Response of tree roots to decomposing organic matter in two lowland Amazonian rain forests

Abstract

Fine roots of tropical rain forests are sometimes associated with decomposing organic matter at the soil surface. This association is considered by some authors to be important in recovery of nutrients by the vegetation. In this paper, experimental evidence is presented to show that the association results from a dynamic process and is not a coincidental result of negative geotropism. The association appears to be the result of random encounters of growing roots with organic matter, followed by increased branching at that site. The concentration of absorbing tissue in such relatively nutrient-rich sites as decomposing organic matter implies more effective ion absorbtion than would result if roots were randomly distributed in the soil volume.