title: Evolution of the delta13C signature related to total carbon contents and carbon decomposition rate constants in a soil profile under grassland.
abstract: Evolution of the total carbon (C) content and the (13)C enrichment (delta(13)C signature) of soil organic matter (SOM) with increasing depth in a soil profile under permanent grassland (C(3) vegetation) were investigated. The relationship between the total C content and the delta(13)C signature at different depths in the upper 30 cm of the soil profile could be well fitted by the Rayleigh equation (y = -29.8 - 2.3x, R(2) = 0.95, p < 0.001), describing the enrichment in (13)C as resulting from isotopic fractionation associated with C mineralization (isotope enrichment factor epsilon = -2.3 per thousand). Potential C dynamics of SOM in four depth intervals of the profile (0-10, 10-20, 20-30 and 30-40 cm depth) were investigated through an incubation study. The C decomposition rate constants decreased with increasing sampling depth from 0.0479 yr(-1) (0-10 cm sampling depth) to 0.0256 yr(-1) (30-40 cm sampling depth) and were highly correlated (y = 0.02 + 0.13x, R(2) = 0.93, p < 0.05) with the corresponding deltadelta(13)C values (average change of the delta(13)C signature per depth increment). These results suggest that changes of the delta(13)C signature of SOM in undisturbed soil profiles under continuous C(3) vegetation may serve as an indicator of the variation of SOM quality with increasing depth.
authors.affiliation: Department of Applied Analytical and Physical Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Belgium. Frederik.Accoe@rug.ac.be
authors.forename: Frederik
authors.initials: F
authors.lastname: Accoe
authors.forename: Pascal
authors.initials: P
authors.lastname: Boeckx
authors.forename: Oswald Van
authors.initials: OV
authors.lastname: Cleemput
authors.forename: Georges
authors.initials: G
authors.lastname: Hofman
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.forename: Rong hua
authors.initials: Rh
authors.lastname: Li
authors.forename: Chen
authors.initials: C
authors.lastname: Guanxiong
mesh_terms: D001673:Biodegradation, Environmental; D015415:Biomarkers / Q000032:analysis; D002244:Carbon / Q000032:analysis* / Q000378:metabolism*; D002247:Carbon Isotopes; D008903:Minerals / Q000378:metabolism; D009930:Organic Chemicals / Q000032:analysis; D012987:Soil / Q000032:analysis*
chemical_list: D015415:Biomarkers; D002247:Carbon Isotopes; D008903:Minerals; D009930:Organic Chemicals; D012987:Soil; D002244:Carbon