Texte intégral de l'article
 
  Printable version
  Version PDF

Carbon storage and global change: the role of oil palm


Oléagineux, Corps Gras, Lipides. Volume 12, Number 2, 154-60, MARS-AVRIL 2005, DOSSIER : recherche, palmier à huile et développement durable


Summary  

Author(s) : Emmanuelle Lamade, Jean-Pierre Bouillet , CIRAD-CP, UPR 80, ETP, IOPRI, Medan, Indonesia, CIRAD-Forêt, UPR 80, ETP, TA/10C, Campus international de Baillarguet, BP 5035, Montpellier Cedex 5, France.

Summary : In the context of global change, potential estimations of carbon storage by the oil palm ecosystem in different ecologies have been calculated for the major productive countries in Africa, Asian and American continents. Comparisons were done with other types of planted ecosystems as eucalyptus and coconut as well as different types of natural forests. Carbon budget components as NPP, autotrophic and heterotrophic soil respiration, litter and fine litter contributions were discussed in regards to the very high rate of carbon sequestration by oil palm ecosystem : from 250 to 940 C m–2 yr –1 (estimations including harvested bunches).

Keywords : global change, carbon storage, Elaeis guineesis, net primary productivity, soil respiration, ecosystem carbon content

Pictures

ARTICLE

Auteur(s) : Emmanuelle Lamade1, Jean-Pierre Bouillet2

1CIRAD-CP, UPR 80, ETP, IOPRI, Medan, Indonesia
2CIRAD-Forêt, UPR 80, ETP, TA/10C, Campus international de Baillarguet, BP 5035, Montpellier Cedex 5, France

Introduction

It is generally accepted that there is a link between the increase in average temperature at the earth’s surface during the 20th century (0.6 °C +/– 0.2 °C) and the higher concentration of greenhouse gasses (GHG) in the atmosphere, particularly CO2 which is responsible for 50% of the overall GHG effect, apart from water vapour [1], and its average concentration increased from 290 ppm in 1900 to 360 ppm in 2000, which is a value that had not been reached for at least 420 000 years1. For 20 years we have been seeing an average annual increase of 3 GtC (3.109 tC) in the atmosphere due to the burning of carbon fossil fuels, and to changes in land use, primarily deforestation (7 GtC and 1 GtC in 2000 [2]). This additional amount only accounts for 0.04% of the C stock in the atmosphere (750 GtC), but at the current rate almost 50% as a cumulated value over 100 years. This would lead by the end of the 21st century to a substantial rise in the average temperature (from +1.4 °C to +5.8 °C depending on the estimates), with major ecological consequences (melting glaciers and ice-floes, rising sea levels, climate change, spread of tropical diseases and changes in biodiversity, etc.).

Aware of these risks, the international community drew up the United Nations Framework Convention on Climate Change (UNFCCC) in 1992 in Rio de Janeiro, the aim being the “stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system”. Under this convention, the Kyoto Protocol, signed in 1997 and implemented since February 2005, calls for a reduction in GHG emissions in industrialized countries “to at least 5% below the 1990 levels in the commitment period 2008 to 2012”. Among the provisions proposed, the CDM (Clean Development Mechanism), provides for the establishment of carbon sinks, through afforestation or reforestation. It should be pointed out that, although only forest species are eligible during this first phase, tropical tree crop plantations may subsequently be involved (www.irrdb.com; www.energybulletin.net).

Of these, oil palm (Elaeis guineensis, Jacq.) plantations, which cover over 12 million hectares on the African, Asian and American continents (www.fao.org/waicent/statistics-fr.asp), could prove to be of particular interest. Indeed, their high biomass production and dynamic expansion make them a potentially important carbon sink. On the other hand, the fact that they are partly planted in deforested zones makes it necessary to estimate the amount of carbon fixed by these plantations compared to the original ecosystem. More generally, this type of knowledge serves to clarify the debate on the environmental impact of such crops in the tropics. For several years, particularly since the “smog” episode in 1997 in Southeast Asia2, oil palm has been at the centre of an environmental controversy [3-6], as oil palm was seen to be a “polluter” using substantial inputs (fertilizers, pesticides), discharging considerable amounts of effluent from oil mills, and consuming large amounts of water during processing. Managers therefore need to have at their disposal not only agricultural results enabling an improvement in bunch yields in plantations, but also an estimation of environmental impacts, of which the carbon balance is a part.

Some clues are available, such as those provided by the Indonesian Oil Palm Research Institute (IOPRI, Medan, North Sumatra) (table 1( Table 1 )), indicating the strong atmospheric CO2 fixing potential of oil palm plantations.

The purpose of this article is to go beyond these initial results starting with an analysis of the key points of the carbon cycle in the “oil palm” ecosystem – on a palm scale, then on a stand scale – and assess the different components of the carbon budget depending on the age of the plantations, under different ecological conditions. A general assessment of CO2 storage potential is given for several palm oil producing countries.

