Recovery Action Plan for Grey Box community
On-ground Management Actions for Grey Box Grassy Woodlands
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- Bu səhifədəki naviqasiya:
- 1.9.2.Woody and Herbaceous Weed Control
- 1.9.3.Grassy Weed Control
- Removal of slashed material / baling
- 1.9.5.Grazing Management
- 1.9.6.Nutrient Control and Removal
- 1.9.7.Supplementary Planting and Habitat Reconstruction
- 1.9.9.Improving/Retaining Habitat Values
1.9.On-ground Management Actions for Grey Box Grassy Woodlands1.9.1.Prevention of Anthropogenic ImpactsGrey Box communities are exposed to many threats and impacts due to their peri-urban nature across much of their range in the Mount Lofty Ranges (as outlined in section 1.4). These are generally associated with unauthorised recreation, including the use of bicycles (particularly mountain bikes), and motorbikes, horse riding, , and off-leash dog walking. The demand for trail-based recreation is increasing and there has been a significant increase in both unauthorised and authorised trails through Grey Box remnants in the last decade. Control of activities in council reserves is difficult due to community expectations of unfettered access, however concerted effort is needed to be protect high value areas. The prevention of these impacts needs to be treated on a case by case basis, as there is no simple overarching solution. However, the following list provides a number of different options that could potentially be used:
Maintenance and prescribed burning to reduce fire risk are also key anthropogenic impacts brought about by the peri-urban nature of Grey Box woodlands – these are discussed further in Section 1.9.8. 1.9.2.Woody and Herbaceous Weed ControlAs many weed species are favoured by increased disturbance, it is important that any weed management strategy uses minimal disturbance techniques to ensure that native vegetation, soil and watercourses are disturbed as little as possible. This not only reduces the chances of weed re-infestation but also increase the likelihood of native plants being restored using the ecosystem’s ongoing natural regeneration processes. Minimal disturbance techniques are highly innovative methods to rid native plant communities of invasive pest plants more effectively, efficiently and safely, while achieving minimal disturbance of native vegetation, soil and the bushland environment. Weeding operations should be carried out in a way that not only reduces disturbance at the site, but also minimises movement across the area to decrease disturbance to surrounding vegetation, soil and watercourses. Appendix F provides detail on appropriate minimal disturbance methods. 1.9.3.Grassy Weed ControlGrassy weeds can be controlled using many of the minimal disturbance techniques described above. Specific herbicides that target grassy weeds could be considered, but would require careful use to avoid impacts on native grasses. For extensive (rather than the intensive methods of 1.9.2) control of grassy weeds, slashing and grazing management could be considered. These are discussed below: 1.9.4.SlashingA reduction in annual exotic grasses can be achieved through slashing during spring (Davies 1997; Robertson 2010). Slashing is most effective for controlling shallow rooted annual weeds and those with a winter growing period (Davies 1997). It can also be used to reduce the seed set of some annual and perennial species (Davies 1997). However, depending on the timing, frequency and height, slashing is also likely to be detrimental to species with a limited growth and flowering season such as orchids (Davies 1997). As such, any slashing program needs to consider the current biological values and conditions within a site. Slashing height is also an important consideration with potential to influence the response of native and exotic species. Generally, the greater the height of slashing, the greater the opportunity for native plant growth, flowering and seed set. (Bond 2011). Barlow (1998) recommends that annual grasses should be slashed about 10 cm above the ground before seed heads develop (usually late winter). Follow up slashing may be required 4-6 weeks later and possibly several more times depending on the weather and the grasses capacity to re-sprout. By preventing seed production, the seed bank will diminish over time (Barlow 1998). Perennial grasses should be slashed then sprayed. They can be slashed any time of the year, although best results will be achieved during winter and spring. Grasses should be left for 3-4 weeks to produce lush growth then spot sprayed. Herbicides work best on healthy active plants, so by removing dead material and stimulating growth you are improving the uptake of herbicide and therefore its success (Barlow 1998).
