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

Hispidon sp. (Perissodactyla: Equidae), Hemiauchenia sp., Lama gracilis, Lama guanacoe (Artiodacytla: Camelidae) and
various Cervidae (Carlini et al. 2004, Norriega et al. 2004). The herbivorous megafauna of South America was comparatively
large compared to other continents, and went extinct from the late Pleistocene into the Holocene (Johnson 2009). It appears
probable that these animals strongly influened the distribution of grasslands and had strong selective effects on the grassland
flora, although knowledge of these palaeoecological relationships is currently very deficient (Johnson 2009)..
Its ancestors may have subject to predation by dinosaurs and probably Gondwanatheria, about which little is known, but which
had teeth which indicate that grasses may have been major components of their diets (Prasad et al. 2005).
Before Spanish occupation in the 14th century, the pampas lacked bovids (cattle and sheep) (Mack 1989) and large herbivores
were scarce from the end of the Pleistocene until European colonisation (Fernández et al. 2009). An array of medium sized
mammals was present, of which the the largest grazers were deer (Darwin 1845), and the camelids, the most important of which
was the guanaco Lama guanicoe (Müller). Large herds of grazing animals were absent at least from the Tertiary until the arrival
of Europeans (Coupland 1992).
The camelids have broad, spreading, soft-padded feet that do not compact the soil (Castillo-Ruiz and Lundrigan 2007) and a
digestive system with foregut fermentation, similar to ruminants (Siebert and Newman 1989). The Guanaco is a moderate sized
herbivore about 1 m tall at the shoulders, which commonly forms herds of 4-18 with males troops of up to 200, and is a grazer
and browser, consuming grasses, lichens, forbs, seeds, fruits, rushes and sedges. It has narrow foot pads and a more hoof-like
nails than camels. The Alpaca Lama pacos (L.) and the Llama L. glama (L.) are domesticated forms, probably of the Vicuna L.
vicugna (Molina) and the guanaco respectively, and all four of these taxa will interbreed. Recent evidence indicates that
domestication of the wild species occurred 6000-7000 years ago. There were probably 10 million alpacas and several million
llamas on the continent when the Spanish arrived in the 14th century, along with similar numbers of the undomesticed species,
but within 100 years the populations collapsed, probably largely as a result of competition with domestic livestock (Long 2003),
but no doubt greatly propelled by the destruction of the indigenous human cultures.
The Vicuna is now restricted to the central and southern Andes in arid and montane grasslands at altitudes of 3500-4800 m, but it
formerly had a more extensive range now occupied by exotic sheep and goats (Long 2003, Castillo-Ruiz and Lundrigan 2007). It
too feeds on grasses and forbs (Long 2003). The reported diet of the alpaca in highland Chile is dominated by grasses including
Festuca spp., Deschampia caespitosa and Agrostis tolucensis (Castillo-Ruiz and Lundrigan 2007).
Darwin (1845) reported that the only large indigenous mammal still common in the extensive grasslands of the Maldonada
region of Uruguay (near Montevideo) by 1852 was the Pampas Deer Ozotoceros bezoarticus L., but rheas Rhea americana (L.)
were also common. The Pampas Deer is now extinct throughout the Rio de la Plata grasslands except in a few small reserves and
ranches (Soriano et al. 1992, Cosse et al. 2009) while rhea populations have sharply decreased due to uncontrolled hunting and
wire fences (Soriano et al. 1992). Cosse et al. (2009) investigated the diet of Pampas Deer on a ranch in south-eastern Uruguay
and found that cultivated rice and Lolium sp. were the most important food plants in this agricultural environment, that the
dietary overlap with sheep was complete, but that there was limited competition for food with cattle. Various grasses were
recorded in the diet, not including Nassella or other Stipeae, although unidentified monocots generally comprised about one third
of material found in faeces.
Wild cattle Bos taurus L. and horses Equus caballus L. became established in Argentina after the abandonment of Buenos Aires
by the Spanish in 1537 (Long 2003). 80,000 horses were present around Buenos Aires by 1585, large numbers of cattle were
present by 1609 (Soriano et al. 1992) and millions of cattle and horses were present on the pampas by 1699 (Long 2003).
According to Darwin (1845 p. 120): “The countless herds of horses, cattle and sheep, not only have altered the whole aspect of
the vegetation, but ... have almost banished the guanaco, deer, and ostrich” (Rhea). Horses and cattle were introduced east of the
Uruguay River by Jesuit missionaries in the 17th century and rapidly proliferated in the feral state (Overbeck at al. 2007). The
whole of the campos and pampas have been grazed by sheep, cattle or horses “generally for centuries” (Soriano et al. 1992 p.
380). Cattle grazing and other agricultural pursuits have greatly altered the landscape, with agricultural ecosystems replacing
native grasslands in most of the region, and large areas of native grassland surviving only in Buenos Aires province due to
wetter, more saline soils (Pedrano et al. 2008). As with other major grasslands lacking a recent history of grazing by hardhooved
livestock (Mack 1989) the pampas grasslands were invaded by a large suite of exotic species after European
colonisation. Livestock grazing in the Flooding Pampas has actively promoted these invaders, 75% of which are annuals and
74% forbs (Perelman et al. 2001).
Livestock grazing of natural grasslands and improved pastures is a major economic activity in the Rio de la Plata grasslands
(Soriano et al. 1992) as is cattle ranching in the natural grasslands of southern Brazil, where 13.2 million head were present in
Rio Grande do Sul state in 1996 (Overbeck at al. 2007). In Brazilian campos, grazing is “often considered the prinicpal factor
maintaining the ecological properties and physiognomic characteristics of the grasslands” (Overbeck at al. 2007 p. 104).
N. neesiana may have existed through much of the Quaternary period and into early historical times under grazing pressure from
large mammals that was relatively light, and was then subjected in much of its core range to unprecedented grazing by feral
livestock. Limited evidence indicates that N. neesiana declines under livestock grazing in its native range in Argentina. After
exclusion of large ungulates from Flooding Pampa grasslands the relative basal cover of the major grass species (Briza
subaristata Lam., Danthonia montevidensis (DC.) et Lam., Sporobolus indicus (L.) R.Br. and N. neesiana) more than doubled to
97% after 4 years, while annual and broad-leaved herbs disappeared (Soriano et al. 1992). Under a management regime of
grazing and winter burning in the Tandilia Range of Buenos Aires province, the major grass components of the flechillar
grassland (including N. neesiana) decreased and the broadleaved Achillea millefolium. and Carduus acanthoides began to
dominate, while under grazing alone C. acanthoides, Cirsium vulgare, Dactylis glomerata L., Vulpia dertonensis (All.) Gola. and
Bothriochloa laguroides became more dominant (Honaine et al. 2009)
The situation appears to be different in Australia where N. neesiana is generally considered to be tolerant of heavy grazing by
sheep and cattle (Storrie and Lowien 2003, McLaren, Stajsic and Iaconis. 2004, Grech 2007a), in part because of its relatively
low palatability to these animals compared with desirable pastures grasses (Bourdôt and Hurrell 1989a, Grech 2007a). It has
relatively low herbage production compared to some such desirable pasture grasses used in Australia, notably Festuca
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