A comparison is made with other planted ecosystems (eucalyptus, coconut). Note that the calculations of this balance only take into account the oil palm growth and production period, and not processing which leads to GHG discharges when making oil.
Table 1 Ecological data on the oil palm and comparison with tropical forest (IOPRI site, “Indonesian Oil Palm Research Institute”, http://www.iopri.id).

Parameters

Unit

Tropical forest

Oil palm plantation

Biomass production

t DM ha–1 yr–1

22.9

36.5

CO2 fixation

t CO2 ha–1 yr–1

9.62

25.7

Photosynthesis

μmol m–2 s–1

13-19

21-24

Absorbed radiation

MJ m–2 yr–1

51.4

82.9

Respiration

t CO2 ha–1 yr–1

121.1

96.5

O2 production

t O2 ha–1 yr–1

7

18.7

Carbon flux on a palm scale

Carbon entrance: photosynthesis

It is photosynthesis that enables atmospheric CO2 to enter the frond when incident radiation is sufficient and when water supply conditions are favourable. Atmospheric carbon assimilation is estimated via an initial photosynthesis module taking into account the maximum assimilation values of the plant, the coefficient of light extinction and apparent quantum yield. The curve for photosynthesis response to radiation (PAR: Photosynthetically Active Radiation) is integrated in accordance with the cover (LAI: Leaf Area Index). For oil palm, it is accepted that the carbon assimilated by a frond (source organ) serves first of all for growth requirements (frond, stem, roots), then once those needs have been met the remainder of the available assimilate is directed to the bunches [7].

Under potential conditions

Photosynthesis measurements on the oil palm reveal a considerable disparity in maximum values at saturating light levels, below 5 μmol m-2 s–1 for Hirsch [8], between 14 and 20 μmol m-2 s–1 for Corley [9] or between 6 and 9 μmol m–2 s–1 for Potulski [10]. New values were measured by Dufrêne and Saugier [11] with 23 μmol m-2 s–1 in Ivory Coast on control family LM2T × DA10D (( figure 1 )) and by Lamade and Setiyo [12] on clones, with 32 μmol m–2 s–1 under optimum conditions for oil palm in North Sumatra. The last values are very high for a C3 plant. The variations found for maximum photosynthesis can be attributed to differences in the measuring methodology, with the instruments becoming increasingly precise and stable under tropical conditions, to the plant material used (more efficient clones), to environmental conditions (e.g. water deficit) or simply to the age of the palm or the position of the frond or leaflet measured.

A simple way of quantifying the daily carbon gain of leaflets is to monitor the increase in dry weight of leaflet laminae (table 2( Table 2 )). It can be seen that this is not insubstantial: more than 25 g dm m–2 (dm: dry matter) of lamina under conditions at the La Mé station in Ivory Coast.
Table 2 Increase in leaf disc weight in one day (according to Dufrêne [7]), A: photosynthetic assimilation of CO2; number of measurements indicated in brackets.

Time

Dry weight (g dm m–2)

A (μmol (CO2)m–2 s–1)

7.30

83 ± 7 (10)

-

9.30

88 ± 3 (10)

25.27 (3)

11.05

96 ± 13 (10)

23.94 (5)

13.10

98 ± 16 (10)

23.54 (4)

15.15

108 ± 13 (10)

21.52 (3)

16.40

102 ± 6 (10)

A variation factor: the age of the palm and the frond

After a year in the nursery, seedlings are planted out in the field: their photosynthesis is already high with values over 19 μmol m–2 s–1. From 4 to 9 years, photosynthesis increases up to 32 μmol m–2 s–1, with the canopy closing up very quickly from 4 years after planting. During that period, there is a very rapid increase in LAI, reaching 4.5. Young palms quickly produce more than 20 fronds per year, which are increasingly large, reaching from 5 to 8 metres in length. The light interception of the canopy at 9 years is over 80%. This is why few oil palm-based intercropping systems or agroforestry systems are exploited for the entire length of the cycle, unlike other crops such as cocoa, coconut or coffee.

Photosynthesis also varies depending on where the frond lies in the crown. A crown contains between 35 and 42 fronds on average: fronds are regularly pruned when bunches are harvested, respecting precise agronomic practices: 35 fronds in Africa and 42 in Asia. Fronds are arranged in eight spirals. This distribution is due to the specific phyllotaxy of the oil palm (angle of rotation of frond emission varying from 135°7 to 137°5). Fronds are numbered in ranks of 1 to 42, or 56. The oldest fronds have the highest numbers and are found low in the crown. Variations in photosynthesis depending on frond rank have been measured: from 20 μmol m–2 s–1 for frond ranks 1 to 3, photosynthesis decreases to 10 μmol m–2 s–1 for frond ranks over 30 [11].

