A Transient Soil Seed Bank for the Yam-daisy Microseris scapigera

4 Pages·1996·0.89 MB·English

by  Ian D Lunt

Contributions
A Transient Soil Seed Bank for the Yam-daisy
Microseris scapigera
Ian D. Lunt1
Abstract
An experiment was undertaken to assess the longevity of Microseris scapigera seeds in the soil.
Seeds were buried in small bags of nylon mesh in a long ungra/ed and long-unburnt Themeda
grassland in Canberra. Keplieale seed bags were unearthed alter 3, X and 12 months. M. scapigera
was found to have a transient soil seedbank, since virtually all seeds germinated rapidly, and no
viable seeds persisted for longerthan 3 months. The implications ofthese results for the eonscrva-
lion management ol M. scapigera in remnant grasslands are discussed. {Ttu Victorian Naturalist 113
(I) 1996, IS 19)
Introduction enables a population to re-establish after
Two centuries ago, Yam-daisies dig. mature plants are killed (e.g. by fire or
I), or Murnong (Microseris scapigera), grazing). By contrast, if all seeds germi-
were abundant across the grassy plains of nate quickly, the population cannot recov-
SOUth-eastertl Australia, providing a nutri- er if all existing plants die before flower-
tious food supply for many Aboriginal ing, unless new seeds migrate intothe site.
tribes (Ciott I983). One European settler
reported 'millions of murnong or yam, all Methods
over the plain', and the wheels of KM. Microseris scapigera seeds (propagules
(nil's dray 'used to turn them up by the of Microseris scapigera are technically
bushel' (Gott 1983). called 'achenes', but are here called
However, Yam-daisies proved extreme 'seeds' lor simplicity) were collected in
ly palatable to sheep and rabbits November 1993 from a remnant Thanccla
(Fan inglon and Mitchell 1966; grassland in Canberra, ACT. They were
Cunningham et al. 1981; Ciott 1983), as dried and stored indoors until early 1994,
noted by Cum 'several thousand sheep not when they were placed in bags of fine
only learnt to root up these vegetables nylon mesh (mesh size 0.85 mm x 0.95
[murnong] with their noses, but they for mm). Twenty filled seeds were placed in
the most part lived on them lor the first each bag, and broken and unfilled seeds
year, after which the root began to gel
scarce' (Curr IXX6, inGotl 1983).
Microserisscapigera is now uncommon
to rare in lowland grasslands and grassy
woodlands, and most large grassland pop
illations occur in ungra/cd remnants on
roadsides, rail lines ami cemeteries
(Prober and Thick- 1993; McDougall and
Kirkpatrick 1994). Fortunately, the species
remains common in other, less disturbed
ecosystems, such as dry sclerophyll
forests. Recently, as part ofa largerexper-
iment with ten grassland species, I invesli
gated the longevity ofM, scapigera seeds
m the soil. Seed longevity is a critical fac-
tor in plant ecology, as long-lived seeds
can form a buried seed bank, which
'School ol Botany, L»Trobe University, Bundoora Fig. l. Microseris scapigera (Photograph
Victorid J083, courtesyofJames Ross).
16
The Victorian Naturalist
Contributions
lwwaeenrrdeeidnbiustrchiaeerMddaedji.nurOaancVl2aol7sleMedyaynTehx1et9m9te4o,dCatahnegbrebarasgrssa- epwereterrdiedbaifrstohe.wrnAeiingfsheitwdeaianntndadct1o2bsvemieoodunsstlwhyesr,ienvbiruaetbcloaevl.-l
Airport. Microseris scapigera germination was
The study site supportedalong-unburnt not inhibited by a dense grass cover or
and long-ungrazed natural grassland with extremely low soil moisture levels. In
a dense, closed canopy of Themeda trian- August 1994, when the first seeds were
dra. Associated species includedAsperula unearthed, the topsoil was completely dry
conferta, Desmodium various, Eragrostis and dusty, and few seeds of the other
trachycarpa, Flantago varia, Tricoryne species studied had germinated (Lunt.
elatior and the exotic herbs, Conyza unpubl.). Drought conditions persisted
species, Hypochoeris radicata and throughout 1994, and there seems little
Tragopogon porrifolius. The soil was a doubt that all M. scapigera seedlings
dark brown, silty clay loam ofpH 6.1 (S. wouldhaveperished.
