1994.jufy

ForestEcologyandManagement96(1997)155-166ForestEcologyandManagementTruffleproductioninold-growthandmaturefirstandsinnortheasternCaliforniaJeffreyR.
Watersa~*,KevinS.
McKelveya,DanielL.
Luoma',CynthiaJ.
ZabelaaUSForestServicePacificSouthwestResearchStation,1700BayviewDriveArcata,CA95521,USAbDepartmentofForestScience,OregonStateUniversity,Corvallis,OR97331,USAAccepted19December1996AbstractFewstudieshaveexaminedfruitingpatternsofhypogeousfungi,andrelationshipsbetweensporocarpproductionofhypogeousfungiandforesthabitatcomponentssuchasorganicsoildepthandamountsofdecayedwoodarepoorlyunderstood.
Wesampledsporocarpsofhypogeousfungi(truffles)infourold-growth(>200years)andfourpaired,mature(ca100years)fir(Abiesspp.
)standsduringfoursampleperiodsin1993andthreesampleperiodsin1994intheLassenNationalForestinnortheasternCalifornia.
Truffleswerecollectedfrom4-m2circularplotssystematicallylocatedat36gridpointsperstandduringeachsampleperiod.
Habitatcharacteristicsweremeasuredin50.
3-m"circlescenteredateachgridpointin1993.
Wefoundatotalof46trufflespeciesin30.
4%ofthe2016totalplots,andthetotalstandingdryweightoftruffleswasequivalentto2.
43kgha-'.
Totalfrequencyandbiomassoftrufflesandnumberoftrufflespeciesdidnotdiffersignificantlybetweenstandtypesin1993or1994,butspeciescompositiondid.
Wefoundnosignificantassociationsbetweenmeasuresoftotaltruffleabundanceandmeasuresofhabitatstructureandcompositionatthe0.
25hagridscaleoratthe50.
3-m2habitatplotscale.
Atthescaleofthe4-m2truffleplot,plotswithdecayedwoodweremorelikelytohavetrufflesthanplotswithoutdecayedwoodduringthefinalsampleperiodofeachyear,buttheassociationwassignificantonlyin1993.
Meanorganicsoildepthwasgreaterinplotswithtrufflesthanplotswithouttrufflesineachsampleperiodinbothyears,butrankedvalueswereonlymarginallysignificantinonesampleperiod.
Goodness-of-fitteststothePoissondistributionindicatedthatindividualtruffleshadclumpeddistributions,butwecouldnotrejectthenullhypothesisofrandomdistributionoftrufflecollections.
Ourresultsindicatethattotaltruffleproductionhadrecoveredfromstand-replace-mentwildfireinthematurestands,andthattotaltruffleabundancewasnotstronglyassociatedwithhabitatcharacteristicswithintherangeofhabitatvariationexhibitedinthesestands.
Individualspecies,however,wereassociatedwithold-growthstandsandotherswithmaturestands.
01997ElsevierScienceB.
V.
Keywords:Abies;Hypogeousfungi;Sporocarps1.
IntroductionMostspeciesoffungithatproducemacroscopic,hypogeous(fruitbelowground)sporocarpsareecto-*Correspondingauthor.
Tel.
:(707)825-2955;fax:(707)825-2901.
mycorrhizalbasidiomycetesandascomycetes(Trappe,1962,1971,Miller,1983)andarecom-monlyreferredtoas'truffles.
'Someofthesporo-carpicspecieswithintheclasszygomycetesformectomycorrhizae(Endogonespp.
),andothersformvesicular-arbuscularmycorrhizae(Glomusspp.
andSclerocystisspp.
)(Maseretal.
,1978,Janusetal.
,0378-1127/97/$17.
0001997ElsevierScienceB.
V.
Allrightsreserved.
PIIS0378-1127(97)00016-9156J.
R.
Watersetal.
/ForestEcologyandManagement96(1997)155-1661995).
Mycophagy(fungusconsumption)isconsid-eredtheprimarymethodofsporedispersalforfungithatproducehypogeoussporocarps(FogelandTrappe,1978).
Hypogeoussporocarpsarecommoninthedietsofsmallmammalsintemperateforestsdominatedbyectomycorrhizalfungithroughouttheworld(e.
g.
