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

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Nassella neesiana “Over the past few years is has become increasingly clear that the introduced grass Stipa neesiana is a serious threat to remnant stands of native grassland ... and can almost completely displace perennial native grasses, including the dominant Themeda triandra ... Prior disturbance does not appear to be necessary for invasion ... We request that urgent attention be given to control of the plant ...” M.J. Bartley, R.F. Parsons and N.H. Scarlett of the Botany Department, La Trobe University, in a letter to the Victorian Department of Conservation and Environment, 7 May 1990 Nassella neesiana is a long-lived, perennial, cool season (winter-spring growing), C 3 , South American, monecious, tussockforming grass, with flexible reproductive mechanisms and a high survival rate of all life stages (Cook 1999, Gardener et al. 1996a 1999, 2003a, Storrie and Lowien 2003, Benson and McDougall 2005). In Australia it is both a serious enivornmental weed (Carr et al. 1992, McLaren et al. 1998) and a problem weed of agriculture (Grech 2007a). N. neesiana is a widely recognised threat to Australian temperate native grasslands. One of the earliest reports was that of McDougall (1987) who recorded it as a weed in native tussock grassland and Eucalyptus camaldulensis woodland in the western region of Melbourne. Carr et al. (1992 pp. 41, 51) considered it to be a “very serious threat to one or more vegetation formations in Victoria”. It has rapidly expanded its range (Lunt and Morgan 2000), is able to actively invade grasslands (Hocking 1998), reportedly without prior disturbance (Bartley et al. 1990), is allegedly potentially able to outcompete C 4 (summer growing) grasses such as T. triandra (Ens 2002a), and is rated, along with Nassella trichotoma, as the most significant weed threat to grassland biodiversity (McLaren et al. 1998, Groves and Whalley 2002). Trengrove (1997) considered it to be “much more invasive” in T. triandra remnants than N. trichotoma. Morgan and Rollason (1995) considered it to pose “by far the greatest threat of any potential new invader” at one grassland, Kirkpatrick et al. (1995 p. 36) classed it as “a major threat to one or more grassland communities”, Morgan (1998d) called it one of the “most potentially threatening species” to T. triandra grasslands and Lunt and Morgan (2000 p. 98) rated it as “perhaps the most serious environmental weed in remnant native grasslands in southern Victoria”. Humphries and Webster (1992 and 2003 p. 2) and Webster et al. (2003 p. 3) wrote that “the aggressive invasion” of N. neesiana at Derrimut and Laverton North Grasslands in Victoria needed “immediate attention if the values of these grasslands [were] to be preserved”. Ens (2005) stated that it “swamps all other ground flora and forms expansive monocultures”. According to Beames et al. (2005 p. 2) it is “particularly well adapted to the intensively cultivated areas surrounding urban areas and poses a signficant threat to mismanaged urban grassland remnants”. N. neesiana is a successful invader because of it wide ecological flexibility, synanthropic dispersal mechanisms, the availability of suitable habitats in a suitable climate, and limited biotic resistance in the invaded communities. It has many of the general charactersitics possessed by successful invasive species (Cox 2004): a large native range, abundance and sometimes dominance in its native range, high vagility (via seed), dispersal by abiotic processes, short generation time, high reproductive rate, ecological flexibility, wide climatic and physical tolerances, reproduction involving a single parent individual and association with humans. In addition many varieties and forms have been described, suggesting that the species has wide genetic variability, at least in South America. Bourdôt and Hurrell (1989a p. 415) attributed its invasiveness in New Zealand sheep pastures not to “high competitive ability” but rather to “adaptations that enable the plant to survive the hazards of semi-arid, low-fertility environments”. It is often generally contended that invasion only occurs as a result of disturbance and that Australia is more subject to invasion than northern hemisphere biomes (e.g. New 1994 p. citing Di Castri 1990). Exotic stipoid grasses in Australia “generally invade plant communities which are already highly degraded and have a history of disturbance” (Gardener and Sindel 1998 p. 76 citing G. Carr pers. comm.), along with “lands with higher fertility soil often previously used for grazing or farming” (op. cit.). Since temperate native grasslands often occupy highly fertile soils, and are communities dependent on disturbance for the maintenance of their natural diversity, this appears to create a significant