Literature review: Impact of Chilean needle grass ... - Weeds Australia
Literature review: Impact of Chilean needle grass ... - Weeds Australia
Literature review: Impact of Chilean needle grass ... - Weeds Australia
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in shifting the distribution, extent and composition <strong>of</strong> <strong>grass</strong>lands. All these major factors are compounded, their individual<br />
influences are difficult to determine from the limited palaeecological records (Hope 1994) and existing remnants may have little<br />
resemblance to their pre-European condition (Trémont and McIntyre 1994). The palaeontolgy <strong>of</strong> temperate <strong>Australia</strong>n <strong>grass</strong>lands<br />
is discussed in the section on <strong>grass</strong>lands origins (above), while the pre-European influences <strong>of</strong> aboriginal <strong>grass</strong>land management,<br />
grazing and fire, and the post European disturbance and management factors are discussed in sections on these topics below.<br />
Aboriginal management<br />
In south-eastern <strong>Australia</strong>, apart from the coast, <strong>grass</strong>land was the main habitat occupied by aborigines (Kirkpatrick et al. 1995).<br />
The earliest undisputed evidence for aboriginal occupation <strong>of</strong> <strong>Australia</strong> remains at around 40,000 ypb in the Kimberley <strong>of</strong><br />
Western <strong>Australia</strong>, close to the limit <strong>of</strong> resolution <strong>of</strong> radiocarbon dating, but evidence using other techniques indicates first<br />
occupation may have occurred c. 60 kybp (Kershaw et al. 2000). Coutts (1982) claimed that aboriginal people were present in<br />
Victoria at least as long ago as 40 kybp, but the oldest south-eastern mainland site known, at Willandra Lakes, is dated at c. 36<br />
kybp (Kershaw et al. 2000). Most <strong>of</strong> <strong>Australia</strong>, including Tasmania was probably occupied by 35 (Hope 1994) or 32 kybp, all<br />
major environments were certainly occupied by 22 kybp, and occupational intensities increased after c. 5 kybp (Kershaw et al.<br />
2000). Aborigines coexisted for many thousands <strong>of</strong> years with the extinct marsupial megafauna in the early prehistoric period<br />
(Coutts 1982, Kershaw et al. 2000).<br />
Aboriginal people managed the land over many thousands <strong>of</strong> years (Zola and Got 1992) and would have witnessed the assembly<br />
<strong>of</strong> many <strong>Australia</strong>n <strong>grass</strong>lands, notably on the Victorian Volcanic Plains, where the most recent terrain was formed several<br />
thousand years ago. The total aboriginal population <strong>of</strong> Victoria in 1788 has been estimated at 15,000 (Coutts 1982) but actual<br />
population is very uncertain. Mulvaney (1964) suggested a population density <strong>of</strong> one person per 13 km 2 in the western district <strong>of</strong><br />
Victoria prior to European settlement, with a total population <strong>of</strong> 1,800. Mulvaney’s estimate is probably much too low, since<br />
800-1,000 western district aborigines were known to gather annually at Lake Bolac (Jones 1999b). The South East <strong>of</strong> South<br />
<strong>Australia</strong> supported an “unusually large population, perhaps numbering 2000” (Pretty et al. 1983 p. 116). The population in that<br />
region is estimated to have declined by half every five years, from the beginning <strong>of</strong> settlement in 1840 (Pretty et al. 1983).<br />
Numerous archaeological sites are recorded on the Victorian Basalt Plains including campsites, earthen mounds (probably long<br />
occupied campsites), burials, canals and weirs <strong>of</strong> basalt rocks used as fish traps, basalt block walls probably ro<strong>of</strong>ed with timber<br />
and used as huts, etc. (Coutts 1982). Indications are that some populations were more or less sedentary, rather than nomadic.<br />
Digging and burning <strong>of</strong> the vegetation were probably the most important aboriginal activities in terms <strong>of</strong> <strong>grass</strong>land ecology, and<br />
areas <strong>of</strong> <strong>grass</strong>land appear to have been extended by aboriginal activities (Kirkpatrick et al. 1995). However in the mid to late<br />
Holocene some societies in more arid areas developed economies based on systematic harvesting and processing <strong>of</strong> <strong>grass</strong> seed<br />
(Kershaw et al. 2000, Gammage 2009). One species exploited was Barley Mitchell Grass, Astrebla pectinata (Lindl.) F. Muell.,<br />
a common and very widespread species <strong>of</strong> the summer rainfall semi-arid and arid zones. It has “relatively large seeds that<br />
separate easily from the chaff” and “at one time provided an important part <strong>of</strong> the diet <strong>of</strong> the Aborigines” (Cribb and Cribb 1974<br />
p. 101). Another grain, with distribution extending into more temperate winter rainfall areas <strong>of</strong> south-eastern <strong>Australia</strong>, was<br />
