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1 The EclgicalSciety Sciety fjapan Japan V!. 25, N. 1 B Jasth F.ig..\ ftts Mar., 1975 smmson I.SOME [[HE RA[[E OT DECA"S( OF WOOD LurER ON THE FQREST FLOORi) PHYSICAL PROPER[[{ES OF DECAYING WOOD TsuyshiYONEDA,Dqpartment f Bikrgy. V}tiversity. Osczka558lhcully f Scienee,Oszzka(]ity ptjll}ctstr6tsntmuts}twgeicee-g-6-ee I. tsditicdigntsutler}c-dvizr Jltpmsizsc\mvgK!itim\eteg )k di pt Synpsis YNEDA, Tsuyshi (Dep Ḅil.,Fac. Sci.,Osaka City Univ,, Osaka).I975.Studies n the rate f decayf wd littern the frestflr.i.sme physicalprpertiesf decayingwd. Jap.J, EcL, 25 :40A. Physicalcharacters f dead wd samples, such as apparent density(p),water cntent (H), ceemcient f desiccatien (Ft), slidity (s), and theirinterrelatins under natural cnditins were studied in the evergreen ak frests f Japan.The water cntent (H) was fairly stable thrughut the year,but itsmean value and variance inereasedwiththe decrease f p. Tlie wet weight fthe samples tended t decteasexpnentially due t desiccatin, and the relative rate f desiccatin n an expnential basis(")was greaterinthe samples with smaller values f p. The E:-prelatin was hyperb!ic, while the g-p regressien was linear Ȧ psitive crrelatin was fund between p and the slidity Cs)deteTmiried by Yamanakas slidity meter. The irnprtane f p as the mst infiuencialfactrin the prcess fwd decmpsitin was suggessted. Ifttrductin Thugh the rate and press f litterdecempsitin within frestecsystems have been studied by many authrs, mst f the studis dealtnly withleaf]itter. Hwever, wd litteralsfrmsa largprprtin f the substrate decmpsedn the frestfir.the nn-leaf litter acceunts fr abeut 1/3 f the tetallitter-fall in mst frests, smetimes as much as l/2in clknax frests (KiRA & SHmEi, l967),and ismstly cmpsed f dead wdy rgans. The wd litter/ttal Iitte rati was O.42 in 1968 in an eyergreen ak frestat Minamata where thisstudy was carried ut (KAwA- HARA, l970).nevertheless,relatiyelylittle attentin paid has been by eclgists n wd decmpsitin (KOHNELT,1961; WATANABE, 1966; SATcHELL, 1971),thugh there were a number f studies en the durabilityf wd materials in practical use (e.g. HENMMi & AKAi, 1945). AcceptedDec. 24,1974 1) Cntributins frm JIBP-PT N, 181. This studyfund was supprted by a speeial prject research frm theministryf Educatin. Ihisstudy was intended1) t assess the part f wd decmpsitinin the material eycle in frest ecsystems, and 2) t analyze the system cmpsed f decmpser rganisms, the wd substratum and itsphysical envirnment, which fbrms a unique subsystem in the ttalfrest ecsystem. Wdy rgans decmpsemre slwly than Ieaves, while their riginal shape and vlume are maintajned fr quite a lng time under the prteetin f bark, which isvery resistant t decay.unlike dead leayes, which are very thin and fragile, the decirrpsing wd remains as a fairly independent system and itslargevlume, aliwsthe analysis f the system withut mierscpical andfr mierbilgical methds ften used frleafdecrrrpsitin study (SAiT, 1955,1956,1960;WipmcAMp,1966,1971). Itisdiflicult t f11wthe curse f wd decmpsitin cntinuusly ver a lng time, but the apparent density(velumedensity; p) may be used. as a cnvement measure f the grade f decay,ifthe apparent vlume remains the sarne inspite f the prgress f decmpsitin.the grade f decay is then given by wlwetrpvypv===p!p 40