dilemma. The disturbance necessary to create gaps in the dominant grass canopy, in which most of the native vascular plant diversity can flourish, simultaneously promotes exotic plants, which comprise the bulk of the seed bank at least at some sites (Lunt 1990b, Morgan 1998c). Gardener and Sindel (1998) advocated quantitative studies to evaluate the biodiversity changes associated with invasion by exotic Nassella species, to determine if any of these changes result from general degradation and to evaluate the impact of Nassella management techniques on the promotion or inhibition of biodiversity. To date, only a single study of N. neesiana, with a narrow focus, has been undertaken, that of Ens (2002a). She found that diversity of insects declined in areas occupied by the plant in Sydney woodlands, although some groups benefited. Monitoring of biodiversity is necessary to provide a sound basis for evaluating the techniques and strategies used to manage N. neesiana as a weed (Grice 2004a). Mangement measures are currently focused on minimising seed production using herbicides or grazing in agricultural (Grech 2007a) and natural areas, and managing the rate of mineralisation of nitrogen to favour C 3 grasses in natural ecosystems (Craigie and Hocking 1998, Hocking 2002 2005b, Groves and Whalley 2002). However there are concerns that some current approaches may be counterproductive, producing grasslands that are more impoverished, and more highly invasible. The success of a plant invader depends on its biological attributes, the attributes of the community or ecosystem invaded and the effects of human activities. These factors are examined in detail in the review below. 20
Taxonomy and nomenclature Stipeae Nassella neesiana is a member of the Poaceae: Stipeae, “a cosmopolitan tribe ... widely distributed” with “major centres of diversity in South and North America, Australia and Eurasia”, “primarily in temperate or warm-temperate regions” and “dominant in many of the arid grasslands of southern Australia, South America and Asia at varying elevations (0-5000 m)” (Arriaga and Jacobs 2006). The tribe contains “approximately 500” (Vásquez and Barkworth 2004 p. 484) or “c. 450” (Arriaga and Jacobs 2006) species. Simon (1993) erected a new subfamily Stipoideae for the tribe, a classification adopted by Watson and Dallwitz (2005), but not followed by others (e.g. Briese and Evans 1998). In the past Stipeae has been included with Poeae in a festucoid group, close to Miliceae, Diarrheneae and Nardeae (Tsvelev 1984). The tribe was sometimes assigned to subfamily Arundinoideae (e.g. Barkworth and Everett 1986), and sometimes to Pooidae (Wapshere 1990) e.g. by Edgar et al. (1991), but molecular evidence indicated that it did “not sit comfortably in either subfamily” (Briese and Evans 1998 p. 94) and was not clearly delimited (Barkworth and Torres 2001). Zucol (1996) argued that phytolith leaf assemblages in Nassella species indicated an affinity with Arundinoideae, while Honaine et al. (2006) considered their phytolith study of Nassella and Piptochaetium spp. supported the assignment to Stipoideae. Molecular data currently indicates that Stipeae is monophyletic (Jacobs and Everett 1996) and it is now often considered a basal lineage within Pooidae (GPWG 2001, Arriaga and Jacobs 2006, USDA ARS 2006), or the largest of six tribes in Stipoideae, along with the monogeneric Nardeae, Lygeae, Ampelodesmae, Anisopogoneae and doubtfully Brachyelytreae (Watson and Dallwitz 2005). The tribe is best defined by characters of the embryo (Jacobs and Everett 1996) which are correlated with a set of characters not exclusive to the tribe: florets with a single spikelet, a coriaceous or firmer lemma with comparatively large unicellular macrohairs (Arriaga and Jacobs 2006), disarticulation of the seed above the glumes and absence of a rachilla extension (Jacobs and Everett 1996) (i.e. the rachilla is not prolonged (Jacobs et al. 1989)), a well-developed callus, and a terminal, usually articulated awn (Barkworth 1993). Stipoids are commonly wiry, “bamboo-like” perennial grasses (Jacobs et al. 1989 p. 570) and generally have a leafless, paniculate infloresence and a lemma that is tougher than the glumes (Barkworth and Everett 1986). For many years a large proportion of Stipeae were considered to be included in a broadly defined genus Stipa. From the late 1970s taxonomic work led to the resurrection of old names and reassignment of species to other genera, some of very long standing (Barkworth and Everett 1986, Barkworth 1993, Jacobs et al. 2000, Barkworth and Torres 2001, Vásquez and Barkworth 2004). The concept of Nassella (Trinius) E.Desvaux was expanded to include species with long florets, formerly in Stipa sens. lat. Barkworth (1990) recognised nine genera in Stipeae: Achnatherum, Anemanthele, Hesperostipa, Nassella, Oryzopsis, Piptatherum, Piptochaetium, Ptilagrostis