Limiting factors

Oil palms are highly susceptible to VPD variations (Vapour Pressure Deficit: corresponds to a certain level of air dryness): as the air dries out, VPD increases and the plant regulates its transpiration by closing its stomata. In Ivory Coast, Dufrêne and Saugier [11] found a considerable drop in stomatal conductance from a VPD value of 1.7 kPa. In Indonesia, such a drop was found for lower VPD values. It is reflected in a very clear decline in carbon entry into the plant. ( figure 2 ) shows a very clear relation between photosynthesis and stomatal conductance. This limitation of photosynthesis by conductance is substantial in dry periods (due in Africa to seasonal variations during the year, or to the harmattan effect for example), during more specific climatic events such as El Niño, or more commonly at noon when the air temperature is high. It should be noted that temperatures over 36 °C drop photosynthesis and promote respiratory losses at the same time.

Variation in the soil’s water reserve is one of the parameters that best explains reduced yields. Under Ivorian conditions, stomata can be seen to close when the water reserve in the soil is less than 67% of the useful reserve [13]. Likewise, variations in the yields found at all the 30 stations in North and South Sumatra, in Indonesia, were primarily explained by the length of the dry season and the severity of the water deficit.

Mineral deficiencies, especially nitrogen, are also a major photosynthesis limiting factor. The photosynthesis of 1-year-old seedlings placed under controlled conditions can be increased by 60% [14] with a standard application of 2 × 35 g month–1 NPK (12/12/17) compared to a control without fertilizer.

Estimation of CO2 assimilation by a whole crown

A preliminary estimation of the net assimilation of an oil palm crown can be carried out using a simple model where the curve for photosynthesis response to radiation (PAR) is integrated in accordance with the cover (LAI) and in line with the exponential variation in radiation in that cover. The SIMPALM model [15] can be used to simulate carbon fixation per palm in two different ecologies, in Africa and Southeast Asia. For an average mature palm in Ivory Coast, a crown consisting of 35 fronds will potentially fix2 300 kg C yr–1 for a capture area of 315 m2 of laminae (radiative conditions: 14 MJ m–2 day–1). In Southeast Asia, under optimum water supply conditions, carbon fixing amounts to 350 kg C yr–1 for a capture area of 340 m2 (radiative conditions: 16 MJ m–2 day–1). By expressing these values on a plantation scale it is possible to estimate the gross primary productivity (GPP) of the ecosystem.

Rules of allocation to the different organs

These allocations do not have a preponderant effect on overall carbon storage, but may influence the quantity of carbon returning to the soil, via root turnover and foliage biomass decomposition in the windrows. For oil palm, genetic origin, the ecology and nitrogen fertilization strongly affect these allocation rules.

Marked differences in C allocation to the root system have been seen between different families in Ivory Coast (rainfall = 1415 mm, water deficit = 300 mm, deep sandy soil) and in Indonesia (North Sumatra: rainfall = 2980 mm, negligible water deficit, soils tending towards clay) (table 3( Table 3 )). In the Ivorian lagoon zone, the oil palm root system reaches a depth of 6 m, whilst in North Sumatra on podzols, the root system mostly develops in the first 40 cm.

Vertical growth can differ in the same ecology: between the two types of germplasm, Deli × La Mé and Deli × Yangambi, carbon allocation to the stem varies from 36 to 42%.

Carbon allocation to bunches (around 17% of the assimilates produced) is a parameter of paramount importance for growers, but it also determines the amount of material exported from the ecosystem, which is not insubstantial in the case of oil palm.
Table 3 Soil carbon contents (%, 0-15 cm) and spatial heterogeneity in the plantation. Changes in soil carbon stock for two genetic stands, Deli × La Mé and Deli × Yangambi, under the ecological conditions of North Sumatra (unpublished data).

North Sumatra

North Sumatra

Ivory Coast

Plant material

Deli × La Mé (%)

Deli × Yangambi (%)

LM2T × DA10D (%)

Leaflets

10

11

7

Rachis

18

22

12

Petioles

14

15

8

Stems

36

42

30

Roots I

9

4

11

Roots II

6

4

16

Roots III+IV

7

2

16

Carbon release

Respiration

Few direct measurements can be found of respiration that results in CO2 release from the different oil palm organs. It should be remembered that respiration has been divided into growth respiration and maintenance respiration [16, 17]. It is thus possible to estimate the cost in assimilates of the biomass formed, corresponding to the palm’s carbon demand.

The maintenance respiration of the stem measured by Dufrêne [7] varied from 0.2 to 0.4 g C kg dm–1 day–1 depending on the temperature. These values correspond to a total release of around 30 to 70 g C per day under African conditions.

Respiratory release during inflorescence growth is greater, at 85 g C released daily [7]. As the leaf respiration rate is directly related to photosynthesis, it is normal to find maximum CO2 release for frond ranks 8-9-10, which are the most photosynthetically active, and those receiving maximum radiation, up to rank 20, irrespective of the height of the sun [18].

Few measurements or estimations can be found of root respiration, except through more general measurements of soil respiration. A soil respiration study conducted by Lamade et al. [19] at Ouidah (Benin), at an average ambient temperature of 27°C, led to an estimation of carbon loss through root respiration of 76 kg C yr–1 palm–1 in a 20-year-old plantation. Henson [20] gave an estimate of 32 kg C yr–1 palm–1 for a younger plantation (10 years old) in Malaysia with a less developed root system.

