Soil carbon stocks after forest conversion to tree plantations in lowland Amazonia, Brazil

The large-scale conversion of Amazonian forest to other land-uses is altering carbon (C) stocks in this important eco-region. and these changes will in turn influence global C cycling. In this study, we evaluated changes of forest floor and surface soil C storage caused by converting primary Amazonian forest to tree plantations at the Curua-Una Forest Reserve, Para, Brazil. The plantations were established between 1959 and 1973 and they consisted of replicated plots of Pinus caribaea var. hondurensis Barrett and Golfari, Carapa guianensis Aubl.. Euxylophora paraensis Hub., and a Leguminosae combination (Parkia multijuga Benth., Dinizia excelsa Ducke, Dalbergia nigra Fr. All. In surface soils (0-20 cm), mean C stocks ranged from 7 (P. caribaea) to 11 kg m(-2) (E. paraensis). Fine litter C inputs ranged from 380 g m(-2) (E. paraensis) to 513 g m(-2) (P. caribaea), and forest floor C stocks (fine material) ranged from 359 (E. paraensis) to 542 g m(-2) (P. caribaea). R caribaea had the smallest fine root biomass-C (less than or equal to2 mm diameter) in the forest floor and surface soils (101 g m(-2)). Relative to adjacent terra fir-me forest, total C stocks in the surface mineral soil, forest floor, and fine roots (live + dead) in the plantations ranged from a net decrease of 13% W caribaea) to a net increase of 7% (E. paraensis). (C) 2002 Elsevier Science B.V. All rights reserved.