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

The greater height and density of N. neesiana swards than those of native grasses has been considered to make it a fire hazard
(Liebert 1996), although no directly comparative quantitative data appears to have been published. Grasslands dominated by T.
triandra are green in summer, while N. neesiana ceases to grow in summer after producing a large quantity of stems in spring
and early summer. There are therefore good a priori reasons to suggest that N. neesiana might alter fire regimes by changing the
seasonal distribution of fuel. Comparisons of total biomass of invaded and natural T. triandra grasslands during a range of
seasons could easily determine this.
Four threatened plant species are listed by ARMCANZ et al. (2001) as threatened by N. neesiana: Sunshine Diuris Diuris
fragrantissima D.L. Jones and M.A. Clem., Small Milkwort Comesperma polygaloides, Plains Riceflower Pimelea spinescens
and Button Wrinklewort Rutidosis leptorhynchoides. More details for D. fragrantissima are provided by Webster et al. (2004)
and Vidler (2004) and for R. leptorynchoides by Humphries and Webster (2003). However the national strategic plan
(ARMCANZ et al. 2001) fails to “identify the biodiversity at risk in a manner that can be used to deliver effective management”
and contains no specific section on impact minimisation (Downey and Cherry 2005 p. 42).
In summary, very little is known about the impact of N. neesiana on biodiversity and what little is ‘known’ appears to be largely
based on simple correlative observations without adequate scientific study. Suggestions that the impacts are major or
catastrophic appear to be founded on the rapid proliferation and high cover of the plant in native grasslands under conditions that
have been poorly documented and in which the supposed impacts may be due to disturbance. Possibly N. neesiana is basically
similar to a native grass and replacement of native grasses by N. neesiana may have little biodiversity impact. In the following
section the atttributes of the temperate native grasslands of south-eastern Australia are examined and the effects of a range of
disturbances on N. neesiana and the native grasses are discussed in more detail.
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