Biomass and Carbon Stocks of Vegetation in the

Annals of Tropical Research 36[Supplement]:70-81(2014)
© VSU, Leyte, Philippines
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 low
biodiversity. These areas can be a good storage of carbon for climate
changemitigationifrehabilitationmeasureswillbedone.Thisstudywas
conducted to quantify the biomass and carbon storage of various plant
species growing in the marginal uplands in Inopacan, Leyte. Sample
quadrats measuring 2m x 2m were laid-out inside the one hectare
experimentalplotsestablishedinthesite.Variousspeciesofgrasses,herbs
and shrubs were identified inside the quadrats. Using destructive
sampling, biomass and carbon content in the above-ground (stems and
leaves)andbelow-ground(roots)weredetermined. Soilsampleswere
alsotakenforbulkdensityvalueandsoilorganiccarboncontent.Results
showedthatthevegetationwasdominatedbygrass,Imperatacylindrica andshrubsnamely:MelastomamalabathricumandChromolaenaodorata
was2.34Mgha-1andtherootswas2.28Mgha-1.Carbonstoredinthestems
-1
-1
andleaveswas1.05MgCha androotscontained1.03MgCha .Soilshold
thehighestpercentageofcarbonwhichamountedto25.93MgCha-1.The
-1
totalcarbonstocksinthemarginaluplandinInopacanwas28.01MgCha .
Keywords:biomass,carbonstocks,marginaluplands,soilorganiccarbon,
InopacanLeyte
Correspondence : R.S. Come Address: CollegeofForestryandEnvironmentalScience,VisayasState
University,Visca,BaybayCity,Leyte6521-AEmail:[email protected]
Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
71
INTRODUCTION
ThePhilippinesisdescribedasacountrywithvasthillylands.Outofits
totallandareacoverof30millionhectares,halfarelocatedintheuplands
orareaswith18%slopeandabove.Theseareaswerepreviouslycovered
with lush vegetation, mostly forests. However, through the years, the
country has experienced a very fast deforestation rate. Many of these
uplandareasareconvertedfromonelandusetoanotheri.e.fromforestto
agricultural areas through shifting cultivation and, leaving them
unproductiveafterbeingcultivatedforyears.Uplandareaswithnoorless
vegetation are described to be more prone to soil erosion due to its
biophysicalcharacteristicsincludingruggedterrainandwithlessfertile
soil. In addition, soil erosion is the most widespread process of soil
degradationinthePhilippines(Asioet.al.,2009).Thisconditionisabig
challengetoagriculturists,forestersandlandmanagerssinceallactivities
in the uplands could affect lowland and coastal resources. The effect of
climate change may worsen these conditions in the uplands where 25
millionFilipinoswhoarealsoconsideredas“poorestamongthepoor”are
living(FDC1985,WorldBank1989).
Countrywide, rehabilitation of many uplands and making them
productiveandecologicallysustainablehasbeenthepriorityformorethan
a century (Chokkalingam et.al., 2006). The government through the
Department of Environment and Natural Resources (DENR) has led
nationalreforestationprogramssuchastheNationalForestationProgram
in1986,UplandDevelopmentProgram,LuntiangKalikasan,andrecently,
the National Greening Program. These programs aimed to rehabilitate
grassland areas in the uplands and regreening of lands under public
domain.Otherapproachesincludingagroforestry,establishingtreefarms,
and recently by adopting organic farming in the uplands were also put
forward.Inaddition,environmentalservicessuchascarbonsequestration,
reductionofsoilerosion,waterconservationandwildlifehabitatarejust
fewofthemanybenefitsthatwecouldderivefromrehabilitationofthese
unproductiveareas.
Countrywide, vast areas covered by Imperata cylindrica cover 35
million hectares (Garrity et.al., 1997) and many of these areas need
immediaterehabilitationastheyarelocatedinwatersheds.Theseareas
storesandsequesterssignificantamountofcarbonfromtheatmosphere.
However,duetothenatureofmanyspecieswhichcanbefoundinthese
areas(i.e.fastturn-overrate),carboncannotbestoredforalongerperiod
72
Come et al.
of time when compared to other land uses including plantations,
agroforestry and second-growth forests. Hence, quantification of the
storageandsequestrationcapacityoftheseareasisimportantespecially
thatfewsimilarstudieshavebeenconductedinLeyte.Findingsmaybe
usefulforagriculturists,foresters,farmersandlandmanagersandcould
serveasabaselinestudytocomparethecarbonstoragewhengrasslands
areconvertedintootherlandusesespecificallyinInopacan,Leyte.
