experiment, the highest survivorship was for an Indigofera suffruticosa and Crotalaria pallida (>80%). The diameter growth was higher in T2 than in T1. The species growing fastest in diameter (>1.5 cm) were Crotalaria cajanifolia, C. pallida and Ochroma pyramidale. Soil amendments provided similar effects on height for most species except for I. suffruticosa. Therefore, C. pallida, I. suffruticosa, C. cajanifolia and O. pyramidale are key species to be considered in reforestation and/or restoration initiatives, due to its potential to acclimate and establish itself in severely degraded areas.

El objetivo del estudio fue evaluar la contaminación de aguas superficiales en la periferia urbana de Puerto Maldonado (amazonia peruana), utilizando análisis biológicos, fisicoquímicos y microbiológicos. Las muestras de agua se colectaron en seis cuerpos de agua (dos ríos, tres quebradas y un lago). Los parámetros fisicoquímicos de cada sitio de estudio no superaron los límites del Estándar de Calidad Ambiental peruano (ECA), excepto el oxígeno disuelto en ríos cercanos a zonas urbanas. La contaminación de los recursos hídricos está relacionada con los vertidos de aguas residuales y la escorrentía de aguas pluviales. Así, los mayores puntos de contaminación fecal fueron en los ríos cercanos a las zonas urbanas, superando el límite establecido por el ECA para la conservación del medio acuático (UFC ml-1 >2000). En el río Madre de Dios, la concentración de coliformes fecales superó en 75 veces al máximo permitido por el ECA, indicando que los ríos Tambopata y Madre de Dios de Puerto Maldonado están fuertemente contaminados.

Anthropogenic activities (e.g., logging, gold-mining, agriculture, and uncontrolled urban expansion) threaten the forests in the southeast of the Peruvian Amazon, one of the most diverse ecosystems worldwide. However, gold-mining generates the most severe impacts on ecosystems and limits its resilience. The natural regeneration of degraded areas in the southeastern Peruvian Amazon have not been studied deeply. The dataset contains floristic inventories of previously uncharacterized or poorly studied secondary forests degraded and abandoned by goldmining activities and an intact forest in the Tres Islas indigenous community, Madre de Dios region, in southeastern Peru. The data presented was obtained from 12 plots (20 m × 60 m) established in three successional forests abandoned by gold mining and an intact forest (without mining impacts), where all trees with a stem diameter at breast height greater than 1 cm were inventoried. To the best of our knowledge, this is the only dataset in the southwest of the Peruvian Amazon that compares the natural colonization after gold-mining and intact forests. This dataset can be useful for long-term study and monitoring of structure and tree diversity in relatively understudied yet important secondary forests after gold-mining abandonment. Also, this dataset could be used to analyze the successional trajectory process of vegetation and the recovery of aboveground biomass. Furthermore, the data could be used to investigate the effects of functional traits and types of mining on vegetation recovery. Hence, understanding the successional processes will help to improve restoration, reforestation, or reclamation strategies for the recovery of degraded lands in the Amazon.