Using the Penning de Vries formulas [17], the SIMPALM model estimates that the annual respiratory cost in carbon, including growth and maintenance of all the organs of a mature oil palm, amounts to 211 kg C yr–1 palm–1 in North Sumatra [15] and 202 kg C yr–1 palm–1 under African conditions.

To conclude, it can be estimated that, on average and under optimum ecological conditions such as those in North Sumatra, a mature palm will release around 750 kg CO2 yr–1, i.e. the equivalent of 200 kg C yr–1 through respiration.

Plant matter: FFB harvesting and frond pruning

Carbon export through FFB harvesting will vary from 18 kg C yr–1 palm–1 (at 3 years) to 43 kg C yr–1 palm–1 (at 9 years) based on production at SOCFINDO (North Sumatra).

During its productive period, an oil palm will undergo two types of pruning, the first to enable ripe bunch harvesting from the crown, the second to maintain an acceptable number of active fronds in the crown. Carbon loss associated with those operations can be estimated at 40 kg C yr–1 palm–1 on average under North Sumatran conditions. That carbon is not completely lost from the ecosystem as fronds are usually piled in the windrows where they rot. They may also be used by local populations, in which case there is a significant drop in the carbons reserve of the soil: in the case of North Sumatran plantations, the reduction is substantial over a period of 10 years (table 4( Table 4 )).
Table 4 Allocation of biomass in mature oil palms (as a % of total dry matter) to the different vegetative organs in two types of ecologies and with two types of planting material (North Sumatra [15]; Ivory Coast: [7]).

Genetic family and location

Benin

Deli x La Mé

Deli x Yangambi

Year

1993

1994

2004

1994

2004

Interrow

0.46

3.15

2.35

Windrow

0.82

2.22

1.94

1.89

1.4

“weeding” circle

0.55

2.17

1.39

1.79

1.38

Harvest path

2.1

1.68

1.84

0.83

Carbon storage in elaborated biomass: variation with age

Carbon storage in the biomass elaborated each year primarily depends on the age of the stand, then secondarily on agroecological conditions. For the stem, Jacquemard and Baudoin [21] found three stem growth phases under Ivorian conditions. From 0 to 3 years: growth in width only; from 3 to 6 years: increase in growth rate; from 6 to 25 years: stabilized growth rate, or even declining, from 10 years onwards. Frond size varies over the years, as does the number of leaflets and, finally, the total “capture” area.

Root growth was studied and modelled by Jourdan [22] under Ivorian conditions. The author mentioned an increase in biomass of 21 kg dm palm–1 at 4 years old to 385 kg dm palm–1 at 16 years old.

Under Asian conditions, Henson [23] found a total annual variation in aerial growth of 1 to 2 t dm ha–1 yr–1 between 8 and 12 years old. The same author showed an annual root system growth rate of 7 kg dm palm–1 between 0 and 5 years old, then 14 kg dm palm–1 between 10 and 15 years old, with a notable drop in that annual growth rate between 15 and 28 years old, at 2.3 kg dm palm–1.

Plantations: a planted ecosystem

After examining what happens on the scale of a single palm and having quantified carbon storage on an individual palm scale, it is necessary to establish the carbon flux balance between captures and releases on a plantation scale. This is characterized by two main vegetation storeys: the palms, and nitrogen fixing cover crops mixed with invasive species. This ecosystem has specific edaphic characteristics, spatial heterogeneity in soil carbon content, and a particular microclimate.

Components of soil respiration

Soil respiration, i.e. total CO2 release from the soil including the activity of the roots and of the rhizosphere, along with the activity of microorganisms and fauna in the soil, is an essential parameter for estimating the carbon budget of the ecosystem. For oil palm, measurements have already been taken by Henson [22], Lamade and Setiyo [24], under Asian conditions, and by Lamade et al. [19] in Benin. Using the Raich and Nadelhoffer equilibrium principle [25], a distinction can be made between the different components of soil respiration (autotrophic respiration (roots), heterotrophic respiration (microorganisms), CO2 losses linked to leaf litter decomposition and root litter decomposition). Using the same principle, it is possible to estimate total carbon allocation to roots and root turnover. On this basis, total annual carbon release from the soil (Rsol) into the atmosphere differs in Benin (1610 g C m–2 yr–1) and North Sumatra (1170 g C m–2 yr–1), due to greater respiratory loss from roots in Benin. Total carbon allocation to the roots (in a mature oil palm plantation) varies from 1438 g C m–2 yr–1 in Benin to around 1025 g C m–2 yr–1 in North Sumatra. A great difference is found between these two ecologies for root turnover: 535 g C m–2 yr–1 in North Sumatra under potential conditions for oil palm growing, and less than 354 g C m–2 yr–1 in Benin (table 5). Irrespective of the ecology, CO2 release in plantations displays typical spatial heterogeneity, in direct relation with the layout of the palms at the tips of equilateral triangles, along with the effect of cultural practices (preferential zones for fertilizer applications, arrangement of pruned fronds on the windrows, slow decomposition of stems in the interrows, etc).

