Authors: Roxana P Eclesia Esteban G Jobbagy Robert B Jackson Marcos Rizzotto Gervasio Piñeiro
Publish Date: 2016/06/16
Volume: 409, Issue: 1-2, Pages: 99-116
Abstract
Although numerous studies have quantified the effects of landuse changes on soil organic carbon SOC stocks few have examined simultaneously the weight of carbon C inputs vs outputs in shaping these changes We quantified the relative importance of soil C inputs and outputs in determining SOC changes following the conversion of natural ecosystems to pastures or tree plantations and evaluated them in light of variations in biomass production its quality CN and above/belowground allocation patternsWe sampled soils up to onemeter depth under native grasslands or forests and compared them to adjacent sites with pastures or plantations to estimate the proportion of new SOC SOCnew retained in the soil and the decomposition rates of old SOC k SOCold based on δ 13C shifts We also analyzed these changes in the particulate organic matter fraction POM and estimated above and belowground net primary production ANPP and BNPP from satellite images as well as changes in vegetation and soil’s CN ratiosThe conversion of grasslands to tree plantations decreased total SOC contents while the conversion of forests to pastures increased SOC contents in the topsoil but decreased them in deep layers maintaining similar soil stocks up to 1 m Changes in POM were less important and occurred only in the topsoil after cultivating pastures following SOC changes Surprisingly both landuse trajectories showed similar decomposition rates in the topsoil and therefore overall SOC changes were not correlated with C outputs k SOCold but were significantly correlated with C inputs and their stabilization as SOCnew similar results were obtained for the POM fraction Pastures although decreased ANPP as compared to forest they increased belowground allocation and CN ratios of their inputs to the soil probably favoring the retention and stabilization of their new C inputs In contrast tree plantations increased ANPP but decreased BNPP as compared to grasslands and scarcely accumulated SOCnew probably as a result of the high C retention in standing biomassWe would like to thank Luís Colconvet Martín Pinazzo Norberto Pahr Santiago Lacorte Hernan Dieguez CamiloBagnato Daniel Castillo Lucía Romero Alberto Sosa Hugo Reis PINDO SA Ricardo Vilm Carlos Navajas Horacio Beltramino HampelHorman and Carlos Vera DANZER SA for allowing and collaborating in our field work We thank to Pablo Baldassini for their support in image processing This research was partially funded by FONCYT PICT 2199 and PICT 061764 UBACYT 0835 and 20020090200128 CONICET PIP 555 and by a grant from the InterAmerican Institute for Global Change Research IAI CRN 3095 which is supported by the US National Science Foundation Grant GEO1128040 Roxana Paola Eclesia was supported by a master degree scholarship from INTA
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