AGRICULTURAL AND FOREST NETEOROLOGYELSEVIER Agricultural and Forest Meteorology 84 (1997) 153-167 Forest plantations of the world: their extent, ecological attributes, and carbon storage Jack K. Winjum a,*, Paul E. Schroeder u a National Council for Air and Stream Improvement, US EPA National Health and Environmental Effects Research Laboratory / Western Ecology Division - Corvallis, 200 S W 35th Street, Corvallis, OR 97333, USA b ManTech Environmental Research Services Corporation, US EPA National Health and Environmental Effects Research Laboratory~Western Ecology Division - Corvallis, 200 S W 35th Street, Corvallis, OR 97333, USA Received 30 September 1995; revised 15 March 1996; accepted 1 April 1996Abstract Forest plantations in the world total approximately 130 × 106 ha, and annual rates of establishment are about 10.5 × 106ha. A total of 124 countries throughout the high, middle, and low latitudes of the world establiSh new plantations each year.In addition to supplying an array of goods and services, plantations contribute to carbon (C~ storage. This analysis integratesinformation across latitudes to evaluate the potential of forest plantations to achieve these goals. For example, mean carbonstorage (MCS) in above- and below-ground phytomass of artificially established plantations generally increases from high tolow latitudes ranging from 47 to 81 t C ha -l. Over a 50-year period, harvests from these plantations are credited withstoring C at 10, 34, 15, and 37 t C ha -1 in wood products in the high, middle, low-dry, and low-moist latitudes,respectively. Using todays distribution of plantations among the four zones of latitude and C storage values from thisanalysis, the worlds plantations can be credited with storing an area-weighted average of 91 t C ha-1 including MCS anddurable-wood products. Based upon these estimates, the world total C storage in forest plantations today is approximately11.8 Pg C with an annual increase of 0.178 Pg C year- LKeywords: Forest plantations; Carbon storage; Terrestrial ecology1. I n t r o d u c t i o n Restoration, in turn, serves the other end-uses as well as enhancing the greenness and recreational potential Forest plantations have historically contributed to of forest landscapes (Palin, 1984).basic human needs. Primary examples are their uses Planting of tree crops for fruit was recorded as farfor: domestic products such as poles, fruit, etc.; back as the 6th Century BC (Levingston, 1984). Inindustrial wood; energy resources; soil a n d water Western Europe as natural forest resources dwindled,conservation; and restoration of degraded land. active tree planting in block patterns was initiated the mid 1700s to renew wood inventories for build- ing materials (Levingston, 1984). Today, there are an estimated 130 X 106 ha of plantations in the w o r d * Corresponding author. (Allan and Lanty, 1991).0168-1923/97/$17.00 ~) 1997 Elsevier Science B.V. All rights reserved.PII S 0 1 6 8 - 1 9 2 3 ( 9 6 ) 0 2 3 8 3 - 0
154 J.K. Winjum, P.E. Schroeder/Agricultural and Forest Meteorology 84 (1997) 153-167 In recent years, scientists and policymakers have ecology from the literature and a recent symposiumbecome mindful of the mitigating role of forests in on planted forests; and (3) a database on worldreducing the buildup of CO 2 in the atmosphere, plantations used to estimate their C storage potential.Natural forests have been reduced from occupying ~ 46% of the earths terrestrial ecosystems in prein-dustrial times to ~ 28% today (Sharma et al., 1992). 