Soil carbon changes in areas undergoing expansion of sugarcane into pastures in south-central Brazil

In Brazil, sugarcane expansion for ethanol production has been predominantly on areas previously used as pasture. Losses of C and N induced by land use change raise controversies about the environmental suitability of biofuel production. Therefore, we conducted a field study within the largest sugarcane producing region of Brazil to evaluate the effects of the primary land use change (LUC) sequence in sugarcane expansion areas (i.e., native vegetation to pasture to sugarcane), on C and N dynamics in the top 1 m soil layer. The LUC sequences caused substantial but varying changes in soil C and N stocks in areas undergoing expansion of sugarcane in south-central Brazil. The increase of C stocks in areas converted from pasture to sugarcane cultivation was 1.97 Mg ha(-1) yr(-1), in contrast to conversion of native vegetation to pasture, which decreased soil C stocks by 1.01 Mg ha(-1) yr(-1) for 0-1.0 m soil layer. The use of C-13 measurements to partition soil C sources showed that the greater C stocks in sugarcane areas compared to pasture was due to retention of the native-C stocks and increased accrual of modern-C comparing to pasture. Finally, the inclusion of deeper soil layers, at least down to 1.0 m depth, is essential to assess the impacts of LUC on C balances in agricultural areas. (C) 2016 Elsevier B.V. All rights reserved.