OM was determined by subtraction of ash content. Total organic carbon was calculated as 58% of OM (Zmora-Nahum et al. 2005).
TN was measured by Kjeldahl method (Bremner 1996).
DOC, CHS extracted with 0.1 mol L-1 NaOH, and CFA from the NaOH extraction at pH 1.0 were determined by potassium dichromate oxidic method (Pereira et al. 2006).