Biomass and Carbon

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INTRODUCTIONThe Malaysian rubber industry spread out over 1.46million hectares (Min. Primary

Industries, 2000)encompasses a gamut of soils, landscape conditions, microclimateandclones. Variations within these factors are known to influence the growth and yield ofrubber. The variation of soil series in influencing biomass production(Lim,1977) and yield(Chan and Pushparajah, 1972; Yew, 1992) is well known. Similarly, the differences inlandscape features (Chan el al, 1974), microclimate (Dijkman, 1951; Yew, 1982) andclones (RRIM, 1998)in varying Hevea growth and yield are also well documented. Thesefeatureswilldetermine the value of the rubber tree as a carbon sink since the amount ofcarbonfixed depends on the biomass production and itsabilityor efficiency to fix carbon.Zahar et al (1987) have shown that the last factor mentioned is a clonal characteristic;cloneslikeRRIM600 and PB 235being ableto fixmore carbon than clones likePR261.

A working group has been set up at SIRIM to document the principles andguidelines for the monitoring, measuring, verifying, certifying and reporting of greenhousegasses emissions. The contribution of this paper is to document the methods used toquantify carbon sequestration inrubber. Some case studiesarealso presented.

MATERIALS AND METHODSThe studyisconductedby aliterature search. The amountofcarbon fixedby the

rubber tree is determined by multiplying the plant dry weight by the concentration ofcarbon,in percentage, of the plant tissue.The carbon is sequestered in the following rubber tree organs namely1) Tree biomass2) Annual leaf, branch and fruit fall and3) Rubber yield measuredaslatexandscrap.The methods used to obtain the dry weights of the three materials mentioned, andhow these results are used to estimate the amount of carbon sequestered in therubber tree will be described in the following sections.

RESULTS AND DISCUSSIONSMethods used

The amount of carbon sequestered is obtained by multiplying plant dry weight withitscarbon concentration.


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Plant Biomass D eterminationThisis often done by destructivesam pling whenthe wholetreeisfelledand the treedivided into different sections. The fresh weights ofthese sections are obtained. Sub-samplesarethentakenfor dryweightestimations.The rubber trees are felled and then divided into four principal components viz.leaves, branches, stems and roots. This is the common method adopted by theresearchers eg. Shorrocks (1965), Lim (1977), Sivanadyan and Ghandimathi (1985) andYew (2000) to study the biomass production of Hevea. However, some variation isencounteredin thedefinitionfor thetypes of branchesasseen inTable 1. Suchvariationin defining branch terminology is not very important, as they still account for all thebranchespresenton thetreeasseeninFigure 1.Similarly, while Shorrocks (1965) considers the root collar or union as part of thetrunk, other researchers such as Lim (1977), Sivanadyan and Ghandimathi (1985) andYew (2000) consider the union as partof the roots. Thus Shorrocks (1965)findsthat therootscompriseonly 15 of thebiomass,whileYew(2000)finds thatthe roots form 16.5

ofthe totaltreebiomass.Soong (1970) has developed a method of determining the amount of fine andmediumsizefeeder roots byusingan auger which has an internaldiameter of 10 cm andwelded to a 67 cmshaftwhichisgraduatedat 7.5 cm intervals.Asingletreeis sampled bytakingten points,with fiveoneithersideof thetree. Ateachsampling point,different soildepths aretaken,up to 40 cmbelowthesoilsurface.Thesoil corescollected from thefieldare kept in clothbags,takento thelaboratory,washed and sorted for roots. The root density is expressed as grams of dry roots per

cubic foot ofsoil.Biomass DryMatterDetermination

Two methods have been used. The most common method is to obtain freshweights of all the plant parts. Sub-sam ples are then taken for oven dry weightmeasurementsandtheseovendryweightsareusedtocalculatethe ovendryweightsofall theplant organssampled. Thismethod has been adopted by Shorrocks (1965), Lim(1977) SivanadyanandGhandimathi(1985)and Yew (2000).

