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

More documents

Recommendations

Info

considerably less diverse than those of herb-rich grassy woodlands in the Grampians and Langi Ghiran areas of western Victoria studied by Lunt (1990d). Areas of grasslands on sedimentary soils and soils derived from granites, which are generally less fertile, are less productive so grow much smaller grass tussocks and consequently tend to have greater floristic richness (Stuwe 1994). Productivity Little attempt appears to have been made to quantify the productivity of the temperate native grasslands of south-eastern Australia, although there has been considerable interest in the amount of above-ground biomass accumulated by dominant grasses, particularly T. triandra. In minimally disturbed (ungrazed and unburnt) communities the matrix species (dominant and subdominant grasses) grow large, accumulate abundant litter and suppress the intertitial forbs (Trémont and McIntyre 1994). Groves (1965) undertook a seminal study of a T. triandra grassland at St Albans. He determined the above-ground biomass of T. triandra versus all other species and the root biomass for all species combined at 3-6 weekly intervals for 15 months from 1962 to 1964. The grassland had been burnt in the summer of 1961-62. T. triandra constituted the major component of above-ground biomass througout the period, with a mimimum of 62% and a maximum of 90%. The standing biomass one year after fire was about two thirds of that two years after the fire, but nevertheless fell to approximately the same level in summer in successive years. Standing biomass fell rapidly to very low levels in mid summer after a late spring- early summer peaks. Maximum levels exceeded 3000 kg ha -1 . Much dead biomass was apparently broken down or moved off site. Only a small fraction of root biomass penetrated below 15 cm. The below-ground biomass followed similar trends to that above ground in one summer and not the other, but consistently peaked in late spring and early summer. The maximum was c. 8000 kg ha -1 . In autumn, rapid growth resumed, many seedlings appeared and a carpet of moss developed. Standing biomass in April was etimated at 1025 kg ha -1 . During winter, growth was inhibited and many shoots of T. triandra died, but Austrodanthonia spp., Dichelachne crinita and the exotic annual grass Rostraria cristata (L.) Tzvelev grew vigourously. In spring rapid growth of T. triandra resumed and the native forbs Eryngium ovinum, Plantago varia and Wahlenbergia stricta grew. Growth ceased when soil moisture fell to the permanent wiliting point. T. triandra growth rate peaks from October to early December and growth continued into summer if there was adequate soil moisture, and there was a minor peak in autumn. Morgan (1998e) calculated annual peak standing biomass for two T. triandra grasslands in the Victorian Volcanic Plains: 1300 kg ha -1 in December for a grassland at Derrinallum burnt annnually in February, and 2600 kg ha -1 for a grassland at Karrabeal, burnt biennially in summer, two years after burning. Annual dry matter production in improved pastures in the New England region of New South Wales varies from c. 8000 kg ha -1 in drought years to 16,000 kg ha -1 (Davidson 1982). Estimates for net above-ground primary productivity of Flooding Pampa grasslands include 5320 kg ha -1 , with green standing crops of 1550-2220 kg ha -1 (Soriano et al. 1992). Dynamics The dynamics of temperate Australian grasslands cannot be adequately explained within the classical botanical framework of succession, and there is no climax formation (Mott and Groves 1994). If the exotic components are disregarded, the composition varies little over time, but widely on a patch scale in otherwise uniform areas (Mott and Groves 1994). Morgan (1998e) investigated patch-scale (0.01 and 1 m 2 ) dynamics of exotic and native vascular species in Victorian volcanic plains grasslands and found a 50% increase in cumulative species richness over 4 years, involving high turnover rates and high spatial mobility of species, but little variation in mean species richness. Life-form characteristics were the main determinants of the patterns of plant movement: annuals and geophytes tended to have higher turnover and mobility while hemicryptophytes often had low turnover. The few species with large, persistent seed banks had high turnover, including exotic annual grasses. High turnover of geophytes was somewhat illusory, being explained by their frequent dormancy and failure to produce above-ground parts, but this ‘pseudoturnover’ was displayed by c. 30% of species (Morgan 1998e). Such pseudo-turnover might be particularly significant with Orchidaceae, which may remain dormant for several years (Smith et al. 2009). About 40% of species had low mobility at the 1 m 2 scale (Morgan 1998e). ‘Dispersal limitation’ at a range of scales is a feature of many native grassland systems (MacDougall andTurkington 2007) and may in part result from loss of native animals that created safe sites for seedlings and dispersed seed, and low fecundity due to loss of native pollinators. Frequent fire has been suggested to be the most important cause of the mobility patterns in Victorian volcanic plains grasslands, but climatic variation may be important for some species (Morgan 1998e). Management history and ‘chance’ appear to be more important determinants of the status of a particular remnant than recurrent major disturbance (Mott and Groves 1994). The absence of a successional climax means that the