Il ruolo della pedofauna nella variabilità spaziale e temporale delle forme di humus: indagini micromorfologiche su sezioni sottili ed osservazioni allo stereoscopio

L'osservazione allo stereoscopio dei campioni di orizzonti diagnostici di diverse forme di humus permette di distinguere l'origine biologica di queste e di riconoscere i grandi gruppi di animali coinvolti nel processo di trasformazione della lettiera e della sua integrazione nel profilo del suolo. - - - - - (ABSTRACT: In a spruce forest of the Autonomous Province of Trento, located on an acid substrate and with a north exposition, within the Village of Pellizzano, a transect has been traced; along this transect 19 humus profiles have been examined, one at every three meters. For each of them, OH and A horizons (respectively the humic organic and the organo-mineral horizon) have been sampled and studied following the methodology formulated by Ponge (1984) and Bernier et al. (1994). The morphological and semi-quantitative observation of these horizons with the stereoscope and the use of an identification key of soil fauna’s faecal pellets (Galvan et al. 2005) allowed us to determine and point out their relative abundance and to formulate interesting remarks on spatial and temporal variability of humus forms in forests. For four profiles of the transect, a micro-morphological study, with the microscope, of the thin sections of every horizon has been carried out as well, in order to observe those more detailed characters such as: the presence of fossilized coprolites, of paleo-aggregates and of those soil fauna’s dung, in particular mites’ faecal pellets, hardly identifiable with the stereoscope. Both methodology of morphological investigation proved to be necessary for an accurate research and to be a substantial aid for a better identification of humus forms, after they have been described in field following the French morphological-genetic approach (Jabiol et al. 1995))