Sharp 1995,pers. comm.). Weathercondi- Little information is available on seed
tions during most of the experiment were persistence in Australian grassland herbs.
extremely dry, as the region was experi- M. scapigera was the only species, of the
encingaseveredrought. ten studied in Canberra, for which no
The bags were arranged (with more seeds remained viable after a year in the
bags containing seeds ofother species) at soil (Lunt, unpubl.). At least 20% of the
regularintervals on agrid measuring 19 m seeds of each of the other species
x 19.5 m. Half of the seed bags were remained viable after 12 months. Indeed,
pinned to the soil surface, beneath the more than 70% of Vittadinia muelleri
closed grass canopy, and the other half seeds, and over 80% of surface seeds of
were buried approximately 1 cm deep. Brizamaxima remained viableaftera year
Eight surface and eight buried bags were in the field (Lunt, unpubl.). Seeds of the
unearthed after approximately 3, 8 and 12 grassland daisies, Chiysocephalum apicu-
months. In total, 160 buried and 160 sur- latum and Leucochrysum albicans, can
faceseeds were unearthedateachdate. remain viable inthe soil forat least a year
(Gilfedder and Kirkpatrick 1993; Lunt
Resultsand discussion 1995), whereas most seeds ofspeciessuch
Virtually all M. scapigera seeds germi- as Burchardia umbellata, Craspedia vari-
nated rapidly, and no viable seeds persist- abilis and Rutidosis leptorrhynchoides
ed for longer than 3 months (Table 1). rapidly germinate in native grasslands,
Two intact and visually healthy seeds with few seeds remaining viable after 6
wererecovered at 3 months (Table 1), but months (Lunt 1995; Morgan 1995). Like
theirviability remains questionable as nei- M. scapigera, R. leptorrhynchoides has
ther could be induced to germinate in a declined dramatically in abundance since
Europeansettlemeni.
Table1.PercentageofMicroserisscapigera froTmhesedeadtsafprroemseonnteedpohpeurleatwieorne, gorbtoawinneadt
seedsremainingviableaftervariousperiodsin one place injust one year, and it remains
thesoil. tobe seen whetherseeds from otherpapu-
Date Event Surface Buried lations behave similarly. The grassland
seeds seeds habitat at Canberra is structurally similar
27May seedssown 100.00 100.00 to any unburntand ungraded grasslands in
1994 south-east Australia (e.g. Lunt 1990;
29August firstrecovery 1.00 0.00 McDougall and Kirkpatrick 1994).
1994 (3months) Microseris scapigera is a variable species
11999J5anuary sec(o8nmdornetchosv)ery 0.00 0.00 pswoiepteuhdlmabtaeihnoaynvsid,iosuatrsincmotcacfyuorrwsmesliln(GdLoietftufecr1o9cb8h3e)rt,ywseauenmnd
6May thirdrecovery 0.00 0.00 albicans(GilfedderandKirkpatrick 1994).
1995 (12 months)
17
Vol. 113 (1)1996
('ontrlhutlons
However, in a concurrent experiment in ing Europeancolonisation.Theunearthing
the Melbourne area, Watson ( 1995) found <>l mature plains, selective grazing of sur-
th.ii less than 2% "I M. scapigera seeds vivingplants,andabsenceofburiedseeds,
remained viable aftei being buried for 6 led tothe irretrievabledemiseofthisonce-
months in a recently burnt native grass abundantspecies.Thisscenarioechoesthe
land, and no seeds remained viable alter conclusion of many writers (e.g. Groves
being buried rot 6 months in an unburnl and Williams l"Kl: Kirkpatrick et. al.