2.1. Extent o f world plantationsThis reduction, along with other human activities,has contributed to the buildup of atmospheric CO 2 The United Nations Food and Agricultural Orga-(from about 289 ppmv in 1800 to about 356 ppmv in nization (FAO) has completed a global assessment of1993; Schimel, 1995). Thus plantations, to the extent the forests of the world as of 1990 (FAO, 1995).they replace natural forests or expand the global Forest plantations were part of the assessment. Dataforest area, may potentially have another significant are presented on a country basis for 177 countries,contribution to humankind through the uptake and both developed and developing. The assessment is anstorage of carbon (C). This paper reviews the extent updated version of a database on world forests as-of plantations in the world today, their ecological sembled by F A O in the early 1980s. Country forestattributes, and their potential contribution toward data are based upon the best-available country-wideglobal C storage, inventories. Estimates based on these data are sup- plemented by FAO through the geographic informa- tion systems (GIS), remote sensing imagery, and modeling techniques. Though data quality varies by2. M e t h o d s country, FAO world summaries of forest coverage are considered to be within acceptable statistical The review is based upon three sources of infor- reliability (FAO, 1995). The World Resources Insti-mation: (1) recent data on the extent of the worlds tute (WRI, 1992) presented similar values that aug-forest plantations; (2) current views of plantation ment F A O s 1990 data on plantations particularly forTable 1For 32 developed countries, the total natural forest in 1990 (FAO, 1995) and the planting rate per year during the early 1980s (WRI, 1992) aCountry Forest area (ha × 103) Country Forest area (ha × 103) Total natural Planting year- l rate Total natural Planting year- rateAlbania 1046 2 Ireland 396 9Austria 3877 21 Israel 102 2Australia 39837 62 Italy 6750 l5Belgium 620 19 Japan 24158 240Bulgaria 3386 50 Netherlands 334 2Canada 247164 720 New Zealand 7472 43Cyprus 140 0 Norway 8697 79Denmark 466 6 Poland 8672 106Finland 20112 158 Portugal 2755 9Former Czechoslovakia 4491 37 Romania 6190 3Former Soviet Union 754958 2600 Spain 8388 92Former Yugoslavia, SFR 8371 53 Sweden 24437 207France 13110 51 Switzerland 1130 7Germany 10490 62 Turkey 8856 82Greece 2512 5 United Kingdom 2207 40Hungary 1675 19 USA 209573 1094a Planting rates for seven countires are the means for the decade of the 1980s: Albania, Cyprus, Denmark, Greece, Romania, and FormerSoviet Union (UN-ECE/FAO, 1992); USA (USDA FS, 1992).
a.K. Winjum, P.E. Schroeder/Agricultural and Forest Meteorology 84 (1997) 153-167 155Table 2For 92 developing countries, the total existing plantation area in 1990 in ha x 1000, and the average annual increase in plantation areaduring the period 1980 to 1990 (FAt, 1995) aCountry Plantation area (ha X 103) Country Plantation area (ha x 103) Country Plantation area (ha x 103) Total Annual increase Total Annual increase Total Annual increaseAlgeria 485 18.3 Guyana 8 0.8 Panama 6 0.4Angola 120 1.0 Haiti 8 0.8 Papua N. Guinea 30 1.5Argentina 547 4.6 Honduras 3 0.3 Paraguay 9 0.7Bangladesh 235 12.3 India 13230 1009.0 Peru 184 8.8Benin 14 0.6 Indonesia 6125 331.8 Puerto Rico 3 0.1Bhutan 4 0.2 lran 79 4.9 Reunion 7 0.1Bolivia 28 1.0 Jamaica 15 0.6 Rwanda 88 4.3Brazil 4900 195.4 Jordan 23 0.8 Samoa 9 0.5Burkina Fast 20 1.1 Kenya 118 1.6 Senegal 112 10.3Burundi 92 7.9 Korea, DPR 1470 77.0 Sierra Leone 6 0.2Cameroon 16 1.2 Kuwait 5 0,5 Solomon Islands 16 0.3Cape Verde 10 0.7 Laos 4 0,1 South Africa 965 15.5Chad 4 0.2 Lesotho 7 0,6 Sri Lanka 139 6.0Chile 1015 54.5 Liberia 6 0.1 Sudan 203 8.8China 31831 1139.8 Libya 210 11.0 Suriname 8 0.2Columbia 126 8.9 Madagascar 217 3.1 Swaziland 72 0.1Congo 37 2.5 Malawi 126 7.0 Syria 127 9.9Costa Rica 28 2.6 Malaysia 81 6.3 Tanzania 154 8.6Cote dIvoire 63 3.2 Mali 14 1.3 Thailand 529 29.4Ct. African Rep. 6 0.6 Mauritania 2 0.2 Togo 17 1.2Cuba 245 13.5 Mauritius 9 0.1 Trinidad/Tobago 13 0.1Dominican Rep. 7 0.3 Mexico 109 5.3 Tunisia 201 11.2Ecuador 45 1.5 Morocco 321 9.6 Unit. Arab Emir. 60 5.9Egypt 34 0.6 Mozambique 28 1.0 Uruguay 156 2.0E1 Salvador 4 0.3 