dynamics of Australian temperate grasslands are best described by ‘state and transition’ models, with disturbance and management regimes determining the dynamics of the plant components. These are discussed in detail below. Areas of bare ground at sites with low vascular plant richness are mostly due to exogenous disturbance, while at sites with high richness, they are more often the result of constrained production (McIntyre 1993) due to near-complete resource utilisation. Sharp (1997) created 1 m 2 areas of bare ground experimentally using glyphosate herbicide in Dry T. triandra and Austrodanthonia grasslands and studied colonisation of the gaps for 18 months. Native grass cover had not recovered to pretreatment levels after 18 months, while exotic grass cover and richness initially increased, but after 18 months decreased to levels similar to those prior to treatment. Native and exotic forb richness and cover was increased. Sharp (1997) also experimentally removed litter in areas dominated by native grasses and tested combined treatments of gap formation by herbicides, litter removal/retention, and soil disturbance (scarification to 2 cm depth). When plant litter was retained, native forb richness and cover were higher than when litter was removed. The opposite response was found for exotic forbs. Soil scarification had no significant effects on recruitment of species. The dominant native grass can reduce species richness in intertussock spaces (McIntyre 1993). This is a common feature of temperate grasslands around the world: in the absence of biomass reduction by fire or grazing, the highly productive dominant casepitose grasses accumulate dead leaves and litter and gradually exclude forbs, “irrespective of their habitus” (Overbeck and Pfadenhauer 2007). Intertussock spaces disappear in T. triandra grasslands not subject to regular biomass reduction because the T. triandra plants accumulate large canopies of dead leaves, which reduce and eventually eliminate bare ground and inter- 100
tussock space (Stuwe and Parsons 1977, Morgan 1995b, Morgan 1997, Morgan 1998b, Henderson 1999). T. triandra is generally the only native plant with high cover and frequency and most native species have low cover and low frequency (Morgan and Rollason 1995). Germination of a high proportion of species requires exposure to light, but otherwise there are no specialised germination requirements in the majority of species (Robinson 2003). Regular opening of canopy gaps, e.g. by burning, is required for forb seedling recruitment (Morgan 1995b, Sharp 1997), but actual removal of vegetation, with associated soil disturbance is probably even more effective (Robinson 2003). The dominant tussock grasses may not only command most of the space and light but may also starve the intertussock species of moisture and nutrients (Keith 2004). T. triandra has been said not to compete directly for resources with the annual (exotic) grasses (Morgan 1994), but agricultural experience suggests that the exotic annuals deplete soil moisture prior to the main T. triandra growth period. Germination and establishment of T. triandra has also been reported to be unaffected by weeds (McDougall 1989, Morgan 1994 citing Hagon 1977) but there is likely to be a threshold above which it will be affected (Morgan 1994). None of the native perennial intertussock species in existing native temperate grasslands are obligate seed regenerators, almost all being obligate resprouters, or resprouting and with limited seedling production, and mostly able to set, and actually setting, seed within 12 months of regeneration (Lunt 1990c, Morgan 1996, Lunt and Morgan 2002). Austral Toadflax Thesium australe R.Br. (Santalaceae) a peculiar semi-parasitic semi-shrub, once common in T. triandra grasslands, has a ruderal strategy, is shortlived (Keith 2004) and apparently dependent on annual seedling recruitment, but populations no longer exist at lowland grassland sites (Scarlett and Parsons 1993). Hosts of this species include T. triandra and a range of other native and introduced herbs and grasses (Keith 2004). At sites investigated by Morgan (1996) all perennial species but one had flowered 12 months after a late-spring fire. Only 19% of native perennials regenerated from seed after a fire at Derrimut (Lunt 1990c) and only one native species was present in the seed bank that was not found in the standing vegetation (Lunt 1990b). In a study of five western Victorian grasslands Morgan (1998c) found that only 12% of species, all annuals, formed large, persistent seed banks and that most native hemicryptophytes and perennials in general had a transient seed bank. T. triandra and perennial native forbs were present in the seed bank at “exceedingly low densities at all times” (Morgan 1998c p. 150). Little is known about the persistence of native forbs in temperate Australian grasslands (Lunt 1996). Morgan (1995) found viable seeds of Rutidosis leptorrhynchoides in the seed bank only immediately after seed shed. All the seed of this species germinated within 4 months of shedding, immediately after autumns rains, and any seed that had not germinated by this time was either dead or had been “eaten by soil invertebrates” (op. cit. p. 5). Lunt (1996) found that no viable seeds of Microseris scapigera (G. Forst.) Sch. Bip. (Asteraceae) buried or placed in mesh bags under the canopy in a long unburnt T. triandra grassland in Canberra remained after 3 months and that virtually all germinated rapidly. Lunt (1995a) tested seeds of three native lilies and three