monocultural coffee systems we estimated aboveground tree C stocks of 7 Mg .... trees of different size were cut, measur
~"ii,;mm
m
~im
!iPos!um
m:m ib 0 n~~~~~~q!!,!~1]Jl.C!!:!!!g
Carbon Stock Assessment for a Forest-to-coffee Conversion Landscape in Malang (East Java) and Sumber-Jaya
(Lampung,
Indonesia)
KurniatunHairiah1),JonniAritinl), Berlianl), CahyoPrayogol) and Meine van Noordwijk2) ~
.Abstract Assessmentof abovegroundC stock were made in upland coffee production areas near Malang (EastJava)and in SumberJayain WestLampung(Sumatra,Indonesia). The abovegroundC stock of monocultural and multistratacoffee basedsystemwere compared with that of remnant natural forest and plantation forestry. For the various systemswe found general agreementbetween the two sites. For the remnant natural forest in Sumberjayawe derived an estimateof abovegroundtree C stock (195 Mg ha-l) that was slightly above the value for a near-maturePinus stand in Malang (175 Mg ha-I). For the monocultural coffee systemswe estimatedabovegroundtree C stocks of 7 Mg ha-1 in Sumberjaya,while this land covertype was not found in Malang. For simple shadecoffee systemsthe values agreed well betweensites (23 and 19 Mg ha-1 for Sumberjayaand Malang, respectively). The Malang version of the multi strata systemshad a higher abovegroundtree C stock than those in Sumberjaya (49 and 34 Mg ha-l, respectively), related to the presence of the larger fraction of 'forest' trees in the plots. Annual abovegroundC stock accumulationrates of mixed coffee systemwas found to be about1.9 Mg ha-' yr-l, nearly double the value (1.0 Mg ha-1 yr-l) found for coffee monoculture system.A ratio of COIg and the Clefvalue that can be expectedfor forest soils of the same texture and pH, sampled at the same elevation and soil type, can be used as a 'sustainabilityindicator'. A value of the COIg /Crefratio of 1 meana "fertile soil" similar to that found in the forest, smallervaluesindicate partial loss of the soil C stocksand related loss of soil fertility. Conversionof (remnant)forest to coffee based systemsreducedthe CorJCref ratio from 0.8 to 0.5, equivalentwith a loss of soil C of about 57 Mg C ha-l.
.Introduction Clearing forest for new agricultural land is usually based on the slash-and-burning techniquewhich causesan immediatereleaseof carbon(C) to the atmosphere,whereasin other clearing techniquesthe C loss would be more gradual.The C initially held in trees and other vegetationincluded in necromassis releasedthrough burning (in the form of 1)Brawijaya University, Faculty of Agriculture, Malang,Indonesia. 2) InternationalCentrefor Researchin Agroforestry (ICRAF) SE Asia, P.O.Box 161,Bogor 16001,Indonesia.
28
! j
I
smoke) or decomposition of above and below ground plant material left in the soil at the time of clearing. Even if the gross and net primary productivity (NPP) of the new agricultural land is as high as it was in the forest, less of the crop production accumulates as litter, and a considerable part of it is harvested and subsequently consumed or respired away from the land where it was grown. This makes the 'net ecosystem productivity' (NEP) muc~ l~wer. Th~ reduction i~ li~er i~put is not initially balanced. by a reduction. in soil respIration, leadmg to a declme m sOlI C stocks. In fac~, the respiratory release IS oftenI enhanced by the cultivation itself, which exposes more of the organic matter to microbial activity and thus causes a net release of nutrients to the crops (and weeds). As a result, some of the C originally held in forest soil is released to the atmosphere after clearing. The C stocks maintained in aboveground biomass, however, do differ between forest and a cropped field, as does the rate of litterfall, leading to differences in soil organic matter (SOM) in soils.
,
~
I
L
f
Opening land for agricultural land reduced total C from tree biomass by about 66 % when slashing and burning were involved, but by only 21 % without burning (Pray30°). The coffee based plots were selected from the fields available that were cleared from forest at least 7 years old, so they represent established coffee based systems. The age of the coffee plants was also at least 15 years. Three replicate fields were sampled for each class.