Bond (2011) noted in her review of current land management practices that land managers did not yet have systems in place that enabled them to optimise slashing timing, and respond to biological triggers such as grass flowering. Significant logistical challenges that prevent precise timing for slashing include: variation in season and biological response, large areas under slashing management regime meaning an extended period of time is required to implement slashing, slashing outsourced to contractors without a high level of control over timing). 1.9.5.Grazing ManagementGrazing management is unlikely to be a viable option for most Grey Box states in the Mount Lofty Ranges region, as it may degrade sites that have not experienced grazing by stock for some time. Areas that could potentially be considered include sites in the Willunga region, where states are predominantly 3a, 3b and 4 (ie have been exposed to grazing in the recent past). It is recommended that grazing management is considered on a case by case basis, with advice from relevant experts sought prior to commencement. However, the following information, reproduced from Oliver, L., Rehwinkel, R. and McLeish, L. (2008), provides broad advice on when grazing may be useful: “Strategic grazing using domestic stock can be an effective method of assisting regeneration of both overstorey and understorey, particularly where the accumulation of biomass is likely to inhibit regeneration or pose a perceived fire hazard. Strategic grazing can be used to reduce degradation of understorey habitat structure and components through trampling, compaction, biomass removal, increased nutrient levels, spread of weed species, loss of litter layer etc, or to assist habitat recovery from such damage due to past levels of domestic stock grazing. Grazing levels should not be increased above historical levels. E.g. if a site has never been grazed by livestock, then other methods (e.g. fire, no intervention) should be used for management. Strategic grazing may be more appropriate than stock exclusion for the maintenance or improvement of grassy woodlands, depending upon the past management and the species that are now present. Strategic grazing is more appropriate where there is a dense grass cover (either exotic or native), or herbaceous weeds can be best controlled using grazing. In some grassland communities of high native plant diversity or with particular ecological requirements for threatened species, the use of ‘pulse’ grazing may be the best form of strategic grazing for biomass control to maintain or increase native diversity or fauna populations. Low Condition vegetation adjacent to remnant vegetation may be assisted to regenerate naturally if grazing is applied in the form of ‘pulse’ grazing to periodically reduce competition from exotic herbaceous species. In some situations this may be a cheaper and ecological preferable method of achieving an expansion of remnant size compared to supplementary planting or re-planting. In sites that are in low to moderate condition the grazing strategy should concentrate on controlling the introduced annual pasture grasses and flat weeds through relatively short but intensive grazing, prior to seed set, between late winter and early spring. As well as reducing seed-set, this style of grazing can also open the groundcover layer to allow other plants to establish. Grazing should be removed after this time to allow the native perennial grasses and forbs, which often grow later in spring, to flower and seed.” 1.9.6.Nutrient Control and RemovalNutrients can enter a Grey Box site through a number of means, including:
It is crucial to prevent ongoing degradation of Grey Box woodlands by preventing this nutrient addition. This can be achieved by a number of means, including:
High weeds burdens can also lead to nutrient cycling, which means the weeds maintain the nutrient levels for their own advantage (Oliver et al 2008). The benefits of baling/removing slashed material is discussed in section 2.4.5. Nutrient manipulation (through addition of carbon sources such as sugar) can be used in conjunction with seed addition to restore native grassy ground cover (Oliver et al 2008). 1.9.7.Supplementary Planting and Habitat ReconstructionRevegetation in grassy woodlands requires careful planning. Up until recently many revegetation projects have focussed on the reinstatement of trees and shrubs. Grassy woodlands are generally open habitats with scattered trees and the density of those trees is vastly lower than is often achieved in revegetated areas. The description of the woodland provided in Section 1.2 of this document should be used as a benchmark for any plantings undertaken in Grey Box woodlands. The following section is broken into two parts to match the two management interventions defined in Table 1.8. Supplementary Planting (adapted from Clarke et al 2010) Grey Box sites that have some, but not all, of the desired plant species left are often the most difficult to plan appropriate actions for, particularly when they often appear at first to be highly degraded. Robertson (2010) notes the need for patience in detecting the regenerative potential of a site, and the initial focus should be on promoting this regeneration. If, over time, ongoing site assessment or monitoring reveals that natural regeneration alone is/will be insufficient to restore all desired plant components then some additional species may need to be introduced through revegetation to reach the goal State. Revegetation methods that require vehicle access and soil disturbance (such as machine direct seeding) are inappropriate for parts of sites that have reasonably good vegetation already. A ‘minimal disturbance’ approach to restoration should be taken in these areas by avoiding damage to any existing native plants where possible. Missing plant species could be reinstated through hand direct seeding or tubestock planting. Note that competition from mature plants may affect the success of newly germinated or planted seedlings, so new plantings should not be planted too close to existing trees and shrubs. To reduce competition, weeds should be spot sprayed, cut and swabbed or ‘weed wiped’ using hand tools as appropriate rather than using boom sprays (refer Appendix F). Soil disturbance should be minimised to reduce the potential for further weed germination. Habitat Reconstruction (adapted from Clarke et al 2010) Reconstruction of habitat from scratch requires a wide range of management techniques and incurs high costs, particularly on very degraded sites with a long history of site disturbance. It is also recognised that reconstructed Grey Box habitats can not provide the same biodiversity attributes as natural woodlands. Reconstruction methods may include a combination of the following:
Re-creating system components will often involve actions in phases that may take many years. Management of weeds and animal pests may be necessary over an even longer timeframe to give the system the best chance of regenerating and becoming self-sustaining. 1.9.8.Fire ManagementFire Management to Achieve Biodiversity Outcomes Fire is a natural ecological process and in the absence of fire, some elements of Grey Box Grassy Woodlands (species or structural habitat features) may decline or be lost. Fire will stimulate the soil and canopy seed banks of some species, causing significant germination events that may be required to replace senescing plants. DEWNR’s Ecological Fire Management Guidelines suggest that species may start to be permanently lost from the seed bank in grassy woodlands that remain unburnt for 50 years or more (DEWNR 2013). However this information is not specific to Grey Box Grassy Woodlands. Fire events also remove dead vegetation, create open spaces, and increase the levels of light reaching the woodland floor. These conditions are likely to promote germination and the establishment of seedlings for some native species. This is particularly important for plants that have been out-competed over time as it allows them to re-establish and reproduce before they again become rare in the community due to competition or natural senescence. However, the extent to which Grey Box Grassy Woodlands rely on periodic fire to reduce ground layer biomass (dead and living plant material) and stimulate germination events is unknown. As is the extent to which some fauna species may benefit from fire through the provision of patches of open ground for foraging and basking in, and through the regeneration of food sources that may have become rare with time since fire. Research has found that grasslands (generally in the eastern States) may benefit from relatively frequent fire (e.g. every 1 - 3 years). These grasslands tend to be dominated by Themeda (Kangaroo Grass) and have a high proportion of species that resprout post-fire. Little equivalent research has been conducted in grassy woodlands or in grasslands dominated by Austrostipa and Austrodanthonia species (as Grey Box Grassy Woodlands in the Mount Lofty Ranges are). The accumulation of thatch that suppresses recruitment of some plant species is not considered to be as significant in grassy communities dominated by the latter species as compared to Themeda dominated communities and therefore the need for fire to remove thatch biomass on a relatively regular basis may not be necessary. Grassy woodlands also often have a more prevalent shrubby mid-storey than grasslands, and therefore these communities are likely to require longer inter-fire intervals to allow these species to reach maturity. DEWNR’s Ecological Fire Mgmt Guidelines suggest a minimum fire interval of 5 yrs for Woodlands with a Grassy Understorey, with no more then two fires in 30 yrs. This minimum fire interval is based on the premise that fire in these communities is likely to be of relatively low intensity and hence somewhat patchy due to the low fuels that occur in many areas. In this situation occasional, relatively short inter-fire intervals are likely to still allow for the retention of sufficient juveniles to maintain a viable population in years to come (M. Wouters pers. comm.). Although fire is a natural process, the response of degraded Grey Box Grassy Woodland communities to fire is largely unknown. In particularly, knowledge is lacking regarding the likely response of native species relative to weed competitors under different fire regimes (i.e. different combinations of fire frequency, intensity and season). Prober et al. (2009) proposed that strategic use of fire, informed by native and exotic species responses, has potential for restoration of temperate eucalypt woodlands. They suggest that effective use of fire is dependent on the following three conditions: 1. most native species are resilient to the fire management regime, 2. target exotics are suppressed (by fire or competition), and 3. resources released by fire are utilized by natives rather than exotics. If fires are not frequent or of high intensity and occur between late Spring and early Autumn (reflecting the most likely natural timing of bushfires in the Mount Lofty Ranges) then the first of Prober’s criteria is likely to be met. However most research in grassland systems to date has found that under any given fire regime, some weed species are benefited and some are suppressed. Further work is therefore required to better understand