other native daisies in the same way and found that >90% of the seeds of all but one species germinated or were unviable after 12 months, although greater longevity was recorded for some species if the seed was buried or on the surface. The daisy Chrysocephalum apiculatum (Labill.) Steetz. appeared to have the highest potential to develop a persistent seed bank, due to small seed size, inhibition of germination in darkness and an ability to remain viable when buried. The perennial native plant seed bank as a whole appears to usually be small and highly transient (Lunt and Morgan 2002), seedlings are generally uncommon (e.g. Morgan 1998d), most seed germinates or dies within 12 months, and only perennial forbs with small seeds (e.g. Hypericum gramineum, Juncus spp., Wahlenbergia spp.) have large, persistent seed banks (Lunt and Morgan 2002). The longterm native seed bank was considered to probably have “little functional importance” and “contribute little to seedling regeneration processes following disturbance” (Morgan 1998c). Scarlett (1994) reported a similar problem with plantings and direct seeding of native dicotyledonous grassland herbs: they set abundant seed, but had very low germination and seedling survival. Species with transient seed banks are a common feature of world grasslands and “are normally able to exploit gaps in grassland canopies ... created by seasonally-predictable disturbances such as fire, drought and grazing”: their seeds usually germinate whether or not suitable seedling establishment sites are available (Morgan 1995a p. 7). In basalt plains grassland sites with a history of frequent fire the hemicryptophyte (‘resprouter’) rosetted forbs, including many of the common native forbs, had low turnover and mobility (Morgan 1997), as would be expected with a very low seed bank (Morgan 1998c). In total, 30% of species (notably geophytes) appeared to remain dormant underground in some years, despite a stable management regime (Morgan 1997). A high proportion of the seed bank in these grasslands consists of annuals which are largely exotic species (Morgan 1998c 1998d, Lunt and Morgan 2002). The annual monocots have a high turnover and high mobility (Morgan 1997). Native hemicryptophytes, chamaephytes and geophytes are largely absent from the seed bank (Morgan 1998c). Exotic species overwhelming dominate the soil seed bank in grazed grasslands in Victoria and Tasmania, with annual grasses, legumes and R. rosea being major components (Lunt 1995a). Dodd et al.(2007) found that native species comprised only 13% of the soil seed bank of six roadside grasslands along a 200 km urban-rural gradient west from Melbourne and that similarities between the species composition of the seed bank and the above ground flora was low and declined in more rural sites. Exotic annual graminoids dominated the seed banks (Dodd et al. 2007) with Juncus capitatus, Isolepis sp. and Aira spp. being the most abundant (Aaron Dodd pers. comm. October 2007). Lack of recruitment of inter-tussock species is a widespread problem in native grasslands: inadequate seed availability appears to be the dominant cause, rather than weed competition or climatic stress (McDougall and Morgan 2005). Many species of native forbs may be physiologically unable to produce seeds with innate dormancy (Morgan 1998c). Instead the plants are long lived and rarely recruit from seed. According to Benson (1994) the major transformation of native grassland have resulted in widespread loss of long-lived, deep rooted perennials and their replacement with more ephemeral exotics. The native grassland flora is also notable for the absence of myrmechorous (ant dispersed) species, in contrast to Australian forests, woodlands and heaths (Berg 1975). Very few of the 87 myrmecochorous genera mentioned by Berg (1975) are present in these grasslands and these may be viewed usually as ‘trespassers’ from grassy woodlands. In general however seed dispersal processes in these grasslands have not been studied. 101
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 and 20:
species tend to be those which tran
Page 21 and 22:
Taxonomy and nomenclature Stipeae N
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
Page 79 and 80: y increased importance of ant grani
Page 81 and 82: BIODIVERSITY “Biodiversity ... on
Page 83 and 84: According to Woods (1997 p. 61) “
Page 85 and 86: 2004, Richardson and van Wilgen 200
Page 87 and 88: negative depending on the particula
Page 89 and 90: Competition with native plants Comp
Page 91 and 92: asexual seed production, so local f
Page 93 and 94: GRASSLANDS Grasses: “... the most
Page 95 and 96: susceptible to N. neesiana invasion
Page 97 and 98: Floristic composition, vegetation s
Page 99: proportion of the flora then presen
Page 103 and 104: Like vascular plant diversity, comm
Page 105 and 106: 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
Page 111 and 112: 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
Page 121 and 122: 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
Page 149 and 150: 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
Page 159 and 160:
was once widespread in south- easte
Page 161 and 162:
eing sluggish and wingless, and exi
Page 163 and 164:
estoration and, if Australia follow
Page 165 and 166:
close to the plant are able to bury
Page 167 and 168:
Species *Chirothrips mexicanus Craw
Page 169 and 170:
Table A2.1 (continued) Species Life
Page 171 and 172:
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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?