Large differences can be seen between natural forest ecosystems and planted ecosystems, such as oil palm or eucalyptus plantations. Natural forests are characterized by much lower CO2 release into the atmosphere through soil respiration and greater enrichment of the soil in carbon through leaf litter (table 5( Table 5 )). However, a similarity is found in results between oil palm and eucalyptus plantations for soil respiration components (table 5).
Table 5 Total soil respiration (Rsoil), annual net primary productivity (NPP), growth, and both aboveground and belowground litter for several types of ecosystems, in g C m–2 yr–1. D*L(Indo) genetic family Deli × La Mé (North Sumatra); D*Y(Indo): genetic family Deli × Yangambi (North Sumatra). Ash, Interior, Edge Forest: Hawaiian tropical forests (Mauna Loa).

Ecosystem

Reference

Rsoil

NPP

  • Leaf
  • litter


Growth

Root litter

D*L(Indo)-oil palm

[24]

1167

1719

133

1094

544

D*Y(Indo)-oil palm

[24]

1198

1937

179

1312

526

Malaysia-oil palm

[39]

1219

2014

150

1312

844

Benin-oil palm

[19]

1610

937

124

687

345

Ash forest

[32]

900

519

475

219

Edge forest

[32]

780

375

280

94

Interior forest

[32]

650

280

250

47

Merapi (Pinus merkusii., plantation) Indonesia

[34]

980

844

432

407

  • Merbabu (Pinus merkusiiI, plantation)
  • Indonesia


[34]

690

460

192

350

  • Eucalyptus (3 yrs plantation)
  • Congo


[33]

1180

1203

676

527

Soil carbon stock and decomposition

Some studies [26-29] measured changes in soil carbon content from destruction of the forest ecosystem to its replacement by an oil palm plantation under Ivorian conditions. When such a replacement is made, there is a notable drop in soil carbon (in the upper horizons, 0-30 cm) in the first 4 years as the young oil palms develop, then that rate seems to stabilize from 9 years old onwards at between 55% and 65% of the previous forest soil content. In the case of replantings, which is now the most common situation, the carbon contribution coming from the slowly decomposing old stems, and the rapid contribution from the leaf and root litter of both vegetation storeys (herbaceous and palms) are combined over the years. Henson [20] developed a model for Malaysia for frond decomposition in the windrows depending on the age of the plantation. Maximum decomposition was found at a young age: at 5 years old, frond laminae rot totally within 255 days. At 25 years old, that period extends to 2 years. Under the drier conditions of Benin, frond decomposition is much slower and it is not rare to find windrows 1.5 m high and 3 m wide if fronds are not removed by the local populations. Typical spatial heterogeneity is found for soil carbon variations in plantations (table 4) usually with higher contents in the windrows and interrows. African situations (Benin) and Southeast Asian situations (North Sumatra) are seen to be highly contrasting.

Eddy covariance method

An estimation of CO2, water and energy flows on a stand scale is currently obtained by using the eddy covariance method. For oil palm, this type of study has only been carried out in Malaysia [30, 31]. It proves to be very useful for a satisfactory estimation of the annual CO2 balance for a large area of vegetation. Henson [31] measured a negative flow (corresponding to the net flow entering the ecosystem) varying from –24 to –29 g CO2 m−2 day–1, i.e. –87 to –106 t CO2 ha–1 yr–1 under average radiative conditions in Malaysia. Those results differ from the ones we estimated by the Raich method [32] (table 6( Table 6 )). The eddy covariance method was used by a CIRAD team for coconut in Vanuatu and eucalyptus in Congo [33] at different ages. For 3-year-old eucalyptus maximum values corresponded to around –1 g CO2 m–2 h–1, much lower in absolute values than for oil palm (up to –4 g CO2 m–2 h–1). This lower sequestration is found in the annual balance with a total flow of –15 t CO2 ha–1 yr–1.
Table 6 Estimation of carbon storage (g C m–2 yr–1) for the oil palm ecosystem (), and comparison with other planted or natural forest ecosystems. (1): Lamade and Setiyo [24]; (2) Henson and Chai [39]; (3) Lamade et al. [19]; (4): Raich [33]; (5): Gunadi [34]; (6): Dewar and Cannell [40]; (7): Nouvellon et al. [37]; (8) Grace and Malhi [41]; (9) Roupsard et al. [42].