and Stipa. Several additional genera are now recognised in the tribe: Jacobs and Everett (1996) assigned all Australian native species formerly included in Stipa to the new genus Austrostipa and provided a key to the then ten genera of Stipeae; Peñailillo (1996) described a new genus Anatherostipa; Jacobs and Everett (1997) resurrected Jarava; Torres (1997) described Nicoraella; Vásquez and Barkworth (2004) defined a new genus Celtica for Stipa gigantea Link and resurrected the genus Macrochloa Kunth for Stipa tenacissima (Loefl. ex L.) Kunth. Barkworth (2006) included the small or monotypic genera Aciachne, Lorenzochloa, Macrochloa, Ortachne, Psammochloa and Trikeraia in her world list of Stipeae. Watson and Dallwitz (2005) included these 15 genera plus, tentatively, Danthoniastrum (possibly Aveneae). Tsvelev’s (1977) concept of Stipeae also included Orthoraphium Nees, Eriocoma Rydb., Streptachne R.Br., Stephanacne Keng and Pappagrostis Roshev. Barkworth (1990) reviewed the complex taxonomic history of Nassella. The name was first used by Trinius 1830 at subgeneric rank. Barkworth (1990) expanded Nassella from c. 9 spp. to include 79 species, with most of the additions, including N. neesiana, being from Stipa sens. lat. Watson and Dallwitz (2005) probably relied on Barkworth (1990), giving a total of “about 80” spp. for the genus. According to Barkworth and Torres (2001) Nassella included at least 116 spp., but Barkworth (2006) listed only 110. Quattrocchi (2006) gave an upper limit of 116. Barkworth (1990) considered Nassella to be most closely related to Piptochaetium and Hesperostipa. Analysis of morphological and anatomical characters placed Austrostipa close to Achnatherum and Ptilagrostis, but study of rDNA indicated a closer relationship to Nassella than to Achnatherum (Jacobs and Everett 1996). Detailed molecular and morphological examination (Jacobs et al. 2000) found Nassella and Piptochaetium to be sister groups; likewise for Austrostipa and Achnatherum. Austrostipa appears to be the most recently evolved genus in the tribe (Jacobs et al. 2000). Nassella is distinguished from other stipoid genera by having 3 stamens (1-3: Quattrocchi 2006); a tough lemma with three or more nerves and strongly and tightly overlapping margins, the outer margin extending 1/3 to 2/3 (25-50% Barkworth and Torres 2001) of the way around the inner, an unridged surface, heavily silicified with round or oval silica bodies in the epidermis, the fundamental cells of the epidermis being extremely short and much shorter than wide, a solid apex often developed into a corona (crown) at the summit of the lemma, with cilia that often appear to be fused at the base; and a flat, veinless, usually glabrous, short, rudimentary palea, less than 30% as long as the lemma, and completely concealed by the lemma (Barkworth 1990, Barkworth 1993, Jacobs and Everett 1996, Barkworth and Torres 2001, Watson and Dallwitz 2005, Barkworth 2006; contra Stace 1997 p. 840: “palea 3x) as long as lemma”). Other common characters in the genus are the presence of both short and long anthers in a species or on the same plant or floret, tuberculate lemma, and abundant apical cilia on the long anthers (Barkworth 1990, Barkworth 2006). A many-noded culm with frequent branching is usual, but also occurs in Achnatherum and some Austrostipa spp. (Barkworth 1990). All Nassella species are caespitose perennials, the glumes are often strongly anthocyanic (anthocyanins = the water soluble glucoside compounds forming colouring matter in many flowers and other plant parts). No vegetative characters that distinguish the genus have been identified (Barkworth 2006). Nassella species are bisexual, mostly perennial, rarely annual, have hollow internodes and open sheaths and “readily deciduous” awns (Quattrocchi 2006 p. 1361). In the Americas Nassella species are found from southern South America to southern Canada at altitudes from 0-5,000 m. Two areas have particularly high diversity: the altiplano of the central Andes, and the pampas of Uruguay, southern Brazil and eastern Argentina (Barkworth and Torres 2001). 21
Page 1 and 2: Literature review: Impact of Chilea
Page 3 and 4: Fire 49 Other disturbances 50 Shade
Page 5 and 6: Conventions and standards Botanical
Page 7 and 8: neesiana appears to be a habitat ge
Page 9 and 10: population densities of existing sp
Page 11 and 12: elated plants have similar defences
Page 13 and 14: For invasion to occur there must be
Page 15 and 16: As yet there appears to be no evide
Page 17 and 18: experimental manipulation of specie
Page 19: species tend to be those which tran
Page 23 and 24: Vernacular names ‘Needlegrass’
Page 25 and 26: to Bouchenak-Khelladi et al. 2009).
Page 27 and 28: 1 m (Walsh 1994), ca. 90 cm (Verloo
Page 29 and 30: Figure 2. Anatomy of the seed of N.