Native Millet or Windmill Grass, Panicum decompositum R.Br., a species “<strong>of</strong>ten associated with temporarily wet places such as<br />
creek beds and flood plains” (Jessop et al. 2006 p. 461). It was a major foodplant (Jessop et al. 2006), extensively cultivated<br />
(Gammage 2009), the seeds being ground into a paste and baked to form bread (Cribb and Cribb 1974). Another arid zone<br />
species harvested was Woollybutt, Eragrostis eriopoda Benth. (Jessop et al. 2006), which has abundant, readily husked, s<strong>of</strong>t,<br />
easily-ground seed that is held on the plant for months (Low 1989). Other Panicum spp. were also used (Low 1989). Perhaps<br />
Hairy Panic, Panicum effusum R.Br., a common associate <strong>of</strong> T. triandra in temperate south-eastern <strong>grass</strong>lands, was used in a<br />
similar manner. Eragrostis tef (Zucc.) Trotter and Panicum miliaceum L. were amongst the <strong>grass</strong>es cultivated in pre-Islamic<br />
civilisations in Arabia (Pohl 1986). Current consensus appears to be that <strong>grass</strong>es were not important in the diets <strong>of</strong> aborigines<br />
living outside the dry interior, and Gammage (2009) has convincingly argued that they were little used in areas with a reliable<br />
supply <strong>of</strong> edible tubers. However the possibility that aboriginal management <strong>of</strong> cereal <strong>grass</strong>es influenced the structure and<br />
biodiversity <strong>of</strong> the temperate <strong>grass</strong>lands <strong>of</strong> south-eastern <strong>Australia</strong> should not be ignored.<br />
Intensive digging took place in the temperate <strong>grass</strong>lands to harvest roots for food, particularly Murnong, Microseris spp., which<br />
was stockpiled and traded (Gott 1983), and Turrac (probably Pelargonium rodneyanum) (Lunt et al. 1998). Numerous other<br />
tuberous or bulbous <strong>grass</strong>land species were eaten (Gott 1999) including Vanilla and Chocolate Lilies Arthropodium spp.<br />
(Wigney 1994, Zola and Gott 1992), Bulbine Lily Bulbine bulbosa (R.Br.) Haw., Milkmaids Burchardia umbellata R.Br. and a<br />
range <strong>of</strong> other lilies and orchids (Zola and Gott 1992). Approximately one quarter <strong>of</strong> the vascular plant species recorded in the<br />
Victorian Basalt Plains were used by aboriginals, <strong>of</strong> which approximately 20% were used as food (Gott 1999). Over 100 plant<br />
species found in the <strong>grass</strong>lands and <strong>grass</strong>y woodlands <strong>of</strong> Tasmania are known to have been used by aborigines elsewhere in<br />
<strong>Australia</strong> (Kirkpatrick et al. 1995). Harvesting <strong>of</strong> roots resulted in improved aeration and water infiltration into the soil and<br />
nutrient incorporation from litter and ash, and would therefore have enabled better plant regeneration. Dug areas would have<br />
increased the availability <strong>of</strong> regeneration niches for many plants (Gott 1999). Recent studies have confirmed that this occurs with<br />
the orchid Diuris fragrantissima, where soil aeration, consisting <strong>of</strong> tilling to 20 cm depth, significantly increased the proportion<br />
<strong>of</strong> spring-planted plants that emerged and flowered (Smith et al. 2009). Aborigine thinned patches <strong>of</strong> the tuberous and bulbous<br />
food plants, deliberately replanted them and traded valued plant production between clans and tribes (Gott 1999).<br />
Burning in the dry season in Victoria may have enhanced the abundance and distribution <strong>of</strong> some plants e.g. Microseris spp.<br />
(Gott 1983). According to Flannery (1994) fire was critical in releasing nutrients into the system to enable regeneration <strong>of</strong> plant<br />
foods, however this may have been <strong>of</strong> limited importance in <strong>grass</strong>lands because <strong>of</strong> the limited nutrient reserves in above ground<br />
vegetation during a significant proportion <strong>of</strong> the fire season. Burning was probably more critical to keep <strong>grass</strong> biomass low: the<br />
tuber feeding people burnt “to expose the tubers, to improve their taste, and to keep <strong>grass</strong> sparse and give tubers and herbs<br />
space” (Gammage 2009 p. 286). Burning was frequent on the Victorian Volcanic Plain prior to European occupation, being used<br />
by aborigines in hunting and to encourage new growth, and probably assisted in maintaining treelessness (Stuwe 1994, DNRE<br />
1997). Fires were reported by early maritime travellers in Port Phillip region in all months from spring to autumn (Jones 1999b).<br />
Aborigines would have increased fire frequency above the background rate as a result <strong>of</strong> deliberate burning, accidental escapes<br />
from camp fires (Stuwe 1994) and possibily the use <strong>of</strong> fire as a weapon against invading non-indigenous people (Flannery 1994).<br />
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