Literature review: Impact of Chilean needle grass ... - Weeds Australia

functioning as natural grassland (Groves and Whalley 2002). In some areas derived grasslands are the only grassland remnants
(Kirkpatrick et al. 1995).
In the absence of grazing, secondary grassland can revert back to woodland or shrubland (Groves and Whalley 2002, Benson
2004). O’Dwyer (1999 p. 324) suggested that livestock grazing had “prevented regeneration of a shrubby woodland” in many
derived Victorian grasslands. Distinguishing anthopogenic grasslands is difficult or sometimes impossible because of continuous
human influences over long periods (Wheeler et al. 1999, Carter et al. 2003), as well as long term climatic fluctuation and large
scale natural disturbances which can alter plant dominance patterns. Many grasslands in South Australia are derived formations
(Davies 1997), and the Riverine Plains Grasslands of south-west NSW were once dominated by Acacia pendula A.Cunn. ex
Don. and Atriplex spp. (Benson 2004, Keith 2004).
The term ‘secondary grassland’ is generally used to designate formations that are a product of post-colonisation management, or
the lack of it. The extent to which grasslands are cultural landscapes resulting from aboriginal land management has generally
been treated as a separate issue in Australia, despite overlap between pre- and post colonisation management regimes and species
invasions, and despite the “persistent legacies of past human impact on species composition ... structure, disturbance regimes and
soil conditions” (Froyd and Willis 2008 p. 1729).
Grassland distribution
Australian grasslands have mostly been well described botanically, but poorly mapped, in particular in terms of their historical
distribution (Groves 1979). Moore’s (1993, Fig. 13.1) map, which supposedly shows the distribution of “herbaceous
communities”, derived from other vegetation communities or not, that were then “used for livestock production” and “composed
essentially of native species” (Moore 1993 p. 315), seems particularly defective for south-eastern Australia. For example large
areas of continuously forested land in eastern Victoria that have never been managed as grazing land are depicted as “Temperate
Tallgrass” grassland. His 1993 and earlier maps have probably caused much confusion over a long period.
Remnants continue to be discovered in areas thought previously to have had no grasslands (Cook and Yugovic 2003, Sinclair
2007). Major vegetation mapping in the last 15 years has greatly improved the situation for current vegetation. The pre-European
distribution of temperate grassland in south-eastern Australia was recently mapped by Lunt and Morgan (2002), although
Kirkpatrick et al. (1995 p. 15) thought it was “no longer possible to map much of the pre-European grassland distribution with
any accuracy” because so much was rapidly and completely destroyed. Lunt and Morgan (2002) found that temperate grassland
was one of the dominant vegetation classes, covering extensive areas, but noted that the ‘grassland’ status of some areas,
particularly in lower rainfall regions, was in dispute (e.g. the NSW Riverina), mainly on the basis that they were recently derived
from other vegetation types as a result of land use. The extent to which these grasslands are ‘natural’ or derived has been an
ongoing area of argument. Kirkpatrick et al. (1995) considered that the riverine plains grasslands are more correctly called
herblands, being often not dominated by grasses, and Groves (1979) considered that temperate grassland “was never very
widespread”. Benson and Redpath (1997) argue that too much emphasis on the records of early explorers may have resulted in
an exaggerated conception of the extent of open grassy vegetation at the time of European settlement, in part because the
explorers were typically tasked with finding new grazing lands and preferentially travelled in country that was easier to traverse
on horseback. Carter et al. (2003) avoid the problems of interpretation of historical information and speculative argument that
characterise the debate, by defining a data cut-off of 1982, which excluded only the most recently derived grassland formations.
The somewhat legalistic definition of Natural Temperate Grassland provided by Carter et al. (2003), adapted from McDougall
and Kirkpatrick (1993), also overcomes some of the other terminological difficulties and areas of scientific dispute. It is a broad
vegetation class defined inter alia as being dominated by tussock grasses of the genera Austrodanthonia, Austrostipa,
Bothriochloa, Chloris, Enteropogon, Poa or Themeda or by Lomandra (Xanthorrhoeaceae), with