Table Of ContentPatterns in Emergence ofAcaciaand Grevillea
Seedlings after Fire
TonyD. Auldand MarkTozer
(CommunicatedbyD.Keith)
Auld,T.D.,andTozer,M.PatternsinemergenceofAcaciaandGrevilleaseedlingsafterfire.
Proc.Linn.Soc.N.S.W.115:5-15(1995).
Post-fireseedlingemergencewasfoundtobepulsedinAcaciasuaveolens,aspecies
whichisknowntohaveitsseeddormancybrokenbysoilheatingduringthepassageofa
fire. Thispost-fireestablishmentdeclinestozerosome15monthsafterfire.Twospeciesof
Grevillea, G. buxifolia and G. speciosa, showed a similar, although slightly more varied
response. Hence,bothAcaciasuaveolensand Grevilleaspp. havegerminationcuedtothe
passageofafireandareabletorapidlyplaceseedlingsintofavourablesitesforgrowthpost-
fire.However,seeddormancyinsix Grevilleaspecieswasnotsignificantlybrokenbyheat-
ing,althoughtemperaturesof110-120°Cwerelethaltoseeds.Inthesegrevilleas,theheat
producedbythefireisnotthecuetobreakseeddormancyanditisexpectedthatsome
other fire-related cue (charred wood, smoke) may be responsible for breaking seed
dormancy.
N.S.W.NationalParksandWildlifeService,P.O.1967HurstvilleN.S.W.2220;manuscriptreceived
19July1994,acceptedforpublication16November1994.
KEYWORDS:germination,seeddormancy,seedheating,soilseedbanks
Introduction
Manyspeciesinfire-pronevegetation communitiespossessasoil seedbank. In the
Sydney region ofsouth-eastern Australia, some 89% ofspecies in fire-prone vegetation
havesomeformofsoilseedbank.Thismaytaketheformofpersistent (74%) ortransient
seedbanks (15%),thelatteroccurringwhereseedshavenodormancyandwillgerminate
when sufficient moisture is available. The remaining species have either a canopy seed
bank (10%) ornoseedbank (1%) (Auldunpubl.).Afterafire,conditionsfavourablefor
seedling growth and survival are enhanced via the release ofnutrients in ash (Raison
1980), the increased availability of light and space and reduced competition levels.
Consequently,themostfavourabletimeforemergenceofseedlingswillbeassoonaspos-
sibleafterafire.Thissituationwillfavourthosespeciesthatareabletorespondrapidlyto
the passage ofa fire, i.e. those species whose germination is cued to fire. There is now
widespreadevidencethatsoilheatingduringthepassageofafirewillbreakseeddorman-
cyinmanyplantspecieswithasoilseedbank.Thishasbeendemonstratedin severalfire-
prone communities in the world in several plant families, although particularly in
legumes (Cushwa etal. 1968; Floyd, 1966,1976; Kruger, 1983; Keeley, 1987;Jeffery etal.
1988;AuldandO'Connell 1991;Bell etal. 1993).IntheSydneyregion,thefirstseedlings
toemergeafterafirearelegumessuchasAcaciaspp.,Dillwyniaspp.andPultenaeaspp.and
flushes ofgermination of such legumes are common after a fire (Auld, 1986). Other
specieswhich have soilseedbanksshownoresponse to soil heating (Keeley, 1991;Auld,
Keith8cBradstockunpubl.),althoughtheirseedlingsmaybenumerousafterfire.Insuch
cases,thepresenceofpost-fireseedlingsmayindicatetheavailabilityofnon-dormantseed
in the seedbank or the breaking of seed dormancy by other fire related cues such as
charredwood (cf. Keeleyetal. 1985; KeeleyandPizzorno 1986; Keeley, 1991), smoke (cf.
deLangeandBoucher1990;Brown, 1993) someotherfire-relatedcueortheinteraction
,
ofheat,charredwoodandsmoke.