Tevis,1953,FogelandTrappe,1978,Maseretal.
,1978,UreandMaser,1982,Taylor,1992,Johnson,1994),aswellastropicalforestsdominatedbyvesicular-arbuscularmycorrhizalfungi(Janosetal.
,1995).
Totalsporocarpproductionandspeciescomposi-tionofmycorrhizalfungiareexpectedtochangeasforeststandsagefollowingdisturbance(DightonandMason,1985,Termorshuizen,1991,Vogtetal.
,1992).
Mostspeciesofectomycorrhizalfungiareconsideredobligatelydependentontheirhostplantsforcarbon(Harley,1971,Hacskaylo,1973,Lastetal.
,1979),sostand-replacementdisturbanceisex-pectedtonegativelyaffecttruffleproductionforsomeperiodoftime,atleastuntilectomycorrhizalhostsbecomereestablished.
Disturbanceoftheor-ganicsoilisalsoexpectedtoaffecttruffleproductionbecausebothectomycorrhizae(Harveyetal.
,1978,1979)andtruffles(Waters,JR.
,Luoma,D.
L.
,per-sonalobservation)areprimarilylocatedinorganicsoillayersandtheuppermineralsoil.
Previousstudieshaveshownthattotaltruffleproductionwaslowinyoungstands.
Vogtetal.
(1981)foundthattruffleproductionwassignificantlylessina23-year-oldstandofAbiesamabilisthanina180-year-oldstand,andthattrufflecompositiondifferedbetweenthetwostands.
Twostudiesfoundthattrufflefre-quencyandbiomassweresignificantlylessinDou-glas-fir(Psuedotsugumenziesii)plantations70yearsoldeitherwasgreaterthanordidnotdiffersignificantlyfromtruffleproductioninlate-seralstands.
Luomaetal.
(1991)foundthatstandingcropbiomasswasgreatestinmesicmature(80-199years)(2.
2kgha-')Dou-glas-firstandsintheCascadeRangeofOregon,followedbymesicold-growth(>200years)(1.
6kgha-'),mesicyoung(standslocatedinWash-ington,butthattrufflebiomasswassignificantlylessin60-year-oldstandsthatoriginatedfollowingclearcuttingandburning(0.
78kgha-I).
Otherstud-iesoftruffleproductionhavefocusedonseasonalandannualvariationinsporocarpproduction(Fogel,1976,FogelandHunt,1979,States,1985,HuntandTrappe,1987,Luoma,1991).
Inapreviousstudydesignedtoevaluateassocia-tionsbetweennorthernflyingsquirrel(Glaucomyssabrinus)densityandforeststructure,wefoundthatmeantrufflefrequencydidnotdiffersignificantlybetweenold-growthand75-95-year-oldfir(Abiesspp.
)stands,butthatbothweresignificantlygreaterthaninshelterwood-loggedfirstands;meantrufflefrequencywasgreatestinold-growthstandsandintermediateinthe75-95-year-oldstands(WatersandZabel,1995).
Tobetterunderstandtherelation-shipsbetweentruffleproductionandstandageandstructure,wedesignedastudyspecificallytocom-paretruffleproductionbetweenold-growthandma-turefirstands.
Ourprimaryobjectiveswereto(1)comparetotalfrequencyandbiomass,numberofspecies,andspeciescompositionoftrufflesbetweenold-growthandmaturefirstandsand(2)evaluateassociationsbetweentotaltruffleabundanceandmeasuresofhabitatstructureandcomposition.
2.
Methods2.
1.
StudyareaStandswerelocatedwithintheSwainMountainExperimentalForest,whichislocatedatthesouthernendoftheCascadeRangewithintheLassenNa-tionalForestinnortheasternCalifornia.
Weusedapairedstudydesigntohelpcontrolforsitediffer-encesotherthanstandage.
Welocatedfourareaswhereanold-growthstandwaslocatedincloseproximitytoamaturestand.
Old-growthandmaturestandswereseparatedby100cm)locatednearthefourold-growthstandswas250years(range:186-383years).
Maturestandsoriginatedafterstand-replacementwildfireandweredenseandhomogeneousinstruc-ture.
