Expansion and retreat of aquatic macrophyte communities in south Bohemian fishponds during 35 years (1941–1976)

Abstract

The aquatic macrophyte communities of southern Bohemian fishponds were analyzed during 35 years (1941–1976). From 61 vegetational units 26 communities may be characterized as being well adapted to modern fishpond management, 4 units are on their way to extinction and 18 units are in regression. Our long-term observations evaluated the following types of destruction: destruction of the community, in which one dominant species retreats and another regenerates (Potameto natantis-Nymphaeetum candidae → Potamogeton natans comm.); destruction of the community, in which only one stratum regenerates (synusia) (Glycerietum aquaticae utricularietosum australis → Utricularia australis comm.). The development of the pleustophytic communities followed two pathways: transformation of more complicated forms into simpler ones (Utricularietum australis → Lemno-Spirodeletum); development of complicated forms from simpler ones (Lemnetum minoris → Lemno-Spirodeletum).