ADAPTATIONS OF STIPAGROSTIS SPECIES TO DESERT DUNES

Four ecomorphological types are recognised in the 'Old World' genus St ipagrostis: (1) species confined to areas of high sand mobility, which require accumulating sand cover for survival; (2) species of sandy ar eas which may be covered with sand or the sand may be removed; (3) spe cies confined to stable or slightly eroding sand sheets; and (4) annua l species of areas with less than 50 mm rainfall annually. Most specie s have a plumose diaspore which glides easily over long distances. Dia spores of a few species have a pappose awn, and are dragged on the dun e surface to a leeward slope where they are covered by sand. (C) 1996 Academic Press Limited