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 ha200-300 m asl400-700 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)

Highly diverse!

• 1330 vascular plant species

• 17 broad EVCs (Muir et al.), including:– Box-Ironbark Forest– Heathy Dry Forest– Grassy Dry Forest– Mallee shrublands

(Photo of Yellow Gum with sparse understorey)

(Photo of Ironbark with dense Flame Heath understorey)

Bendigo Creek from main road to Eagle Hawk, 1852 (University of Ballarat)

Clearing for agriculture (Museum Victoria) (1869 Land Act)

Pegging out at midnight, under The Land Act 1869 (State Library of Victoria)

Cutting firewood for railway engines (Museum Victoria)

Ecological processes also changed• Animals hunted or forced out

Swamp Rat

Common Dunnart

12 of 43 mammal species no longer in N.C. region (Menkhorst 2010)

Eastern BettongEastern Quoll

• 4 of the 12 no longer found in Victoria

(+ Rufous Bettong+Bridled Nailtail Wallaby)

Eastern Hare Wallaby (Gould painting)

White-faced Rabbit Rat (Gould painting)

• 2 of the 12 are extinct

Ecological processes also changed• Animals introduced

(Photo of European Rabbit)(Photo of Red Fox)

Ecological processes also changed

(Photo: Alan Yen)

(Introduction of honey bees)

(Photo of Hair Grass and Quaking Grass weeds)

(Photo of hollows and piles and Moliagul from gold digging)

(Photo of bare, recently mined area)

(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

92.8

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

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 ForestBeige 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

(Photo of peat core)

Mooney et al. (2011) Late Quaternary fire regimes of AustralasiaQuaternary Science Reviews 30, 28-46. 223 records, Australasia.

Mooney et al. (2011) Late Quaternary fire regimes of AustralasiaQuaternary 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

So should we burn?• Maybe, maybe not

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

Define site objectives

Define logical burn

units

Collate spe cies lists

Identify key response

species

Determine time - since -

fire

Determine tolerable fire

intervals

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

KFR Daphne Heath Spreading Wattle

Occurrence Widespread Widespread

Seed germination Complete germination Partial germination

Juvenile period 10 years 5 years

Establishment conditions Tolerant Intolerant

Maximum density >30 years after fire 10-30 years after fire

Lifespan of plant >50 years 10-50 years

Time to local extinction >50 years (100?) 20-50 years

Years 0-10 10-20 20-30 30-40 40-50 50-60 70+

Burchardia umbellataGoodenia geniculataThysanotus patersoniiDaviesia leptophyllaDaviesia ulicifoliaAcacia genistifoliaAcacia paradoxaAcacia pycnanthaCorrea reflexaAcacia acinaceaAstroloma humifusumDillwynia cinerascensPlatylobium formosumAcrotriche serrulataBursaria spinosaPultenaea prostrataCassinia arcuataExocarpos cupressiformisBrachyloma daphnoidesJoycea pallidaThemeda triandra

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

Define site objectives

Define logical burn

units

Collate species lists

Identify key response

species

Determine time-since-

fire

Determine tolerable fire

intervals

PLAN BURN

Is actual time-since-last-fire less than Lower

Tolerable Fire Interval?

DO NOT BURN

YES

NO

Is actual time-since-last-fire approaching

Upper Tolerable Fire Interval?

NO CLEAR CASE FOR BURNING

NO

Will fauna species be negatively

affected by a burn?

YES

Can impact be acceptably reduced?

NO

YES

PLAN BURN

YES

Will habitat become unsuitable

if not burnt?

NO

PLAN BURN

DO NOT BURN

YES NO

UPDATE REGIONAL FIRE-AGE

DATABASE

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