Selection harvests in Amazonian rainforests: long-term impacts on soil properties

Surface soil properties were compared among disturbance classes associated with a single-tree selection harvest study installed in 1979 in the Brazilian Amazon. Response variables included pH, total N, total organic C, extractable P, exchangeable K, Ca, Mg, and bulk density. In general, concentrations of all elements displayed residual effects 16 years after harvests with N, P, K, and C being inversely related to disturbance 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 disturbance intensity. Higher intensity disturbance classes were associated with increased bulk density. Soil impacts apparent after 16 years suggest a combination of direct effects of harvests (e.g. as in the case of bulk density) combined with indirect influences of the ecophysiology of the Cecropia sp. which dominate disturbed areas.