Effects of a fire event on the soil organic matter of a pine forest and a pasture

The effects of a fire onto the organic components of soils from a pine forest and a pasture, one close to the other and both located in the Italian Presidential Estate of Castelporziano (Roma), have been investigated. Chemical and biochemical indicators of soil organic matter (SOM) from two horizons, i.e. 0-5 and 5-20 cm, have been considered. Data were correlated with those obtained by means of solid state NMR spectroscopy (CPMAS 13C-NMR). The latter was applied to both whole soil and selectively extracted SOM and the percentage of aromatic functional groups and the alkylic to O-alkylic carbon ratio were measured. In pine forest the formation of recalcitrant and hydrophobic molecules, e.g. resins, melanoidins and condensed polymers, occurred. In pasture soil TEC, TOC, CHA+FA and microbial biomass increased in inverse proportion to the carbonyl group amount estimated by CPMAS 13C-NMR.