Annals of Tropical Research 36[Supplement]:70-81(2014)© VSU, Leyte, Philippines
Correspondence : R.S. Come Address: CollegeofForestryandEnvironmentalScience,VisayasStateUniversity,Visca,BaybayCity,Leyte6521-AEmail:[email protected]
Biomass and Carbon Stocks of Vegetation in the Marginal Uplands in Inopacan, Leyte, Eastern
Visayas (Philippines)
Renezita S. Come, Marlito M. Bande, Manilyn Camutuhan, May Joy B. Alip and Rowela Porazo
CollegeofForestryandEnvironmentalScience,VisayasStateUniversity,Visca,BaybayCity,Leyte6521-A
ABSTRACT
Marginal uplands are characterized by unproductive soils and lowbiodiversity. These areas can be a good storage of carbon for climatechangemitigationifrehabilitationmeasureswillbedone.Thisstudywasconducted toquantify thebiomassandcarbonstorageofvariousplantspecies growing in the marginal uplands in Inopacan, Leyte. Samplequadrats measuring 2m x 2m were laid-out inside the one hectareexperimentalplotsestablishedinthesite.Variousspeciesofgrasses,herbsand shrubs were identified inside the quadrats. Using destructivesampling,biomassandcarboncontent in theabove-ground(stemsandleaves)andbelow-ground(roots)weredetermined. Soilsampleswerealsotakenforbulkdensityvalueandsoilorganiccarboncontent. Resultsshowedthatthevegetationwasdominatedbygrass,Imperatacylindrica andshrubsnamely:MelastomamalabathricumandChromolaenaodorata
-1 -1was2.34Mgha andtherootswas2.28Mgha .Carbonstoredinthestems-1 -1
andleaveswas1.05MgCha androotscontained1.03MgCha .Soilshold-1thehighestpercentageofcarbonwhichamountedto25.93MgCha .The
-1totalcarbonstocksinthemarginaluplandinInopacanwas28.01MgCha .
Keywords:biomass,carbonstocks,marginaluplands,soilorganiccarbon,InopacanLeyte
INTRODUCTION
ThePhilippinesisdescribedasacountrywithvasthillylands.Outofitstotallandareacoverof30millionhectares,halfarelocatedintheuplandsorareaswith18%slopeandabove.Theseareaswerepreviouslycoveredwith lush vegetation, mostly forests. However, through the years, thecountry has experienced a very fast deforestation rate. Many of theseuplandareasareconvertedfromonelandusetoanotheri.e.fromforesttoagricultural areas through shifting cultivation and, leaving themunproductiveafterbeingcultivatedforyears.Uplandareaswithnoorlessvegetation are described to be more prone to soil erosion due to itsbiophysicalcharacteristicsincludingruggedterrainandwithlessfertilesoil. In addition, soil erosion is the most widespread process of soildegradationinthePhilippines(Asioet.al.,2009).Thisconditionisabigchallengetoagriculturists,forestersandlandmanagerssinceallactivitiesin theuplandscouldaffect lowlandandcoastal resources.Theeffectofclimate changemayworsen these conditions in the uplandswhere 25millionFilipinoswhoarealsoconsideredas“poorestamongthepoor”areliving(FDC1985,WorldBank1989).
Countrywide, rehabilitation of many uplands and making themproductiveandecologicallysustainablehasbeenthepriorityformorethana century (Chokkalingam et.al., 2006). The government through theDepartment of Environment and Natural Resources (DENR) has lednationalreforestationprogramssuchastheNationalForestationProgramin1986,UplandDevelopmentProgram,LuntiangKalikasan,andrecently,the National Greening Program. These programs aimed to rehabilitategrassland areas in the uplands and regreening of lands under publicdomain.Otherapproachesincludingagroforestry,establishingtreefarms,and recentlybyadoptingorganic farming in theuplandswerealsoputforward.Inaddition,environmentalservicessuchascarbonsequestration,reductionofsoilerosion,waterconservationandwildlifehabitatarejustfewofthemanybenefitsthatwecouldderivefromrehabilitationoftheseunproductiveareas.
Countrywide, vast areas covered by Imperata cylindrica cover 35million hectares (Garrity et.al., 1997) and many of these areas needimmediaterehabilitationastheyarelocatedinwatersheds.Theseareasstoresandsequesterssignificantamountofcarbonfromtheatmosphere.However,duetothenatureofmanyspecieswhichcanbefoundintheseareas(i.e.fastturn-overrate),carboncannotbestoredforalongerperiod
71Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
of time when compared to other land uses including plantations,agroforestry and second-growth forests. Hence, quantification of thestorageandsequestrationcapacityoftheseareasisimportantespeciallythatfewsimilarstudieshavebeenconductedinLeyte.Findingsmaybeusefulforagriculturists,foresters,farmersandlandmanagersandcouldserveasabaselinestudytocomparethecarbonstoragewhengrasslandsareconvertedintootherlandusesespecificallyinInopacan,Leyte.
