Population ecology of a Stratiotes aloides l. stand in a riverside lagoon in N. Sweden

Abstract

A stand of Stratiotes aloides L. in a riverside lagoon, Abborravan on the Vindelälven river in N Sweden, was studied for 3 years (1975–1977). The stand was vegetative, at all times submerged and therefore never flowering. On average each plant produced 3 adventitious roots and 40 leaves. One or two turions were also produced each year, together with stolons and associated offsets. At the beginning of June 1977 the population density was 42 plants/m² and the biomass was 290 kg/ha (dry wt. basis). At the end of September that year the respective values were 90/m² and 756 kg/ha. The dry wt./fresh wt. ratio of the biomass changed little during that period, from 6.4 to 6.5%. These and other results are compared with the respective data for Stratiotes stands in Central European lakes. In Abborravan Stratiotes seems well-adapted to survive the prevailing, hard, winter conditions. Freezing in situ is quite normal and is only lethal if the overwintering basal rosettes become frozen solid. The turions are quite frost-hardy.