SELECTION HARVESTS IN AMAZONIAN RAIN-FORESTS - LONG-TERM IMPACTS ON SOIL PROPERTIES

Surface soil properties were compared among disturbance classes associ ated with a single-tree selection harvest study installed in 1979 in t he Brazilian Amazon. Response variables included pH, total N, total or ganic C, extractable P, exchangeable K, Ca, Mg, and bulk density. In g eneral, concentrations of all elements displayed residual effects 16 y ears after harvests with N, P, K, and C being inversely related to dis turbance intensity while Ca and Mg levels as well as pH were directly related. Elemental contents exhibited fewer residual effects except in the cases of Ca and Mg contents which generally increased with distur bance intensity. Higher intensity disturbance classes were associated with increased bulk density. Soil impacts apparent after 16 years sugg est a combination of direct effects of harvests (e.g. as in the case o f bulk density) combined with indirect influences of the ecophysiology of the Cecropia sp. which dominate disturbed areas. (C) 1997 Elsevier Science B.V.