Measurement of tree biomass Methods for quantifying tree biomass were used as specified in the ASB (The Alternatives to Slash and Bum) protocol (Palm et al., 1996; Hairiah et al., 2002). For the vegetation and soil sampling area was based on a 40 x 5 m2 transect. Two transects were made in each plot one uphill (top) and another downhill (bottom). The uphill transect was made at a distance from the top of the hill of about 10% of the slope length, and all transects were made along the contour. Usually tree biomass (forest) is estimated by the 'generic' allometric equation developed by Brown (1997) which is not suitable to be used to estimate trees biomass of pruned coffee. The pruned coffee has different tree branching pattern than other forest trees, it formed more site branches. An allometric equation for coffee and other trees which has different branching patterns was developped based on destructive sampling. About ten trees of different size were cut, measured for stem diameter and height and weighed freshly and subsampled for dry weight calculations. To avoid the need for measuring wood density p for every individual tree, a database of literature values was developed, recording lower bound, upper bound and medium values. Currently the databaseholds entries for 2800 tree species and will be shortly made available via www.icraf.cgiar/sea. Wood density can be classified as light (density less then
30
I !i
r
.', I
~
~
, f
0.6 Mg m-3),medium (between0.6 to 0.75 Mg m-3), heavy (0.75 to 0.9 Mg m-3) and very heavy(more than0.9 Mg m-3)(Anonymous,1981) Understoreyand herb layer vegetation were measuredin ten 0.25 m2 quadrat samples,total fresh weight was measuredand subsampleswere collected for determining dry mattercontent.Diameterand length of deadwood was measuredwithin the 40 * 5 m2 transectand convertedto volume on the basisof a cylindrical form; three apparentdensity classeswere used. Surfacelitter (including wood < 5 cm diameter)of eachland use was measuredi.e. (a) litter thickness (mm) by pressingthe litter layer and measuredits thickness from the surface of the mineral soil, (b) Litter biomass (giO.25 m2) was collected down to the surfaceof the mineral soil in ten 0.25 m2 samplesand sub sampleswere taken for dry mattercontent. Soil sampleswere collected (composite from 10 sample points) for the 0-5, 5-10, 10-20cm depthzone below the litter layer, for analysisof texture (sand,silt, clay~ pH (IN KCI), pH(H20), Corg(Walkeyand Black), Ntot(Kjeldahl)., Adimensionless'C saturation deficit', CsatdefWaS calculatedas the differencebetween the currenttotal C or Corgcontentand and the amountthat would be expectedfor a forest soil, C ref,with a long history of large litter inputs, for the sametype of soil. Csatdef = (Cref-CorJ f Cref= 1 -( Corgf C ref) Where,CorgfCref = soil organic carbon contentrelative to that for forest soils of the sametexture andpH, Cref= a referencesoil C level representativeof forest soil. The equationfor Corg"ref for upland soils in Sumatra(excluding peatand wetland soils as well as recentvolcanic andisols)is: Cref(adjusted) = (ZsamplJ 7.5)-0.42 exp(I.333 + 0.00994* %Clay + 0.00699* %Silt -0.156 * pHKcl+ 0.000427* Elevation) Where,Zsample is the soil depth i.e. 0-5 cm, 5-15 cm. The elevation of the study area is about850 m abovesealevel.
.Results
I
Allometric equationsfor pruned coffee,bamboo and banana Comparedto the 'generic' Brown (1997) allometric equation, use of tree-specific allometrics that include estimatesof wood densitytend to lead to lower biomassestimates (Figure 1), especially in the low-to-medium biomasss categories. The developped allometric equationbasedon destructivesampling in Malang was used further to estimate prunnedcoffee biomassin Sumberjaya.
31
For pruhed coffee, bamboo and banana separate allometric equations were used; for coffee was W = 0.28lD2.o6,the power of which agrees with the Ketterings et al. (2001) equation, as c = 0.08 (H = 1.79 DO.O8). For banana biomass an allometric equation based on pseudostem diameter was derived by Jom (2001) as : W = 0.030 D2.13.For the giant bamboo (Dendrocalamus asper (Schultes f.) Backer ex Heyne) Priyadarsini (1998) derived: 0.131 D2.28.
Aboveground C-stock For the Malang site, the aboveground C stock of the pinus woodlot was estimated, using a D and H equation, to be around 175 Mg ha-l. Amultistrata coffee system have a maximum C stock of about 49 Mg ha-land for shaded coffee system was about 19 Mg ha-1only. For the Sumberjaya site, the average aboveground tree biomass in the multistrata coffee system was about 74 Mg ha-l(estimated C stock 34 Mg ha-I), about 51 Mg ha-1 of shaded coffee system (estimated C stock 23 Mg ha-I), and only 16 Mg ha-1 for coffee monoculture system (estimated C stock 7 Mg ha-I). Under natural forest, the average aboveground tree biomass was about 435 Mg ha-l, with an estimated C stock of 195 Mgha-l.
