Dendrochronologie von Kräutern und Sträuchern im Vorfeld des Morteratschgletschers

Abstract

The reconstruction of chronosequences of vegetation recolonization in recent glacier forefields is possible with dendrochronological age determination of herbs, dwarf shrubs and shrubs. We identified plant age based on growth zones in the root collar of 854 individuals from eight herb and dwarf shrub species in the front of the Morteratsch glacier in the eastern Swiss Alps. Each dendrochronological date is related to intervals of five years of land exposure. We found the following maximum age on single plants (individual maximum age) and maximum average plant ages (mean maximum age of a population; in brackets) in the deglaciated terrain since 40 years (since 1960): Salix daphnoides 29 (18), Rumex scutatus 28 (16), Myricaria germanica 19 (10), Achillea erba-rotta 15 (12), Epilobium fleischeri 10 (7), Trifolium pallescens 10 (7), Hieracium staticifolium 8 (6), Oxyria digyna 9 (6), Sempervivum arachnoideum 8 (5), Lotus corniculatus 6 (3) years. In the first year after ice retreat germination was observed for Epilobium fleischeri, Rumex scutatus, Myricaria germanica, Trifolium pallescens, Oxyria digyna, and Salix daphnoides. After a time lag of two and three years indivuduals of Achillea erba-rotta and Hieracium staticifolium were noted. Sempervivum arachnoideum germinated 8 years after ice retreat. Maximum ages of Epilobium fleischeri and Oxyria digyna were reached after 10 (1990), Achillea erba-rotta after 30 (1970) and the other species after 25 years (1975) following deglaciation.