FortheshrubspeciesinsandstonecommunitiesaroundSydney,thereisgenerallya
ProcLinn.Soc.N.s.w., 115,1995
)
6 T.D.AULDAND M.TOZER
gradualdecayofseedsfromdormanttonondormantin thesoilseedbank,independent
offire (Auld, 1986,Auld etal. 1993). Asimilarpattern exists in othercoastal plants, e.g.
Acacia longifolia (Weiss, 1984), and some semi-arid and arid plants (Grice and Westoby
1987,Auld, 1995) Consequendy,twosimplealternativeseedbankresponsesafterfireare
.
possible:
1 thereisapulseofgerminantsafterfireasadirectresponsetodormancybreaking
cues associatedwith the fire. This response would be expected in manylegume species
where thesoilheatingproducedduringafirebreaksseeddormancy. Germinationlevels
would be expected to decline with time since fire. Such species would exploit the
favourablepost-fireenvironmentforestablishment;or
2) thereisnopulseofgerminantsafterafireasthefirehasnoimpactonseeddor-
mancy.Thelevelofpost-fireemergencewouldreflecttherateofdecayofseedsinthesoil
fromadormanttoanondormantstate.Germinationlevelswouldbeexpectedtobefairly
constantthroughtime,althoughtheremaybepulsesrelatedtoseedfallifacomponentof
annualseed-cropsarenondormant.Suchspeciesmaystillexploitthefavourablepost-fire
environment for establishment if establishment is not successful at other times. This
group ofspecieswould include those thatshownoresponse to soilheatingorotherfire
cuesorthosespecieswhichcanrespondtosoilheatingbutwheresoilheatingduringthe
firehasbeeninsufficienttobreakseeddormancy (cf.AuldandO'Connell 1991).
Thisstudyaimedtoexaminetheemergencepatternsofseedlingsafterthepassage
offire. A legume species with a known heat response, Acacia suaveolens (Smith) Willd.
(Auld 1986) wascomparedto Grevilleaspecieswhichhaveacontrastingseedmorphology
andanunknownresponsetoheat.
Methods
Studyarea
Sites were located in the Sydney Region (33°53'E, 151°13'S) of south-eastern
Australia.AnnualprecipitationforSydneyisaround1300mm,whiletheaveragemonthly
maximum/minimumtemperaturesare26/18°Cinsummerand 16/8°Cinwinter.
EffectofheatonseeddormancyinGrevillea
The effect ofheat on seed dormancywas examined in six Grevilleaspecies. These
wereallshrubscomprisingacomponentoftheunderstorey (woodlands,forests) ordom-
inants (heaths) of sclerophyll vegetation. Three species are common and widespread
(G. buxifolia (Smith) R.Br., G. linearifolia (Cav.) Druce and G. speciosa (Knight)
McGillivray) while the remaining three species are rare plants (G. caleyi R.Br. 2ECi, G.
longifolia R.Br. 2RC- and G. shiressii Blakely 2VCit, codes follow Briggs and Leigh 1991,
AXZECC 1993) All these Grevilleaspp. are killedbyfire and relyon germination from a
.
soil seedbank for establishment post-fire. Two species, G. caleyi and G. longifolia, have
toothbrush flowers and seeds lacking an aril (Auld et al. 1993), while the remainder all
have 'spider-flowers' andseedswithanaril.
