“…The total amount of P, S, Ca, Mg, Fe, Al, and K was determined by inductively coupled plasma optical emission spectrometry (ICP-OES; Arcos II, Kleve, Germany, Ameteck Spectro). Each soil sample was analyzed three times, and the data were calibrated using International Reference Materials (BCR) and internal laboratory standards [39]. The organic carbon (OC) and total nitrogen (N) contents of the finely ground samples were determined by a CHN elemental analyzer (Flash 2000, Thermo Fisher Scientific, Waltham, MA, USA) coupled with an isotope ratio mass spectrometer (IRMS Delta C or DELTA+XL, Thermo Finnigan MAT, Bremen, Germany) for the stable carbon and nitrogen isotope ( 13 C and 15 N) determination, expressed as δ 13 C (‰) and δ 15 N (‰) with respect to the V-PDB universal reference standard for 13 C and air for nitrogen.…”