2 Vl.25,N. 1 JAPANESEJOURNAL OF ECOLOGY Mar.,1975 where w. and ve refer t the initial and current dry weight f a dead wd sample, and p. and p te the initialand current apparent density respectively. Nainely p represents the grade f decempsitinas far as p is the sarne in all sainples. Therefre, emphasis was laidinthis study n the apparent dcnsity f dead wd samples and itsinfiuencen ther physical characters was examined. I we much and express my gratitude t Pr TatsuKiRA, Pr Kazu HzuMI and my clleaguesin the Osaka City Universityfrtheiradvice and criticism. Researchsite Materia1and Methds Fieldexperiments were carried ut mstly inthe evergreen ak frestat Minamata, Kumamt Prefecture,Kyushu, with supp]emcntary studies in a similar frestn (Mt.)Kasugayarna,Nara Prefecr ture,eentral Henshu. a) Minarnata SpeeialResearch Area f IBP The Minamata SpecialResearch Area fribpi PT Research (33ha) issituated near the Kumamt PreefKagshima Pref.brder,sme 16 kn east f Minamata City and between450 m and 637 m in altitude. The area has been abandned fbr years after tb defrestatinfr charcal preductin,and isnw cvered by regenerated secndary frests predminated by (lastanpsis cuspidta species. The dctaiied and a few evergreen 2uercus deseriptinf the vegetatin was givenby OMuRA et al. (l969), Dead wd samples frthe present study were 230C (KiRiTA, cllected,arund Plt1,2 and 3, permanent quadrats established n the NW slpe inthisarea. The annual mean temperature,is abut 13eC; the temperatureat the sil surface ranges frm 40C t 1971); theestimated annual precipitatin isabut 2000 mm. b) Kasugayama frest This isals an evergren ak stand f the warmtemperate zne in the preserved natural frest area at Nara, where CZistanpsis cuspiclata ard Cuercus grlva werc the mst imprtant species (cflkirmra (1971)fr furtherdescriptin f the frest).[i{he estirmated armual mean temperature isabut l30c; the temperature at the sil surface ranges frm 2eC t 250C (ICiRiTA, 1971).and the estimated annual precipitatinis abut 1500 mm. Dead wd samples were cellected near the stand studied by KIRITA (1971). lhterial Dead wed samples (fvarius species, unidentified, but nt includingcnifers) f a standard size (3-4 cm in diameter;cutintthe lengthef abut 12 tm) were used fr the experiments. Physical parameters measured were wet weight (PV), dry weight (w), length (l) and diametersat bth ends (bachin tw directiens,di, d2 and dla,dal)ṫhe as a trun- ttal apparent vlume (apprximated cated cnej (V), apparerit density (p) and water cntent (H) were calculated by the fllwing.equatlns, V=-O.065 {(th+de +de +ct4)2 - (di+de) (de+mp} l p==wlv H- (Pif-w)1ni Experiments The,date,place and ther cnditins f the experiments are shwn in Table 1. Results 1. Apparentdensity(p) and water cntent <H) under natural cnditins The relatinship between.the mean apparent densitylp) andmcan water cntent (H) f the dead Table 1.0utlinesf theexperiments cvered by this paper. Exp. n. * Seasn PlacePhysical Number parameters f measured sarnples ,.Apr Minamatap,p, 16* ** p,p,p,p,p,p,p,p, H EHffHHHHHHHHHHHpsHH " Nv , Mar. 72 July 46 Sept. S2 Nv. 43l ,Jan. Mar May Aug June 29 July Aug. Dec. 1970, Apr. 1971, Mar. Sept. 1973,Dec. 1970, July Dec. Kasugayama p, p,p,p,p,p,p,p,p,p, Minamata 37 Lab. at 30.0ec." at 27.2 ec

3 Vl. 25, N. 1 B 7is ts ge.\k di Mar., 1975 Table2. Ayeragewater cntent (H)and it standard deviatin(a)freach p-elassin Exps.9 and 10. pig/cmsl Exp.9 Exp. 10 H [glgla O -O.05 O.05--O.tO.l-e.ls.Is-.2e O.20-O.25 O.25-O.30 O.30-O.35.3sn.c O.40-O.45 O.45-O.5O O.50-O.S5.ssn.6 H [gfgla O.82O.66O.54.4eO O.73O.59e.48O.34O.28O.19O.10O O.70O.61e.57O O.97O.74O.49O.42O.32O.23O.61O.10 e.s Table 3. Values f theparametersa and B f Eq. (1) estimated in respctive expriments. Seasn Exp. A n. iglcms] Bie/gl A/BIg/ems] Minamata Jan Mar Mar Apr May 1972 July 1971 Aug Sept Nv Nv Kasugayama June 1969 July ,O -xmvm-lk--8t8tstslg-ee O.2 O,1 O.1 2.D 1,O e 02 e.fi 738l O.416O.418O.426O.683O.540.ssgO.536O.640O.670O.256 O.40O.24O.26O.26O:71O.30O.671.e.67O O O.80,."1..se 1112 O.497O.527 O.69O.17 O Average O.514O wd samples under natural cnditins isshwn in Table 2 and Fig. 1, in which the samples were classined int p-classes and the mean values f p and Hin