Presentation on theme: "Box-Ironbark Forest: How Much Fire is Enough? Presentation for Connnecting Country, Campbell’s Creek Community Centre 25-8-2011 Arn Tolsma."— Presentation transcript:
Box-Ironbark Forest: How Much Fire is Enough? Presentation for Connnecting Country, Campbell’s Creek Community Centre 25-8-2011 Arn Tolsma
(Map of LCC Box-Ironbark ecosystem) 250,000 ha 200-300 m asl 400-700 mm p.a.
593 mm p.a. at Castlemaine. Graph showsriest in March, wettest in August
Typical Mediterranean climate graph, hot in summer and cool in winter
Highly diverse! Mix of Bassian and Eyrean species –213 bird species –54 mammal species –43 reptile species –14 frog species Some “stronghold” species –Squirrel Glider –Grey-crowned Babbler –(Swift Parrot) –(Brush-tailed Phascogale)
(Photo of revegetated mine with few species other than those planted)
Ecological processes also changed Selective cutting –Allocasuarina? Clearing of scrub and litter Fragmentation –animal and plant movement Changes in burning regimes?
How do we manage now? Calls for increased burning Fuel reduction burning –various levels depending on veg types and locality –may or may not have +ve ecological outcomes Ecological burning –to promote biodiversity –may or may not have fuel reduction outcomes Justification is “following Aboriginal burning practices” or maintaining “natural” regime But what is the ‘natural’ fire regime??!
What is the ‘natural’ fire regime? Assumed pre-1788 (more like pre- 1830s here) –by natural causes –deliberate by traditional owners What patterns? –Which vegetation types? –how big were they? –how frequent? –what was the resulting fire mosaic? –what proportion was deliberate?
Is this a ‘natural’ fire regime? 1849 fires, 1983/4 to 2002/03, Bendigo FD 7.2%
Before the 1830s Picture of Ron Hateley’s book: The Victorian Bush – Its ‘Original and Natural’ Condition.
Historical records mention burning –for hunting, promoting desired plants, communication, as a response to threat But historical records often vague: –about the location –about the vegetation involved –or the source or purpose of the fires –or the size of the fires Nothing specific enough to suggest deliberate burning in forests Before the 1830s
Clues in the early vegetation –dense, dark forest –thick, scrubby understorey –everything was not “park like”, and trees were not always “widely spaced”
Before the 1830s “..the trees grow very close together; in some places they are so thickly set that the rear-guard of the escort cannot see the advance guard..” [Ellen Clacy, Black Forest, 1852, cited in Hateley (2010)]
Before the 1830s “..the forest between the First White Hill and our railway station, and, indeed, up to Golden Gully, was so thick and dark that people often lost their way..” [Robert Haverfield, circa 1851, from Mackay (1891) cited in Hateley (2010)]
Alfred Selwyn (1853). Plan of the General Survey from the Town of Malmsbury to the Porcupine Inn, from the sources of Forest Creek to Golden Point, Shewing the Alexandrian Range also Sawpit Gully Bendigo and Bullock Creeks. Picture of Selwyn map
Alfred Selwyn (1853), ‘rubber-sheeted’ to fit in GIS
“Rocky scrubby Ranges densely timbered principally with Box interspersed with Stringy Bark” “Bold rocky scrubby Ranges with Stringybark and Box, destitute of pasture”
Green is EVC Box-Ironbark Forest Beige is EVC Heathy Dry Forest
Before the 1830s Clues still in the forest and the earth
Photo of Grey Grass-tree: only found in high density in long-unburnt forest
Before the 1830s Slow build up of litter –4-8 t/ha c.f. 9-26 t/ha Wombat Forest –> (4) 8 yrs to approach pre-fire load Common BIB species don’t rely on fire –on-going recruitment –most species persist 50+ years –little species change after fire Peat cores provide local or landscape- scale information
Mooney et al. (2011) Late Quaternary fire regimes of Australasia Quaternary Science Reviews 30, 28-46. 223 records, Australasia.
Mooney et al. (2011) Late Quaternary fire regimes of Australasia Quaternary Science Reviews 30, 28-46. SE Australia records only.
Current understanding Extent of Aboriginal burning overstated –grasslands and open woodlands burnt –no evidence that forests were burnt… –…and strong evidence that they were not –myth derived from vastly different areas –fire probably played a minor role in shaping f&f here Forget about pre-1830s –forests and processes changed –must manage for what we have now Therefore vital that we understand impact of fire on extant forest
“Develop and implement appropriate fire management regimes to sustain ecological processes in key private land remnants…” Picture of report: Tolsma, A., Cheal, D. & Brown, G. (2007) Ecological Burning in Box-Ironbark Forests: Phase 1 – Literature Review. Report to North Central Catchment Management Authority. Arthur Rylah Institute for Environmental Research.
Effects of fire on understorey Heavily dependent on: –site history & extant sp. (hence propagules) –season of burn –post-fire conditions & herbivory Frequency of fire (and time since fire) very important –frequent fire, species drop out quickly –very infrequent, species may drop out slowly
Some species promoted by a fire - heat Acacia pycnantha Daviesia ulicifolia Acacia paradoxa Pultenaea pedunculata (Paul Gullan / Viridans)
Some species promoted by a fire - smoke Hibbertia sericea Lomandra longifolia
….but few species NEED it Pultenaea prostrata ?
