|Ngarri-djarrang, May 2009.
Photo courtesy J. Booth
Ecological burning has always been crucial to management of Ngarri-djarrang Grassland in Reservoir.
Ngarri-djarrang Grassland has been tended by Merri Creek Management Committee since the early 1990s.
This article presents some analysis of fire management by MCMC and the resulting ecological improvements achieved over twenty years.
Fire in an urban grassland reserve
Ngarri-djarrang Grassland Reserve (formerly Central Creek Grassland Reserve) is a nine hectare remnant of Plains Grassland in the northern suburbs of Melbourne, Australia. Restoration of this site has been a commitment of the Merri Creek Management Committee (MCMC) since 1992 when the site was threatened by development, weed invasion, erratic biomass reduction and uncontrolled access. Works are funded by Darebin City Council, the formal managers of the Grassland, supplemented by regional, state and federal grants and developer funds.
A ten year community–led campaign saw removal of a freeway reservation and the current grassland area protected from housing development. In the early 1990s the Grassland was subject to massive weed invasion and the necessary biomass reduction only occurred as a consequence of uncontrolled fires. The grassland, however retained areas of high quality and diversity.
When management works began in 1992, the implicit overall goals were:
- to prevent any further degradation of biodiversity values and
- to improve the quality of the Grassland over time.
Secondary goals recognised the value of the area for education and as a seed source.
Targeted grassland management began with:
- mapping of vegetation quality to identify protection priorities,
- ecological burns in late summer with the aim to burn a third of the grassland every year and all areas burnt at least every five years and
- control of weed species through targeted herbicide application
Protection of the site from dumping and vehicles was assisted by fencing some boundaries in 1999. Fencing of the remaining boundaries, induction for construction workers and regular inspections minimised the impact of adjacent housing construction in the early 2000s. Special attention to the design of interface with this housing balanced resident amenity with conservation needs, including ensuring ongoing feasibility of ecological burning.
Fire; scheduling burns in five year blocks attaining biomass reduction goals.
Number of burns since 1992- warmer colours indicate higher frequency of burns
Number of burns between 2007 & 2011- warmer colours indicate more burns
Cooler colours indicate greater number of years since burn.
Since 1992, 36 documented burns have occurred in Ngarri-djarrang including 9 wildfires and 27 managed burns.
pManaged burns are termed 'ecological burns' and their primary role is to reduce biomass as an ecological process essential for regeneration of indigenous vegetation.
pSecondary aims are to reduce the prevalence and extent of wildfire and to create the optimum conditions for intensive strategic weed control.
pThe northern section of the grassland only entered regular maintenance in the early 2000's after Reserve boundaries were confirmed.
Scheduled burns aim to achieve biomass reduction over the Grassland EVC at three year intervals with a contingency of two years.
Burns are generally scheduled for late summer and early autumn.
Slivers of higher frequency indicate where burn outlines have been deliberately 'wobbled' and where burn zone outlines were changed between the first and second five-year action plan.
Further refinement of biomass reduction burns at this reserve being considered include increasing the frequency and variation in timing of burns.
Burn zone boundaries retain a mosaic of unburnt fauna and flora refugia in each of the reserve 'blocks' for fauna such as quail and reptiles.
A longer interval was selected for the north west corner where a Stony Knoll shrubland community is allowed to mature across six-years, retaining habitat for shrubland birds.
A small wetland area has a variable burn regime that is responsive to seasonal conditions– aiming to retain frog and wetland bird habitat.
For 2012, a burn similar to the 2009 pattern shown in the photo at top of article was carried out in the areas shown as 2-4 year (bluish-purple) on this map.
Weed management: strategies built on programme of biomass reduction.
Weed control effort is concentrated in post burn areas; utilizing optimum weed control conditions. The post-burn disturbance is also the main regeneration period for indigenous plants so reducing weed competition in this period is essential for the ‘assisted regeneration’ approach predominantly used at this site.
Vegetation quality mapping in 1994, 2004, 2006 and 2008 have been used to target weed control. In conjunction with scheduled burns, the quality maps allow allocation of resources in advance.
The four-colour mapping reflects primarily the weed cover. Floral diversity is not always correlated with high indigenous vegetation cover so additional flora mapping has commenced.
|Mapping in 1994 was completed using aerial photographs. Green indicates high quality (greater than 75% indigenous cover), blue is moderate quality, orange low quality and red is areas that have been almost entirely replaced by exotic plant species.||10 year later, mapping using on-ground GPS identified many areas of apparent deterioration and some improvements however some may have been artefacts of the different mapping method. The deterioration due to lack of management applied to the northern-most areas is consistent with on-ground observations.||By 2006, the use of mapping improved planning of works to follow scheduled burns. In particular- targeting moderate quality areas for intensive weed control and doing replacement of smaller weedy patches using revegetation.||In 2008, some reversals in some areas were apparent (the result of freshly revegetated areas having deteriorated due to planting failures), however further improvements are also apparent.|
The correlation between on-ground weed control works and ecological burning can be seen in this mapping of recent restoration effort under the current Caring for Our Country grant.
Warmer areas indicate where areas have been revisited more often. Eradication of the intractable weeds requires re-visiting to treat regrowth and seedlings. The grassland has a diversity of weed species that will each have optimum months for treatment. Achieving lasting reduction in weed cover therefore requires a sequence of weed control visits.
Works, primarily eradication of grassy weeds have been concentrated in regrowth areas burnt in March 2011.
The regrowth period allows the best conditions for spot spraying among mixed indigenous /exotic grasses. Improved conditions for spot-spraying may persist for over twelve months depending on the rate of regrowth of the grass sward.
Making friends with fire – community engagement.
|Burns were unexpectedly smoky during the wet summer of 2011. MCMC has adapted our burn procedures to require the degree of grass curing to be greater than 70% prior to burning- a measure that should avoid a repeat.|
Informing the public that ecological burns are safely conducted, essential for conservation and planned to minimise nuisance is a valuable investment.
The process of communication includes:
- Distribute information leaflets to all houses in the vicinity of the area to be burnt at least 3 working days before the scheduled burn day, recording on a map which houses have been leafleted.
- The leaflet explains the reason for the burn, the scheduled date, a map showing location of area to be burnt and provides a contact name and phone number of responsible staff member who residents can speak to for further information.
- On the day of the fire, door-knocking surrounding streets immediately prior to light-up. Residents are warned about smoke and advised to bring in washing and remain indoors if asthmatic. Laminated photos of ecological burns are used to assist in communication with residents whose primary language is other than English.
Where to? A vision for a small urban grassland.
Blue Grass Lily, Caesia calliantha, is a species that has increased since regular fire management began at Ngarri-djarrang.
The Ngarri-djarrang Grassland Reserve is among the best documented sites for the continuous management and restoration for an urban Victorian Volcanic Plains grassland reserve. It has scientific and conservation values as well as a role as a case study for other urban grasslands in Melbourne.
Current projects aim to;
- Enhance visitor experience to the grassland reserve.
- Support aspirations of the traditional custodians, the Wurundjeri to engage in cultural renewal through on-ground roles in cultural land management practices.
- enhance the reserve’s capacity to support local fauna
- provide sites to implement field applications of academic research on ecological
- provide a secure translocation site for local provenances of plants of local significance and VROT from elsewhere in the Merri Creek valley.
The ecological burning programme creates a rhythm of disturbance and regeneration that underpins the holistic management of native grasslands.