Primary vegetation succession and the serpentine syndrome: the proglacial area of the Verra Grande glacier, North-Western Italian Alps

Abstract

Initial stages of pedogenesis are particularly slow on serpentinite. This implies a slow accumulation of available nutrients and leaching of phytotoxic elements. Thus, a particularly slow plant primary succession should be observed on serpentinitic proglacial areas. The observation of soil-vegetation relationships in such environments should give important information on the development of the “serpentine syndrome”. Plant-soil relationships have been statistically analysed, comparing morainic environments on pure serpentinite and serpentinite with small sialic inclusions in the North-western Italian Alps. Pure serpentinite supported strikingly different plant communities in comparison with the sites where the serpentinitic till was enriched by small quantities of sialic rocks. While on the former materials almost no change in plant species composition was observed in 190 years, 4 different species associations were developed with time on the other. Plant cover and biodiversity were much lower on pure serpentinite as well. Extremely low P and high Ni contents in soil were strongly related with these differences, but none of them could be interpreted as the actual limiting factor for plant development on pure serpentinite. Other nutrients or bases were not related with the different primary succession speed and species composition.