Fewresiduallogs,snags,ortreeswerepresent.
Becausematurestandshadclosedcanopies,virtuallynoherbaceousplantsorshrubsoccurredintheun-derstory.
Oldshrubstemsindicatedthatmaturestandsweredominatedbybrushfieldsforsomeperiodoftimeafterwildfireoccurred.
Weestimatethatthesestandsrangedfrom80to110yearsold.
Themedianageestimatefromcoring20randomlyselecteddom-inantandcodominanttreeswas84years(range:64-108years).
WeobtainedweatherdatafromastationlocatedinChester,California,ca16kmsouthwestofthestudyarea.
Totalprecipitationwas86cmin1992,105cmin1993,and70cmin1994.
Average(1947-1989)annualprecipitationattheChesterweatherstationwas84cm.
Most(280%)oftheprecipitationatSwainMountainExperimentalForesttypicallyfallsassnow.
2.
2.
SamplingproceduresWithineachoftheeightstandsweestablisheda6X6gridwith10-mspacing(0.
25ha).
In1993wemeasuredhabitatcharacteristicsin50.
3-m'circularplots(4-mradius)centeredateachgridpoint.
Withineachofthesehabitatplotswemeasuredthediameteratbreastheight(DBH)ofalltrees212cmDBHandtalliedtreesl-5cmDBHand6-11cmDBH.
Wealsomeasuredthelength,mid-pointdiameter,anddecayclass(Maseretal.
,1979)ofportionsoflogswithinthehabitatplotwithamid-pointdiame-ter>10cm.
Truffleswerecollectedwithin4-m"circularplots(1.
13-mradius)positionedsystematicallyneareachofthe36gridpoints.
In1993truffleswerecollectedduringfoursampleperiods,andthefourplotswereclusteredaroundeachgridpoint.
In1994truffleswerecollectedduringthreesampleperiods,andthethreeplotswereclusteredaroundeachof36pointsoffsetfromthe1993points.
Plotswereneverlocatedonpreviouslysampledareas.
Wesampledatmonthlyintervalswiththefirstsampleoccurring6-7weeksaftersnowmelt.
Thetwoupperelevationpairsweresampled2-3weekslaterthanthetwolowereleva-tionpairsbecauseofdelayedsnowmelt.
In1993.
SamplePeriod1beganonJuly7,Period2onAugust3,Period3onSeptember8,andPeriod4onOctober13.
In1994SamplePeriod1beganonJune21,Period2onJuly26,andPeriod3onAugust19.
Afterestablishingthe4-m2truffleplot,wemea-suredthelengthanddiameterofportionsofdecayedlogs(classes4-5;Maseretal.
,1979)withinthetruffleplot.
(Decayedlogsweresoftandellipticaltoflatincross-sectionalshape.
)Nextwedugashallowsoilpitca30cmwideandmeasuredthedepthoftheorganicsoillayer(litterandhumuslayerscombined)atthreesystematicallypositionedpoints.
Decayedlogsandorganicsoildepthweremeasuredwithintruffleplotsinallsampleperiodsexceptthefirstsampleperiodof1993.
Wethenusedfour-tinedrakestocarefullyrakethroughthelitter,humus,andupper5-10cmofmineralsoil.
Trufflecollections(alltrufflesofthesamespeciesfoundinaplot)weresenttoCorvallis,Oregontobeidentified,air-dried,andweighed.
Tocomparesoilmoisturebetweenstandtypes,wecollectedsoilsamplesthreetimesduringthe158J.
R.
Watersetal.
/ForestEcologyandManagement96(1997)155-166study:Octoberof1993andJulyandOctoberof1994.
Weusedasmallcan(5cmdiameterX8.
5cmlength)tocollectmineralsoilsubsamplesfromadepthof5-10cm.
Thirty-sixsystematicallylocatedsubsampleswerecombinedintoonecompositesam-pleforeachgrid.
Soilsampleswereoven-driedat105°Cfor48h,andsoilmoisturewasdeterminedgravimetricallyforeachcompositesample.
2.
3.
AnalysesWecomparedmeansofhabitatvariablesbetweenold-growthandmaturegridsusinganalysisofvari-ance(ANOVA).
