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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Proximity to urban development appeared to be the most important predisposing factor for N. neesiana invasion in the ACT, and<br />
use <strong>of</strong> the land as urban open space appeared to almost guarantee that it would become infested, probably as a result <strong>of</strong> seed<br />
dispersal by mowing (Bruce 2001).<br />
No-one appears to have comprehensively evaluated past disturbance in relation to present N. neesiana infestations. Historical<br />
disturbance patterns are more difficult to determine and there are more difficulties in assessing their intensity, frequency and<br />
duration. Consensus opinion appears to be that disturbances <strong>of</strong> various types can facilitate invasions and it appears likely that in<br />
those cases where invasion has been recorded without disturbance, there has been inadequate appreciation <strong>of</strong> the effects <strong>of</strong> prior<br />
disturbances. The effects <strong>of</strong> various disturbances including fire, grazing and herbicides on N. neesiana establishment and<br />
survival are discussed in more detail below.<br />
Shade<br />
N. neesiana has been called a sun loving (“heliófilas”) species (Martín Osorio et al. 2000 p.39) but is adapted to moderate shade<br />
(Muyt 2001). It has considerable shade tolerance, up to medium level tree densities, e.g. in wooded areas around Bendigo,<br />
Victoria (Hocking 1998). Bruce (2001) found it was commonly present in shaded areas in the ACT , e.g. in windbreaks, very<br />
open woodlands, under oak trees, pines, eucalypts including Eucalyptus melliodora A. Cunn. Ex Schauer, Acacia spp. and<br />
shrubs. It grew in both shaded and unshaded locations at 59% <strong>of</strong> sites investigated (Bruce 2001). In the Sydney region it occurs<br />
in woodlands with Eucalyptus moluccana Roxb. and E. tereticornis Sm. (Benson and McDougall 2005). In New Zealand, N.<br />
neesiana plants growing under 25 year old Pinus radiata are generally weaker than plants growing in the open and have reduced<br />
seeding potential (Slay 2002a). N. neesiana was present in 3 <strong>of</strong> 6 treed paddocks examined by Bourdôt and Hurrell (1989a) in<br />
New Zealand. In the Canary Islands it “thrives” under the evergreen Laurus azorica (Seub.) Franco and the deciduous Castanea<br />
sativa Mill. (Verloove 2005).<br />
The literature appears to contain no precise informat.ion on the effects <strong>of</strong> solar radiation levels. N. neesiana plants growing under<br />
Eucalyptus in the ACT in early-mid summer were much greener and in an earlier reproductive stage than those in the open<br />
(Bruce 2001). Plantations with 2500 trees per ha have been established in New Zealand to examine the effects <strong>of</strong> shading as a<br />
possible control option (Slay 2002a 2002c).<br />
Soils and nutrients<br />
N. neesiana occupies areas on a wide range <strong>of</strong> geological substrates with a diversity <strong>of</strong> soil types. The soils may heavy or light<br />
textured (Cook 1999) and have low or high fertility (Muyt 2001, Slay 2002c).<br />
In Argentina it is found on well-drained, drought-prone soils (Bourdôt and Hurrell 1989b citing Cabrera and Zardini 1978, Lewis<br />
et al. 1985). In the Argentine pampas it is found on deep, generally fertile loessic silts and clays (Gardener 1998). These soils<br />
were formed on very deep (>c. 300 m) deposits <strong>of</strong> silt or loess, rich in swelling clays, and are mainly mollisols (commonly very<br />
deep, high fertility argiudolls) or frequently vertisols, <strong>of</strong> very young age (Soriano et al. 1992). In the Flooding Pampa t is not a<br />
component <strong>of</strong> the floristic groups characteristic <strong>of</strong> deep, non-saline, well-drained soils, nor the group that characterises areas<br />