OBJECTIVESOFTHESTUDY
ThestudygenerallyaimedtoquantifythecarbonstocksofgrasslandinthemarginaluplandsinInopacan,Leyte.Specificallythestudyaimedto:
1. Quantify the biomass and carbon stored in the above-ground
(stalksandleaves)andbelow-groundvegetation(roots);and
2.Determinethecarbonstorageinthesoil
MATERIALSANDMETHODS
StudySite
ThestudyareaissituatedinBarangayLinao,SitioBatuan,Inopacan,Leyte.Itisa5thclassmunicipalityintheprovinceofLeyteandoneoftheprovinces in Easter Visayas, Philippines (10°31'48"N 124°49'44"E). Climateischaracterizedwithrainfallthatisevenlydistributedthroughouttheyear(TypeIV).Thesitehasanaveragetemperatureof27°Cwithahighrelativehumidityof84%.Maximumelevationinthissitereached1,000masl(MunicipalProfileofInopacan,Leyten.d.).(Figure1).
Plotlay-outandSampling
Aonehectareexperimentalplotwasestablishedinthesiteownedbyaprivateindividual.Theareawasdividedinto25plotsmeasuring20mx20mandwasfurthersub-dividedinto16sub-plotsmeasuring5mx5m(Figure2).A total of twenty fourquadratsmeasuring2mx2mnestedwithin5mx5msub-plotswererandomlylaid-out.Allspeciesofgrasses,herbsandshrubsfoundwithinthequadratswereidentified.Also,usingdestructive samplingallplants containedwithin the randomly selectedquadratswereharvestedtogetthefreshweight.Sub-samplesweretakentothelaboratoryforoven-dryingat70°Cfor48hoursoruntilconstant
72Come et al.
weightwasattained.Inthesameplotswereabove-groundvegetationwasharvested, roots were collected up to one meter depth. Samples werewashed and sieved using 2mm wire mesh to separate them from theattachedsoil.Samemethodstheabove-groundvegetationwasappliedtodeterminethefreshweightandoven-driedweightofrootssamples. Core sampling method was used for determining bulk density.Animprovisedcanisterwithadimensionof5.4cmdiameterand6cmheightwasused.Samplesforbulkdensitywerecollectedwithinthefollowingsoildepth:0-10cm,10-30cm,30-50cmand50-100cm.Sampleswerecarefullytaken-out from the canister and placed in a sealed plastic. Thesewerebought to the laboratory foranalysis.Three (3) representative samplesweretakenfromeverydepth forsoilbulkdensitydeterminationwhilefour(4)samplesweretakenforsoilorganiccarbonanalysis.AnalysiswasdoneintheVisayasStateUniversity,BaybayCity,LeyteCentralAnalyticalLaboratory.
73Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
Figure1.LocationmapofthestudyareainSitioBatuan,Brgy.Linao,Inopacan,Leyte.
Figure2.Lay-outoftheonehectareexperimentalplots.
74Come et al.
DataAnalysis
Descriptive statistics including mean and standard deviation wasperformedforthisstudy.Inaddition,thefollowingformulawereusedintheanalysisandinterpretationofdata.
Above-GroundandBelow-GroundBiomass
Biomassvaluesforgrass,shrubsandherbswerecalculatedusingthefollowingformula:
Equation1
ODW(g)=TFW—(TFW*(SFW–SODW))
SFW
Where:ODW=Oven-DryWeightTFW=TotalFreshWeightSODW=sampleoven-dryweight
75Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
Tocalculatethecarbonstorageinplants:
Equation2
TotalC=Biomass*carboncontentofplanttissue(weused45%asDefaultvalue)
Soil
Equation3
-3Bulkdensity(gcm )=
Thedryweightofsoilandcarbonstockwascomputedusingthefollowingformulae:
Equation4
Soilmassatspecifieddepth(Mg)=Bulkdensityatspecifieddepth(Mg-3 2m )x10,000m xdepth(m)
Soilorganiccarbonstocks(Mg)
Equation5
-1TotalSOC(MgCha )=
Dryweightofsoil(g)
Volumeofthecanister(cc)
soilmassatspecifieddepth(Mg)x%organiccarbonatspecifieddepth
100
76Come et al.
