Shoot Growth in <i>Typha angustifolia</i> l. and <i>Typha latifolia</i> l. in the Kokemäenjoki River Delta Western Finland

Abstract

The growth dynamics of two tall littoral helophytic plants, the narrow-leaved cattail (Typha angustifolia L.) and broad-leaved cattail (Typha latifolia L.; Typhaceae) were studied in the rapidly changing estuarine habitats in the Kokemäenjoki River delta, western Finland. The two cattails form uniform, single-species communities (monocultures) throughout the plant-covered estuary. Of the two taxa compared, the shoots were taller in T. angustifolia (mean 166 cm) than in T. latifolia (mean 120 cm). But due to the robust leaves, the relation in the average weight of individual ramets was opposite: The mean weight of T. angustifolia was 9.6 g (dry wt), and that of T. latifolia was 16.5 g. In a separate study, the leaf height was compared between the fertile (flowering) and sterile (non-flowering) ramets. In flowering ramets the average leaf length was 35 cm taller in Typha angustifolia than in T. latifolia. The differences were even more pronounced in sterile ramets, where the leaves of Typha angustifolia were 70 cm taller than those of T. latifolia. The differences were statistically highly significant. Interspecific competition between the two Typha species is negligible, because the microhabitats differ from each other. T. angustifolia grows in considerably deeper (mean depth 42 cm) waters than T. latifolia (mean depth 19 cm). The optimum range in the water depth is markedly stricter in T. angustifolia than in T. latifolia. The differences between the rooting depths of the two cattails were statistically highly significant. The physico-chemical characteristics of the rooting zones (rhizospheres) of the two cattails are similar, with the locally produced (autochthonous) organic matter dominating and determining the fertility of the habitats.