Forest humus in the Province of Trento (Italian Alps)

The Centro di Ecologia Alpina (Trento-Italy) has been involved in the study of forest humus in Trentino since 1994. In 1995 we sampled the most representative beech and fir forests of western-central Trentino. Thirty-six sites, including the sub-montane thermophile beech forests, the mesophile and the acidophile beech and fir forests, are object of the present paper. The research scrutiny of the groups issued from the statistical processing of the floristic lists allowed us to point out the relationships between vegetation communities, soils and humus forms. The present study indicates that the nature of the substrate, whether it be of siliceous or calcareous substrate, is important both in the pedogenesis and in the humification processes. Out of 36 sites, 9 were chosen to evaluate the turnover of the organic and humic matter and the biological activities of the humic substances. Taking into account the difference among the organic parameters the main goal of this work regards the different hormone-like contents of the humic matter, that is gibberellin-like (GA) in the beech forests and auxin-like (IAA) in the fir forests. The different bioactivities of the humic fractions were further evaluated in the Picea abies seedlings, which were grown in the same humic fractions, by studying the invertase and peroxidase activities enzyme markers for GA and IAA hormones respectively.