Simulation of the effects of land use changes in soil carbon dynamics in the Piracicaba river basin, Sao Paulo State, Brazil

The objective of this study was to test adequability of the CENTURY model t o simulate the effects of land use changes on soil carbon content and net p rimary production to specific subtropical Brazilian environmental condition s. After parameterization, simulations were performed for forested areas, p asture and sugarcane cultures which have economical importance and represen tative areal extension in the Piracicaba River basin, Sao Paulo State, Braz il. The results obtained indicate that changes in use/cover from forest to agricultural practices resulted in lower soil carbon stocks. The simulation s of the transition from forest to sugarcane indicated a decrease of 28% in soil carbon stocks for the first 12 years and 42% for 50 years of sugarcan e cultivation The simulation of the transition from forest to pasture and t hen to sugarcane resulted in a 24% loss of soil carbon stock for the first transition (forest-pasture) and of 22% for the second one (pasture-sugar-ca ne). The net primary production results obtained for forest (6.6 ton ha(-1) yr(-1)), sugarcane (77, 82, 80 ton ha(-1) yr(-1)) and pasture (6.5 ton ha( -1) yr(-1)) were similar to those observed by other authors in field measur ements.