Leaf sesquiterpenes and phenolics in Copaifera multijuga on contrasting soil types in a central amazonian rain forest

Abstract

Insignificant differences were found in leaf sesquiterpenes and phenolic compounds in Copaifera multijuga (Leguminosae) occurring on soils with contrasting physical and chemical characteristics in a central Amazonian rain forest. The results support earlier studies of Copaifera and the related genus Hymenaea indicating little phenotypic plasticity in leaf sesquiterpene composition with regard to physical environmental factors. Although studies by others of leaf phenolics in numerous species of trees in an African forest on contrasting soils supported the hypothesis that tropical plants occurring on nutrient-poor soils are richer in secondary compounds than those in more fertile ones, this study of a single species indicates that nutrients directly from the soils may not be as significant a factor as that from the phytomass. Soil nutrients in these two Amazonian soils were generally significantly different, yet most leaf nutrients in C. multijuga trees on these soils were quantitatively similar. These data are consistent with ‘closed’ nutrient cycling, indicating perhaps little dependence upon soil minerals for nutrients. This possibility adds another perspective in assessing the hypothesis that secondary compounds will be higher on nutrient-poor than more nutrient-rich tropical soils.