Natural grasslands in Canberra: their distribution, phenology and effects of mowing

Abstract

A method of mapping natural grasslands in the Canberra region using infra-red colour and natural colour photography is described. Five grassland types are identified depending on the relative proportions in them of the four native grasses,Themeda australis, Bothriochloa macra, Stipa bigeniculata and Danthonia species. The inter-relationships of these grassland types to the habitat and different land uses are discussed. The phenology of the four major native grass species was studied to help understand their seasonal behaviour. Observations of the four species indicated differing photoperiod requirements, stem and leaf yield and reproductive tillering patterns. Bothriochloa grew, flowered and shed seed much later than the other three species. A species list for a Canberra grassland site, together with the flowering times, is presented. The peak of flowering occurred in October-November. A study was made of the effect of five mowing frequencies 0n two grassland types. The responses of the four dominant species present were different when subjected to the same sequence of treatments. Themeda and Stipa appeared to be less tolerant of frequent mowing than Danthonia or Bothriochloa, especially when percentage basal cover and foliage cover measurements were considered. Mowing periods timed with regard to the seasonal behaviour of the grass species could alter the relative contribution of these species to the grassland. The presence of grasslands may be seen as a result of many environmental factors such as fire incidence, grazing and climate acting on the vegetation.

Limitations of the study are discussed and proposals for further research suggested.

Management schedules for maintaining five different grassland types in Canberra are recommended. They involve mowing before and after periods of active grass growth. Show more