Field collections of seeds for each study species were made during November,
December andJanuaryof1989, 1990 and 1991. For G. caleyi, G. longifoliaand G. shiressii
large developing fruits were bagged and seeds were collected after the fruits had
dehisced. For the otherspecies, mostfruitswere collected by handwhen ripe, although
some bagging was done for G. buxifolia. In the laboratory, intact seeds were stored in
envelopesatroom temperature.Theeffectofarangeoftemperaturesatonedurationof
heating on seed germination were examined in the laboratory. Ten temperature levels
wereexamined;ambient (control),40,50,60, 70,80,90, 100, 110and 120°C,forasingle
duration ofexposure (1 mins).Thirtyseedsweretestedforeachtemperaturetreatment,
ProcLinn. Soc.n.S.w.. i15, 1995
.,
ACACIA AND GREVILLEA SEEDLINGSAFTERFIRE 7
although occasionallysufficientseedswereavailable to use additionalseedsasreplicates
in the control.Asmallvolume ofair-driedsoilfrom thefieldwasenclosedin aluminium
foil and preheated in an oven to the desired temperature. Once preheated, the soilwas
removed from the oven and seeds added. Athermometerplaced in the soilwasused to
monitor the soil temperature. After exposure in the oven for the required time, seeds
wereextractedfromthesoilusingasieve (mesh2x2mm) andallowedtocool.Individual
seedswerethenplacedonWhatmangrade2filterpapermoistenedwithdistilledwaterin
9 cm diameter petri dishes. Germination was followed for eight weeks, after which all
seedswhichhadnotgerminatedwerescarifiedandallowedtogerminateinordertoesti-
matetheviabilityoftheseedlotused.Anyseedswhichstilldidnotgerminateweretested
forviabilityusingthetetrazoliumtest (Lakon, 1949) Comparisonsbetween temperature
.
treatmentsweremadeviaatwofactorialmodelinGLIM (Aitkineta\. 1989) withabinomi-
alerrorstructure.
Seedlingemergenceinthefield
Post-fireemergenceofseedlingswasrecordedatfourstudysitesinGarigalNational
ParkinthenorthernsuburbsofSydney.ThreeofthesiteswereburntinNovember 1992,
whilethefourthwasburnt2monthsearlier.Vegetationatthesiteswasamixtureofheath
and open woodlandwith a shrub understoreyon Hawkesbury sandstone. Ateach site a
quadratwasmarkedoutandallemergingAcaciaand Grevilleaseedlingsweretaggedat2-3
monthlyintervalsforupto 15monthspost-fire. Quadratsizevariedbetweensitesandwas
governedbytheabundanceofemergents.Samplinginvolvedrepeatedcountsatthesame
quadratsovertimesothateachemergentseedlingcouldbeassignedtoaparticulartime
intervalpost-fire.Itwasassumedthatcorrelationsbetweencountsfromthesamequadrats
acrosstimeintervalswereminimal. EmergentseedlingswereAcaciasuaveolensatallsites,
Grevilleaspeciosa (3sites) and G. buxifolia (2sites). Patternsofemergencewereexamined
forAcaciaand pooled Grevilleaspp. across time intervals using the number ofseedlings
emerged in a particular time interval as a fraction of the total number of seedlings
emergedoveralltimeperiods. DatawereanalysedbyathreefactorialmodelGLIMusing
abinomialerrorstructure.Appropriatepost-hoc testsweremadeusingaZstatistic (Zar,
1974) Arangeofcurveswerefittedtoproportionalemergenceacrosstimetoestimatethe
.
bestfittothedata.
Results
There was no clear evidence that heating broke seed dormancy in any ofthe six
Grevilleaspeciesexamined (Table 1,Fig. 1).Therewasconsiderablevariationin thelevel
ofnon-dormantseedsbetweenspecies. Inallspecies, temperaturesof120°Cwerelethal
toseeds,whilesomeseeddeathalsooccurredat110°C.Significanttemperatureeffectsin
specieswererelatedtothisseeddeathathightemperatures.TheonesignificantSitetimes
Temperatureinteraction (G. linearifolia,Table 1) mainlyreflecteddifferentseedmortali-
tylevelsat 100and 110° C (Fig. lc). Forsomespecies, therewasahighlevelofseeddor-
mancyatalltreatments (G. caleyi,Fig. lb),whileforothers, highlevelsofnon dormancy
were apparentin all treatmentsbelowthe lethal temperatures (G. linearifolia, Fig. lc, G.
speciosa,Fig. If).
