Our research focuses on the population dynamics of plants and how they are influenced by impacts of natural disturbances and global environmental change. We are particularly interested in the interactive effects of fire, grazing and drought in grasslands and woodlands in southern Australia, and how climate change, fragmentation and shrub encroachment affect ecosystems.

Monday, 18 November 2013

Kangaroo Grass; Rooigrass; Red Grass

Kangaroo Grass, Wonangatta Valley, Victoria

One of my favourite plants of grasslands in southern Australia is the dominant grass Themeda triandra. So much of grassland ecology revolves around the species: competition, gaps, nutrient cycling, fire, litter, habitat. And I'm intrigued by its capacity to be so adaptable. In Victoria alone you can find it growing in dune swales at Wilsons Promontory, in subalpine plains near Mt Hotham at about 1350 m and in vegetation verging on mallee at 400 mm near Quambatook.

Two new reviews on Themeda triandra have been published in the last year and I thought I'd bring them to your attention. They focus primarily on distribution, cytology, germination biology, forage quality, fire response and ecosystem processes. I've include the Abstracts below in case you want to chase them up.

Some things you may not know about Themeda triandra:
  • The species is found in all states of Australia, South Africa, Indonesia, New Guinea, Japan, India, Saudi Arabia, southern Turkey and Mongolia! It's also become naturalised in New Zealand.
  • In Australia, there are two main genetic races - the diploids that occur south and east of the Great Divide (i.e. coastal populations), and tetraploids that occur in drier, inland areas.
  • The species probably evolved in tropical Asia and migrated down the east coast of Australia (although there is a crazy hypothesis that suggests that Themeda colonised Australia via the importation of camels from Asia and Africa in the 19th century!!)
  • there have been no crossing trials between South African and Australian populations to see if they can breed.
  • it is an important forage species in Africa for impala, antelope, wildebeest, zebra and buffalo.
  • Themeda can decline in the absence of disturbance because tillers are shade-intolerant, and flowering culms are rarely produced on plants that are moribund.
  • up to 94% of seed falls within 50 cm of maternal plants.
  • Almost without exception, sheep have been shown to negatively impact Themeda.

Dell'Acqua et al. (2012) A tropical grass resource for pasture improvement and landscape management: Themeda triandra Forssk. Grass and Forage Science 68, 205-215.

Themeda triandra Forssk. is one of the most widespread grasses in the dry to mesic prairie ecosystems of Africa, Asia and Australia. It is of particular interest due to its high value as a forage species for wildlife and livestock, and its potential use in landscaping practices. In this review we have collated information from the many studies that have been devoted to this species since the 1960s to provide information about the species’ distribution, taxonomy, morphology, ploidy and reproduction, and to describe its vegetation and germination and their relationship with the most important ecological aspects of its preferred habitats. Agronomic aspects are considered in detail, with particular focus on the role of T. triandra as a forage species and the relative importance of grazing, fire and rainfall regimes for its management. We also explore how this species can help with the rehabilitation of degraded areas, soil and water conservation, countering exotic species invasion and landscaping in general. We conclude with a brief discussion of the as yet unresolved taxonomic relationship between the African species T. triandra and the Australian species Themeda australis.

Snyman et al. (2013) Themeda triandra: a keystone grass species. African Journal of Range and Forage Science 1-27.

Themeda triandra is a perennial tussock grass endemic to Africa, Australia and Asia. Within these regions it is found across a broad range of climates, geological substrates and ecosystems. Because it is widespread across these areas it has great economic and ecological value, as it is a relatively palatable species across most of its range. It is of critical importance in supporting local populations of both native and introduced herbivores, and is thus central to wildlife and livestock production, and consequently rural livelihoods. It is an important climax or subclimax species that is well adapted to fire, a common element in many areas where it is found. Inappropriate grazing management, however, can result in a decline of Themeda, as it is not well adapted to an uninterrupted, selective grazing regime. A decline in abundance of Themeda in a grassland is usually coupled to a decline in grazing value, species richness, cover and ecosystem function. In spite of its significant ecological and economic importance, there has been no attempt to review and synthesise the considerable body of research undertaken on this grass. Our aim is to summarise and synthesis work previously undertaken and identify areas where further research is required.



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