Fine root biomass in gaps of Terra Firme forest in eastern Amazonia

Abstract

Fine roots (< 5 mm) contribute to the uptake of water and nutrients by plants and play important roles in biogeochemical cycling. Nevertheless, little is known about the influence of logging on the production of these roots. The aim of this study was to evaluate the mass of fine roots in a ‘Terra Firme’ forest in the municipality of Moju, state of Para, after natural and anthropogenic disturbance. Five gaps created by selective logging, five natural gaps caused by falling trees, and five undisturbed areas were selected. In each area, three replicates of soil samples were collected at different depths and all individuals with diameter at breast height (DBH) ≥ 5 cm were measured. The fine roots were separated into very fine roots (diameter < 1 mm), fine roots (diameter between 1-5), living and dead. Only the mass of live very fine roots was higher in intact forest compared to natural gaps and gaps formed by selective logging. The mass and necromass of roots decreased with soil depth. There was no significant relation between fine root mass and density of trees. Plots that underwent selective logging 14 years prior to the time of the study did not significantly recover the biomass of very fine and fine roots. Mass of very fine roots is more susceptible to forest disturbances.