delta 13C soil

Olive orchard in a typical, hilly landscape in southwestern Sicily, Italy (37°44’14’’N 12°57’46’’E).

An EA-IRMS (Elemental Analyser Isotope Ratio Mass Spectrometry, Carlo Erba Na 1500, model Isoprime 2006, Manchester, UK) was used for  isotopic analysis. The reference material was IA-R001 (Iso-Analytical Limited wheat flour standard, d13CV-PDB = 26.43m). IA-R001 is traceable to IAEAeCHe6 (cane sugar, d13CV-PDB = 10.43m). IAR001, IA-R005 (Iso-Analytical Limited beet sugar standard, d13CVPDB = 26.03m), and IA-R006 (Iso-Analytical Limited cane sugar standard, d13CV-PDB = 11.64m) were used as quality control samples. The International Atomic Energy Agency (IAEA), Vienna, distributes IAEA-CH-6 as a reference standard material. The results of the isotope analysis are expressed as d values (m) relative to the international Pee Dee Belemnite standard as follows:

            eq. 1

where, R = 13C/12C, s = sample, and st = standard. Inorganic carbon was removed before stable isotope analysis by acid fumigation following the method of Harris et al. (2001).

The used model was developed by Novara et al. (2015) to estimate soil redistribution (from the area of detachment to the area of deposition) based on measurements of the variation of  d13C between the soil surface and the reference value in the flat area.