Isotopic evidences for microbiologically mediated and direct C input to soil compounds from three different leaf litters during their decomposition

• Published in: Environmental chemistry letters Vol. 7; no. 1; pp. 85 - 95
• Main Authors: Rubino, M, Lubritto, C, D’Onofrio, A, Terrasi, F, Kramer, C, Gleixner, G, Cotrufo, M. F
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.02.2009; Springer Berlin Heidelberg; Springer Nature B.V
• Subjects: alkanes; Analytical Chemistry; Cercis canadensis; Decomposition; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Fungi; Geochemistry; Isotopes; laboratory experimentation; Leaf litter; leaves; linoleic acid; Liquidambar styraciflua; Original Paper; phospholipid fatty acids; Pine trees; Pinus taeda; plant litter; Pollution; Pyrolysis; Soils; SOM; PLFA; C; δ; Pyrolysis-GC/MS-C-IRMS; Alkanes; Litter decomposition
• ISSN: 1610-3653; 1610-3661
• DOI: 10.1007/s10311-008-0141-6

We show the potentiality of coupling together different compound-specific isotopic analyses in a laboratory experiment, where 13C-depleted leaf litter was incubated on a 13C-enriched soil. The aim of our study was to identify the soil compounds where the C derived from three different litter species is retained. Three 13C-depleted leaf litter (Liquidambar styraciflua L., Cercis canadensis L. and Pinus taeda L., δ13CvsPDB ≈ −43‰), differing in their degradability, were incubated on a C4 soil (δ13CvsPDB ≈ −18‰) under laboratory-controlled conditions for 8 months. At harvest, compound-specific isotope analyses were performed on different classes of soil compounds [i.e. phospholipids fatty acids (PLFAs), n-alkanes and soil pyrolysis products]. Linoleic acid (PLFA 18:2ω6,9) was found to be very depleted in 13C (δ13CvsPDB ≈ from −38 to −42‰) compared to all other PLFAs (δ13CvsPDB ≈ from −14 to −35‰). Because of this, fungi were identified as the first among microbes to use the litter as source of C. Among n-alkanes, long-chain (C27–C31) n-alkanes were the only to have a depleted δ13C. This is an indication that not all of the C derived from litter in the soil was transformed by microbes. The depletion in 13C was also found in different classes of pyrolysis products, suggesting that the litter-derived C is incorporated in less or more chemically stable compounds, even only after 8 months decomposition.