Ecosystems

Location (latitude, longitude) and ecology (elevation, annual rainfall, average temperature)

C storage not accounting for harvesting

Storage after harvesting

D × L oil palm (8 years old), Indonesia

2°55N, 99°05E, 370 m, 2900 mm, 24.7°C (1)

1100

620

D × Y oil palm (8 years old) Indonesia

Ditto (1)

1230

940

Oil palm, Malaysia

(2)

1340

250

Oil palm, (20 yrs old) Benin

6.23°N, 2.08°E, - , 950 mm, 27°C (3)

650

Interior rainforest, Mauna Loa volcano (Hawaii)

19°45’N, 155°15’W, 1660 m, 2600 mm, 13°C (4)

43

P. merkusii (Java)

7°30’S, 110°30’E, 800 m, 3700 mm, 21°C. (5)

403

Temperate forests

England (6)

20 - 50

Eucalyptus, 3 yrs old Congo

4°S 12°E, 50 m, 1200 mm, 25°C (7)

390 - 470

50

Forests (total)

(8)

150

Coconut, 20 yrs old Vanuatu

15.29’S, 167°14’E, 40 m, 2900 mm, 25°C (9)

125-530

Annual balance and carbon sequestration

Estimations were made by Lamade and Setiyo [24] following the work by Raich [32] on several types of ecosystems including 4 types of oil palm plantations located in different ecologies (Malaysia, Benin, Indonesia), 2 Pinus merkusii plantations on the island of Java in Indonesia studied by Gunadi [34] and 3 types of forest ecosystems studied by Raich [32] in Hawaii to establish the carbon balance. Net Primary Productivity (NPP) is estimated from growth (stem diameters, heights), from standing biomass, from annual production of aboveground material such as fronds and inflorescences, from the production of root biomass and root turnover. Carbon sequestration is estimated by subtracting the heterotrophic component of respiration. The annual storage of a mature oil palm plantation is very high: without bunch harvesting it is potentially 1340 g C m–2 yr–1 (i.e. 13.4 tC ha–1) under optimum ecological conditions (table 6). These values are much higher than those for forest ecosystems (150 g C m–2 yrn–1 on average). Harvesting and continual exportation of FFB causes this storage level to fall (250 g C m–2 yr–1), but it remains higher than that for the tropical forest (43 g C m-2 yr–1). Nevertheless, it can be less than other planted ecosystems such as eucalyptus (390-470 g C m–2 yr–1) in the hypothesis where plantations serve as carbon sinks. When trunks are utilized at the end of the cycle, the balance turns back in favour of oil palm.

Emission credit: what oil palm can contribute …

To round off this evaluation, it is necessary to distinguish between stored carbon (the capacity of an ecosystem to maintain a certain biomass), carbon “parking”, which is a more restrictive concept (what happens over a period of twenty years, for example), and sequestered carbon, the net CO2 taken by the ecosystem from the atmosphere. As a first approximation, we can take a figure of US$ 20 per tonne [35] irrespective of the situation. For oil palm, we simply estimated this emission credit as a function of the areas harvested, of the ecology and of yields, based on the dry matter produced each year. Global carbon storage by the oil palm can be estimated at 73 Mt C yr-1 for 12 million hectares (table 7( Table 7 )). This value is well below the 336 Gt of storage for forest ecosystems, but the areas bear no relation either. The oil palm can store 4 times more per hectare than a forest ecosystem in what are essentially biomass terms. Looking at things another way, the net storage of French forests is 10.5 Mt C yr–1[36]. The most sensitive point for the planted oil palm ecosystem is the low litter production and its decomposition. ( figure 3 ) illustrates the substantial release of CO2 by the soil in oil palm plantations and a very low return of that carbon via litter, compared to forest ecosystems. In order for this system to increase carbon storage in the soil, management of organic supplies need to be improved. One way would be to limit frond exports by local populations, and reintroduction of empty fruit bunches into the ecosystem (which is already done on some estates), along with waste from oil extraction. In addition, if such storage were remunerated, each planter would be likely to receive US$ 130 per ha per year.
Table 7 Estimation of carbon storage per country and continent, along with corresponding emission credits (Total Africa: 22 countries, Total Asia: 5 countries, Total America: 7 countries).

Countries and continents

Production Mt

Areas harvested (ha)

Total carbon storage, harvest removed (t)