Time-averagedC-stock Time averaged C-stock under forest, monoculture and multi strata coffee in Sumberjaya had been reported by Van Noordwijk et al ( 2002), The data for soil C, root biomass and aboveground biomass of trees, necromass, litter layer and understorey or herb layer, were combined to derive time-averaged C stocks (above a soil depth of 0.3 m) for the first 25 years of monoculture and multi strata coffee of 52 and 82 Mg C ha-l, that are considerably below that of the remnant forest (262 Mg C ha-l) or the young secondary forest (remnant of 'shifting cultivation'), at 96. Mg C ha-1(Figure 2). From this study, for 15 years mix coffee systems (shaded and multistrata systems) provided aboveground biomass about 34 Mg C ha-1 The average annual increase in C-stock of mixed coffee systems is about 1.9 Mg ha-1yr-1 and that for coffee monoculture systems is only about 1.0 Mg ha-1yr-l.
Soil OrganIc Matter The ratio Corg/Cref of four land-uses tested in Sumber Jaya is shown in Figure 3. There is no major difference between the CorgiCrefratiosfor the 0-5 cm and 5-15 cm layers for the forest soil, suggesting that the sample depth correction in the Crefequation is appropriate. The average CorgiCrefratio under forest condition was about 0.73, suggesting that the soil carbon status of this forest has declined from the undisturbed condition. .An increase of the land slope tends to reduce the Corg/Cref for all land uses, but the effect was smaller than expected. The Corg/Cref ratio of the coffee production systems was about half that of the remnant forest. The Multistrata coffee systems apparently maintains only slightly higher soil C levels than the coffee mono cultures and simple shaded coffee. No consistent
32
1 i ~
~
.
" """'#"" ,,+
differencebetweenthe lattertwo was found, as maybe expectedfrom the higher N content and more rapid decomposition of the legume tree litter in this systems compared to coffee.
.Discussion For the various systemswe found generalagreementbetweenthe two sites. For the remnantnatural forest in Sumberjayawe derived an estimateof abovegroundtree C stock (195 Mg ha-l) that was slightly abovethe value for a near-maturePinus stand in Malang (175 Mg ha-I). For the monocultural coffee systemswe estimatedabovegroundtree C stocks of 7 Mg ha-1in Sumberjaya,while this land cover type was not found in Malang. For simple shadecoffee systemsthe valuesagreedwell betweensites (23 and 19 Mg ha-1 for Sumberjayaand Malang, respectively).The Malang version of the multi stratasystems had a higher abovegroundtree C stock than those in Sumberjaya (49 and 34 Mg ha-l, respectively),relatedto the presenceof the largerfraction of 'forest' trees in the Ilots. The annualC accumulationrate of the coffee-basedsystems(1 and 1.9 Mg C ha-1yr-l) is well below the value (2.5 Mg C ha-1yr-l) for the jungle rubber agroforestrysystemsin Jambi about2.5 ha-1yr-1 (Tomich et aI, 2000). The lower annualincrementin combination! with shorterlife-spansof the system,leads to substantiallylower time-averagedC stockr estimates.,
.Acknowledgement This financial supportprovided by APN (Asian Pasific Network) for study in Malang site, and ACIAR for Sumberjayasite throughthe ASB Project(Phase3). The authorsalso wish to thank to Jr. Subekti Rahayufor her help on statisticalanalysis,to Jr Rudi Harto Widodo and Jr. Pratiknyo Purnomosidhifor their technicalassistant.