Myanmar 235 19.6 Vanuatu 7 0.4Ethiopia 189 12.0 Nepal 56 4.3 Venuzuela 253 16.6Fiji 78 5.0 N. Caledonia 9 0.4 Vietnam 1470 49.0Gabon 21 0.8 Nicaragua 14 1.3 Zaire 42 2.6Ghana 53 1.1 Niger 12 0.8 Zambia 48 2.1Guatemala 28 1.8 Nigeria 151 3.7 Zimbabwe 84 1.4Guinea 4 0.1 Pakistan 168 4.2a Includes only countries with reported average annual increases in plantation area from 1980 to 1990 that were > 100 ha.d e v e l o p e d nations. T h e s e data w e r e e x a m i n e d statis- forests in the w o r l d (Keating, 1993). Prior totically for m e a n s and trends p r o v i d i n g insights to U N C E D , the role o f forest plantations in the w o r l dw o r l d interest in forest plantations (Tables 1 and 2). had b e e n the focus o f several r e v i e w s and confer- ences in past decades (Fenton, 1965; F A t , 1967;2.2. Current views o f plantation ecology F o r d et al., 1979; W i e r s u m , 1984; W i n j u m et al., 1991). Since U N C E D , the Planted F o r e s t S y m p o - Forest plantations h a v e periodically b e e n the fo- sium was h e l d during June 1995 in Portland, Oregon,cus, at least in pan:, o f international gatherings so U S A ( B o y l e et al., 1997). Results f r o m all o f thesethat v i e w s on plantation e c o l o g y can be tracked o v e r events w e r e e x a m i n e d and s u m m a r i z e d for the m a j o rtime. Recently, the f o r e m o s t e x a m p l e was the U n i t e d e c o l o g i c a l positives and n e g a t i v e s o f plantations (Ta-Nations C o n f e r e n c e on E n v i r o n m e n t and D e v e l o p - ble 3). T h e s e v i e w s are a s s u m e d in this analysis tom e n t ( U N C E D ) in 1992 at R i o de Janeiro. K e y be indicators o f whether plantations will continue too u t c o m e s w e r e the Forest Principles and A g e n d a 21, be v a l u e d and established around the w o r l d throughw h i c h generally e n d o r s e d increased use o f planted the next h a l f century.
156 J.K. Winjum, P.E. Schroeder/ Agrtcultural and ForestMeteorology 84 (1999) 153-1672.3. Potential plantation C storage elell~eS that gave about 500 useful datapoints. The datapoints included the m e a n a n n u a l increment ( M A I ) A plantation database was assembled tn 1992 as and rotation ages of plantations representing thepart of an assessment of C storage by ~vodd forests major forest regions of the world. For M A I and( D i x o n et al., 1993). A detailed description of the rotation length, medians and interquartile values weredatabase and e n s u i n g analysis have been published determined for each of four zones of latitude or( W i n j u m et al., 1997). Briefly, a review of the environment, i.e. high, middle, l o w - d r y , and l o w -technical literature produced approximately 200 ref- moist (Table 4). It is assumed that these zones ofTable 3Commonly cited ecological attributes of forest plantationsAttributes Selected referencesEcological positivesA. Contributes to environmental quality through: 1. Restoring or maintaining biog~)ehenileal cycles a. Improving soil nutrition Sedjo (1983) b. Regulating water runoff FAO (1967) 2. Stabilizing soil and reducing erosion Brown and Lugo (1994) 3. Creating habitat favoring biodiversity Sedjo (1983) 4. Taking up and storing carbon Winjum et al. (1997) 5. Improving microclimate Kanowski et al. (1992) 6. Greening landscal~S Wiersum (1984) 7. Reducing deforestation pressures Kanowski et al. (1992) 8. Protecting watersheds Buckman (1997)B. Enhances forest productivity through: 1. Rapid growth in a. Trees Laarman and Sedjo (1992) b. Biomass accumulation Mlinsek (1979) 2. Accelerating secondary succession 3. Improving yields by a. Matching species with site Matthews et al. (1979) b. Improving genetics Budowski (1984) c. Combining with agriculture Evans (1997)Ecological negativesA. Risks environmental quality through monocultures which may be prone to: 1. Seedling