Humic Profiles Research Articles

Chemical characterization of soil organic profiles for assessing the European morphogenetic reference base of humus forms in Mediterranean environments

In the Castelporziano Reserved Area (Tyrrhenian coast near Rome, Italy), the organic horizons of 14 forest sites were chemically characterized to assess the European reference base of humus classification in Mediterranean ecosystems and evaluate the impacts of typical ecological disturbances on humification processes. Soils were sampled in three diagnostic horizons OL (litter), OF (fulvic) and OH (humic), and the biological type of humus were investigated on a morpho-functional basis and assigned to the taxonomic levels Mull, Amphi and Moder. For each diagnostic horizon, the total organic carbon (TOC%), the C/N ratio, the extractable carbon (TEC%), the humic and fulvic acids carbon (CHA%, CFA%), the degree (DH%) and the index of humification were determined. All data were statistically analyzed (ANOVA, post hoc HSD Tukey’s). In the OF horizon of some OL/OF sites, the CHA values were found very high, indicating the presence of a not-detected OH horizon. Conversely, part of the sites sampled with a complete humus profile, did not show differences between OF and OH, which should thus be grouped into a single diagnostic horizon. The humification parameters showed a fairly good correlation with the humus forms, limited to the first taxonomic level and the OF horizon. Overall, several discrepancies were found between humus classification and the chemical fingerprint of the humic profiles. In this regard, the use of screening analytical methods, i.e., the chemical characterization of OM, may provide a powerful support in modeling the morpho-functional references of humus forms on the peculiar features of Mediterranean forest environments.

Approccio morfologico-funzionale nello studio dei suoli: relazioni tra gli epipedon umiferi e gli orizzonti organo-minerali in alcuni profili pedologici di ambiente alpino

In order to understand the role and the mutual influences of humus and soil in alpine spruce forest ecosystems we studied and classified 7 soil - humic profiles on the 4 main forestry dynamics: open canopy, regeneration, young stand, tree stage. We studied the role of humification process in the pedologic process involving soils and vegetations studing humic and soil horizons. Study sites are located at an altitude of 1740 m a.s.l near Pellizzano (TN), and facing to the North. The parent soil material is predominantly composed of morenic sediments, probably from Cevedale glacier lying on a substrate of tonalite from Presanella (Adamello) Tertiary pluton. The soil temperature regime is frigid, while the moisture regime is udic. The characteristics observed in field were correlated with classical chemical and physical soil analyses (MIPAF 2000). In order to discriminate the dominant soil forming process, the soils were described and classified in each site according to the World Reference Base (FAO-ISRIC-ISSS 1998). Humus was described and classified using the morphological-genetic approach (Jabiol et al. 1995). The main humus forms are acid and they are for the greater part Dysmoder on PODZOLS. The main pedogenetic processes is the podzolization, locally there are also hydromorphic processes. We associate a definite humus form with a pedological process at a particular step of the forest evolution. We concluded thath the soil study for a correct pedological interpretation must take count of the characteristics of the humic epipedon.