Effects of Amazonian Dark Earths on growth and leaf nutrient balance of tropical tree seedlings

Abstract

Background and aims: Amazonian Dark Earths (ADE) are ancient anthropogenic soils distributed in the Amazon basin. They are characterized by high nutrients such as phosphorus, calcium, potassium and nitrogen. We studied the effect of ADE on growth, morphology and physiology of 17 tree species from a Bolivian tropical moist forest. Methods: We conducted a greenhouse experiment where seedlings were grown for 2–4 months on ADE and non-ADE. We evaluated soil nutrient concentrations, seedling growth, leaf and root functional traits, and leaf nutrient concentrations. Results: Soil type affected 10 out of 24 evaluated seedling traits. Seedlings did not invest more in roots in non-ADE, but they invested in leaves and leaf area in ADE, although this did not lead to faster growth rate. Species responded differently to soil Ca increment; some species seemed to suffer from Ca toxicity as indicated by low survival, others from nutrient imbalance, whereas other species increased their leaf calcium, phosphorus and nitrogen concentration in ADE. Only for this latter group of nutrient accumulators, there was a positive interspecific relationship between leaf Ca and seedling growth rates. Conclusions: ADE did not lead to increased seedling growth. The ability of plants to colonize patches of ADE might depend on plant responses to increased soil Ca and their capacity to regulate internal tissue calcium to balance nutrition.