  • Emission credits
  • US $


Republic of Benin

244 000

20 000

110 000

2 200 000

Indonesia

55 000 000

3 175 000

24 765 000

595 300 000

Malaysia

68 050 000

3 670 000

9 175 000

183 500 000

Total Africa

15 754 000

4 300 900

27 956 000

559 120 000

Total Asia

128 550 000

7 134 000

43 018 000

860 360 000

Total America

5 620 600

379 549

2 315 000

46 300 000

Total

-------------

----------

73 289 000

1 465 780 000

Conclusion: more quantitative studies

We have just seen that a mature oil palm plantation displays considerable net primary productivity (NPP): 2015 g C m–2 yr–1 in Malaysia compared to 520 g C m–2 yr–1 for a natural forest in Hawaii, or 845 g C m–2 yr-1 for a Pinus merkusii plantation. However, respiratory losses, particularly from the soil, are also substantial: 1610 g C m–2 yr–1 in Benin compared to 810 g C m–2 yr–1 for a eucalyptus plantation in Congo [37]. Another characteristic of the oil palm ecosystem is the lower contribution of leaf litter compared to forest ecosystems: 130-180 g C m–2 yr–1 in Sumatra compared to 390-500 g C m–2 yr–1 for natural forests [38]. From that point of view, it is important to have more quantitative data on the herbaceous storey (cover crops invaded by a host of opportunistic species), which is considerable in young stands, in order to estimate carbon balances more effectively. Be that as it may, the oil palm has major potential for atmospheric CO2 sequestration, and that is a parameter which needs to be taken into account when judging the environmental impacts of this perennial crop. However, the data obtained so far are only very partial and need to be completed by studies applying appropriate methodologies (eddy correlation study design), in different types of ecologies and on a range of ages that are representative of the way an oil palm plantation evolves. Likewise, comparative studies on changes in the carbon balance in plantations derived from deforestation or from a simple rotation may make it possible to quantify more effectively the changes in the soil’s carbon stock, which is one of the most important components in the process of carbon storage by an ecosystem3.

References

1 Bergonzini JC. Changements climatiques, désertification, diversité biologique, et forêts. Riat : Silva, 2004 ; (146 p).

2 Jancovici JM. L’avenir climatique. Science ouverte. Paris : Editions du Seuil, 2002 ; (288 p).

3 Casson A. The political economy of Indonesia’s oil palm subsector. In : Colfer CJP, Resasudarmo IAP, eds. Which way forward? : people, forests and policy making in Indonesia. Washington DC : CIFOR-ISEAS, 2002 : 221-45.

4 FRIENDS OF THE EARTH. The social and ecological impacts of large scale oil palm plantation development in Southeast Asia. London : Greasy Palms, 2004 ; (44 p).

5 WWF. Oil palm. Position paper, February 2002, 1 p.

6 WWF. Forest conversion. Position paper, February 2002, 1 p.

7 Dufrene E. Photosynthèse, consommation en eau et modélisation de la production chez le palmier à huile (Elaeis guineensis Jacq.). Thèse de doctorat en Sciences, Ecologie végétale, Université de Paris XI, 1989, 156 p.

8 Hirsch PJ. Premiers travaux sur l’assimilation photosynthétique du palmier à huile (Elaeis guineensis Jacq.). La Mé, Côte d’Ivoire : Mémoire ORSTOM/IRHO, 1975.

9 Corley RHV. Photosynthesis and age of oil palm leaves. Photosynthetica 1983 ; 17 : 97-100.

10 Potulski N. Effects of soil and atmospheric drought on leaf exchange rates of plantation palms. Ph. D. Thesis, University of Cambridge, 176 p, 1990.

11 Dufrêne E, Saugier B. Gas exchange of oil palm in relation to light vapour pressure deficit, temperature and leaf age. Funct Ecol 1993 ; 7 : 97-104.

12 Lamade E, Setiyo I. Variation in maximum photosynthesis of oil palm in Indonesia : comparison of three morphologically constrasting clones. Plantation, Recherche, Développement Nov Dec 1996 : 429-38.

13 Dufrêne E, Dubos B, Rey H, Quencez P, Saugier B. Changes in evapotranspiration from an oil palm (Elaeis guineensis Jacq.) exposed to seasonal soil water deficits. Acta Oecologica 1992 ; 13 : 299-314.

14 Lamade E, SETIYO IE, PURBA A. Gas exchange and carbon allocation of oil palm seedlings submitted to waterlogging in interaction with N fertilizer application. In : Proceedings of the 1998 International Oil Palm Conference. Bali : Nusa Dua, 1998 : 573-84 ; (September 23-25).

15 Lamade E, Setiyo I. Test of Dufrêne’s production model on two contrasting families of oil palm in North Sumatra. In : PORIM, Proceedings of the 1996 PORIM International Palm Oil Congress. Competitiveness for the 21st century. Malaisie : Kuala Lumpur, 1996 : 427-35 ; (Agriculture conference (Pre-edited)).

16 Mc Cree KJ, Troughton JH. Prediction of growth rate at different light levels from measured photosynthesis and respiration rates. Plant Physiol 1966 ; 41(4) : 559-66.

17 Penning De Vries FWT. Respiration and growth. In : Rees, Cockshull, Han, Hurd, eds. Crop Processes in controlled Environments. London : Academic Press, 1972 : 327-47.

18 Dauzat J. Simulation des échanges radiatifs sur maquettes informatiques de Elaeis guineensis. Oléagineux 1994 ; 49(3) : 81-90.

19 Lamade E, Djegui N, Leterme P. Estimation of carbon allocation to the roots from soil respiration measurements of oil palm. Plant Soil 1996 ; 181 : 329-39.

20 Henson IE. Estimating ground CO2 flux and its components in a stand of oil palm. Porim Bulletin 1994 ; 28 : 1-12.

21 Jacquemard JC, Beaudoin L. Contribution à l’étude de la croissance du palmier à huile. Présentation d’un modèle descriptif. Oléagineux 1987 ; 42(10) : 343-9.