each class were taken as p and HL H decreased hyperblically with the increase f Pinevery experiment, althughthe varianee f H was fairlylarg(table2).t[herelatin uld be apprximated by theequatin, jelr-=ca/p)-b (1) where A and B are the censtants specific t the axperiment cncerned. The values f the parameters A and B f Eq. (1) estimated frthe respective experiments are given in Table 3.A isrelated directly t the misture cntent f deadwd, and ranged frem O.416 crn3142 e.s e z 1.0.s O.2 O.1 e,2,1 O.2 OS O.1,2 O.5 zq 1. as a2 O.2 D.5 Mean apparent density,p (glcms) Fig.1.Crrelatinbetweentheaverage water cntent (H) and mean apparent density(p)in dead wd samples under natural cnditins n the frest fir. g t O.670 cm3/g except inexp. 6, in which the samples were very dry,the narrw range f A suggests that the humidityf the sll, n which thc samples were left, was fairlystable independently Qf seasns. The parameters B, n the ther hand, varied widely acrding t the experiments. lhe rati f A t B, the theretical maximum value f p at the extreme cnditin where the wd becmes t dense t cntain water (H=n, was 3), It fairlywell g/cm3) f the dead wd samples, measured by the Air Cmparisn.Pycnmeter (Beckman-Tshiba Mdel 93Q). As shwn intable 2, the standard deviatin f H inereasedwith the deereasef p. Z. [[imetrend ef desiccatinf wet samples 1.27 gxcm3 n an average CI]able crrespnded t,thereal density(1.30 The Issf wet weight (PV)f the wd samples, initially saturated with water, was measured experimentally under a cnstant temperatur e7.2"c). Time curses f the change f M are shwn in Fig.2. va decreasedaimst expnentially during the

4 VL 25,N. 1 JAPANESE JeURNAL OFEcLOGY Mar t e,t :asi fia="il3xl "lggsi:.ggtsglss e e,1o.2o,3e.4o.5 1 Time, ttdey) Fig.2. Time curse f freshweight decreasef dead wd samples under a cnstaat temperature (27.2 q in Exp.2. ;.)-Ks=gi: :-s8 Appatentdensttv, p 1tipm) Fig.3.Crrelatinbetween the cafflcient f ddsi- atin (") f Eq. (2)and apparent density(p). first. week, but laterthe dsiccatin became Iess rapid. During the phase f expnential decrease, the time trend f PV can be apprximated.equatlnby the. M(t)=: PPI,e-"t (2) in which PV(t)and M, respectively stand frthe weight at the time t,and att == e. pt may be cailed the cemcient f desiecatin. Tlierelatinship between pt and p was examined in Exp. 16 (Fig. 3),resulting inthe linearrelatinship, p;-mp+n (3) in which m and n are the cnstants dependingn the cnditien f theexperiment. Namely,the relative rate f desieatin was higher in the larger rarlgas f p. in Exp. 18, the prcess f wet weight decrease was bseyved under natural cnditins with dead wd sarnples having diffbrent p values, [he sarnples were placed in a small area (abut1 m2) n the frestflrat Minamata s thattheymight be expsed t nearly the same cnditins. The relative rate f wet weight decrease((pvi,- e,1.2.3 " O.F Apparemt elensitv,.p (fcmi) Fig.4.Relatin betweenthe apparcnt density(p)f dead wd samples and the relative rate ef theirwet weight deerease at difibrent tifne intervals under natural cnditins n the frest firat Minamata. PV(t))/PPI,) f each sample was calculated fbr different time intervals. The rate decreasediinearlywith the inereasef appar nt densityin each. perid (tb cafficient f crrelatin rangd frm O,79t rate O.89 (Fig. 4).This crre$pnds apprximtely t p f Eq. (3)as discussedlater. Tbe desiceatin f dead wd under natural cnditins seems t fllwthe same laws given by Eqs.(2)and (3) btained experimentally under cntrlled cn- ditioiis. 3. Relatinshipbetv-een apparent density(p)and salidity (s) The slidity f the dead wd.samples was ineasured with a sil sliditymeter (YAMANAKAs typej,by which the slidity isgivenas the gramweight required frthrustinga unit vlume f cirqular cne intsil.the diameterf thetested $amples ranged frm1.5 cm t 4.0 cm. The gmetric mean f ttie values measured at fur pints n the uter surfae fa wd sample, tw near the mid-pint arid tw at bth ends, was taken as the mean slidity f the sample. [[lierewas a mre r lesslincarelatinship between p glcm3 and s g/cm3 n lg-igcrdinates as shwn in Fig.5.[[heregressin lineisgivenby 43

