Microlaena stipoides, a C3 perennial grass, is common within grazed native pastures in the high rainfall zone (> 550 mm average annual rainfall) of south-eastern Australia. Microlaena has the ability to survive and persist in environments within this zone that commonly experience soil water deficits during the summer months. Our knowledge of the summer drought survival mechanisms of Microlaena to sustain its populations is incomplete. Using field, glasshouse and laboratory studies and experiments, this thesis researched key components of the population biology of Microlaena. The thesis investigates the extent to which Microlaena populations in the summer-dry environment of south eastern Australia are maintained by adult plants and/or seeds and seedling recruitment.Microlaena has a unique morphology: its shoots arise from corm-like structures that are located approximately 20 mm below the ground surface. The location of the active buds and their depth of burial may provide Microlaena with the ability to withstand close grazing and protection from hot, dry summers. There was no evidence that Microlaena exhibited summer-dormancy, which is characteristic of Mediterranean species. When irrigation was applied, even with high soil temperatures, it responded by producing new buds and tillers. Microlaena was able to withstand short (up to 30 days) but not prolonged dry periods. The survival of Microlaena over protracted dry periods, typical of southern Australia, either requires deep roots or is related to the position in the landscape where Microlaena most commonly occurs, or both.Microlaena is not dormant, but quiescent, during summer droughts and has the ability to respond to summer rainfall events. Its underground structures (rhizomes and corms) allow it to respond rapidly to favourable soil moisture conditions.
|Qualification||Doctor of Philosophy|
|Award date||13 Mar 2013|
|Place of Publication||Australia|
|Publication status||Published - 2013|