Weusedarandomizedcomplete-blocksANOVAdesignforthisandeachsubsequentANOVAtest;eachpairofold-growthandmaturegridswasablock.
Logsindecayclassesl-3wereclassifiedasundecayedandlogsindecayclasses4-5wereclassifiedasdecayed.
Weusedrepeated-measuresANOVA(samplepe-riodwastherepeatedfactor)totestwhethertotaltrufflefrequency(percentageof36plotsinwhichoneormoretrufflecollectionwasfound),totaltrufflebiomass(dryweight),andnumberoftrufflespeciesvariedbetweenold-growthandmaturegrids.
ANOVAswereperformedseparatelyfor1993(foursampleperiods)and1994(threesampleperiods).
Biomassvalueswerelogtransformedtoreduceskewness.
Tocomparetrufflecompositionbetweenstandtypes,weusedacontingencytabletotestwhethertherewassignificantassociationbetweenstandtypeandtrufflespecies.
Numbersoftrufflecollectionswerepooledacrosssampleperiodsandyearsforthistest.
Weincludedtenspeciesinthisanalysisthatmetthefollowingconditions:presentinthreeormoreofthefourgridsandoneormoreofthetwostandtypes,andcomprised>2%ofthetotalnumberofcollectionsfoundduringthestudy.
Expectedfrequencywas>5foreachcellwithinthis2X10table.
Weevaluatedassociationsbetweentrufflepres-enceorabundanceandmeasuresofdecayedwoodandorganicsoildepthatthreespatialscales,andbetweentotaltruffleabundanceandothermeasuresofhabitatstructureandcompositionattwospatialscales.
Atthescaleofthe0.
25hagrids,wecom-putedSpear-manrankcorrelationsamongtheeightgridsbetweentotalfrequencyandbiomassoftruffles(pooledacrosssampleperiodsandyears)andeightmeasuresofhabitatstructureandcomposition:whitefirbasalarea,redfirbasalarea,snagbasalarea,numberof1-5-cm-DBHstems,numberof6-1l-cm-DBHstems,surfaceareaofundecayedlogs,surfaceareaofdecayedlogs,andorganicsoildepth.
Valueswerethemeansfromthe36habitatplotssampledineachgrid.
Atthescaleofthe50.
3-m2habitatplots,weevaluatedassociationsbetweentwomeasuresoftotaltruffleabundanceandhabitatcharacteristicsusingthe1993data.
Thefirstmeasureoftruffleabundancewasthenumberofplotsateachgridpointinwhichoneormoretrufflecollectionswerefoundduring1993;valuesrangedfrom0to4becausefourplotsweresampledateachgridpointin1993.
(In1994truffleplotsfelloutsideofthe50.
3-m2habitatplots.
)Thesecondmeasureoftruffleabundancewasthesumdryweightoftrufflecollectionsfoundinthefourplotsateachgridpoint.
Wepooledacrossstandtype(n=288gridpoints)andperformedastepwisemultipleregressionforeachmeasureoftruffleabun-dance.
Independentvariableswerethesameeightvariablesusedinthepreviousanalysis,excepttheywerenotaveragedacrosshabitatplots.
Thesignifi-cancelevelforentryandremovaltothemultipleregressionmodelwas0.
15.
Atthescaleofthe4-m2truffleplot,wealsoevaluatedassociationsbetweentrufflepresenceand(1)presenceofdecayedwoodand(2)organicsoildepth.
Weuseda2X2contingencytabletotestforassociationbetweentrufflepresence(plotswithtruf-flesandplotswithouttruffles)andpresenceofde-cayedwood(plotswithnodecayedwoodandplotswithatleastsomedecayedwood).
WeusedtheWilcoxonrank-sumtest(SASInstituteInc.
,1989,p.
1196)tocompareorganicsoildepthvaluesbetweenplotswithtrufflesandplotswithouttruffles.
TestswereperformedseparatelyforSamplePeriods2-4in1993andl-3in1994.
Wealsousedthefrequencydistributionsofindi-vidualtrufflesandtrufflecollectionstocharacterizetheirspatialdistributions.
Weusedgoodness-of-fitteststothePoissondistribution(Zar,1984,p.