5 Vl.25, N. 1,H )N th ma#k di Mar., 197s g-..s Esks; s-egvah.pt-+:v5c App-entdensity, P (rrns] Fig. 6. Crrelatinbetweenthe maximum water centent (Hmax)and apparent density(p)f waterlgged samples in Exp. 19. es Apparent density cubed.p [{glcm3)s] Fig. 5. Regressin between theapparent densitycubed (p3) and the mean slidity (s)f dead wd samples n lg-lg crdinates. lgstt6.76lg p+7.89 pa) Thismay be useful frestimating the value f p withut dry weight and vlume determinatins. Diseussin Apart frm the temperature,the water cntent (ED may be the mst imprtant physical prperty which aifectsthe rate f decmpsitin f dead wd. Itistherefre t be nted thath isclsely crrelated with the apparent density(p) undcr natural cnditins as Eq. (1) shws; Hwever, p and Hare nt perfectly independent f each ther. The ttal vlume f a deadwd sample (V)is pr-wlpg+pti, (s) in which p$ and Pl respectively dentethe real densityf the slid substrate and thettalvlume f pen spaces in the sample. By definitin, w== pvl Therefbrethe rati f Vlt Vr the prsity (L) ef the wd sample is giyenby Pr=Pl,/V=1Lplps (6) Namely, Pr increaseswith the decreasef p. The pssible maximurn water cntent f a deadwd sample (Hmax), at which all the spaces are filled with water, eari then be frmulated as = j!l/max( V},X l)fw == Vl1( Vm Pl)ps =11p-lfps (7) Eq. (7)shws the inerease f H;.a= with the decrease f p. Thisexplains the facthatthe variance f H became smaller with the increase 2),The relatinship between,p and Hmax,experimentatly btained by fi1]ing the sarnples with water, f p (Table isshwn in Fig. 6. The relatin satisfies the e-.quatln, t. ffmax=1/p -1 (8) In thisexperiment, the water cntent at the time when the samples sank under water was taken as Hinam.Eq. (8) can be deriyedfrm the definitin f p and PVif M===V 1. On the ther hand, the cemcient f desiccatin (pt) jncreasedlinearly with the decreasef p (Eq. (3)). This may als increasethe variance f ll in the sarnples with smaller p values. Tlie relative rate f wet weight lssduringa certain perid under natural cnclitins deereased linearly with the increasein apparent densityirrespective f the length f the perid (Fig. Since a s,imilar linearitywas als fund experimentally under cnstant temperature(eqs.(2) and (3)), Iet us ex.amine the reasn fbr this crrespndence. If we assume t.hat Eqs.(2)and (3)hld.under natural cnditins during a shrt intervalf time (tit) in which envirenmental cnditins may be regarded 44

6 VL 25, N. 1 as cnstant, the wet weight f the dead wd samples (PV(t)) JAPANESEJOURNAL OF after the lapsef time t(==rki+ At2-l- - -l-lte)isgivenby the flawingequatin. PV(t)=:PPI,e-{-(midti+m2kit2+- +mtdtt)p+ (n.1"t!+n2dc2+ -+ntdet>] { M==iniAti+m2At2+ +mtatt ==niati+n2dt2+ - +nttitt N in which PZ,,M and N respectively indicatethe initial wet weight f a dead wd sample and the =M,eMp-N (9) enstant specific t the cases. Accrdingly, the relative rate f wet weight decrease{(vab-pv(t))1 PYb}isgiyenby (PVb-M(t))IPVb=(PL--viteMpN)fppz == l -e-n(1 +Mp +(M72)p2+ - ) =N-Mp (10) M==Me-N {N==1-e-N The results f Exp. (16) apprximately satisfied Eq. (10) as already shwn in Fig.4. Eqs. (9)and (10)crrespnd t Eqs. (2) and (3), shwing that the latterequatins are als applicable t the time curse f desiecatin f dead wd under natural cnditins. The riginal shape and vlume f wd litter tend t be maintained fr a censiderably lng per;din spite f the prgress f itsdecay,which thus results in the increasef prsity r the