22 Jourdan C. Modélisation de l’architecture et du développement du système racinaire du palmier à huile. Th. Doct. Univ., Montpellier II, (243 p), 1995.

23 Henson IE. Notes on oil palm productivity. I. Productivity at two contrasting sites. J Oil Palm Res 1998 ; 10 : 57-67.

24 Lamade E, Setiyo I. Characterisation of carbon pools and dynamics for oil palm and forest ecosystems : application to environmental evaluation. In : International Oil Palm Conference. Indonésie : Nusa Dua, Bali, 2002 ; (Juillet 8–12).

25 Raich JW, Nadelhoffer KJ. Belowground carbon allocation in forest ecosystems : global trends. Ecology 1989 ; 70 : 1346-54.

26 Ollagnier M, Lauzeral A, Olivin J, Ochs R. Evolution des sols sous palmeraie après défrichement de la forêt. Oléagineux 1978 ; 12 : 537-48.

27 Olivin J. Relation entre l’écologie et l’agriculture de plantation. 1980 ; 35 (2) : 65–78.

28 Djegui N, Boissezon De P, Gavinelli E. Statut organique d’un sol ferrallitique du Sud-Bénin sous forêt et différents systèmes de cultures. Cah Orstom Sér Pedol 1992 ; 27 : 5-22.

29 Haron K, Brookes P, Anderson J, Zakaria Z. Microbial biomass and soil organic matter dynamics in oil palm (Elaeis guineensis Jacq.) plantations, West Malaysia. Sol Biol Biochem 1998 ; 30 : 547-52.

30 HENSON IE. Carbon assimilation water use and energy balance of an oil palm plantation assessed using micrometeorological techniques. PIPOC, 20-24 September 1993, 43 p.

31 Henson IE. Notes on oil palm productivity. II. An empirical model of canopy photosynthesis based on radiation and atmospheric vapour pressure deficit. J Oil Palm Res 1998 ; 10(2) : 25-8.

32 Raich JW. Aboveground productivity and soil respiration in three Hawaiian rain forests. For Ecol Manage 1998 ; 107 : 309-18.

33 Nouvellon Y, Bonnefond J-M, Hamel O, et al. CO2 fluxes and carbon sequestration within Eucalypt stands in Congo. 2nd CarboEurope meeting, 4-8 March 2002. Budapest : Hungary, 2002.

34 Gunadi B. Litterfall, litter turn-over and soil respiration in two pine forest plantations in Central Java, Indonesia. J Trop For Sci 1994 ; 6 : 310-22.

35 Ramirez OA. The carbon cycle and the value of forests as a carbon sink : a tropical case study. In : Dore MHI, Guevara R, Elgar E, Cheltenham, eds. Sustainable Forest Management and Global Climate Change. USA : UK and Northampton, 2001 : 107-46.

36 Dupouey J-L, Pignard G, Badeau V, et al. Stocks et flux de carbone dans les forêts françaises. Rev For Fr 2000 : 139-54 ; (LII-numéro spécial).

37 Nouvellon Y, Roupsard O, BONNEFOND, et al. The carbon budget of eucalyptus and coconut plantations estimated from different methods. In : Séminaire Carbone. Montpellier, 2004 ; (16-18 novembre).

38 ONG JE, GONG WK, WONG HC. Ecological survey of the Sungai Merbok Estuarine Mangrove ecosystem. Universiti Sains Malaysia : Penang, 1980 ; (quoted by Whitten et al., 2000).

39 Henson IE, Chai S. Analysis of oil palm productivity. II. Biomass, distribution, productivity and turn-over of the root system. Elaeis 1997 ; 9 : 78-92.

40 Dewar RC, Cannell MGR. Carbon sequestration in the trees, products and soils of forest plantations : analysis UK examples. Tree Physiol 1992 ; 11 : 49-71.

41 Grace J, Malhi Y. The role of rain forests in the global carbon cycle. Progress in Environmental Science 1999 ; 1(2) : 177-93.

42 Roupsard O, Bonnefond J-M, Jourdan C, et al. Carbon sequestration by Coconut plantations in Oceania (Vanuatu). In : 2nd CarboEurope meeting, 4-8 March. Budapest : Hungary, 2002.

2 Variations in the carbon content of oil palm organs: in all our calculations, we use “45%” of dry matter carbon content, but this can vary from 42 to 50% (unpublished results from carbon isotope analyses).3 The July to November 1997 period was particularly dry in Indonesia, linked to an “El Niño” episode. It was characterized by numerous fires, mostly on the island of Kalimantan and in Riau province (Sumatra) on forest regrowth and on cleared forest intended for oil palm growing. These fires resulted in a thick cloud of smoke over the entire region, covering parts of Malaysia, Sumatra and Kalimantan. The fire in Riau province spread to zones of thick peat. It therefore developed down to a depth of several metres and was very difficult to bring under control. The fires in 1997 and 1998 in Indonesia caused what was considered to be a worldscale ecologial disaster (www.cifor.cgiar.org).1 (WWW.ipcc.ch/pub/spm22–01.pdf)