409)totestthenullhypothesesthatindividualtrufflesandtrufflecollectionswererandomlydistributed.
Forthefirsthypothesis,wecomparednumbersoftrufflesfoundpertruffleplotwithnumbersexpectedbasedJ.
R.
Watersetal.
/ForestEcologyand/Management96(1997)155-166onthePoissondistribution.
Wetestedeachyear-by-sampleperiodcombinationseparately(n=288plotsforeachoftheseventests).
Forthesecondhypothe-sis,wecomparednumbersoftrufflecollectionsfoundpergridpointtonumbersexpectedbasedonthePoissondistribution(fourplotspergridpointweresampledin1993andthreeplotspergridpointweresampledin1994).
Wetestedeachyearseparately(n=288gridpointsforeachofthetwotests).
Wepooledacrossstandtypeforbothsetsoftestsbe-causecontingencytablesindicatednosignificantas-sociationbetweenstandtypeandnumbersoftruf-fles/plot(x2=1.
51,d.
f.
=3,P=0.
679)orbe-tweenstandtypeandnumbersoftrufflecollectionspergridpoint(x2=2.
27,d.
f.
=6,P=0.
894).
Wepooledfrequencyclassessothatnoclasshadanwerewhitefir,onewaslodgepolepine(Pinuscon-torta),andonewasJeffreypine(P.
jeffreyi).
Old-growthgridshadmuchgreatermeanvaluesfortreesl-5cmDBH,trees>90cm,snags>52cm,andpercentgroundcoverofundecayedanddecayedlogs>25cm(Table2).
Maturegridshadmuchgreatermeanvaluesfortrees12-27cm,trees28-52cm,andsnags12-52cm.
SoilmoistureinOctoberof1993wasslightly,butsignificantly,greaterinma-turegrids.
Organicsoildepthdidnotdiffersignifi-cantlybetweenold-growthandmaturegrids.
3.
2.
Trufflefrequencyandbiomass,speciesrichness,andcompositionexpectedfrequency12cmDBHcountedwithinthe288habitatplots,530wereredfir,704Table2Wesampled8064m2over2yearsandfoundtrufflesin30.
4%ofthe2016plots;totalstandingdrybiomasswasequivalentto2.
43kgha-'.
Neithermeantotalfrequency(Fig.
1)ormeantotalbiomass(Fig.
2)oftrufflesdifferedsignificantlybetweenold-growthandmaturegridsin1993or1994.
In1993meantotalfrequencyandbiomasswerelowestinJuly1,butin1994declinedfromJune1throughAugust3.
Means(x),standarderrors(SE),andPvaluesfromANOVAtestscomparinghabitatvariablesbetweenfourold-growthandfourmaturefirstandsOld-growthMatureStandtype,PaXSEXSETreesl-5cmDBHha-1Trees6-l1cmDBHha-'Trees12-27cmDBHha-]Trees28-52cmDBHha-'Trees53-90cmDBHha-tTrees>90cmDBHha-'Snags12-52cmDBHha-'Snags>52cmDBHha-'%Groundcoverundecayedlogs10-25cmdiam.
%Groundcoverundecayedlogs>25cmdiam.
%Groundcoverdecayedlogs10-25cmdiam.
%Groundcoverdecayedlogs>25cmdiam.
Organicsoildepth(cm)%SoilmoistureOctober1993July1994September1994355.
1158.
333.
2353.
7117.
9182.
4349.
5100.
0708.
7172.
735.
4530.
592.
627.
669.
123.
54.
70.
045.
66.
5193.
45.
52.
30.
00.
880.
222.
371.
330.
450.
380.
730.
171.
325.
351.
510.
625.
180.
174.
6520.
648.
946.
345.
311.
20.
058.
90.
00.
540.
200.
380.
120.
2928.
40.
819.
20.
616.
40.
831.
720.
717.
00.
50.
0240.
80.
2870.
80.
5760.
1480.
2990.
0300.
0010.
3190.
0840.
0460.
2510.
0520.
176aDegreesoffreedomforeachtestwere1forthenumeratorand3forthedenominator.
160J.
R.
Watersetal.
