| Abstract: | Abstract. Ca. 360 relevés of pleustonic vegetation were recorded in South America between 1983 and 1996.245 relevés, containing three or more pleustonic species, were classified according to the methods of Braun-Blanquet. Within the class Lemnetea (minoris) the following two orders with alliances (All.) and associations (Ass.) can be distinguished: 1. Lemnetalia gibbae All. Azollo filiculoides-Lemnion gibbae Ass. Lemno minutae-Lemnetum gibbae Azollo filiculoides-Wolffielletum oblongae 2. Lemnetalia aequinoctialis All. Salvinio minimae-Lemnion minutae Ass. Lemno minutae-Wolffielletum lingulatae All. Salvinio minimae-Lemnion aequinoctialis Ass. Lemno aequinoctialis-Wolffielletum lingulatae Lemno aequinoctialis-Wolffielletum welwitschii All. Woljfio columbianae-Lemnion obscurae Ass. Woljfio globosae-Lemnetum obscurae The occurrence of the four alliances is mostly dependent on climate and geographical situation. The usefulness of creating pleustonic unities is discussed. |