grassland, which accords with the results I98K), that the most dramatic changes to
found here, grassland ecosystems occurred extremely
The absence ol ,i persistent seed hank quickly, within the lirst lew yearsofoccu
foi M ficapigeru has three major implies pationby Europeansandtheirsheep,
lions for conservation management, espe
eialiv in productive grassland remnants Acknowledgments
which rupidly accumulate a (hick grass This projeel was funded by the Australian
cov1e.tI.I11imiiatiun,r-e M scapigera plants are rNeasteuarrech<CgornasnetrvaadtmiionniAsgteernecdy,byuntdheeraacgrtasPsalraknsd
absent before a hie oi othei distnihanee. ^andConservation Service Considerable thanks
Hi... no seedling rccruitmenl can be duetoSarahSham,whocollectedtheseeds,
expected aftei the disturbance, unless "cl?cted '"' *,ud* Slle and i""1'"'1''1 •klom"1"
s,M,se,.esdSc,ls'atlia,'pyiieg'ta'iln'ndtltiolsiea,hecuikl,sesil,h.ea,Ianvte,th,heaeryl,saiitjae*.pep/(peaAainlp.dlipa,hugosen,se,hiit de„doniiehioniili,n(iiH,a.»|i||nie-|di-i^1anidtlm,'ii;aiiil,iMi.s.Is.weineiilndl.lMi.lavo.entsdasaKsniads/.ltlasn,Mneh.icwiee|r>dll;,il|ni|t,Mi.iho|,hei|emslls,n'^peieenddt,
aisnodlasteeeddrseamrneanutnslibkeylywitnod)h,e dispersed into ssc„ri;pllt,aShn;d|1J|a,mkie|s|(|R|yoscsompmroevnitdee<d|t„h,e„„p,ho„tuo.g,r„a.,p.,h..,
2, II mature plains do occur at the silo,
then substantial recruitment can only References
aofnclyco)uw.ervriiaamb.nlm,ededssieeaeetd,deslpwyirlo,ald1f,tuheceitipuorneys,oeanajts. i•olnfeowht.i,h(geihrf ' miSS"oneudutthgUhhW[Waaa>m'll,ueessG'.SM"y.(dS,on(ileMly"u)sCllob1nesme,rlv'lWa'"t.,iBto.'n,'"SMeiWrlevtishctoerepruenl,NNPe.eLww.
years(Lunt 1994) Curr, E.M (1886) 'The Australian Race',
1, II mature plants do occui ai the sue. (Government Printer: Melbourne),
otmchoecsnutrs(iielmemdneoltdiin.aagltl)er.leseye.reiadifstielrwmieslnlplunhi,as-veubnuglreinrkimenilgny,alatso F«T(IV|uiirncn.tgip/otnurio)ib'na.l.IP'MVeRMalenbpudoovurmMrtin,tjeici)ihSieolliKlla.liCAlounlss(e1m9r6v,6ia)tViiio-flntoeiiAiEuifntfheIoc'ntrisivvtolyl.
ed earlier in the year. Small seedlings are Olifedder.l endKirkpatrick, l.fl (1993) Qemtinable
(,l,iS,keeeld"y.l..itnogbereckirlulietdmebny•tamahiyghocicnutrensi,int*yfutfiurree ,rw,al,r1,e,,sn„"„a'•t1i',v„e'""ts'hpee"c"Mi"eiisd"'la"an"nd,dvse''xo»TtJia«cs«sm«a»in™ni*aa«.Ps»eBmbiieotlnwoaegiiencniaalli
years though), ConstivaitanM, m * 119,
tl.hoerI.efsptrhiwiinstc.ti.mi'poatdlreainlsmipp'earncotivesoosilltofsierbeeedoCnohrar*gn~erkcasts,slmtahaneydn GUfe,a!enmTdidadmnoogrre,prTheo'dilVo'pgeyra'e'non"df!n"it,ao"Klu"ir"rdpka'oi"ppsauy"t,lTraitLc^iekou.nllcs"o"o'c)l".h"aBr:,yT"as1su-(m1m>a9"n9"ai4l"ba)"l,n'
he (0 enable existing plants to produce eani AustralianJournalofBotany41,A3] 440,
more (lowers and seeds liom which new <;""^' "J|I"L,SM ^MurXnong^M^lcrosteris scapigera! a
seedlings can grow in the following yea, * """
tins scenario ol delayed post Ine recruit Oroves, Kit. ami Williams, u it. (1981), Natural
ineni differs from the model ofdirect, fire grasslands, '» 'Australian Vegetation' Bd R.H.
promoted recruitment from a sod seed Qreves.(CambridgeUniversityPress:Cambridge).