how the elements of a fire regime influence the response of different weed species before we can confidently assess whether criteria 2 and 3 are likely to be met in any given Grey Box Grassy Woodland patch. To some extent mechanical or chemical weed control can be used to counteract post-fire increases in some weeds. In fact, in some instances fire can form a beneficial component of an integrated weed control program, increasing the efficiency of weed control efforts. However a large number of the most significant weeds in Grey Box Grassy Woodlands are inherently difficult or impractical to control on a scale that is necessary to benefit the community due to their ecology, extent, abundance and the likely off-target impacts that will be a consequence of broad-scale control. Bulb and grassy weeds are particularly notable in this regard. In summary, infrequent low to moderate intensity burning of intact Grey Box Grassy Woodlands between late Spring and early Autumn is likely to be beneficial to these communities. Burning of slightly degraded systems under the same conditions has the potential to be beneficial if sufficient resources are dedicated to post-fire weed control and the weeds in the community are feasible and practical to control without causing significant off-target damage. Until further information is available about the responses of weed species under different fire regimes, there is a significant risk that burning moderately to highly Grey Box Grassy Woodlands will cause systems to become more degraded. Given the range of factors discussed above, it is therefore recommended that burning for biodiversity outcomes within grassy woodlands requires significant expertise to assess the values, processes and threats within a site. This needs to be done on a site by site basis, and can not be prescribed by State (from the State and Transition model) alone. Appropriate monitoring and adaptive management (as discussed in Section 1.10) is also critical to using fire as a management tool, as our predictive knowledge of response to fire is still relatively poor. Recording and disseminating outcomes and associated knowledge from any biodiversity related fire management activities is also crucial, to help enhance collective knowledge of this management tool. Fire Management to Reduce Bushfire Risks If management of Grey Box Grassy Woodlands is being considered from a fuel reduction perspective (to help reduce bushfire risks in an area) then slashing, weed control and selective native shrub removal should be considered in addition to or instead of prescribed burning. Most intact Grey Box Grassy Woodlands should have fuel loads that are naturally relatively low. At a maximum fuel loads in these systems will reach ‘Very High’ but most are likely to be in the range of Low to High (A guide to fuel hazard assessment can be found here on the DEWNR website : http://www.environment.sa.gov.au/firemanagement/Fire_and_the_Environment/Assessing_fuel_hazards). If the area in question is moderately or highly degraded then, as mentioned above, prescribed burning may cause the condition of the habitat patch to deteriorate. In addition, the most significant fuels in degraded grassy woodlands are likely to be weeds. Prescribed burning will not reduce some of these weedy fuels (e.g. large olives) and may lead to an increase in other weedy fuels as many woody weeds are fire responsive (e.g. broom and boneseed), as well as grassy, herb and bulb weeds. Where woody weeds are significantly influencing elevated fuels, controlling these alone may be sufficient to achieve an acceptable Overall Fuel Hazard. If the overall fuel hazard is too high and this is being driving by an elevated fuel layer of native shrubs (once woody weeds have been removed) then reducing the density of these shrubs will reduce the fuel hazard (approval under the Native Vegetation Act (1991) is required for removal of native shrubs). If woody weed control or selective shrub removal is undertaken it is important to remove these weeds and shrubs from the site unless they are likely to break down quickly (e.g. boneseed) as this will increase the proportion of fine, dead aterial in the near surface layer that contributes to the overall fuel hazard. Dead olives that are left standing contribute little to the overall fuel hazard because of the separation of the dead, fine fuels in their small branches from the near surface fuel layer. If overall fuel hazard is too high because surface fuels at the site are Very High or Extreme, burning is likely to be the only way of reducing this fuel hazard. Slashing will reduce the height but not the cover of surface fuels and therefore will not reduce your overall fuel hazard (unless elevated fuels are also slashed). Burning will only reduce surface fuels for a short time period (1-2 years) unless surface fuels were initially high because of the amount of fine, dead material in them, in which case a fire that removes this element may effectively reduce fuels for a longer period of time. When burning is to be used to reduce fuels this may stimulate significant germination of shrubs and woody weeds which may over time increase the elevated fuels above pre-fire levels. In this situation post-fire weed control and selective shrub removal will need to be implemented to maintain fuel loads to an acceptable level.
Whilst not included in the list of Management Actions by State (as these features do not generally relate to State), there are important habitat attributes for fauna that occur within Grey Box woodlands. They include:
Management interventions to promote or retain these habitat values include:
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