subject to long flooding, nor in areas with saline alkaline soils (Perelman et al. 2001). It is most frequent in areas with higher<br />
topographic position, being scarce in depressions and lower lying areas, and occurs over a pH range <strong>of</strong> c. 6-8.2, disappearing in<br />
the more alkaline soils that occur in wetter depressions and are correlated with salinity (Perelman et al. 2001). In the Ventania<br />
land system in south-west Buenos Aires Province the soils are formed on a more complex mosaic <strong>of</strong> Palaeozoic sedimentary<br />
rocks (Soriano et al. 1992) and are“Typic and Lithic Argiudolls and Hapludolls developed from pure loess sediments or mixed<br />
with rock detritus”, slightly acid (pH 6.4-6.8), a high saturation with bases, organic carbon levels > 5.5. g kg -1 and total N > 0.4 g<br />
kg -1 (Amiotti et al. 2007 p. 535). In the Gualeguay area <strong>of</strong> Entre Rios province it is found on light loam, with much organic<br />
matter to a depth <strong>of</strong> 40-60 and pH in the range 5-6.8 (Marco 1950). In the Tandilia Range it occurs on soils derived from loess<br />
over quartzite, that are typic Haludolls 10-25 cm deep and Argiudolls 20-70+ cm deep with organic horizons less than 5 cm deep<br />
(Honaine et al. 2009). Although widely dominant in the Rolling Pampas, it is replaced by Sporobolus spp., Jarava plumosa and<br />
other plants where the soils are slightly alkaline (Soriano et al. 1992). Mollisols and vertisols predominate also in the southern<br />
campos (Soriano et al. 1992). Soils <strong>of</strong> the Southern Pampa and Flooding Pampa are noteably deficient in P (Soriano et al. 1992).<br />
In Europe it is generally found on well-drained, “sometimes slightly eutrophic” soils and on rocky slopes (Verloove 2005 p.<br />
108). On Tenerife, Canary Islands, it prefers the nitrogen-enriched ruderal areas <strong>of</strong> fringe roads (Martín Osorio et al. 2000).<br />
In New Zealand the substrate rock types are loess, mudstones, and sandstones on slopes commonly 16-25° (Bourdôt and Hurrell<br />
1989a), and it prefers acidic soils, low in phosphate, calcium and summer moisture (Esler et al. 1993, Champion 1995). It is<br />
recorded from Yellow Grey Earths, particularly when acidic or low in P, Ca or summer moisture (Bourdôt and Hurrell 1989b).<br />
Slay (2002a p. 4) considered it “apparently better adaptated to low fertility sites” in that country.<br />
Gardener (1998 p. 10) considered it was then generally found in <strong>Australia</strong> on “more fertile ... predominantly volcanic” soils, but<br />
noted its presence on granitic soils at Tenterfiled and Emmaville, NSW, on rich clay at Lucindale, South <strong>Australia</strong>, and alluvial<br />
soils near Melbourne. Infestations are widespread on the primarily heavy clay soils derived from basalts on the Victorian<br />
Volcanic Plains. Liebert (1996) found infestations on granitic and sedimentary soils in North Central Victoria. In the ACT it does<br />
not tend to establish on slopes with westerly aspects and shallow soils (Bedggood and Moerkerk 2002). In the Sydney region it<br />
occurs on clays on shale substrates with medium nutrient levels (Benson and McDougall 2005).<br />
According to Bedggood and Moerkerk (2002 p. 6) N. neesiana “does not establish well where nutrient levels are really low such<br />
as hillsides”, but “does better on flats where nutrient levels are moderate”. When P is added to pastures, desirable pasture <strong>grass</strong>es<br />
respond better than N. neesiana (Bedggood and Moerkerk 2002) and increase their basal cover at its expense, with the effect<br />
apparent with or without strategic grazing at 300 DSE ha -1 (McWhirter et al. 2006). Grech (2007a 2007b) found that N. neesiana<br />
responds to phosphorus fertilisation.<br />
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