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

Landform
N. neesiana is widespread in the pampas, which generally consists of completely flat plains alternating with gently undulating
landscapes (Soriano et al. 1992), although it appears to be restricted to slightly elevated areas, i.e. away from minor depressions
in Flooding Pampa (Perelman et al. 2001). N. neesiana occurs in the vegetation of other landforms in Argentina including rocky
terrain in the low hills of the Tandilia Range of south-east Buenos Aires provine (Honaine et al. 2009).
Bruce (2001) found that N. neesiana occurred mostly in the ACT on slopes (rather than valleys, watercourses, gullies or flats),
where it had a wide range of abundances, and at sites with combinations of these landforms. Slay (2002c) considered that it
colonised the dry northerly faces of hills in New Zealand.
Water, drainage and flooding
N. neesiana reportedly tolerates seasonal water-logging (McLaren, Stajsic and Iaconis. 2004) but the tolerable frequency and
duration of such stress are not precisely known. In Argentina, Gardener et al. (1996b) found that it did not occur on wetter,
often-inundated low ground, although such depressions were often saline, or on deep clays. Stipoids do not occur in the saline
and alkaline soils of halophytic steppes of shallow, wet depressions of Flooding Pampa (Perelman et al. 2001) and appear to be
entirely absent from saline soils in the pampas (Soriano et al. 1992). N. neesiana is not an important species in the Flooding
Pampa of Argentina, an area subject to drought and very dry summers, and flooding “almost every year”, mainly lasting c. two
weeks and 5-10 cm deep, with “extensive and lenthy flooding ... 3 to 6 times per century” (Soriano et al. 1992 pp. 394 and 374).
In Australia N. neesiana was found on alluvial flats subject to seasonal waterlogging at Wattle Park, Burwood, Victoria by Geoff
Carr (McLaren et al. 1998), often establishes in damp depressions (Liebert 1996) and on land subject to periodic inundation
(Muyt 2001), and is “more common in low-lying, wetter areas” (Hocking 1998 p. 90). Swarbrick and Skarratt (1994) erroneously
isted a single habitat known to be invaded, saline wetlands (atttributed to Carr and Yugovic 1989). Bruce (2001) found that it
occurs in wetter areas in the ACT, as well as on slopes, and that an association with drainage lines, streams and damp
depressions was apparent at most sites surveyed, with an infestation in one case radiating up-slope from a creekline. She
illustrated a plant overhanging a drain, downstream of which patches of further plants were found. Kirkpatrick et al. (1995 p. 35)
stated that it “can grow in a large range of soil moisture regimes”. Slay (2002c) noted that it thrives under moderate to severe
stress due to low soil moisture.
High rainfall in spring promotes panicle proliferation (Cook 1999) and plants flower in response to summer rain (Bedggood and
Moerkerk 2002). N. neesiana prospers on roadsides where there is run-off and good soil moisture (Bedggood and Moerkerk
2002). F. Overmars (in Iaconis 2006b) reported that it was growing and setting seed in drains in the Melbourne area in October
2006 during severe drought.
Other plants
Other plants or plant associations in areas invaded by N. neesiana might provide biotic resistance to invasion, or may alone or in
combination faciltate or prevent N. neesiana establishment or survival.
The pampas grasslands, which have probably persisted without major change since the late Miocene (c.14 mybp ) (Webb 1978),
are treeless and dominated by caespitose grasses with a wide variety of smaller herbs. In the Argentine pampas N. neesiana
occurs as one element of a diverse grassland flora that normally includes summer growing grasses, including Bothriochloa,
Panicum and Paspalum as common components (Gardener et al. 1996b). In the Flooding Pampa it is closely associated with
Jarava plumosa and Bothriochloa laguroides, and is commonly found in communities with high frequencies of Paspalum
dilatatum Poir., Piptochaetium montevidense, P. bicolor (Vahl) Desvaux, Vulpia sp., Bromus catharticus J. Vahl and other
grasses and with a rich array of forbs (Perelman et al. 2001). It is “one of the dominant grassland species” in the pastoral zone
around Buenos Aires (Gardener et al. 1996b). In the department of Gualeguay in south-west Entre Rios (Argentina) it is of
secondary importance as a winter grass in pastures of the high campos (better drained areas with grasses maintaining a height of
20-40 cm), along with N. hyalina, the more important winter-spring forage plants being Bromus catharticus, Lolium multiflorum
Lam. and Medicago spp. (Marco 1950). The co-occuring spring-summer grasses of most importance include Paspalum spp.,
Axonopus compressus (Sw.) P. Beauv., Setaria spp., Andropogon saccharoides Sw. and Eleusine tristachya (Lam.) Lam. (Marco
1950). In the Ventania land system in south-west Buenos Aires Province it naturally occurs in association with Stipa ambigua
Spegazzini and Amelichloa caudata (Trin.) Arriaga and Barkworth in grassland with isolated trees of Prunus mahaleb L.
(Amiotti et al. 2007). Genera that include dominant or subdominant species south of Buenos Aires include Agropyron, Aristida,
Briza and Piptochaetium. Other Nassella species are widespread components with N. hyalina and Jarava plumosa common
around Buenos Aires. In drier western areas Jarava ichu Ruiz and Pavon, N. tenuissima and N. trichotoma are more prominent,
along with Poa ligularis (Mack 1989).
In southern Santa Fe province (Pampean phytogeographical province) it is a characteristic species of a flechillar community
along with N. hyalina and Jarava plumosa, with Bothriochloa laguroides, Sporobolus africanus and Carex bonariensis Desf.ex
Poir. (Feldman et al. 2008). The Espinal phytogeographical province occurs in dier areas to the north, west and south-west of the
Pampean phytogeographical province. Espinal vegetation is woodland or savannah with Prosopis, Acacia and Celtis as the main
(woody) dominants but in San Cristóbal county of Santa Fe province includes a flechillar grassland community over 1 m tall
strongly dominated by N. neesiana (Feldman et al. 2008).
In the Tandilia Range of south-east Buenos Aires province it is a major species in a community of diverse grasses, the most
abundant of which include Piptochaetium biocolor (Vahl) Desv., P. medium (Speg.) M.A. Torres, P. hackelii (Arech.) Parodi,
Stipa bonariensis Henr. and Parodi, Briza spp. and Bothriochloa laguroides (DC.) Pilger, and some shrubs, but not in the
monospecific pajonal community which is dominated by Paspalum quadrifarium, a grass that produces large accumulations of
dead standing biomass in its tussocks (Honaine et al. 2009).
N. neesiana is not a grass of major importance in the semi-arid Caldenal of Argentina, where the vegetation was orginally grassy
steppe, but which is now largely savannah grassland with scattered trees, mainly Prosopis caldenia Burkart, known as caldén,
and shrubland with rich shrub diversity. The main grasses are other species of Stipeae and Poa ligularis (Fernández et al. 2009).
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