1 23 Rendiconti Lincei SCIENZE FISICHE E NATURALI ISSN 2037-4631 Rend. Fis. Acc. Lincei DOI 10.1007/s12210-014-0376-z Chemical characterization of soil organic profiles for assessing the European morphogenetic reference base of humus forms in Mediterranean environments Valentina Baratella, Marco Renzaglia & Alessandra Trinchera