and juvenile mortality Cleary et al. (1978) 2. Pest attacks Rosoman (1994) 3. Pathogenic losses Rosoman (1994) 4. Natural disturbances Laannan and Sedjo (1992) 5. Reduced biodiversity Sheldon (1989) 6. Invade adjacent ecosystems Bliss (1997)B. Reduces forest productivity through: 1. Successive crops which may a. Deplete nutriems Adlard (1979) b. Reduce soil moisture Kanowski et al. (1992) 2. Treatments which may include a. Heavy machineryfor • Site preparation Laarman and Sedjo (1992) • Harvests Laarman and Sedjo (1992) b. Chemical pollution from • Fertilizers Rosoman (1994) • Pesticides Rosoman (1994)
J.K. Winjura, P.E. Schroeder /Agricultural and Forest Meteorology 84 (1997) 153-167 157Table 4Mean annual increment (MAI), mean annual biomass C (MABC), and rotation lengths for plantations in high, middle, and low (dry andmoist) latitudes of the worldVariables Latitudes High Middle Low -dry Low-moist Q1 a Med. Q3 (n) b Q1 Med. Q3 (n) Q1 Med. Q3 (n) Q1 Med. Q3 (n)M A I ( m a h a - j year - I ) 1.5 2.3 2.7 (13) 4.1 9.9 20.7 (129) 10,1 14.9 20.7 (104) 15.4 20.4 33.4 (274)M A B C ( t C h a -~ year-~) c 0.61 0.96 1.1 (13) 1.7 4.1 8.6 (129) 4.2 6.2 8.6 (104) 6.4 8.5 13.9 (274)Rotation (years) 55 80 80 (13) 20 25 35 (107) 12 19 23 (102) 9 15 20 (264)a Medians and interquartile values (Q1 and Q3) based upon analyses for non-normally distributed datasets (Devore and Peck, 1986).b Observations (n) are from approximately 200 references cited in the technical forestry literature.¢ MABC in t C ha- i year- l was computed from m 3 ha- i year- l by Eq. (1) in Methods.latitudes are analogous to, but not exactly the same The calculation of MCS is made in two steps:as, the boreal, temperate, and tropical regions of the 1. Convert MAI in stemwood volume to mean an-world, nual biomass C (MABC; Table 4) by: Based upon these data, estimates can be made ofthe mean carbon storage (MCS) of plantations, both MABC = MAI × WD X 1.6 X 0.5 (1)above and below ground, as well as the C storage in where:wood products resulting from harvests. For each of MABC is in t C ha-~ y e a r - l ;these plantation characteristics, the median and in- MAI is in m 3 h a - ~ year- 1;terquartile values were calculated representing plan- WD is wood density, here an average value istations within the four zones of latitude describedabove (Tables 4-7). used of 0.52 t m - 3 ; 1.6 is the conversion factor to compute The concept of MCS assumes that once a planta- whole-stand biomass from stemwood biomass;tion is established, it will be maintained, harvested • 0.5 is the conversion factor to estimate the Cand replanted continuously, and that there is no yield content of whole-stand biomass in t C t -1 .reduction in later rotations (Winjum et al., 1997). The conversion factors in Eq. (1) are adaptedSpecifically, MCS is the same as the average amount from Brown and Lugo (1982) and Sedjo andof C on site over one full rotation. Also, since any Solomon (1989).number of biological, climatic, or social events could 2. Calculate MCS (Table 5) by:contribute to some level of yield reduction that can-not be predicted (Wenger, 1984; Smith, 1986), the r MABCapproach presented here may represent an upper MCS = ~ R (2)bound, year= 1Table 5Calculated values for me~m carbon storage (MCS) for plantations of Table 4Variables MCS (t C h a - 1) Latitudes High Middle Low-dry Low -moist Q1 ~ Median Q3 Q1 Median Q3 Q1 Median Q3 Q1 Median Q3Above-ground b 17 39 45 18 53 155 27 62 103 32 68 146Below-ground c 3 8 9 4 11 31 6 12 21 6 13 29Total 20 47 54 22 64 186 33 74 124 38 81 175a Medians and interquartile values (Q1 and Q3) based upon analyses for non-normally distributed datasets (Devore and Peck, 1986).b Above-ground values are calculated from MABCs and rotation lengths in Table 1 and Eq. (2) in Methods.c Below-ground values are estimates based upon 0.20 times the above-ground biomass (references in Methods).
