Sur la propagation récente de quelques thérophytes nitrophiles le long de la Loire et de l'Allier

Abstract

Summary The actual distribution of three nitrophilous therophytes, Chenopodium rubrum, Ch. glaucum and Atriplex prostrata, that are extending on the lower course of Loire and Allier, is presented. It is supplemented by an arrangement of floristical and ecological data taken from floras and herbarium specimen. The study reveals a connection between their multiplication and some soil parameters. At twenty ecologically similar study sites, distributed all along the two rivers, populations of the three species were investigated quantitatively and seven physicochemical parameters were mesured. Three soil parameters, pH, electric conductivity and carbonate show some correlations with the biomass of the three plants, both increasing from the upper to the lower parts. High values for electric conductivity in the lower part of the Loire river are interpreted as a strong sign for hypertrophication. The spread of these plants, reputed as indicators of eutrophication and water pollution, thus ecological degradation, is taken as a signal of alarm, which needs further supervision.