SeedlingemergencepatternsinAcaciasuaveolensandpooled Grevilleabuxifoliaand
G. speciosawere similar,with an initial post-fire pulse declining toverysmall to no emer-
gencesome 15 monthsafterthefire (Fig. 2) Whileone site hadasignificantincrease in
.
seedlingemergencein Grevillea2Xthesecondtimeintervalcomparedtothefirst (Fig.2b)
thesameoverallpatternofadeclinethroughtimewasapparentatallsites.Thisisreflect-
ed in asignificantthree-wayinteraction in the GLIM analysis (Table 2).An exponential
modelwasthebestfittothedataintermsofdeclineinemergencethroughtime (Fig. 2)
ProcLinn.Soc.n.S.w.,i15,1995
T.D.AULDAND M.TOZER
These regressions accounted for 96% and 71% ofthe variation in emergence through
timeforAcaciasuaveolensandpooled Grevilleaspecies,respectively.
1.0
1 i
a)
0.8 -- -
0.6 -
CD
O
m
0.4
o
^ 0.2 ^"^ --AX\ -
O
Q ¥-~¥*
0.0 . W~1K) '
50 100 150
TJ
CD
CD
CO
o
c
_o
o
Q_
o
a. 0.4 -
50 100 150
Temperature (°C)
Fig. LEffectofheatonseeddormancyin Grevilleaspp.Differentlinesrepresentdifferentyearlysamplesand/or
sites.Barsrepresentstandarderrors.Thepositionofpointsonthex-axishavebeenadjustedslightlyforclarity,
a) G.buxifolia;b) G.caleyi;c) G.linearifolia;A) G.longifolia;e) G.shiressii;t) G.speciosa
Proc.Linn. Soc.N.S.w., 115, 1995
ACACIA AND GREVILLEA SEEDLINGSAFTERFIRE
150
50 100 150
Temperature (°C)
Fig. 1,cont'd. Effectofheatonseeddormancyin Grevilleaspp.Differentlinesrepresentdifferentyearlysamples
and/orsites.Barsrepresentstandarderrors.Thepositionofpointsonthex-axishavebeenadjustedslighdyfor
G
clarity,a) G.buxifolia;b) G.caleyi;c) G.linearifolia;d) longifolia;e) G.shiressii;f) G.speciosa
Proc.Linn.Soc.n.s.w.,i15, 1995
10 T.D.AULDAND M.TOZER
CZ
CD
O
m
o
c
cd
o
Q
150
CO
TD 1.0 ~~i 1 1 r ~[ 1 r
CD
CD
CO
o 0.8
cz
_o
0.6
o
Q.
O
Q_" 0.4
0.2
0.0 1 I L. -1B-
50 100 150
Temperature (°C)
Fig. 1, ront'd. Effectofheatonseeddormancyin Grevilleaspp.Differentlinesrepresentdifferentyearlysamples
and/orsites.Barsrepresentstandarderrors.Thepositionofpointsonthex-axishavebeenadjustedslightlyfor
clarity,a; G.buxifolia;h) G.caleyi;c) G.linearifolia;d) G.longifolia;e) G.shiressii;f) G.speciosa
Proc. Linn. Soc.n.S.w., 115, 1995
ACACIA AND GREVILLEA SEEDLINGSAFTERFIRE 11
Table 1
ComparisonoftheeffectofheatonseeddormancyinsixGrevilleaspeciesusingGLIM.
Species Factor Changedf Changedev P1
G.buxifolia Site 1 0.01 ns
Temperature 9 26.48 **
SitexTemperature 9 9.16 ns
G.caleyi Site 1 0.42 ns
Temperature 9 11.26 ns
SitexTemperature 9 10.92 ns
G.linearifolia Site 2 0.99 ns
Temperature 9 304.9 ***
SitexTemperature 18 83.3 ##*
G.longifolia Site 2 42.66 ***
Temperature 9 44.64 ***
SitexTemperature 18 8.17 ns
G.shiressii Site 1 10.13 **
Temperature 9 19.47 *
SitexTemperature 9 3.13 ns
Gspeciosa Site 1 9.54 **
Temperature 9 182.9
SitexTemperature 9 10.9 ns
1,ns,nonsignificant
* 0.05>/M).01
** 0.01xR>0.001
*** P<0.001
Table2
GLIMcomparisonsoftheproportionofseedlingsemergingatvarioustimeintervalspost-fire
forAcaciasuaveolensandGrevilleaspp.