In addition, Yew (2000) has also used a method to measure the volume of thetrunks and branches andthen relatingthemto weights. Thismethod provides a quickerway to estimatetree biomass. In this method, the plant organs are separated into thevariousplantparts. The volume of the branches and trunks, is recorded byinitiallysawingthem intopieces ofwood or log, 30 cm long. The volume isestimatedforeachpiece ofwoodbyusingthetruncatedcone formulaasfollows:Volume=n/12[D1 +D2]2- D1D2]L whereD1 is the large end volume, D2 is thesmallend volume and L is the length of thelog. A smaller pieceofwoodabout2.5 cmthick isthensawn offfrom eachlog and thevolumes of these representative samples are recorded. These samples are then oven


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dried andtheirweights recorded. Theovendryweightsand thevolumesarethenusedtoestimatetheweightsof thewholetrunk and branches. Thefresh weightsof the leaves,twigs,tertiarybranchesandotherroot parts(tap and secondary roots) aremeasuredsincevolume measurements are not recorded for thesesamples. A representativesample istaken fromeachoftheseplant parts after recordingtheirfreshweightsand the oven dryweights ofthesesamplesareusedtocalculatethetotaloven dryweightsofthesetissues.

Table1 :Plantpartsusedtodetermine rubbertreebiomass

^ SourcePlantparts^Roots:Collar+

Tap rootsLateralRoots

Trunk

Primary branch

Secondarybranch

Tertiarybranch

Quarternarybranch

Quinternarybranch

Green branches

Leaves+petioles

Shorrocks(1965)

*s/

Remainingbranches

Greenbranches

Lim(1977)

v

^

Otherbranches

v'

v'

Sivanadyan&Ghandimathi(1985)

*^

A

-

-

Yew(2000)

--v'

Twigs

v'


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Organic CarbonDeterminationAfter the sub-samples have been used for oven dry weight estimations, they areground and analysed for their carbon content using Wakley and Black's Rapid TitrationMethod (Piper, 1950). Inthis method, the carbon present as organic matter in 0.2 g ofground plant sample is estimated by oxidising it with a known excess of a solution ofpotassium dichromate in concentrated sulphuric acid and back titrating the potassiumdichromatewith a standard solution of ferrous ammonium sulphate using diphenylamineasaninternalindicator.

LeafFall MeasurementThe methodof Tan (1975) is described. A container measuring1 mx1 mx1m,madeup ofwire nettingof 2 cmmeshisused. Thecontainerhas 4wooden legswitha 15cm clearance from theground.Twounitsare placed in the interrows of the rubber trees and leaflitter is collectedfortnightly. Thefresh weightistaken. A subsampleisdriedat 75 - 80C and itsmoisture

contentdetermined.DeterminationofYieldofRubberTree

The wet weight of the latex for each tapping is first obtained. The dry rubbercontent ofthis latex isobtainedby using a metrolac, which is aformofhydrometer, asdescribedby Abu Bakar (1985).

The cup lump or scrap rubberyield isobtained bymeasuring itsweight. The dryweightisobtainedafterthemoisturecontentis determined.CaseStudiesCarbonSequestrationStudies inRubber

Carbonisfixedin thefollowingHeveatreetissues. Theseare1) Tree biomass,inclusive of aerial and subaerial portions2) Leaffallas aresultofwintering3) Branch fall4) Seedfalland5) Latex production

As no concerted studies per se have been made to study the amount of carbonsequestered by Hevea, values of carbonsequestered by Hevea (Wan andSivakumaran,1998;Sivakumaran et al, 1999) havebeen arrived at basedonestimation. Theamountsofcarbonfixedin the variousrubber treeorgans are as follows.


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CarbonFixed in Tree BiomassThe drymatter production increases with tree age as seen inTable 2. For RRIM

501,theweightincreases from 2.84 kg/tree on the first year to 1095.6kg/tree on the24thyear.

The tree dryweight also differs between clones. The seedling Tjir 1 weighs fivetimes morethanthe clone RR IM 600 at thetimeoffellingwhichis on the 33rdyearforTjir1 and at the34thyear for RRIM600.Table2 : Dry matterproductionofrubbertreesaccordingto age kg/tree)

\sCloneAgeX.