RESULTSANDDISCUSSION
Speciescomposition.Resultsfromthisstudyshowedthatthestudyareaismainlydominatedbycogon(Imperatacylindrica)with16.09%ofthetotal vegetation. Cogon is characterized as very flammable, and theiroccurrenceindicatesthattheareahasanacidicsoil.Thiswasfollowedbyshrubspeciesnamely:hantotoknaw(Melastomamalabathricum),hagonoy(Chromolaema odorata) andmalagabon or kukug banug (Elephantopusspecatus)wereallofthemcomprisedperspecies.Otherplantspeciesthatare present in the area includes mani-mani (Desmodiumtriflorum),bugang/talahib (Saccharum spontaneum), bario-bario (Piperaduricum),malacogon,cropslikecamote,cassava,pineappleandbanana.Also, fewtreesofGmelinaarboreawereobserved in thearea,however,treesareplantedoutsidetheonehectarestudyplot.Atotalof25plantspecieswereidentifiedinthestudysite(Table1).
Abovegroundbiomassandcarbonstocks.Thecomputedbiomassofthe-1abovegroundpartofthegrasslandareahasatotalof2.34Mgha .Itranges
-1from0to0.50Mgha .Thisresultwasverydependenttothekindofspeciesthatwerefoundintheplotandhowmuchthesamplesthatwereabletotakefromtheplot(Pulhin,2008).Forexample,inplot18therewereonly3species of grass that were collected. This is because plot 18 has beencultivated forcropplantationpurposes.On theotherhand,plot11hasmore10speciesofgrassandithasthehighesttotalfreshweightwhichis
-17.94 Kgha The total carbon storage of above-ground vegetation has.-1amountedupto1.05Mgha .
Belowgroundbiomassandcarbonstocks.Rootbiomasshasatotalof-1 -1
2.28Mgha . Value ranges from 0.01 to 0.30Mgha . The result can beexplainedbythehighamountofrootsthatweretakenfromtheplots.The
-1carbon storage of the roots has a total of 1.03Mgha (Figure 3). Rootbiomassisalmosthassimilaramounttothebiomassintheabove-groundvegetation.Thisisduetoitsrootssysteminwhichgrasshasashortlengthofrootsanditcannotholdcarbonforlongerperiodoftime,comparedtotherootsystemoftreeswhichcanpenetratedeeperandhaslongerlength,soithasmorecapacitytostoredcarbonforlongtime.
AsstatedbyLugoandBrown(1992)inasystembiomasshasdifferentvalues, in which resulted from the different degrees of anthropogenicactivity and other natural disturbances. A grassland area with higher
77Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
biomassdensitiesmeansitsexperiencinglesserdisturbances.Whileiftheareahave lowerbiomassdensities thatmeans it is experiencinghigherdisturbancesuchasfrequentburningofthegrasses.
Likewise,manyfactorscouldaffectthebiomassandcarbonstorageofvegetationandoneofthatistheweather,whichisthewetanddryseason.Biomass and carbon storage in rainy season is indeedgreater than thebiomassandcarbonstoragethatisbeingaccumulatedduringsummer.Forin rainy season the grassland vegetation is faster to regenerate, hencehigherbiomassisexpected.Inaddition,carbonstorageduringthisseasonis also greater because its result is very dependent to the amount ofbiomassgathered.
Bulkdensityandsoilorganiccarbon.Thebulkdensitiesofthesoilinall-1 -1sampledplotsrangedfrom0.30gcc to0.70gcc .Plot7containsboththe
lowestandhighestbulkdensityofthesoil.Itwasnotedthatalloftheplots-1havebulkdensitiesof >0.90gcc ,whichindicatesthatsoilbulkdensities
derivedfromthegrasslandisstillcompactedandlessdisturbed.ThisfitsthetypicalcharacteristicofgrasslandareasinthePhilippineswhereinhighsoilbulkdensityindicatesthatsiteisdisturbed(Pulhin,2008).
-1Soilorganiccarbon(SOC)rangedfrom16.61to30.34MgCha foundinvarious soil layerswhere sampleswere taken.On the otherhand, bulk
-1densityrangedfrom1.05to1.22gcc (Table2).Carbonstorageinsoilsatvariousdepthsingrasslandsshowednopatternandtheaveragewas25.93
-1MgCha .Resultsofthestudyshowedthatsoilholdsthehighestamountofcarbon.ThecarbonstoredthatwasderivedfromthisstudyisalmosthalftotheresultsofstudiesthatwereconductedinLeyte,whichhaveacarbon
-1densityvalueof52.70Mgha (Lasco,et.al.2000).
Table2.Samplebulkdensityandcarbonstorageofthesoil.