Effects of fire on understorey Minimum interval ~ 20 years –common BIB species don’t rely on fire –most species persist 50+ years –some species take ~ 10 years to produce viable seeds You won’t get back to pre-1830 –maintain, rather than enhance diversity
Effects of fire on canopy Depends on intensity of fire –most Eucalypt species fire-tolerant –prescribed fires unlikely to kill areas of overstorey Frequent fire –coppice increase? –kill off juveniles Fire not needed for overstorey persistence –most species with continual recruitment –Ironbark? 60 years for full recovery of structure if severely burnt
Effects of fire on litter Litter important in nutrient cycling and for habitat –fungi –invertebrates –reptiles, small mammals, ground birds Frequent burning (< 3-5 yr) may disrupt natural processes –C and N reduce
Effects of fire on invertebrates 95% of fauna sp., but often overlooked –role in nutrient recycling etc. –short-term effects often linked to burning of litter Few detailed studies –inverts have high natural variability – confusing/conflicting results Some impacts from single fire – springtails, earthworms, some beetles – some ants Frequent fire may replace litter-dependent species with more tolerant species Burning at < 3-5 yr intervals should be avoided
Effects of fire on birds Direct and indirect –dependent on severity, scale & mobility –vegetation strata & bird trophic guild –prescribed fire < wildfire Ground nesters/foragers disadvantaged in short term Carrion and reduced cover Promotion of new growth – seeds
Bush Stone-curlew : –nests, roosts and feeds on ground –affected by loss of cover after spring burn
Brown Treecreeper & White-winged Chough : –ground-feeding, litter important –affected by spring and autumn burns
Little and Painted Button-quails, Brown Quail, Emu: –predominantly seed-eaters –benefit from increased seeds after spring and autumn burns
Effects of fire on birds Frequency important –minimum fire interval ~ 25 yrs
Effects of fire on mammals Linked to fire severity, scale & season –and avoidance by animal Arboreal mammals only by severe fire
Small mammals affected by ground fire - (esp’y autumn) Bush Rat Yellow-footed Antechinus
Burning of logs and dead trees Brush-tailed Phascogale Echidna
Succession tied to vegetation - black rats & house mice often first back
Western Grey Kangaroo, Eastern Grey Kangaroo, Black Wallaby, European Rabbit*: –drawn to flush of new growth
Effects of fire on mammals Recolonisation may be difficult –especially small mammals –especially in remnants Minimum interval ~ 20 yrs
Effects of fire on reptiles & frogs Little research –thin on ground in BIB Ectothermy = lower metabolic needs? Increased predation & competition Affected by loss of litter and ground layer –e.g. Coventry’s Skink, Grass Skink Indirect effects of run-off and water quality on frogs Season of burning important –affects breeding
Striped Legless Lizard, Olive Legless Lizard, Burton’s Snake-Lizard, Common Scaly-foot, Hooded Scaley- foot: –ground-dwelling –most active and breed in spring
Brown Toadlet, Southern Toadlet: –ground-dwelling –lay egg masses in soil or litter in autumn
Effects of fire on reptiles & frogs Barriers to recolonisation –especially remnants Minimum fire interval?
Overall, big variations in response Due to: –season –site factors and history –life characteristics of plants and animals –ability to colonise or disperse No single burning regime will advantage or disadvantage every species group –hence mosaic important Minimum period of 20-25 years allows full recovery of vegetation structure No regime yet determined for fauna… –..and we don’t know what a suitable mosaic looks like
Picture of report: Tolsma, A., Cheal, D. & Brown, G. (2007) Ecological Burning in Box-Ironbark Forests: Phase 2 – Management Strategy. Report to North Central Catchment Management Authority. Arthur Rylah Institute for Environmental Research.
So should we burn? What are you trying to achieve? Then depends on specific site –what extant plants are there? –what is in the soil seedbank? –what native animals are there? –what is time since last fire? Minimum & Maximum tolerable fire interval –not too soon and not too late “No” if below Tolerable Fire Interval “Yes” if vegetation senescing –but unlikely to restore ‘missing’ stuff
How do we determine time-since-fire? Local records/knowledge –fire mapping if available –previous owner, neighbours, field nats Actual vegetation on site –because species mix will change –Key Fire Response species
Tolerable Fire Interval Shortest TFI: species that takes longest time to reproductive maturity (x 2) –Brachyloma daphnoides, Exocarpos cupressiformis, Grevillea alpina & Leptomeria aphylla (10 x 2 years) Longest TFI: species that takes shortest time to local extinction –e.g. Acacia genistifolia, Dillwynia cinerascens, Astroloma humifusum, Pultenaea largiflorens (1/4 at least 20-50 years, 3/4 50-100) –Daviesia leptophylla needs checking
Conclusions No evidence that Box-Ironbark forests deliberately burnt pre-1830s… …and no strong evidence that Box- Ironbark must have fire applied to it… Box-Ironbark copes with fire provided not too frequent Ecological burning useful if vegetation is getting “old”… …but missing species won’t come back Must have a clear idea of what you are trying to achieve Plan carefully with due regard to TFIs
Acknowledgements North Central CMA & fire workshop participants David Cheal - ARI Geoff Brown - ARI Nick Clemann - ARI Alan Yen - DPI Andrew Bennett – Deakin University Greg Horrocks – Monash University Kevin Tolhurst – Melbourne University Evelyn Nicholson – DSE Doug Ralph for Selwyn map & Keshia Atchison for GIS rectification