Grass vs. tree origin of soil organic carbon under different land-use systems in the Brazilian Cerrado

Silvopastoral management of tree plantations is becoming popular in Brazil. The impact of this practice on carbon dynamics of these soils is unknown, and predicting it is difficult because historical land-use records of the region do not exist. The objective of the study was to quantify the relative soil organic carbon (SOC) contributions of C3 and C4 plants in different land-use system. We evaluated total δ13C, the contribution of C4 and C3-derived soil organic C in three fraction-size classes of soils in six land-use systems (Eucalyptus hybrid plantations established in 1985 and 2005; a native forest; silvopasture stands of Brachiaria brizantha under eucalyptus established in 1994 and 2004; and an open pasture), and undertook carbon dating (14C) for three of those systems, an Oxisol in Minas Gerais, Brazil. From each system, soil samples were collected from four depths (0–10, 10–20, 20–50, and 50–100 cm); samples were fractionated into 250–2000, 53–250, and