In:
Radiocarbon, Cambridge University Press (CUP), Vol. 46, No. 1 ( 2004), p. 465-473
Abstract:
Radiocarbon measurements of different lipid fractions and individual compounds, isolated from soil samples collected on 2 different agricultural long-term study sites, located in the rural area of Rotthalmünster (Germany) and in the city of Halle/Saale (Germany), were analyzed to obtain information about sources and the stability of soil organic matter (SOM). Different lipid compound classes were isolated by automated solvent extraction and subsequent medium-pressure liquid chromatography. Generally, 14 C contents of lipid compound classes from topsoil samples of maize plots at Rotthalmünster are close to the modern atmospheric 14 C content. Lower 14 C values of aliphatic and aromatic hydrocarbons isolated from neutral lipids suggest a contribution of old carbon to these fractions. In contrast, 14 C values of bulk soil (52 pMC) as well as isolated lipid classes from Halle are highly depleted. This can be attributed to a significant contribution of fossil carbon at this site. Extremely low 14 C contents of aromatic (7 pMC) and aliphatic hydrocarbons (19 pMC) reflect the admixture of fossil hydrocarbons at the Halle site. Individual phospholipid fatty acids (PLFA), which are used as a proxy for viable microbial biomass, were isolated by preparative capillary gas chromatography (PCGC) from topsoils at Rotthalmünster and Halle. PLFA 14 C values are close to atmospheric 14 C values and, thus, indicate a clear microbial preference for relatively young SOM. At Rotthalmünster, the 14 C concentration of short-chain unsaturated PLFAs is not significantly different from that of the atmosphere, while the saturated PLFAs show a contribution of sub-recent SOM extending over the last decades. At Halle, up to 14% fossil carbon is incorporated in PLFAs n -C17:0 and cy -C18:0, which suggests the use of fossil carbon by soil microorganisms. Moreover, it can be concluded that the 14 C age of soil carbon is not indicative of its stability.
Type of Medium:
Online Resource
ISSN:
0033-8222
,
1945-5755
DOI:
10.1017/S0033822200039771
Language:
English
Publisher:
Cambridge University Press (CUP)
Publication Date:
2004
detail.hit.zdb_id:
2028560-7
SSG:
11
SSG:
13
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