/ForestEcologyandManagement96(1997)155-16660-(a)50-JulyAugustSeptemberOctoberJuneJulySamplePeriodTAIIAugustFig.
1.
Meansandstandarderrorsoftotaltrufflefrequencyinfourold-growthandfourmaturefirstandsduring(a)foursampleperiodsin1993and(b)threesampleperiodsin1994.
StandtypeeffectfromrepeatedmeasuresANOVAwasnotsignificantin1993(F,,,=0.
10,P=0.
775)or1994(F1,3=0.
62,P=0.
488);sampleperiodeffectwasnearlysignificantin1993(F,,,=3.
32,P=0.
071)andsignificantin1994(Fz,6=13.
39,P=0.
006).
Wefoundatotalof46speciesoftruffles(Table3).
Fourofthesespeciesweresecotioidfungi(Table3)whichareconsideredevolutionaryintermediatesbetweengilledmushroomsandtruffles.
Wegroupedsecotioidspecieswithtrufflesbecausetheywereecologicallysimilarinbeingmycorrhizalandprimar-ilyhypogeousinfruitinghabit.
Onlythreespeciesindividuallycontributed>4%ofthetotalnumberofcollectionsfoundandtenspeciescontributed>2%.
Gautieriamonticolawasthemostabundantspecies;itcomprised30.
1%ofthetotalnumberoftrufflecollectionsand56.
5%oftotalbiomass.
ThenexttwomostcommonspecieswereAlpovatrappei,whichcomprised8.
4%oftotalcollectionsand6.
6%oftotalbiomassandGymnomycesabietis,whichcomprised8.
8%oftotalcollectionsand4.
0%oftotalbiomass.
Thirty-eightspecieswerefoundinbothold-growthandmaturegrids.
Meannumberoftrufflespeciesdidnotdiffersignificantlybetweenstandtypesin1993(F1,3=0.
74,P=0.
452)or1994(F1,3=0.
16,P=0718).
Associationbetweenstandtypeandtrufflespecieswassignificant(Fig.
3)indicatingthatcompositionFig.
2.
Meat1sandstandarderrorsoftotaltrufflebiomassinfourold-growthandfourmaturefirstandsduring(a)foursampleperiodsin1993and(b)threesampleperiodsin1994.
StandtypeeffectfromrepeatedmeasuresANOVAwasnotsignificantin1993(F1,3=3.
38,P=0.
163)or1994(F,,,=0.
68,P=0.
470);sampleperiodeffectwassignificantin1993(F3,9=23.
17P0.
320),norwereanyofthecorrelationswithtrufflebiomass(P>0.
139).
Atthescaleofthe50.
3-m2habitatplots,littleofthevariationineithermeasureoftruffleabundancewasexplainedbytheeightObservedfrequencyExpectedfrequency200-150--loo-50,r-lo-f23>3NumberofTruffles/Plot120100806040200009I01277(a)83PlotswithnotrufflesPlotswithtruffles1205-j--6f-+74204;214_-AugustSeptemberOctoberNumberofCollections/GridPoint108JuneJufyAugustFig.
6.
(a)Observedfrequenciesoftruffleplotswithdifferentnumbersoftrufflesfound/plotforthe288truffleplotssampledinAugustof1993andexpectedfrequenciesbasedonPoissonexpec-tations;goodness-of-fitresult:x2=201.
40,d.
f.
=3,P3truffles/plot(tailsofthedistribution)thanexpectedbasedonPoissonexpec-tations(e.
g.
,Fig.
6a),indicatingdistributionsoftruffleswereclumped(SokalandRohlf,1981,p.
89).
Wefoundnoevidence,however,ofclumpeddistributionsoftrufflecollectionsatthegrid-pointscale(e.
g,Fig.
6b).
4.
DiscussionOurresultsareconsistentwiththoseofNorthetal.
(1997)infindingnosignificantdifferenceintotaltruffleproductionbetweenmatureandold-growthconiferstands.
Luomaetal.
(1991)didnotstatisti-callycomparetruffleproductionamongstandageclasses,butfoundthatstandingcropbiomasswasgreaterinmesicmaturestandsthaninmesicold-growthstands.