13571/2101524/253033/34

RRIM501

2.84a38.71a

153.92a-

968.72a-

1095.60a--

TJIR1

-------

2118.83a

RRIM600

_

45.3c---

473.605b-

350d419d

PB260

_

28.8c168.9e246.0e

--

513d--

PB235

_

35.0c172.7e

------

PB330

_

14.1c123.2e

-----

Source: a :Shorrocks (1965);b :Lim(1977);c :Sivanadyanand Ghandimathi(1985);d :Yew(2000),e:Zulkipli (private communication)Notes:(1) Numberoftreessampledis 1 - 3 for a, 1 for b, 3 - 5 for c, 3 for dan'd 15fore.

(2) For (a), trees at 24th and 33rd year, root weight was estimated as 15 ofweightoftree.(3) For (c) and (e) roots were not extracted. Weights presentedare whole treedry weights,withrootweightsestimatedas 15 of theweightoftree.

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At the time of felling, a rubber land with 270 trees/ha, contains 158 tonnes/ha ofbiomass andthis locks up 72.3 tonnes of carbon as seen inTable 3. The big bulk of theweightisconcentratedin thetree trunkand primarybranches. Together they form56 ofweightof thewholetree. Theseare the mainportionsof thetree whichareremovedfromthefieldto be processed as Heveawood.

Table3 : Dry matter andcarboncontent ofrubbertreesatfelling

^ ^^^^


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petioles, falls in a year. The leaf litter of Tan (1975) consists of leaf laminae only. Thepetioles areexcludedandtheyform 15 of the leaflitter.

Table4 : Estimated carbon fixedin annualleaffall litter

Parameter Value

Drymatter 3291kg/ha/yr(a)Carboncontent 47.1 (b)Amountof Cfixed 1550kg/ha/yrTotalamountof Cfixedover22years 34,100 kg/ha

Source:a:Tan(1975) b:Tan Pushp arajah (1985)Notes : 1) Dry matter includes laminae andpetioles

The amount of carbon fixed in the annual leaffall of mature rubber trees, beforefellingat the29thyear, isestimatedto be 34,100 kg/ha asseen inTable4. Immaturerubber trees do not undergo an annualwinteringand the amount of leaffall has not beenstudied. Hence, the amount of carbon fixed in thefallen leaves of the immature rubbertrees has notbeenincludedin theestimationbutthisis notexpectedto belarge.Carbon inAnnualBranchFall

The annual branch fall has not been studied and the amount of carbon fixed is,therefore,unknown.Carbon in Seed Fall

Shorrocks (1965) has estimated anannualfruitfall of 160 kg per hectare. Thiswillamount to 3,520 kg/ha over a 22year period of maturity. The amount of carbonfixed inthefruitshas notbeenstudied.Carbon inLatexand Cuplumps

The annual average production of rubber per tree forclones RRIM 600 andGTI,over a 25year period is 1680 kg/ha/yr (Sivakumaran etal, 1999). Based on aneconomiclifeperiod of 22 years, the amount of carbon fixed inlatex andcuplumps is32.5tonnes/haasshown inTable5.


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Table 5 :Amountofcarbonfixedinlatexandcuplumps

Item Amounttonnes/ha)Totalrubber produced

Totalcarbonfixed*36.9632.52

Source : Sivakumaran etal (1999)Notes:* Based on assumption thatcarbonis 88 of the basic isoprene unit.TotalAmountof CarbonSequesteredin a Hectare ofRubber

Thetotal amountofcarbon sequesteredin ahectareof 29 year oldrubber treesatthe time offellingis given inTable6. About 139tonnes of carbonarefixed in ahectareofrubber land. Thisfigureexcludes the contributions from thefollowing organswhich havenotbeenstudied,namely,a) feeder rootsof rubberb) annualbranchfallc) annual seedfall

Table 6 :Totalamounto fcarbonsequestered b y a hectare o f rubbertrees

Plant organ

TreebiomassLeaffallBranchfallSeedfallRubber produced

Total

Amount(tonnes/ha)