158 J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167 where: the a b o v e - g r o u n d s t o r a g e for the h i g h a n d m i d d l e • M C S is the m e a n C s t o r a g e in t C h a - l ; latitudes ( K u r z et al., 1992; U n i t e d N a t i o n s E c o - • R is the r o t a t i o n l e n g t h in years; a n d n o m i c C o m m i s s i o n for E u r o p e / F o o d a n d A g r i c u l - • M A B C is in t C h a -1 y e a r -1 f r o m Eq. (1) ture O r g a n i z a t i o n o f the U n i t e d N a t i o n s , U N - ( S c h r o e d e r a n d L a d d , 1991). ECE/FAO, 1992) as well as f o r the l o w - d r y a n d E s t i m a t e s o f b e l o w - g r o u n d C in roots w e r e calcu- l o w - m o i s t latitudes ( F e a m s i d e , 1992; B r o w n et al.,l a t e d u s i n g p r o p o r t i o n a l a d d i t i o n s to a b o v e - g r o u n d C 1992) ( T a b l e 5).in b i o m a s s . D a t a are v e r y l i m i t e d o n the root b i o m a s s F o r e a c h h e c t a r e t h a t is p l a n t e d , the C t h a t iso f forests r e l a t i v e to the a b o v e - g r o u n d b i o m a s s . F o r stored in p r o d u c t s m a d e o f h a r v e s t e d w o o d f r o m thethe p u r p o s e o f this analysis, it w a s a s s u m e d t h a t the plantation merits an accounting. Estimates were madebelow-ground C storage was an additional 20% of o f this a m o u n t o f stored C in s e v e r a l steps. First, theTable 6Calculations leading to long-term storage of C in harvested wood at the end of each rotationVariables Latitudes High Middle Low-dry Low-moist Q1 a Median Q3 Q1 Median Q3 Q1 Median Q3 Q1 Median Q3Sternwood at harvestVolume (m 3 ha- 1) b 82 184 216 82 247 724 121 283 476 138 306 668Weight Total (t C ha -j ) ¢ 21 48 56 21 64 188 31 74 124 36 80 174 Removed (t C ha- J ) d 19 43 50 19 58 169 28 66 111 32 72 157Percent (%) of harvested wood used for: eFuel/charcoal 20 15 65 35Paper products 40 45 25 40Solidwood products 40 40 10 25Allocation of harvested wood (t C ha - 1)Fuel/charcoal 4 9 10 3 9 25 18 43 72 11 25 55Paper products Total 8 17 20 9 26 76 7 17 28 13 29 63 Yield (50%) f 4 8 10 4 13 38 4 8 14 6 14 31Solidwood products Total 8 17 20 8 23 68 3 7 11 8 18 39 Converted (1.75:1) g 5 10 12 4 13 39 2 4 6 5 10 22Long-term C storage from harvests at end of rotation (t C ha - I)Paper products h 2 4 5 2 6 19 2 4 7 3 7 16Solidwood products i 4 9 10 4 12 35 1 4 6 4 9 20Total 6 13 15 6 18 54 3 8 13 7 16 36a Medians and interquartile values (Q1 and Q3) based upon analyses for non-normally distributed datasets (Devore and Peck, 1986).b Computed by rotation length (year) × MAI (m 3 ha- 1 year - 1) = m 3 ha- 1.¢ Weight of C at rotation age (t C ha- 1) is volume (m 3 ha- l) × 0.52 t m - 3 wood (density) × 0.5 t C t - J wood.d Weight of C removed at harvest is t C ha- 1 × 0.9 (i.e. harvest efficiency).e Percentages developed from references discussed in Methods.f Paper yields average about 50% in weight per weight of roundwood harvested.g Conversion efficiency for sawn or peeled roundwood logs from plantation average 1.75 units of harvested logs to 1 unit of solidwoodproducts.h Assumes 50% of the carbon in paper products remains in long-term products (e.g. books, discarded paper retained in landfills, etc.) forseveral decades.i Assumes 90% of the carbon in solidwood products remains in wood structures for several decades.