Totalcarbonstorageofgrassland.Overall,theone-hectaregrassland-1storedthetotalcarbonstocksof28.01Mgha .Variouscarbonpoolsinclude
-1soilswith25.93Mgha ,above-groundbiomass (stemsand leaves)with-1 -11.05Mgha and below-ground biomass (roots) with 1.03Mgha . Soil
stores the highest amount of carbon while above-ground and below-
Soil Layers BD (g cc-1) C (MgCha-1) 0-10cm 1.05 16.61± 2.15 10-30cm 1.22 25.90±9.11 30-50cm 1.07 20.91±13.96 50-100cm 1.14 30.34±22.39
Common Name Scientific Name Family Name Classification No. Of occurrence
N=86
Frequency (%)
Cogon Imperata cylindrica Pocaeae Grass 14 16.28 Hantotoknaw Melastoma malabathricum Melastomataceae Shrub 11 12.79 Hagonoy Chromolaema odorata Asteraceae Herb 11 12.79 Malagabon Elephantopus specatus Ateraceae Herb 11 12.79 Mani-mani Desmodium triflorum Fabaceae Herb 5 5.81 Fern Neptirolepis tirsutula Dryopteridaceae Fern 4 4.65 Daat Scleria sphaecocarpa - - 4 4.65 Carabao grass Paspalum conjugatum Poaceae Grass 3 3.49 Baryo-baryo Piper aduricum Piperaceae Herb 3 3.49 Makahiya Mimosa pudica Fabaceae Herb 3 3.49 Dysmodium Desmodium ovaliforium Fabaceae Herb 2 2.33 Bugang/Talahib Saccharum spontaneum Poaceae Grass 2 2.33 Cotton-cotton Desmodium ovaliforium - - 2 2.33 Malagabon Elephantopus tomentosus Asteraceae Herb 1 1.16 Gabon Blumea balsamifera Asteraceae Herb 1 1.16 Alibangbang Piliostigma sp. Fabaceae Tree 1 1.16 Malacogon Ǽ � - 1 1.16 Mini-mani mani Alysicarpus sp. Fabaceae Herb 1 1.16 Kadena de Amor Antigonon leptopus Polygonaceae Vine 1 1.16 Dawa-dawa Pancum maximum Poaceae Grass 1 1.16 Batung-batong Calopogonium mucunoides Fabaceae Herb 1 1.16 Amorseco Chrysopogon aciculatus Poaceae Grass 1 1.16 Bukot-bukot Centella sp. Apiaceae Herb 1 1.16 Unidentified grass Ǽ � Grass 1 1.16 Total 86 100
Table1.Description,numberofoccurrenceandfrequencyofplantspeciesinthestudysite.Com
e e
t al.
78
79Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
Figure3.TotalstocksinthevariouscarbonpoolsinthestudyareainInopacan,Leyte
IMPLICATIONSANDRECOMMENDATIONS
ImportantbaselinedataonthecarbonstoragecapacityofgrasslandsinmarginaluplandsinInopacan,Leytewasderivedfromthisstudy.Resultsshowedthatsoilisanimportantcarbonpoolandhashighercapacitytostorecarbonthanabove-groundandbelow-ground(roots)pools. Sincegrasslandsareknowntohavehighturn-overrateduetotheirnatureandpronetoburningandgrazing,carboncannotbestoredforalongerperiodof time compared to other land uses including agroforestry and treeplantations. It is therefore recommended that marginal uplands inInopacan be converted intomore productive and diverse ecosystem inorder to maximize the benefits of the areas both ecologically andeconomically. Further studies including quantification of carbon in
groundvegetationstoredmoreorlessthesameamountofcarbon.Soilsareknowntostoremoreorganiccarbonandholdsitforalongerperiodoftime.Inaddition,thecapabilityofthesoiltostoresoilorganiccarbonisbeinginfluenced by the following factors: (1)mean annual precipitation; (2)degree of forest disturbance; (3) extent of land use change (Lugo andBrown,1993).ItwascitedbyPulhin(2008)thatinordertoenhancesoilsequestrationthefollowingstrategiesmustbedone.(1)reduceerosionthrough reforestation; (2) improving soil fertility; (3) reduce shiftingcultivation;(4)removemarginallandsfromagriculturalproduction;(5)retainingforestlitteranddebris(Lascoetal.,2000).
different grassland communities is also recommended. Carbon stocksassessment of marginal uplands during rainy season could also beconductedtocomparetheresultsofthisstudy.Otherimportantspeciesofgrasses,shrubsorherbsmightbepresentduringthisseasonwhichwerenotdocumentedduringtheconductofthisstudy.
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