Comparative analysis of nutrient concentrations in generalist and specialist tree species on clay and sandy soils in the Central Amazon

Abstract. Tropical forest soils generally have low nutrient availability. Some species exhibit specialized behavior, occurring exclusively in a single soil type, while others are generalists, thriving across different soils and water table depths. This study assessed the influence of topographic variation on leaf and trunk macronutrient and carbon amounts of tree species occurring only in one topographic position and species occurring across topographic positions and their relationship with soil macronutrient and carbon stocks. We selected nine species occurring in different topographic positions: three plateau specialists, three valley specialists, and three generalists (with four replicates each, totalling 35 individuals), where leaf and trunk samples were collected from each individual, and soil samples for carbon and nutrient analysis and quantification. Leaf and trunk nutrient concentrations varied across specialist and generalist functional groups, with valley specialists showing the highest concentrations of leaf and trunk nutrients and carbon. Nutrient concentrations within generalists remained consistent across topographic positions, underscoring their adaptive strategy to sustain productivity across environments. The concentrations of certain trunk nutrients of plateau and valley specialists and generalists mirrored those found in leaves, albeit at lower relative concentrations. Trunk carbon concentrations did not vary significantly compared to leaves, suggesting that other biological or environmental factors influenced tree nutritional status. We found evidence of variations in plant carbon and nutrient concentrations between generalist and specialist species inhabiting plateau and valley habitats in Central Amazonia, and a weak correlation between the stocks of some soil nutrients and leaf and trunk nutrient amounts.