72.334.1NdNd

32.5

138.9

Stand: 270trees/ha


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In anearlierstudy, Sivakumaran et al (1999)estimated that 318.7tonnes ofcarbon are sequestered in one hectare of rubber trees. The greatest discrepancybetween the results from this study and that of Sivakumaran et al (1999) lies in the leaflitterand branches. Sivakumaran et al postulated that all thebranches,smaller thanthequaternary branches inclusive, willfall down annually. They estimated thatthe carbonsequestered by the leavesandsmaller branchesis209.3tonnes/ha.FastMethodsofEstimatingCarbonSequ estrationGirth

Shorrocks et al (1965) have realized that it is rarely practicable to fell andweightrees atintervalsin order todeterminetree growth. They have,thus,relatedshoot(ie.all above-ground parts), dry weights andgirthis as follows:Y = 2.7826 X - 2.5843 where Y denotes log shoot dry weight (kg) and X

denotesloggirth (cm)Earlier, Constable (1955) has related total tree weight (Ib) and girth (in) bythe regressionequation:Logweight=2.408loggirth- 0.355

Diameter/Height FunctionsInforestry, dendrometers (Cailliez, 1980) have been used toestimateforestvolume and yield prediction. A dendrometer ruler is a ruler equippedwith aplumb lineattached to one corner. Diameter/heightfunctionsare then obtained. Similartechniques,

although nottriedfor rubber, havepotentialitiesas quick methods.LeafAreaIndex

Hemisphericalphotography hasbeenusedtoestimate leaf areaindex (LAI).For rubber, a good correlation has been obtained between LAI obtained fromhemispherical picturesand LAIobtainedfrom insitu litter collectionofHevea(Leonget al,1982). LAI can be used to estimate dry matter production of the aerial portion of thetrees.RemoteSensingMethods

Earth observing satellites are playing an increasing role in the evaluation,extent of degradation and depletion of renewable natural resources. Added to this thecomputer revolution has given a new tool for analysing satellite imagery. Once data isconverted into digital format, they can be integrated with conventional informationcontained in maps and tables and it becomes possible tobuild predictive models underthe geographicinformationsystems (GIS),as pointed out by Mohan(1991). Hence,the


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use ofsimpleaerial photography to measureheightof trees(Kilford,1973) and the use ofLANDSATandCIStoestimatedrymatterproduction may be possible forrubber.CONCLUSIONS

The amount of carbon sequestered in a rubber planting over one life cycle of 29years,i.e.formthetime ofplantingin thefield untilthetimeoffelling, variesfrom 139to319tonnes per hectare. Thesedifferences are attributed to a lack of information on theexactamount ofannual leaf, branch andsee fall. It is also knownthat a lot offeederroots are produced over the life cycle of the rubber tree. As these have not beenmeasured, theamountofcarbonfixed bythemisunknown.Thepresentmethods ofobtaining tree biomass bydes tructivesampling and

obtaining dryweightfromweightor volume measurements are time consuming. It isfeltthat other rapid methods such as relating (a) tree girth and/or height and (b) remotesensing techniques,withbiomass production need to beexplored.

ACKNOWLEDGEMENTSThe authors are grateful to Dato' Abdul Hamid Syawal (Director-General,Malaysian Rubber Board) for his permission to present the paper. Dr. Ismail Hashim

(Director of Production Development Division, Malaysian Rubber Board) and Dr. ZainolEusof (Head of Crop Management Unit, Malaysian Rubber Board) are thanked for theircritical review ofthis paper aswell as their support during the preparation of the paper.We alsothank En.Zulkefly Sulaimanforproviding us some of his unpublisheddata. Thepainstakingefforts ofMissZadariahNoh fortypingthispaperisgratefullyacknowledged.

REFERENCESAbu Bakar,H.A. (1985). TeknologiGetahAsli, RRIM, pp477.Cailliez, F. (1980). Forest volume estimation and yield prediction. Vol 1 - volumeestimation. FAOForestrypaper 22/1,pp 98.Chan,K.W.(1999). GH G projects in practice: An A sian casestudy. Mal PalmOilInd,1-3.Chan, H.Y.and Pushpa rajah, E. (1972). Productivity potentials of Hevea on WestMalaysian soils.Proc. Rubb.Res.Inst. Ma laysiaPlrs.Conf.,Kuala Lumpur,97-126.Chan, H.Y., Wong, C.B.,Sivanadyan, K. and Pushparajah,E.(1974). Influence of soilmorphology and physiography on leafnutrient content andperformance of Hevea. Proc.Rubb.Res.nst. MalaysiaPlrs.Conf., KualaLumpur,115-126.Constable,D.H. (1955). Girthandgrowthmeasurements as an aid tomanurial diagnosisintropicalhorticulture.Rep.XlVthInt.Hort. Congr. 1955,2, 1346.


