Undestanding the ecology of invasive unpalatable perennial grasses to help in their control. The case of unpalatable perennial grasses native to central Argentina

DISTEL, R.A.; BADGERY, W.B.

Corowa

Conferencia; 17th. New South Wales Weeds Conference; 2013

The Weed Society of New South Wales

Native unpalatable perennial grasses (UPG) have been steadily invading semiarid grasslands formerly dominated by palatable perennial grasses (PPG) in central Argentina. The objective of this paper is to synthesise key aspects of the ecology of UPG, and from that to derive management practices for their control. Studies have shown that PPG have higher competitive ability than UPG. However, selective grazing of PPG reduces their competitive ability, favouring growth and seedling establishment of UPG. Once UPG attain dominance they impair seedling establishment of PPG even in the absence of grazing. UPG produce tissues with high C/N ratio, which slow down litter decomposition and nutrient release rates. They are less productive than PPG, which in combination with their low nutritive value can markedly reduce carrying capacity and livestock productivity. Current knowledge available on the ecology of UPG suggests that a key approach to their control is through allowing PPG to express their superior competitive ability. Experimental evidence from Australian native grasslands also supports that a more successful way of controlling Nassella trichotoma (serrated tussock, an UPG native to Argentina) in the long term is with an integrated weed management system focusing on enhancing the competition from native perennial grasses rather than repeated herbicide applications.