OBJECTIVESOFTHESTUDY
Thestudygenerallyaimedtoquantifythecarbonstocksofgrasslandin
themarginaluplandsinInopacan,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.Itisa5thclassmunicipalityintheprovinceofLeyteandoneofthe
provinces in Easter Visayas, Philippines (10°31'48"N 124°49'44"E). Climateischaracterizedwithrainfallthatisevenlydistributedthroughout
theyear(TypeIV).Thesitehasanaveragetemperatureof27°Cwithahigh
relativehumidityof84%.Maximumelevationinthissitereached1,000m
asl(MunicipalProfileofInopacan,Leyten.d.).(Figure1).
Plotlay-outandSampling
Aonehectareexperimentalplotwasestablishedinthesiteownedbya
privateindividual.Theareawasdividedinto25plotsmeasuring20mx
20mandwasfurthersub-dividedinto16sub-plotsmeasuring5mx5m
(Figure 2). A total of twenty four quadrats measuring 2m x 2m nested
within5mx5msub-plotswererandomlylaid-out.Allspeciesofgrasses,
herbsandshrubsfoundwithinthequadratswereidentified.Also,using
destructive sampling all plants contained within the randomly selected
quadratswereharvestedtogetthefreshweight.Sub-samplesweretaken
tothelaboratoryforoven-dryingat70°Cfor48hoursoruntilconstant
Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
73
weightwasattained.Inthesameplotswereabove-groundvegetationwas
harvested, roots were collected up to one meter depth. Samples were
washed and sieved using 2mm wire mesh to separate them from the
attachedsoil.Samemethodstheabove-groundvegetationwasappliedto
determinethefreshweightandoven-driedweightofrootssamples.
Core sampling method was used for determining bulk density.An
improvisedcanisterwithadimensionof5.4cmdiameterand6cmheight
wasused.Samplesforbulkdensitywerecollectedwithinthefollowingsoil
depth:0-10cm,10-30cm,30-50cmand50-100cm.Sampleswerecarefully
taken-out from the canister and placed in a sealed plastic. These were
bought to the laboratory for analysis. Three (3) representative samples
weretakenfromeverydepth forsoilbulkdensitydeterminationwhile
four(4)samplesweretakenforsoilorganiccarbonanalysis.Analysiswas
doneintheVisayasStateUniversity,BaybayCity,LeyteCentralAnalytical
Laboratory.
Figure1.LocationmapofthestudyareainSitioBatuan,Brgy.Linao,Inopacan,Leyte.
74
Come et al.
Figure2.Lay-outoftheonehectareexperimentalplots.
DataAnalysis
Descriptive statistics including mean and standard deviation was
performedforthisstudy.Inaddition,thefollowingformulawereusedin
theanalysisandinterpretationofdata.
Above-GroundandBelow-GroundBiomass
Biomassvaluesforgrass,shrubsandherbswerecalculatedusingthe
followingformula:
Equation1
ODW(g)=
TFW—(TFW*(SFW–SODW))
SFW
Where:
ODW=Oven-DryWeight
TFW=TotalFreshWeight
SODW=sampleoven-dryweight
Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
75
Tocalculatethecarbonstorageinplants:
Equation2
TotalC=Biomass*carboncontentofplanttissue(weused45%as
Defaultvalue)
Soil
Equation3
Dryweightofsoil(g)
-3
Bulkdensity(gcm )=
Volumeofthecanister(cc)
Thedryweightofsoilandcarbonstockwascomputedusingthe
followingformulae:
Equation4
Soilmassatspecifieddepth(Mg)=Bulkdensityatspecifieddepth(Mg
m-3)x10,000m2xdepth(m)
Soilorganiccarbonstocks(Mg)
TotalSOC(MgCha-1)=
Equation5
soilmassatspecifieddepth(Mg)x
%organiccarbonatspecifieddepth
100
76
Come et al.
RESULTSANDDISCUSSION
Speciescomposition.Resultsfromthisstudyshowedthatthestudyarea
ismainlydominatedbycogon(Imperatacylindrica)with16.09%ofthe
total vegetation. Cogon is characterized as very flammable, and their
occurrenceindicatesthattheareahasanacidicsoil.Thiswasfollowedby
shrubspeciesnamely:hantotoknaw(Melastomamalabathricum),hagonoy
(Chromolaema odorata) and malagabon or kukug banug (Elephantopus
specatus)wereallofthemcomprisedperspecies.Otherplantspeciesthat
are present in the area includes mani-mani (Desmodium
triflorum),bugang/talahib (Saccharum spontaneum), bario-bario (Piper
aduricum),malacogon,cropslikecamote,cassava,pineappleandbanana.
