Use of micromorphology for humus characterization and classification in some mediterranean calcareous soils

A micromorphological approach is potentially useful in the classification of humus systems. However, the systematic description of organic material found in thin sections of humus profiles is poorly developed in comparison to already existing guides for mineral soils. This study presents the use of thin section microscopical analyses combined with digital images in order to set the highly detailed method of qualitative description and classification of some Mediterranean humus forms. Three forests and one meadow were selected for topsoil sampling in the Catalan Pre-Pyrenean mountain region. Fourteen thin sections were prepared, scanned and analyzed using the petrographic microscope. This resulted in the description of seven micromorphological fabric units based on their amount, shape, color, size, distribution and degree of decomposition. Digital images from thin section scans helped to classify three Amphi (Pachy-, Eumacro-, Eumesoamphi), and two Mull (Oligo-, Eumull) humus forms.