Althoughwefoundnosignificantdifferencesintotalfrequencyorbiomassoftrufflesandnumberoftrufflespecies,speciescompositiondiddiffersignificantlybetweenold-growthandma-turestands.
Ofthetenmostfrequentlyfoundspecies,fourweresimilarlyabundantinbothstandtypes,fourwerefoundmorefrequentlyinold-growthstands,andtwowerefoundmorefrequentlyinma-turestands.
Inapreviousstudy,wefoundnosignifi-cantdifferenceintotalfrequencyorbiomassoftrufflesamongunitswithinalargewhitefirstandthathadnotbeenthinned,moderatelythinned,andheavilythinned10yearspreviously,butcompositiondifferedsignificantlyamongthinlevels(Watersetal.
,1994).
Wefoundnosignificantassociationsbetweento-taltruffleabundanceandmeasuresofstandstructureandcompositionatthe2500-m"gridscaleor50.
3-m"habitatplotscale.
ThesmallR2softhemultipleregressionmodelssuggestthattotaltrufflecollec-tionswererandomlydistributedwithinthestandswesampled.
Wecautionthatourhabitatanalyses,aswellastheanalysesoffrequencydistributionsoftrufflecollections,werewithtotaltrufflecollections,notcollectionsofindividualtrufflespecies.
Ourstudywasnotdesignedtoevaluatehabitatassocia-tionsorspatialdistributionsofindividualspecies,andwewouldhaveneededlargersamplesizestoperformsimilaranalysesatthespecieslevel.
Associationsbetweentrufflepresenceandpres-enceofdecayedwoodandorganicsoildepthatthe4-m2truffleplotscalewereweak.
Twopublishedstudieshavequantitativelyevaluatedassociationsbe-tweentruffleproductionanddecayedlogs.
Amaran-thusetal.
(1994)andClarksonandMills(1994)foundsignificant,positiveassociationsbetweentruf-fleproductionanddecayedlogs.
Althoughwefoundsignificantassociationatthetruffleplotscalebe-tweentrufflepresenceandpresenceofdecayedwoodinonlyoneofsixcomparisons,associationwasgreatestinbothyearsduringthelastsampleperiodwhensoilsweredry.
Decayedlogsretainlargeamountsofwaterandmayinfluencetruffleproduc-tionmostwhensoilsaredriest(Amaranthusetal.
,1994).
Wefoundevidencethattotaltruffleswereclumpedbutnoevidencethattotaltrufflecollectionswerenonrandomlydistributed.
Thetendencyoftruf-flestobefoundinclustershasbeenshownornotedJ.
R.
Watersetal.
/ForestEcologyandManagement96(1997)155-166165byseveralauthors(Fogel,1976,States,1985,HuntandTrappe,1987).
5.
ConclusionsWeconcludethattotaltruffleproductionhadrecoveredfromstand-replacementwildfireinthematurestandswithinca100yearsofstandorigin.
Weakassociationsbetweentotaltruffleabundanceandhabitatcharacteristicssuggestthattotaltrufflecollectionswererandomlydistributedwithinthestandswesampled.
Speciescompositionoftruffles,however,diddiffersignificantlybetweenstandtypes;somespeciesshowednoassociationwithstandtype,otherswereassociatedwithold-growthstands,andotherswithmaturestands.
AcknowledgementsWethankthefollowingpeoplefortheirhardworkinthefield:K.
K.
Busse,J.
A.
Ditto,T.
H.
Heinz,T.
L.
Hines,G.
R.
Hodgson,M.
E.
Kamprath,T.
D.
Lesh,C.
V.
Ogan,D.
A.
Reese,K.
L.
Shimizu,K.
F.
Steele,C.
R.
Voss,J.
L.
Wanamaker,andD.
P.
Wheeler.
M.
J.
Castellano,D.
L.
Luoma,andJ.
M.
Trappeidentifiedthetruffles.
WethankB.
D.
HafarforhertremendoushelpwithdataprocessingandB.
J.
DitmanoftheLassenNationalForestforherenthusiasticsupport.
WealsothankJ.
BaldwinforhisstatisticalreviewandM.
J.
CastellanoandM.
P.
Amaranthusfortheirhelpfulcommentsonthemanuscript.
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