02854naa a2200385 a 450000100080000000500110000800800410001902400350006010000190009524501310011426000090024552017290025465000170198365000110200065000200201165000260203165000190205765000250207665000120210165000120211365000190212565000180214465000230216265000090218565300250219465300180221965300260223765300280226365300230229165300340231470000160234870000190236470000150238377300700239820730432017-12-04       2017    bl uuuu     u00u1 u    #d7 a10.1007/s11104-017-3347-12DOI1 aTONUCCI, R. G.  aGrass vs. tree origin of soil organic carbon under different land-use systems in the Brazilian Cerrado.h[electronic resource]  c2017  aAbstract: Background and Aims: 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. Methods - We evaluated total delta13C, 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 &lt53 µm size classes, and their delta13C determined. Carbon dating (14C analysis) was done for whole soil samples from 0 to 10 cm and 50-100 cm depth classes of three land-use systems. Results - The delta13C values increased (showing increase in C contribution by C4 plants, i.e., grasses) with soil depth at all sites and all size-classes. The older systems showed a higher contribution of C4-derived SOC at all depths. Carbon dating indicated that the area had been cleared about 300 years ago. Conclusions - Silvopastoral and pasture systems can be considered as good carbon sinks. We infer that the study site was grassland with high proportion of C4 plants in the past, not a forest as it is today.  aAgroforestry  aBrazil  aGrassland soils  aSilvopastoral systems  aSoil chemistry  aBrachiaria Brizantha  aCarbono  aCerrado  aEucalyptus spp  aFracionamento  aMatéria orgânica  aSolo  aAgroforestry systems  aCarbon dating  aSistema silvopastoril  aSistemas agroflorestais  aSoil fractionation  aStable isotope ratio analysis1 aNAIR, V. D.1 aNAIR, P. K. R.1 aGARCIA. R.  tPlant and Soilgv. 416, p. 1-12, 2017. Online first 21 July 2017.