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Dijkman,M.J. (1951). Hevea: Thirty years of research in the Far East. Coral Gables,Florida,pp329.Kilford,W.K.(1973).Elementaryairsurvey.PitmanPublishing,U.K,pp363.Leong, W., Lemeur, R. andYoon P.K. (1982). Characterisation of leaf index andcanopylight penetration of Hevea brasiliensis Muell. Arg.by hemispherical photography. J ofRRIM.30(2),80-90.Lim, T.S.(1977). Nutrient uptake of clone RRIM 600 in relation to soil influence andfertilizer needs. Proc.Nat. Rubb. Conf.Kuala Lumpur1977,166-185.MinistryofPrimary Industries(2000).Statisticsoncommodities 1999,pp192.Mohan, S.R.(1991). Remote sensing and geographic information system for naturalresourcemanagement.AsianDev. Bank,pp202.Piper,C.S.(1950).Soiland plant analysis. Univ.Adelaide.RRIM (1998).Plantingof latex timber clones.Plrs.Bull.3,1-46.Shorrocks,V.M.(1965). Mineral nutrition,growth andnutrientcycle of Hevea brasiliensis.I.Growth andnutrientcontent. J.Rubb.Res.Inst.Malaya. 19,(1),32-47.Shorrocks, V.M., Templeton, J.K.and lyer, G.C.(1965). Mineral nutrition, growth andnutrient cucle of Hevea brasiliensis.III The relationship between girth and shoot dryweight.J.Rubb.Res. Inst.Malaya.19,(2),85-92.Sivakumaran, S., Yew, F.K.,Johari, H. and Wan A. R. (1999). Carbon sequestration inrubber: Implicationsand economicmodelstofundcontinuedcultivation,pp 25.Sivanadyan, K. and Ghandimathi H. (1985). Influence ofnitrogen fertilization on variousaspectsoftreedevelopmentinHeve a brasiliensis. Proc.Nat.Rubb. Conf.Kuala Lumpur1985,610-638.Soong,N.K. (1970). A study of the root distribution of Heveabrasiliensis inrelation to itsnutritionand growthonsometypical Malayan Soils. M.Agr.Sc.Thesis, Univ. Malaya, pp79.Tan, K.H. (1975). Hevea leaf litterfall and chemical changes during litterdecomposition.Proc.3rdASEANSoilConf.,Kuala Lumpur,147-157.Tan,K.H. and Pushparajah, E.(1985).Studies on nitrogensoils V. Mineralisation of leaflitter nitrogen and itsavailability to rubber seedlings. J. Rubb. Res. Inst. Malaysia. 33(1),26-36.Wan A. R. and Sivakumaran, S. (1998). Studies on carbon sequestration in rubber.UNCTAD/IRSG Rubb. Forum, Bali,Indonesia, pp 66.


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Yew,F.K.(1982). Contributionstowards thedevelopmentof aland evaluation systemforHevea brasil iensis Muell. Arg.cultivation in Peninsular Malaysia. Dr. Sc. Thesis Univ.Ghent, Belgium,pp 327Yew,F.K.(1992).Soilsuitabilityfor rubber cultivation:Rubb.Res.Inst. Mal., Plrs. Bull.,207,47-51.Yew, F.K.(2000). Impact of zero burning on biomass and nutrient turnover in rubberreplanting. InternationalSymposiumon Sustainable LandManagement,Sri Kembangan,p p 9 .Zahar, S., Tan,H. and Yoon, P.K. (1987). Correlation studies on photosynthetic rates,girthand yield inHeveabrasiliensis.JNat.Rubb.Res.,2,1,46-54.ZulkeflyS.(2001). Unpublisheddata(privatecom munication)

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Biomass and Carbon