Also, few trees of Gmelina arborea were observed in the area, however,
treesareplantedoutsidetheonehectarestudyplot.Atotalof25plant
specieswereidentifiedinthestudysite(Table1).
Abovegroundbiomassandcarbonstocks.Thecomputedbiomassofthe
abovegroundpartofthegrasslandareahasatotalof2.34Mgha-1.Itranges
from0to0.50Mgha-1.Thisresultwasverydependenttothekindofspecies
thatwerefoundintheplotandhowmuchthesamplesthatwereableto
takefromtheplot(Pulhin,2008).Forexample,inplot18therewereonly3
species of grass that were collected. This is because plot 18 has been
cultivated for crop plantation purposes. On the other hand, plot 11 has
more10speciesofgrassandithasthehighesttotalfreshweightwhichis
7.94 Kgha-1. The total carbon storage of above-ground vegetation has
amountedupto1.05Mgha-1.
Belowgroundbiomassandcarbonstocks.Rootbiomasshasatotalof
-1
-1
2.28 Mgha . Value ranges from 0.01 to 0.30 Mgha . The result can be
explainedbythehighamountofrootsthatweretakenfromtheplots.The
carbon storage of the roots has a total of 1.03 Mgha-1 (Figure 3). Root
biomassisalmosthassimilaramounttothebiomassintheabove-ground
vegetation.Thisisduetoitsrootssysteminwhichgrasshasashortlength
ofrootsanditcannotholdcarbonforlongerperiodoftime,comparedto
therootsystemoftreeswhichcanpenetratedeeperandhaslongerlength,
soithasmorecapacitytostoredcarbonforlongtime.
AsstatedbyLugoandBrown(1992)inasystembiomasshasdifferent
values, in which resulted from the different degrees of anthropogenic
activity and other natural disturbances. A grassland area with higher
Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
77
biomassdensitiesmeansitsexperiencinglesserdisturbances.Whileifthe
area have lower biomass densities that means it is experiencing higher
disturbancesuchasfrequentburningofthegrasses.
Likewise,manyfactorscouldaffectthebiomassandcarbonstorageof
vegetationandoneofthatistheweather,whichisthewetanddryseason.
Biomass and carbon storage in rainy season is indeed greater than the
biomassandcarbonstoragethatisbeingaccumulatedduringsummer.For
in rainy season the grassland vegetation is faster to regenerate, hence
higherbiomassisexpected.Inaddition,carbonstorageduringthisseason
is also greater because its result is very dependent to the amount of
biomassgathered.
Bulkdensityandsoilorganiccarbon.Thebulkdensitiesofthesoilinall
sampledplotsrangedfrom0.30gcc-1to0.70gcc-1.Plot7containsboththe
lowestandhighestbulkdensityofthesoil.Itwasnotedthatalloftheplots
havebulkdensitiesof >0.90gcc-1,whichindicatesthatsoilbulkdensities
derivedfromthegrasslandisstillcompactedandlessdisturbed.Thisfits
thetypicalcharacteristicofgrasslandareasinthePhilippineswhereinhigh
soilbulkdensityindicatesthatsiteisdisturbed(Pulhin,2008).
Soilorganiccarbon(SOC)rangedfrom16.61to30.34MgCha-1foundin
various soil layers where samples were taken. On the other hand, bulk
densityrangedfrom1.05to1.22gcc-1(Table2).Carbonstorageinsoilsat
variousdepthsingrasslandsshowednopatternandtheaveragewas25.93
MgCha-1.Resultsofthestudyshowedthatsoilholdsthehighestamountof
carbon.Thecarbonstoredthatwasderivedfromthisstudyisalmosthalfto
theresultsofstudiesthatwereconductedinLeyte,whichhaveacarbon
densityvalueof52.70Mgha-1(Lasco,et.al.2000).
Table2.Samplebulkdensityandcarbonstorageofthesoil.
Soil Layers
0-10cm
10-30cm
30-50cm
50-100cm
BD (g cc-1)
1.05
1.22
1.07
1.14
C (MgCha-1)
16.61± 2.15
25.90±9.11
20.91±13.96
30.34±22.39
Totalcarbonstorageofgrassland.Overall,theone-hectaregrassland
storedthetotalcarbonstocksof28.01Mgha-1.Variouscarbonpoolsinclude
soils with 25.93 Mgha-1, above-ground biomass (stems and leaves) with
1.05 Mgha-1 and below-ground biomass (roots) with 1.03 Mgha-1. Soil
stores the highest amount of carbon while above-ground and below-
78
Table1.Description,numberofoccurrenceandfrequencyofplantspeciesinthestudysite.
