Contrasting Diaspore and Vegetation Attributes of Grasses From Natural and Disturbed Habitats in an Urban Eucalypt Forest Reserve

Abstract

Forty one species of grasses from a eucalypt forest reserve near Brisbane, Australia, were allocated to groups characteristic of undisturbed forest, regularly mown areas, and road banks. Morphological attributes of diaspores, height and growth habit of mature plants, species origin, flowering times and life history were determined for each species.

Species characteristic of the mown areas had lighter diaspores than the forest gasses and did not possess awns; if a callus was present it was blunt and did not have antrorse hairs. Species from mown areas also differed from the forest species in being mainly short stoloniferous exotics which flowered for longer than the forest species.

Species characteristic of the natural forest and road bank areas had diaspores of similar mass, similar diaspores attributes (awns, callus and antrorse hairs) and species of both habitats were mainly tall and tufted. The road bank species differed from the forest species in being mainly of exotic origin and in flowering for up to 9 months per year longer than the forest species.

That grass species of mown areas successfully compete with forest species in mown areas may be because of a mowing regime which selects for short, mainly stoloniferous, species which have longer periods of diaspore production than the forest species. As road banks are not subjected to regular mowing, an extended pattern of flowering which ensures a continuous supply of diaspores may account for road bank species successfully competing with forest species in disturbed areas.