LAUSR

Abstract Our objective was to determine how biophysical drivers impact on C sequestration and dynamics in Mollisols and Oxisols under grassland of South-America. We performed a literature review to obtain data on soil C stocks in grasslands and tree plantations on Mollisols and Oxisols and combined it with information from a local soil survey. A simple estimate of the C retention efficiency (CRE) was calculated as the ratio between soil C pool size data and modeled C inputs. Although soil C inputs were higher in tree plantations than in grasslands, this only translated to higher soil C stocks in temperate climates. The CRE was generally much lower in tree plantations as compared to grasslands, and this difference was strongest in tropical sites The CRE was much higher in the subsoil than in the topsoil, probably associated with a more effective physico-chemical protection of soil C by minerals. Our analysis suggests that a combination of trees and grasses in silvopastoral system might be a solution for soil C sequestration in tropical soils.