Factor Changedf Changedev
Species 1 0.04
Site 3 0.05
Time 4 3137
SpeciesxSite 3 0.46 ns
SpeciesxTime 4 76.5 ***
SitexTime 12 430.8 ***
SpeciesxSitexTime 12 125.8
1,ns,nonsignificant
***P<0.001.
Proc.Linn.Soc.n.s.w.,lis,1995
12 T.D.AULDAND M.TOZER
1.0
0.8 -
0.6 -
<D
D) 0.4 -
k.
<D
E
LU 0.2 -
(0
O)
j= 0.0
0.0 2.0
0)
0)
I.U
I I ' i
c b)
o 0.8 _ \ • -
o
a
\°
o 0.6 A -
a\
0.4 * -
A °a\\
0.2 A -
•
no
2 !=*=
I i 1
0.0 0.5 1.0 1.5 2.0
Time (years)
Fig. 2.Post-Fireemergenceofseedlings.Linesrepresentlineofbestfit(seetext).
Differentsymbolsrepresentdifferentsites,a) Acaciasuaveolens;y=8.117.e-9,285*
b) Grevilleabuxifoliaand G. speciosacombined,y= 1.402.e-'"x
Proc.Linn. Soc.n.s.w., iis, 1995
acacia and grevillea seedlingsafterfire 13
Discussion
The Grevilleaspecies examined contrastwith Acaciaspp. (seeAuld and O'Connell
1991) inthattheyshownobreakingofseeddormancybyheating.Itisunlikelythatlonger
durations ofheating may have affected seed dormancy (Auld 8c O'Connell 1991) and
such durations are not typical ofsoil heating in the field during the passage ofa fire
(Bradstock and Auld 1995). Consequently, while itwould be expected that Acaciaspp.
would showapulse ofgerminantspost-fire, the expected response from Grevilleaspp. is
unclear. Nopulsewouldbeexpectedwhere thereisnoseedresponsetothepassageofa
fire. Insuchasituationseedlingemergenceisdependentupon therateofdecayofseeds
fromadormanttoanondormantstateinthesoilseedbank.Alternatively,somecueasso-
ciatedwiththepassageofafireapartfromheatmayberesponsibleforbreakingseeddor-
mancy. Such a cue could be leachates from charred wood (cf. Keeley et at 1985) or
chemicals derived from smoke (cf. Brown, 1993). Should such afire-related cue existin
Grevillea,thenapulsedresponsewouldbeexpected.
Theexaminationofpost-fireemergenceinthefieldconfirmedthepredictedpulse
for Acaciasuaveolens (Fig. 2a). The exponential regression (Fig. 2a) was able to explain
some 95.6% ofthevariation in seedlingemergence overtime and isagoodpredictorof
thelikelyemergencepatternin thisspecies. Dependingon the timingandmagnitudeof
post-firerainfall,thepositioningofthiscurvemayvary,howeveritsshape shouldremain
roughlythesame.
For Grevilleabuxifoliaand G. speciosatherewasalsoastronglypulsedpatternofpost-
fire emergence (Fig. 2b). In this case, the exponential regression accounted for some
71% ofthevariation in emergence over time. For Grevilleaspecies therewasmorevaria-
tion between sites in the initial magnitude and timingofthe pulse, however, the overall
patternwasstrikinglysimilartoA. suaveolens. In thecaseofGrevilleaspp., thebreakingof
seeddormancybyheatingofthesoilduringthepassage ofthefire cannotbeinvokedto
explaintheobservedresponse.Clearly,thereisadistinctpost-firepulseofgerminantsbut
the fire-related factor responsible for breaking seed dormancy remains unknown. It is
possible that Grevilleaspp. respond tofire cuessuch assmoke orleachatesfrom charred
woodandthisremainsaninterestingareaforfutureresearch.
