Variabilità delle forme di humus in due siti campione di pecceta altimontana trentina

Humus form variability at two experimental sites in the mountain Norway spruce forest, Trentino, Italy. In the Region Trentino Alto-Adige, 59 humus profiles were studied and classified in order to understand the variability of humus forms in alpine forest ecosystems. In particular, the evolution of humus forms was investigated in relation to the development of vegetation cover, with the aim of determining whether a humus form can be representative of a specific forest phase. For the study of humus profiles, transects were traced so as to cut across all 4 principal dynamic phases of forest evolution: open canopy, regeneration, intermediate and mature. Two sub-sites (of about 1000 m2) were selected at an altitude of 1700 m. a.s.l., on parent soil material of morenic sediments on acid substrate and with a vegetation cover of alpine spruce forest: the first, having a north exposition, is located within the Municipality of Pellizzano in Val di Sole, near Mount Nambino; the second, with a south exposition, is located near Madonna di Campiglio, in Val Rendena, near Mount Ritorto. The soil temperature regime is frigid, while the moisture regime is udic. Our investigation pointed out a wide evolutionary variability of forest humus in the studied sites, permitting to identify a probable association trend between different growing-phases of forest and specific humus forms.