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

Floristic composition, vegetation structure and ecology
“Unfortunately, there exists no really satisfactory description of the vegetation when the grazier first began to exploit the
country” (Wadham and Wood 1950 p. 87). Eighty years after exploitation commenced, Schimper (1903 p. 503) noted that there
were “no available descriptions of the extensive savannahs and steppes of the interior of New South Wales and Victoria”. Some
decades later, McTaggart (1936), as part of an Australia-wide ‘survey’ of pastures, provided a description of the open grasslands
(in which he included “savannah”, now grassy woodland) of south-eastern Australia, but it is evident from his text and the listed
information sources that no detailed compositional and structural knowledge then existed for most areas.
The earliest detailed studies of Australian grassland vegetation, made in the decades preceding 1950, provide “no guide to the
proportions of the various species, or the composition of the vegetation from the standpoint of grazing value” of the areas before
grazing commenced, but it is known that “profound” changes had occurred, particularly where rainfall was low or highly
variable (Wadham and Wood 1950 p. 87). By 1875, for example, the grasslands of South Australia had “mostly disappeared” by
conversion to cereal growing (Schimper 1903 quoting Schomburgk 1875). The “lack of adequate description before alteration
occurred” (Jones 1999b p. 29) is an ongoing problem. Lunt (1990a p. 47) thought that an accurate representation was “almost
impossible”, while Lunt et al. (1998) considered “any reconstruction of the original vegetation must be somewhat speculative,
particularly at a detailed level”. The pre-European composition is still considered to be “poorly understood” (McIntyre and
Lavorel 2007) but pre-European grassland was probably more diverse than current reference areas, and many species have
presumably been eliminated or greatly depleted in most areas (Sharp 1997).
A similar situation exists with the temperate grasslands of South America. One of the first floristic surveys of pampas vegetation
was made by L.R. Parodi in 1930 by which time so-called “virgin grasslands” were rare (Soriano et al. 1992 p. 381) and after
which agricultural development greatly intensified.
Early historical descriptions
One of the earliest Australian descriptions is Schomburgk’s (1875, quoted by Schimper 1903 pp. 504-505) portrait of South
Australian grasslands, in which the grasses mentioned are already a mixture of native and introduced species, although the forbs
appear to be entirely native: “The plains near the coast ... the soil mostly fertile, extending often to the sea ... The grasses consist
of more nourishing kinds ... Poa, Panicum, Festuca, Agrostis, Aira, Andropogon, Cynodon, Stipa, Pennisetum, Bromus,
Eriachne, Anthistiria [Themeda], Hordeum ... The banks of the rivers and creeks, which mostly cease running druing the
summer, are lined with majestic gum-trees ... the shrubs extending more or less on the plains, according to the nature of the soil
... the appearance ... has during the dry season, the ... sunburnt yellow character ... destitute of all green herbage ... In the month
of May the rainy season generally commences ... a few showers change the aspect ...into a green and beautiful carpet ... in a few
days the plains appear clothed with luxiarant verdure ... With the grasses are also recalled to new life Ranunculus ... Oxalis ...
Hypoxis glabella ... Drosera ...Wahlenbergia gracilis ... Anguillaria [Wurmbea]... Stackhousia ... Every week adds new colours
to the beautiful carpet ... Kennedya [sic] prostrata...Swainsona procumbens ... and S. lessertiaefolia [sic] ... Thysanotus ...
climbing up the dry grass stalks ... Compositae are seen blooming over the plains in all colours ... But by the middle of
November the number of flowering plants already lessens considerably, the annual grasses and other herbaceous plants begin to
dry up, droop and disappear, and in January the grass land resembles a ripe thinly-sown cornfield, and we find only ... a few
plants of Convolvulus erubescens, Lobelia gibbosa ... and Mesembryanthemum australe [?Disphyma crassifolium] ... The seeds
of the annual plants have been scattered, perennial herbage returned to its dormant state ... and the plains have during the summer
months a dismal, dried-up appearance”.
The earliest study of note for Victoria is Sutton’s (1916-1917) “Sketch of the Keilor Plains flora” at the drier, eastern end of the
Victorian volcanic plains. He provided a valuable census of the vascular flora that included species from neighbouring
vegetation associations, but deliberately excluded all of the exotic species. Patton (1935) provided a list of vascular plants for
Victorian basalt plains grasslands, discussed their structure, composition and seasonal dynamics and the climate and soils.
Contemporary studies
A much greater range of more detailed studies have taken place in the last fifty years, commencing with investigations such as
those of Willis (1964) and Groves (1965). These describe grassland generally dominated by perennial tussock grasses including
T. triandra, Poa, Austrodanthonia and Austrostipa species, with the latter two genera being more dominant in drier areas (NSW
Riverina, Northern Plains of Victoria and Northern Lofty region of South Australia) (Kirkpatrick et al. 1995, Sharp 1997, Lunt
and Morgan 2002). Bothriochloa, Enteropogon and Chloris may also be dominant grasses, while Lomandra is the major
dominant in some South Australian formations (Carter et al. 2003).
Based on readings of historical records T. triandra is thought to have been the dominant species across much of the plains before
European occupation, although this is based on the assumption that the vernacular term “kangaroo grass” was applied only to T.
triandra (Lunt et al. 1998). T. triandra was almost certainly the most widespread and dominant grass (Groves 1965, Mack 1989,
Moore 1993, Kirkpatrick et al. 1995) and is considered the major dominant in Victoria, but is replaced by Poa spp.,usually Poa
labillardieri Steud. on wet sites and in higher rainfall areas (Willis 1964, Moore 1993, Entwisle et al. 1994). Austrodanthonia
and Austrostipa species were the dominant grasses in drier areas including the Murray River plains grasslands and in parts of
South Australia (Kirkpatrick et al. 1995). Moore (1993) considered Austrostipa bigeniculata was the principal T. triandra
associate in drier sites. Sutton (1916-1917) found Austrodanthonia penicillata (Labill.) H.P. Linder to often be the dominant in
drier areas of the Keilor Plains with Poa, Austrostipa setacea (R.Br.) Jacobs and Everett, A. semibarbata (R.Br.) Jacobs and
Everett and Dichelachne crinita (L.f.) Hook. f. more prominent in moister areas along with “Panicum” spp. Willis (1964) found
that Austrodanthonia spp. became less prevalent in wetter areas. A large proportion of these grasslands have been modified by
grazing and became dominated by shorter grasses such as Austrodanthonia auriculata (J.M. Black) H.P. Linder, A. carphoides
(Benth.) H.P. Linder and Austrostipa scabra (Lindl.) S.W.L. Jacobs and J. Everett (Moore 1993). Shrubs are rare and
substantially absent (Entwisle et al. 1994, Lunt et al. 1998). Except for T. triandra, the dominant grasses have the C 3
photosynthetic pathway and grow mostly in spring and autumn (Groves and Whalley 2002). Most have seeds with an ‘after
ripening’ period (Groves and Whalley 2002) which presumably acts to prevent germination in the dry season (summer) and
delay it until adequate soil moisture is more likely to be available for seedling establishment. Annual native grasses are rare.
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