Page 31 and 32: are the seeds larger/smaller, longe
Page 33 and 34: also based on a misunderstanding of
Page 35 and 36: Table 2. Modified Feekes Scale for
Page 37 and 38: Argentina, in the provinces of Chac
Page 39 and 40: Figure 3. Recorded distribution of
Page 41 and 42: 1994). Only 3 of 186 exotic grasses
Page 43 and 44: According to Morfe et al. (2003) th
Page 45 and 46: populations have been found in the
Page 47 and 48: (Honaine et al. 2006). The flechill
Page 49 and 50: In Australia the altitudinal range
Page 51 and 52: Proximity to urban development appe
Page 53 and 54: In the southern Brazilian campos of
Page 55 and 56: arundinacea (Gardener et al. 2005).
Page 57 and 58: al. 2008). Cues for masting may be
Page 59 and 60: Approximately 200 alien grass speci
Page 61 and 62: Dispersal of seed in contaminated s
Page 63 and 64: In New Zealand, Hurrell et al. (199
Page 65 and 66: No emergence was observed in undist
Page 67 and 68: and high impact (“ability to caus
Page 69 and 70: also noted that despite a wide rang
Page 71 and 72:
a small reduction in seedhead produ
Page 73 and 74:
Slashing and mowing Slashing can re
Page 75 and 76:
Themeda re-establishment McDougall
Page 77 and 78:
species (Lawton and Schroder 1977 p
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y increased importance of ant grani
Page 81 and 82:
BIODIVERSITY “Biodiversity ... on
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According to Woods (1997 p. 61) “
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2004, Richardson and van Wilgen 200
Page 87 and 88:
negative depending on the particula
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Competition with native plants Comp
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asexual seed production, so local f
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GRASSLANDS Grasses: “... the most
Page 95 and 96:
susceptible to N. neesiana invasion
Page 97 and 98:
Floristic composition, vegetation s
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proportion of the flora then presen
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tussock space (Stuwe and Parsons 19
Page 103 and 104:
Like vascular plant diversity, comm
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Opinions differ on the nature and i
Page 107 and 108:
Species Common Name Family Aust ACT
Page 109 and 110:
in shifting the distribution, exten
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of these systems is largely explain
Page 113 and 114:
pasture. The least understood trans
Page 115 and 116:
tend to benefit more from relaxed c
Page 117 and 118:
Bovids crop their food between the
Page 119 and 120:
are therefore less likely to distur
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esult in a “short-term flush” o
Page 123 and 124:
Fire effects on weeds Moore (1993 p
Page 125 and 126:
Table 8. Typical nutrient levels in
Page 127 and 128:
grasses produced sigificantly more
Page 129 and 130:
Fossorial vertebrates are or were o
Page 131 and 132:
(Rosengren 1999). Approximately one
Page 133 and 134:
Table 12. Areal extent and conserva
Page 135 and 136:
Foreman (1997) investigated the eff
Page 137 and 138:
Willis (1964) considered that the f
Page 139 and 140:
Austrostipa-Enneapogon) from around
Page 141 and 142:
Woodlands and New England Grassy Wo
Page 143 and 144:
Thylogale billardierii), Peramelida
Page 145 and 146:
Its original habitat on the mainlan
Page 147 and 148:
Table 17. Endangered reptile specie
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equirement, but unlike plants and v
Page 151 and 152:
e assigned the same biodiversity sc
Page 153 and 154:
Nematodes are mostly minute animals
Page 155 and 156:
found in all mainland states, O. co
Page 157 and 158:
Keyacris scurra, Melbourne (1993) o
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was once widespread in south- easte
Page 161 and 162:
eing sluggish and wingless, and exi
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estoration and, if Australia follow
Page 165 and 166:
close to the plant are able to bury
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Species *Chirothrips mexicanus Craw
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Table A2.1 (continued) Species Life
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Table A2.1 (continued) Species *Het
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Nematodes of grasses and grasslands
Page 179 and 180:
REFERENCES Aceñolaza, F.G. (2004)
Page 181 and 182:
Benson, D. and McDougall, L. (2005)
Page 183 and 184:
Chan, C.W. (1980) Natural grassland
Page 185 and 186:
DNRE (Department of Natural Resourc
Page 187 and 188:
Fuhrer, B. (1993) A Field Companion
Page 189 and 190:
Groves, R.H. and Whalley, R.D.B. (2
Page 191 and 192:
Iaconis, L. (2004) Chilean needle g
Page 193 and 194:
Levine, J.M., Adler, P.B. and Yelen
Page 195 and 196:
McDougall, K.L. (1987) Sites of Bot
Page 197 and 198:
Morfe, T.A., McLaren, D.A. and Weis
Page 199 and 200:
Perelman, S.B., León, R.J.C. and O
Page 201 and 202:
Saunders, D.A. (1999) Biodiversity
Page 203 and 204:
Thellung, A. (1912) La flore advent
Page 205 and 206:
Weiss, J. and McLaren, D. (2002) Vi
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