Common Name
Imperata cylindrica
Melastoma malabathricum
Chromolaema odorata
Elephantopus specatus
Desmodium triflorum
Neptirolepis tirsutula
Scleria sphaecocarpa
Paspalum conjugatum
Piper aduricum
Mimosa pudica
Desmodium ovaliforium
Saccharum spontaneum
Desmodium ovaliforium
Elephantopus tomentosus
Blumea balsamifera
Piliostigma sp.
Ǽ
Alysicarpus sp.
Antigonon leptopus
Pancum maximum
Calopogonium mucunoides
Chrysopogon aciculatus
Centella sp.
Ǽ
Family Name
Pocaeae
Melastomataceae
Asteraceae
Ateraceae
Fabaceae
Dryopteridaceae
Poaceae
Piperaceae
Fabaceae
Fabaceae
Poaceae
Asteraceae
Asteraceae
Fabaceae
Fabaceae
Polygonaceae
Poaceae
Fabaceae
Poaceae
Apiaceae
Classification
Grass
Shrub
Herb
Herb
Herb
Fern
Grass
Herb
Herb
Herb
Grass
Herb
Herb
Tree
Herb
Vine
Grass
Herb
Grass
Herb
Grass
No. Of
occurrence
N=86
14
11
11
11
5
4
4
3
3
3
2
2
2
1
1
1
1
1
1
1
1
1
1
1
86
Frequency
(%)
16.28
12.79
12.79
12.79
5.81
4.65
4.65
3.49
3.49
3.49
2.33
2.33
2.33
1.16
1.16
1.16
1.16
1.16
1.16
1.16
1.16
1.16
1.16
1.16
100
Come et al.
Cogon
Hantotoknaw
Hagonoy
Malagabon
Mani-mani
Fern
Daat
Carabao grass
Baryo-baryo
Makahiya
Dysmodium
Bugang/Talahib
Cotton-cotton
Malagabon
Gabon
Alibangbang
Malacogon
Mini-mani mani
Kadena de Amor
Dawa-dawa
Batung-batong
Amorseco
Bukot-bukot
Unidentified grass
Total
Scientific Name
Biomass and Carbon Stocks of Vegetation in the Marginal Uplands
79
groundvegetationstoredmoreorlessthesameamountofcarbon.Soilsare
knowntostoremoreorganiccarbonandholdsitforalongerperiodoftime.
Inaddition,thecapabilityofthesoiltostoresoilorganiccarbonisbeing
influenced by the following factors: (1) mean annual precipitation; (2)
degree of forest disturbance; (3) extent of land use change (Lugo and
Brown,1993).ItwascitedbyPulhin(2008)thatinordertoenhancesoil
sequestrationthefollowingstrategiesmustbedone.(1)reduceerosion
through reforestation; (2) improving soil fertility; (3) reduce shifting
cultivation;(4)removemarginallandsfromagriculturalproduction;(5)
retainingforestlitteranddebris(Lascoetal.,2000).
Figure3.TotalstocksinthevariouscarbonpoolsinthestudyareainInopacan,Leyte
IMPLICATIONSANDRECOMMENDATIONS
Importantbaselinedataonthecarbonstoragecapacityofgrasslandsin
marginaluplandsinInopacan,Leytewasderivedfromthisstudy.Results
showedthatsoilisanimportantcarbonpoolandhashighercapacityto
storecarbonthanabove-groundandbelow-ground(roots)pools. Since
grasslandsareknowntohavehighturn-overrateduetotheirnatureand
pronetoburningandgrazing,carboncannotbestoredforalongerperiod
of time compared to other land uses including agroforestry and tree
plantations. It is therefore recommended that marginal uplands in
Inopacan be converted into more productive and diverse ecosystem in
order to maximize the benefits of the areas both ecologically and
economically. Further studies including quantification of carbon in
80
Come et al.
different grassland communities is also recommended. Carbon stocks
assessment of marginal uplands during rainy season could also be
conductedtocomparetheresultsofthisstudy.Otherimportantspeciesof
grasses,shrubsorherbsmightbepresentduringthisseasonwhichwere
notdocumentedduringtheconductofthisstudy.
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