Table 7Extent of world plantations, estimated C storage per ha, and totals for all plantations by latitudes .~Variables Latitudes High Middle Low-dry Low-moist Total ~"Plantation estimates in the world for 1990 .~ Total area (ha× 106) a 18 82 18 12 130 Annual net increase between 1965 and 1990 0.27 1.24 0.27 0.18 1.96 c ( h a × 106 year- i) b ~ Q1 d Med. Q3 Q1 Med. Q3 Q1 Med. Q3 Q1 Med. Q3 Area-weighted values e .~ Q1 Med. Q3 ~.C storage credit (t C h a - 1 ) ~" Plantation MCS f 20 47 54 22 64 186 33 74 124 38 81 175 26 64 157 Products at 50 years g 6 10 12 14 34 79 11 15 19 25 37 63 13 27 60 Total at 50 years 26 57 66 36 98 265 44 89 143 63 118 238 39 91 217 ~-Totals, world plantations C storage in 1990 (Pg C) h 0.5 1.0 1.2 2.9 8.0 22.0 0.8 1.6 2.6 0.7 1.4 2.9 5.0 11.8 28.2 Annual n e t i n c r e a s e i n C i s t o r a g e 0.007 0.0015 0.018 0.043 0.122 0.329 0.012 0.024 0.039 0.006 0.021 0.043 0.076 0.178 0.425 (Pg C year- i )a References: Allan and Lanly (1991), FAO (1993), U N - E C E / F A O (1992).b Assumes net increases in plantation area by latitudes is in the same proportions as total area by latitudes. Reference: Allan and Lanly (1991).d Medians and interquartile values (Q1 and Q3) based upon analyses for non-normally distributed datasets (Devore and Peck, 1986).e Area-weighted values based upon plantation areas by latitudes and C storage credits by latitudes. ~~f Values from Table 5.g Values from simulations whose results for medians are depicted in Fig. 1.h Values are total area ( h a × 106)×total C storage at 50 years (t C ha -1 ). --4i Values are annual net increase (ha × 106 year- i ) × total C storage at 50 years (t C h a - l ).
160 J.K. Winjum, P.E. Schroeder/Agricultural and Forest Meteorology 84 (1997) 153-167 22 a. 7O b. 2O 18 60 16 50. 14 10 ~ 30- 20- ,01 01 50 100 150 200 250 300 50 100 150 200 250 300 Yrs Yrs 30 70 j C• ] d. 25 60- 5O 2O 40 i 30 I 2O 60 100 160 Yrs 200 250 300 i 1 50 100 160 Yrs 200 250 300Fig. 1. For plantations in the high (a), middle (b), low-dry (c), and low-moist (d) latitudes, simulated trends of C storage in durable-woodproducts for repeated rotations of 80, 25, 19, and 15 years, respectively. The saw-tooth peaks occur at the end of each rotation and thedownward-connecting-curved lines represent a 1% decay rate in diagrams (a) and (b) and 2% for diagrams (c) and (d). The dotted line from50 years on the horizontal axes projected through the curved wood-product storage line to vertical axes gives an estimate of C storage creditin wood products for plantations in each latitudinal zone (Winjum et al., 1997).above-ground biomass values of Table 4 were con- defect in the forest (adapted from Briggs, 1994).verted to harvested stemwood C (Table 5) by the The flow of stemwood C into forest products, i.e.equation: fuel/charcoal, solidwood, and paper, was calculated by multiplying the proportion of products producedSWC = MAI × R × WD × 0.5 × 0.9 (3) in latitudinal zones as developed from the literature (Herendeen and Brown, 1987; Kuusela, 1992; WRI,where: 1992; Powell et al., 1993) times the harvested stem- SWC is stemwood C in t C ha-l; wood C per hectare. The proportions (%) of C flow MAI is stemwood growth in m 3 ha-~ year-1 into various products by latitudes were (Table 6): (Table 1); R is rotation length in years (Table 1); Latitude Fuel/charcoal Paper Solidwood WD is wood density in t m -3 as for Eq. (1); High 20 40 40 0.5 converts total tons of stemwood to tons of C, Middle 15 45 40 i.e. t C t-1 stemwood; and Low-dry 65 25 10 0.9 is the harvest efficiency assumed for planta- Low-moist 35 40 25 tions that allows for wood lost to breakage and
