Document ID: chunk:federal_register_of_legislation:F2024L00346:reg:4:p5
Version: federal_register_of_legislation:F2024L00346
Segment Type: reg
Provision Reference: reg 4 (pt 5/7)
Character Range: 63917–67046

across sites. The risk is greatest in the smaller, more isolated and heavily disturbed sites where populations will almost certainly be lost without active weed and biomass management (Foreman 2012).
In the absence of biomass reduction, the dominant perennial tussock grasses tend to out-compete and suppress the less competitive smaller plants, such as Spiny Rice-flower. Successive years without appropriate biomass reduction will result in loss of many herb species and senescence and death of kangaroo grass tussocks (Lunt & Morgan 1999 cited in DSE 2008). Open spaces may then be colonised by opportunistic perennial weed such as canary-grass (Phalaris aquatica), flax-leaf broom (Genista linifolia) and tall wheatgrass (Lophopyrum ponticum), which are known to be particularly strong competitors to Spiny Rice-flower (DSE 2008). Other weed species including sheep sorrel (Acetosella vulgaris), common bent (Agrostis capillaris), cock's foot (Dactylis glomerata), and perennial ryegrass (Lolium perenne) are also detrimental to spiny rice-flower plants (Foreman 2012).

Grazing by domestic stock and native herbivores
Most populations are threatened by introduced herbivores including European rabbits (Oryctolagus cuniculus) and hares (Lepus europaeus), while populations on private land have the additional pressure of grazing by domestic stock (Carter & Walsh 2006). Effective site management has improved the size of populations−for example at Lake Borrie, plant numbers increased by 33% between 2006 and 2008 following the elimination of rabbits by fencing and weed eradication by spot spraying and routine burning (Cropper 2009; TSSC 2016).
Overgrazing can adversely impact grassland habitats by disrupting habitat structure and increasing nutrient loads and potential disturbance to seedlings. Light grazing regimes (low stocking levels and rotational systems) may provide benefits for spiny rice-flower plants by maintaining an open habitat and by reducing competition from weeds but at a slower rate compared to fire (Foreman 2012). Anecdotal observations suggest that light grazing by native mammals and domestic stock is not detrimental to plants, and may provide benefits through a reduction in surrounding biomass. The digging action of marsupials such as bandicoots create microsites for germination and assist with dispersal of mycorrhizae (which may be beneficial for germination). However, exposed roots have been observed as a result of digging at sites with dense rabbit populations. Grazing of germinants and seedlings by mice and introduced invertebrates (snails, slugs and millepedes) has been observed in the field and laboratory, and may be having a detrimental impact on population recruitment.

4.3                 Threat matrix
This risk assessment considers the likelihood of a threat occurring (probability), extent and the level of significance of the threat (consequence). These variables are combined in a matrix to provide an ordinal level of risk associated with particular threatening process ranked from 0 (being circumstances where no threat exists) to 3 (where a catastrophic level of