Concentração de nutrientes da precipitação interna em uma floresta manejada experimentalmente na Amazônia Central

Abstract

The Amazon rainforest plays an essential role in biogeochemical and hydrological cycles due to its contribution to the global climate balance. In this region, nutrient dynamics can involve various interactions within the compartments of the ecosystem itself, one of the mechanisms responsible for keeping them highly functional in soils that are generally quite weathered. In addition, there can also be an external contribution of nutrients through the flow of water from precipitation that reaches the forest cover. Thus, this study sought to investigate whether the impacts caused 35 and 29 years ago are still evident in the throughfall (rainwater passing through the forest canopy) and in the concentration of nutrients (N, P, K, Ca and Mg) in Central Amazonia, during the dry and rainy seasons, in plots that were subjected to forest management, in addition to the control treatment, totaling three treatments. This research was carried out at the ZF-2 experimental station in Manaus - AM, within the BIONTE (Forest Biomass and Nutrients) project area, where nine internal precipitation collectors were installed in each treatment and their respective repetitions, totaling 81 collectors inside the forest and a further three collectors outside the forest. Water measurements and collections were carried out weekly in September, October, January and February in all treatments. To better understand the influence of the canopy on the effects of management, hemispherical images were also captured monthly at each point of the 81 collectors. Over the total monitoring period, the concentration of nutrients in the throughfall showed a decreasing sequence of K+ > Ca2+ > (NO2-)+(NO3-) > Mg2+> PO43-. All concentrations showed high variability, with a consistent trend towards higher concentrations in the dry season (September and October). The impacts caused by the removal of 50% of the commercial biomass 35 and 29 years ago are no longer evident in the throughfall or nutrient concentration of this pathway. This suggests that after approximately 30 years the structure of the forests in managed and unmanaged areas is similar. Nutrient dynamics are indifferent to the treatments but are strongly affected by seasonal conditions. Finally, this study sought to provide important information on the dynamics of rainwater nutrients and rainfall in managed and unmanaged areas in the Amazon.