Spatio-temporal trends of mercury levels in alluvial gold mining spoils areas monitored between rainy and dry seasons in the Peruvian Amazon.

Artisanal and small-scale gold mining (ASGM) in the Amazon has degraded tropical forests and escalated mercury (Hg) pollution, affecting biodiversity, ecological processes and rural livelihoods. In the Peruvian Amazon, ASGM annually releases some 181 tons of Hg into the environment. Despite some recent advances in understanding the spatial distribution of Hg within gold mine spoils and the surrounding landscape, temporal dynamics in Hg movement are not well understood. We aimed to reveal spatio-temporal trends of soil Hg in areas degraded by ASGM.,. We analyzed soil and sediment samples during the dry and rainy seasons across 14 ha of potentially contaminated sites and natural forests, in the vicinities of the Native community of San Jacinto in Madre de Dios, Peru. Soil Hg levels of areas impacted by ASGM (0.02 ± 0.02 mg kg-1) were generally below soil environmental quality standards (6.60 mg kg-1). However, they showed high variability, mainly explained by the type of natural cover vegetation, soil organic matter (SOM), clay and sand particles. Temporal trends in Hg levels in soils between seasons differed between landscape units distinguished in the mine spoils. During the rainy season, Hg levels decreased up to 45.5% in uncovered soils, while in artificial pond sediments Hg increased by up to 961%. During the dry season, uncovered degraded soils were more prone to lose Hg than sites covered by vegetation, mainly due to higher soil temperatures and concomitantly increasing volatilization. Soils from natural forests and degraded soil covered by regenerating vegetation showed a high capacity to retain Hg mainly due to the higher plant biomass, higher SOM, and increasing concentrations of clay particles. Disturbingly, our findings suggest high Hg mobility from gold mine spoil to close by sedimentary materials, mainly in artificial ponds through alluvial deposition and pluvial lixiviation. Thus, further research is needed on monitoring, and remediation of sediments in artificial to design sustainable land use strategies.

Forestry performance of Bertholletia excels Humn. & Bonpl Lecythidaceae under different fertilizers after two years of planting / Desempenho silvicultural de Bertholletia excelsa Humn. & Bonpl Lecythidaceae sob diferentes adubações após dois anos de plantio

Bertholletia excels is a species is frequently used in reforestation due to its high degree of adaptability and its excellent initial growth. Thus, this work aimed to study the growth of B.excelsa according to different types and concentrations of fertilization, seeking to contribute to the silvicultural development of this species. For this purpose, seedlings of B. excelsa were planted in the Madre de Dios region on a property near the province of Puerto Maldonado in Peru. The seedlings were selected when they presented an average height of 22 cm for all treatments, being T1: Dolomite + SPT; T2: Dolomite + NPK; T3: Dolomite + SPT + Agricultural plaster; T4: Dolomite + NPK + Agricultural plaster, and T5: A control treatment without fertilization modifications. The experimental design was randomized blocks with five treatments and four replicates of six seedlings each. Once the ANOVA assumptions were met, the data were subjected to analysis of variance, with significant differences between the data, the means were compared using the Tukey test (p <0.05). Survival (%) was evaluated from the number of live individuals in two years of measurement. The treatment T4 presented great silvicultural potential, as the fertilization provided the development in height and diameter. Treatments T1 and T3 did not perform well when compared to the control, presenting the lowest growth rates in height and diameter, and the lowest survival rate. The control treatment did not differ statistically from T4, thus concluding that pre-plant fertilization of B. excelsa is not necessary.

A espécie Bertholletia excelsa é frequentemente utilizada em reflorestamentos pelo alto grau de adaptabilidade e seu ótimo crescimento inicial. Com isso, esse trabalho objetivou estudar o crescimento de B. excelsa de acordo com diferentes tipos e concentrações de adubação, buscando contribuir para o desenvolvimento silvicultural dessa espécie. Para isso, foram plantadas mudas de Bertholletia excelsa na região de Madre de Dios em uma propriedade próxima a província de Puerto Maldonadono Peru. As mudas foram selecionadas quando apresentaram altura média de 22 cm para todos os tratamentos, sendo T1: Dolomita + SPT; T2: Dolomita + NPK; T3: Dolomita + SPT + Gesso agrícola; T4: Dolomita + NPK + Gesso agrícola e o tratamento controle sem modificações por adubação. O delineamento experimental utilizado foi em blocos ao acaso com cinco tratamentos e quatro repetições de 6 plântulas cada. Uma vez atendidos os pressupostos da ANOVA, os dados foram submetidos à análise de variância, havendo diferenças significativas entre os dados, as médias foram comparadas pelo teste de Tukey (p <0,05). A sobrevivência (%) foi avaliada a partir do número de indivíduos vivos em dois anos de medição. O tratamento T4 apresentou grande potencial silvicultural pelo que a adubação proporcionou ao desenvolvimento em altura e em diâmetro. Os tratamentos T1 e T3 não obtiveram um bom desempenho quando comparado ao controle, apresentando as menores taxas de crescimento em altura e em diâmetro, e as menores taxa de sobrevivência. O tratamento controle obteve um bom resultado não diferindo estatisticamente de T4, assim concluindo que não é necessário a adubação pré-plantiode B.excelsa.

Habitat Quality Differentiation and Consequences for Ecosystem Service Provision of an Amazonian Hyperdominant Tree Species.

Ecosystem services of Amazonian forests are disproportionally produced by a limited set of hyperdominant tree species. Yet the spatial variation in the delivery of ecosystem services by individual hyperdominant species across their distribution ranges and corresponding environmental gradients is poorly understood. Here, we use the concept of habitat quality to unravel the effect of environmental gradients on seed production and aboveground biomass (AGB) of the Brazil nut, one of Amazonia's largest and most long-lived hyperdominants. We find that a range of climate and soil gradients create trade-offs between density and fitness of Brazil nut trees. Density responses to environmental gradients were in line with predictions under the Janzen-Connell and Herms-Mattson hypotheses, whereas tree fitness responses were in line with resource requirements of trees over their life cycle. These trade-offs resulted in divergent responses in area-based seed production and AGB. While seed production and AGB of individual trees (i.e., fitness) responded similarly to most environmental gradients, they showed opposite tendencies to tree density for almost half of the gradients. However, for gradients creating opposite fitness-density responses, area-based seed production was invariable, while trends in area-based AGB tended to mirror the response of tree density. We conclude that while the relation between environmental gradients and tree density is generally indicative of the response of AGB accumulation in a given area of forest, this is not necessarily the case for fruit production.