decrease f apparent density(p), The apparent density istherefre an adequate measure f the degreef decmpdsitfnin dead wd. It als aflrected ther physicalprperties f dead wd such as water cntent, relative rate f desiccatin and slidity, and in turn the rate f decmpsitin.the fllwingpapers, planned t be published, will deal with the rate f dead wd decmpsitinwith the apparent densityas themain parameter. Summary 1. Physicalprperties f decayingwd litter were studied under natural cnditins in evergreen ak frestsf Japan with dead wd sampls f a standard size (3-4 cm in diameter and 12 cm in length). 2.The prgress Df decay increasesthe prsity f dead wed, while the riginal shape and vlume remain mre r lessthe same. Therefre,the apparentdensjty(p)becmesa gd measure f the grade f decay. 3. The water cntent (H) ten,ded t increase hyperblically with decreasingapparent density(eq. 45 EcLOGY Mar (1)) under natural cnditins. Hwever, the water cntent became mre variab]e with the deereasef p- 4. The wet weight f a water-saturated dead wd sampje decreasednearly expnentially during the experimental desiccatin under cnstant temperature (Eq.e))Ṭhe relative rate f desiccatin (p) was linearlycrrelated with p accrding te Eq. (3)Ṭhe same relatins were als applicable t the curse f desiccatien under natural cnditins. 5.The yalue f p was psitivelycrrelated with the slidity f dead wd determined by Yamanakas slidity meter. 6. It was cncluded that the apparent density, which refiects bth the degree f decay and the intcrnalcnditins f dead wd, was a usefu1 parameter in the analysis f the rate f wd litter decmpsitin. References HENMMI, T. & AKAI,S Wd pathlegy. 496 pp. Akakura-sheten,Tky. (injapanese) KAwAHARA, T The amunts f mineral nuuients retumed t the sil by the litter-fa11 in a warmtemperate evergreen frestat Minarnata.Prgr. Rep, fr 1969, JIBP-II"-Minamata, (in Japanese, Mimegr.) KIRA, T. & SmDm, T Ilrimaryprductien and turnver f rganic matter in different frestecsystems f the WesternPacific.Jap. J. Ecel., 17: KllirrA, H Studiesf sil respiratin in warmtemperate evergreen bradleaf frests f shutheastern Japan.fld.,21: (injapanesej KtiHNELT,W SilBilgy,with special refeirence t the animal kingdm, 397 pp. Faberrand Faber, Lndn. OMuRA, M., MiyATA, I.& HsKAwA, T Frest vegetatin f Minamata SpecialReseaTchArea f IBP. Mem. Fac,Sci.,Kyushu Univ.,SeT.E-S:77-94.SArT, T [[he signmcance f plate cunts f sil fungiand detectinf their mycelia. Ecl.Rev.. 14: Micrbial decmpsitin f beech litterṫhid.,14: An apprach t the mechanism f micrebial decmpsitin Qf beech litter.sci. Rep. Theku Univ.,Ser,4,26: SATcHELL,J.E Feasibility study f an energy budg t frmeathp Wed. "Prductivity ef frest ecsystems" (ed. DuviGNEAuD, P.), UNESCO, Paris. WATANABE, H, 1966.Weight lssf red pine and beech test sticks and assciatect animals, Bull. Kyt

7 The Elgial Eclgical Sciety Siety f Japan V 星.25, N.1 日本生熊学会誌 Mar.,1975 Unlv.Frests., 38:1 14 ( n Japanese ) WrlrKAM ]P,1> 廷 _1966.1)ec 凪 ps 重耄 in f leaflitter in re 置 atin t envirnment, micr 且 ra,and Inicr b 祕 respiratin.eclgy, 47 : Frest si1 皿量 crfira and 皿 i 皿 era1 ( rycling. 1, ヤ6du( 沈 iv 量 ty f frest ecsystems DuvlGNEAuD,P. ), UNESCO,PariS. 摘 要 (ed. 1. 照葉樹林林床上における枯死材の物理的牲質を調 べた. 直径 3 4Cl 皿の枯死材を 12 cm に切りそろえ供試材どした. 2. 枯死材は, 腐朽ぷ進むにっれてしだいに多孔化するが, 材の原形 ( みかけの体積 ) は, かなり長い期間保 持される. したがって, みかけの密度 ( ρ) は腐朽度をあ らわす測度として適当である. 3. 自然条件下における枯死材の含水率 (H ) は, みかけの密度 (ρ) の小さい材ほど大きな値を示した ( 式 ( 1 ). しかし,p が小さいほど H の変動は大きかった. 4. 水で飽和した枯死材の湿重量 (w ) は, 一定温度 下でほぼ指数関数的に減少し ( 式 ), 乾燥係数 (μ) と ρ との間にはほぼ直線的な関係が認められた ( 式 (3)). 実験条件下で得られたこれらの関係は, 自然条件下での枯死材の乾燥過程にもあてはまることを示した. 5. 山中式土壌硬度計で測った枯死材の硬度と p との間には, 式 (4 ) で示すような相関関係があった. 6. みかけの密度は, 枯死材の腐朽度を示すとともに, 材内部の様々な環境条件を規定しているので, 枯死材の 分解速度を解析するうえで有用なパラメータであることが分った. 46 NII-Electrnic N 工工一 Eletrni Library Service