hhmiainentsk.i euwich,o,i.sc.yih,st,ie,smcso(memgo,nPluiyrdireeplolr>t/.7e;diW,farrokm KirGk.rp&aat,srsilc(a.kln,irdkJss„,aO„nladlfeCGderdmaeesrts,eyrIiWeosaonddlTFaaensndmssahn'aima,'(sTRa.Rsem(m1a9nn8ai8na)tn.
eta], l')X7). ConservationTrust:Hobart),
The absence ofa persistent seed hank in ' '""' ' " ||,""') A Hortotk survey ol the Derrlmut
tthh«.ea vsr.oanpdiidi,n,d,a.esmi,p„rs,oe,\.;oiidie.ma..n.sacdaidlpi.it'igotnraali fcoliluleowt-o Gn,.r„a„ms,s,l,a,,n„d,, „R,es,„e,rv«e,,„„/M,i„-,ii„.i,mvn(n1/c.VhV„i„c,t„or,i»a2.
18 The Victorian Naturalist
Contributions
Lunnitmi,pnleIi.cDga.rtai(so1sn9ls9a4fn)od.rsgVrpaaerscisialetasinodnwimitanhnfatlgioemwemeersniptnrcoaednudfcitrreie,sotnoarnoadf- Nrgaeetnluearttaiilcoisnstotf1or10et,mhen3ia0rn-t3c6og.rnassesryvawthiitoen.boTxhweooVdilcatnodrsiainn
LMucnDtJat'ioo,Cocuuonllrg.n.onasDPsa.leaelrlcd(vi,o1faf9Tit9KBhci5.oeo)Ct.nmoaanennSosddyefeear4KdLv3ito,arlrtwok4iilnp3aogaan9netd-nvrr4Bdiai4itc9oyNgk.lra,ooatfgsiJys.vslBie1ax.,nGn3d(ar.5eta9disA-svsu3)e6sl6taf(.orn1ra9dbl9ssi4)aii.nnn WPuarrJdbMRikoaueeru,gr,rreninnRiMoate.n.ltrWgC,oa..ft,PBi(i.n1ooHW9tn.h7ad7inr(b)ty1.yye92,E8s5a7s,er)cMel.3l.yd5eDR-rs.ge4ot,e6gap.reghnmeRyseiolrnbloaaefttriirvtoeoesgnngeo.ennotef,AaruathtDsiei.toaoJrntn.a,hlaaifatnIaneIdnd.r
South-eastern Australia.' (World Wide Fund for heath woodlandinthenorth-easternOtway Ranges
Nature:Sydney). following the wild-fire of February 1983.
Morgan,J.W.(1995).Ecologicalstudiesoftheendan- ProceedingsoftheRoyalSocietyofVictoria99,51-
gered Rutidosis leptorrhynchoides. I. Seed produc- 88.
tion, soil seed bank dynamics, population density Watson, S. (1995). Seed Ecology Of Five Native
andtheireffectsonrecruitment.AustralianJournal Forbs.In'ABasaltPlainsGrassland'.(Unpublished
ofBotany43, 1-11. thesis, Victorian College of Agriculture and
Prober,S.M.andThiele,K.R.(1993).Theecologyand Horticulture,Burnley:Melbourne).
Mueller - Commemorative Issue
The Victorian Naturalist
August 1996
1996 is thecentenary ofthedeathofBaron Ferdinand von Mueller. A special
issue ofThe VictorianNaturalistwill bepublished in August 1996tocommem-
orate Mueller's involvementwith theFNCV as afoundation member, andasits
firstpatron.
For this issue we have invited a number ofauthors to write on a variety of
topics including Mueller's collecting work, his and theclub's involvementwith
Wilsons Promontory, the FNCV's contribution towards his monument in St
Kildacemetery, aswell asotheraspectsofhis widernatural history interests.
We inviteYOUtocontributetothiscommemorativeissuebywritingonany-
thing you know about Mueller. Ifyou do not want to write, perhaps you have
some suggestions for topics or articles that you would like to see included?
Please letus know,assoon aspossible, ifyou haveanysuggestionsorare able
to write for the journal. Written material will be needed by the end of May
1996.
Theeditors arelookingforwardtohearingfromyou.
Allrepliesto:TheEditors, The VictorianNaturalist,
LockedBag 3,
POBlackburn3130,
orphone(home)0394359019.
19
Vol. 113(1)1996