.References Antin, J., 2001. Estimasi cadangankarbon pada berbagai systempenggunaanlahan di kecamatanNgantang, Malang. Studentthesis, Soil ScienceDepartment,Universitas I Brawijaya, Malang, Indonesia.59 pp Brown S. 1997. Estimatingbiomass changeof tropical forest, a primer. FAO Forestry Paper134,FAO, Rome. Hairiah K and Sitompul SM, 2000. Assesmentand simulation of abovegroundand belowgroundCarbondynamics.APN/IC-SEA,Bogor. Hairiah,K., Sitompul, SM, van Noordwijk, M. and Palm, C.A., 2001. Methods for samplingcarbonstocksaboveand below ground. ASB_LN 4B. In: Van Noordwijk, M,
33
Williams, S.E. and Verbist, B. (Eds.) 2001.Towards integrated natural resource managementin forest marginsof the humid tropics: local action and global concerns. ASB-LectureNotes 1 -12. InternationalCentrefor Researchin Agroforestry(ICRAF), Bogor, Indonesia.Also availablefrom: h!ill:/ /www.icraf.cgiar.orgLsea/TrainingLMaterials/ASB-TM/ ASB-ICRAFSEA-LN.htm Ketterings QM, Coe R, van Noordwijk M, Ambagau Y and Palm CA. 2001. Reducing uncertaintyin the use of allometric biomassequationsfor predictingabove-groundtree biomassin mixed secondaryforests.ForestEcology and Management120, 199-209. Priyadarshini, R., 1998. Estimasi modal C (C stock), masukan bahan organic dan hubungannya dengan populasi cacing tanah pada system wanatani. MSc thesis Brawijaya University, Malang. 76 pp Tomich, T.P., Van Noordwijk, M., Budidarsono, S., Gillison, A., Kusumanto, T., Mudiyarso, D., Stolle, F. and Fagi, A.M., 1998. Alternatives to Slash-and-Bumin Indonesia. Summary Report & Synthesis of Phase II. ASB-lndonesia and ICRAF-S.E.Asia Van Noordwijk M, Rahayu S, Hairiah, Wulan, Y.C., Farida, Verbist B, 2002. Carbon stock assessment for a forest-to-coffeeconversionlandscapein Sumber-Jaya(Lampung, ~donesia): from allometric equationsto land use c~angeanalysis.J..Sc.Chin~ (spe~ial Issueon Impactsof land use changeon the terrestrialcarboncycle m the AsIa PacIfic region)(in press).
34
I I
.
,
, f ~
",Co""'
2.2
Pruned
coffee
30 .~
E 2.1 -~ +J
25
'-
.'a,
20
..c::
-.
C)
(/)
.-(/)
Q) 2.0 ..c::
(\J 15 E
Q)
0
Q) '-
.-10 ..0
I-- 1.9
Q) ~ 5
I-1.8 0 10
2 Banana
4
6
8
0 12 0 50
10
2
4
6
8
10
12
Q)
8
E
t
-
.~
40
+J
,
C)
:E-~ 6
-30
C)
(/)
.-(/)
Q)
(\J
..c::
E
~
:a
Q) 4
0 20
,
I--
Q)
2
~ 10 I--
0
0 0
c
12
5 Bamboo
10
15
20
25
30
0
5
10
15
20
25
30
14
!
'10 ,
~ 12 '+J
E
-a, 10
-8
~
:E
~
.2' Q)
(/) (\J
..c::
6
Q) Q)
I
E
8 6
0 4
..-,'-
..0
I--
4
Q) Q)
2
~
2 I
0
0 0
2
4
6
80
2
Stem diameter at 1.35 m, cm
"mr88
~
Allometric biomass
relationships (dry
weight)
between for
4
6
8
Stem diameter at 1.35 m, cmLc
(pseudo
pruned
bamboo (Priyadarsini, 1998). ,
35
coffee
)stem and
diameter banana
and (Arifin,
plant
height 2001)
orr and
-~
-Q-mixed .monoculture 6. fallow
.forest 0 mixed (incl. older trees)
;
y = 1.8666x. R2 = 0.5768 ~ ~ ~ . ~ ~
+damar
tII" (1)
..~
co E 0 100.00 I
0
:c
~- ~
u
l::.~ ~ ~ ~ ~~ ~ ~
~. ~
~
~
-"""
~
~
-"""
y = 0.9469x
-"""
R2 = 0.6642
"1,
Age of coffee
garden,
year
.If:
"'
..".=-
,
j
Relationship between aboveground C stock and age of coffee gardens (presumably since last clear-felling or slash-and-burn land clearing, but note that for some of the shade coffee gardens the age of the coffee plants is used as X-axis as the age of the garden is unknown) (Van Noordwijk et ai,
2002).
0-5 cm -+
-Nat.Forest
-*-Shaded
0,8 0,7 '; 0,6 '; 0,5 U -a. 0,4
5-15 cm ---Multistrata
-+
-.-Monoculture
-*-Shaded
---Multistrata -.-Monoculture
0,8 ...0,7 ."
... ~+-
'; 0,6 '; 0,5 U 0,4 -a.
-+
I= :::=t::~;~==t
9 0,3 u 0,2 0,1
., A.
9 0,3 u 0,2 0,1
'
0,0
~ --8=:::::::::;::::::=:::::=--==--
0,0 0
10
20
30
40
50
Slope,o ~.".~-
-Nat.Forest
0
,1G.
20
30
Slope,o
The ratio of Corg/Crefof different land use types in Sumber Jaya (Bodong)
36
40