Auldand O'Connell (1991) predictedthatthe amountofthe soilseedbankthatis
stimulatedtogerminatebythepassageofafirein specieswithdormancybrokenbyheat
willvarydependingontheamountofsoilheatingthatoccursduringafire.Thisinturnis
controlledbytheamountoffinegroundfuelsthatareburntduringafire,acomponentof
fireintensity(BradstockandAuld1995).Ingeneral,fireswithhighlevelsoffinefuelcom-
bustionwillcause thegreatestdepletionofthesoilseedbankthrough high post-fire ger-
mination levels. Following from this, patterns ofthe depth ofemergence ofseedlings
shouldbecloselytunedtosmall-scalelitterandfinefuelpatterns.Predictedlevelsofseeds
emergingfromthesoilseedbankinA. suaveolensrangefrom 1.1 to32.9%,dependingon
theamountofsoilheatingthatoccurs (AuldandO'Connell 1991).Additionalseedsnear
thesoilsurfacewillbekilledbylethaltemperatures.Clearlyunderthisscenario,seedswill
be depletedfrom certain depths and remain available atgreater depths, depending on
thelevelofsoilheating,i.e.thereisasoildepth-relatedimpactforspecieswhoseseeddor-
mancyis broken byheat. Itremains to be seenwhetheran equivalentsoil depth-related
response occurs in species whose dormancy is broken by a fire-related cue other than
heat, althoughthe seedbankwillbedepletedatthesoilsurface asseedsare killedbysoil
heating.
Therelativespeedwithwhichseedlingsofparticularspeciesemergeinthepost-fire
environmentwillreflecttheirstrategyofseedstoragebetweenfiresandwhetherapersis-
tentseedbankismaintainedornot.Speciesthatstoreseedsinthesoilandhavepersistent
seedbanksarelikelytobe the quickesttoplaceseedlingsin thefavourablepost-fireenvi-
ronmentiftheyhavetheirdormancybrokenbythepassageofafire.Specieswithacanopy
seedbankmustwaitforseedstobereleasedfromthewoodycones,andthismaytakemany
ProcLinn. Soc.n.S.w.,115, 1995
.
14 T.D.AULDAND M.TOZER
weeksafterthefirehaspassed. Speciesthatrelyondispersalfromoutside theburntarea
mustwaitfortheseasonoffruitmaturationinunburntcommunitiesandthiswillnotnec-
essarilycoincidewith thefavourable immediate post-fire period. Finally, there are those
speciesthathavetransientsoilseedbanksandthatrelyonapost-firepulseoffloweringto
placeseedlingsinthepost-fireenvironment.Thesespeciesmaytakefromafewweeksup
to 2years toflowerafterfire and therefore are the slowestto place seedsin the post-fire
environment.
For species with a soil seedbank, the pattern ofpost-fire emergence ofseedlings
shouldreflectmoistureconditions,theinfluenceoffire (heat,charredwood,smokeetc.)
onbreakingseeddormancy,andthebreakingofseeddormancybymeansotherthanthe
passage ofthe fire. While A. suaveolensand Grevilleaspp. have differentmechanismsfor
havingseeddormancybrokeninrelationtoafire,thismakesnodifferencetothetiming
ofthe post-firepulse ofemergentseedlings. Thismaybebecause both dormancybreak-
ingmechanismsoperateatthe timethefirepasses.Alternatively,asseedsmustwaituntil
thereissufficientmoisture in ordertogerminate, anydifferencesbetween the timingof
dormancybreakingbydifferentfire-cuesmaybeeliminated.
Acknowledgements
Thanks to Rachael Thomas, Maria Matthes, Karyn Maling and Andrew Denham
whocarriedoutthelaboratoryheatingexperimentsandtoDaveBrown,AndrewMarshall
and numerous assistants who organised and carried out the experimental burns in the
field. RossBradstockmadehelpfulcommentsonthemanuscript.
References
—
Aitkin,NM.e,wAYnod—rekr.son,D.,Francis,B.andHinde,J.,1989. StatisticalModellinginGLIM.OxfordUniversityPress,
Anzecc,1993. Th—reatenedAustralianFlora.AustralianNatureConservationAgency.
Auld,T.D.,1986. PopulationdynamicsoftheshrubAcaciasuaveolens(Sm.) Willd.:fireandthetransitionto
seedlings.Au—stralianJournalofEcology11:373-385.
Auld, T.D., 1995. Soil seedbank patterns in four trees and shrubs from arid Australia.Journal ofArid
Environments29:33-45. —
Auld,T.D.,Bradstock, R.A. andKeith, D., 1993. Fire asathreatto populationsofrare plants.Australian
NationalParks&WildlifeServiceE—ndangeredSpeciesProjectNo.31
Auld,T.D.andO'Connell,M.A.,1991. Predictingpatternsofpost-firegerminationin35easternAustralian
Fabaceae.AustralianJournalofEcology16:53-70.—
Bell, D. T., Plummer,J. A. andTaylor, S. K, 1993. Seed Germination Ecologyin Southwestern Western
Australia. TheBotanicalReview.59—:24-73.
Bradstock,R.A.andAuld,T.D.,1995. Soiltemperaturesduringbushfiresinrelationtofireintensity:conse-
quencesforlegumege—rminationinsouth-easternAustralia.JournalofAppliedEcology32:76-84.
BriggsJ.aAndLeighJ.,—1991. RareorthreatenedAustralianPlants.ANPWSspecialpublicationNo14.
Brown,N. C,1993. PromotionofgerminationofFynbosseedsbyplant-derivedsmoke.NewPhytologist.123:
575-583. —
Cushwa,C.T.,Martin,R.E.andMiller,R.L.,1968. Theeffectsoffireonseedgermination.JournalofRange
Management21:250-254. —
DE Lange,J.H. and Boucher, C, 1990. Autecological studies on Audouinia capitata (Bruniaceae). I. Plant-
derivedsmo—keasaseedgerminationcue.SouthAfricanJournalofBotany56:700-703.
Floyd,A.G, 1966. EffectoffireuponweedseedsinthewetsclerophyllforestsofnorthernNewSouthWales.
AustralianJo—urnalofBotany14:243-256.
Floyd,A.G,1976. Effectofburningonregenerationfromseedsinwetsclerophyllforest.AustralianForestry39:
210-220. —
Grice,A.C.andWestoby,M., 1987. Aspectsofthedynamicsoftheseed-banksandseedlingpopulationsof
AcaciavictoriaeandCassiaspp.inaridwesternNew—SouthWales.AustralianJournalofEcology12:209-215.
Jeffery, D.J., Holmes, P. M. and Rebelo,A. G, 1988. Effectsofdryheaton seed germination in selected
indigenous—andalienlegumespeciesinSouthAfrica.SouthAfricanJournalofBotany54:28-34.
Keeley,J.E.,1987. —RoleoffireinseedgerminationofwoodytaxainCaliforniachaparral.Ecology68:434-443.
Keeley,J.E., 1991. Seedgermination and life historysyndromesin the Californian chaparral. TheBotanical
Reviewbl:H\-\16. —
Keeley.J.E.,MORTON,B.A.,Pedrosa,A.andTrotter,P.,1985. Roleofallelopathy,heatandcharredwoodin
thegerminationofchaparralherbsandsuffrutescents.JournalofEcology73:445-458.
ProcLinn. Soc.n.s.w., lis, 1995