JK. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167 161 It is recognized that these wood-utilization cate- wood products are utilized (Kiirsten and Burschel,gories (fuel/charcoal, solidwood, and paper) and 1993). These decay rates and the values noted abovetheir proportions among latitudes are only approxi- from Tables 4 and 6 were entered into a simulationmations that represent a mix of wood removals from routine that determines the declining amount of Cboth natural forests and plantations. However, they storage in wood products over a rotation. The simu-are intended to repre:~ent the primary pathways and lation is run through enough successive rotations sopools of forest C following harvest of plantations at that the upward trend approaches a horizontal linea global scale. (about 250 years in each of the four latitudinal For the harvested wood that is manufactured into zones; Fig. 1). The midpoint of the vertical linespaper and solidwood products, conversion efficien- from the saw-tooth peaks at the end of each harvestcies must be considered. Here, it is assumed that the represents the C stored, on average, throughout eachaverage yield from the harvested wood allocated for rotation. The curve connecting these midpoints takespaper products is 50% (Briggs, 1994). Also used is the form of an ascending curve that approaches anan average conversion efficiency for sawn or peeled upper limit asymptotically (Fig. 1). Differencesroundwood logs frora plantations of 1.75 units of among the curves represent differences in: (1) Charvested logs to one unit of solidwood products accumulation in wood products at the end of each(Centre for Agricultural Strategy, CAS, 1980; Direc- rotation (Table 3); (2) decay rates; and (3) rotationtorate General of Forest Utilization, DGFU, 1989; length. To determine the product C credit for aSedjo and Lyon, 1991); Harmon et al., 1990; Briggs, 50-year period (i.e. closer to the period of concern1994). for mitigating increasing atmospheric CO2), a point Other assumptions were that 90% of the solid- on the vertical axis was also projected from thewood products made from harvested plantations 50-year point on the horizontal axis (Fig. 1).would remain in some structural use for several The estimate of total long-term C storage perdecades, e.g. wood-flame houses and other durable- hectare for the plantations was determined simply bywood products (Row and Phelps, 1992). Also half of summing the C above-ground, below-ground, and inthe harvested wood used for paper products is as- durable-wood products (Table 7). The estimate as-sumed to contribute to long-term storage of C through sumes that: (1) when new plantations are established,retention in books, recycling, landfills, or other each hectare will be continuously managed for suc-long-term paper forms (Row and Phelps, 1992). cessive forest crops; and (2) at maturity each crop To credit the C sequestered in durable-wood prod- will be harvested with the wood utilized in theucts to plantations maintained through an indefinite approximate proportions noted above for: (1)number of rotations, estimates for product C are fuel/charcoal without C storage and (2) paper andneeded that can be added to the MCS in biomass, solidwood products with portions in long-term CThe amount of C in wood products credited to such storage (Table 7).plantations was calculated in the computer simula-tion described below. Simulations were conductedfor plantations in each of the four latitudinal zones(Fig. 1). Input value:~ were rotation ages (Table 4), 3. Resultsthe total values (medians, Q1, and Q3 values) for Cin durable-wood products at harvest (Table 6), and adecay rate for durable-wood products. The method is Results from the assembled information and cal-described in detail in previous papers (Kiirsten and culations above are additive in support of a contin-Burschel, 1993; Winjum et al., 1997). ued and expanded role for plantations in the world. Adopted for this analysis, the decay rate for the There is wide-spread plantation establishment amonghigh and middle latitudes, a relatively cooler climate, countries in all latitudinal regions; ecologically, thereis 1% annually and fi~r the warmer low latitudes, 2% are strong positives as well as cautions to be heededannually. The rates are assumptions that reflect the from the negatives; and estimates show that thelatitudinal zone where a predominant amount of the potential for plantation C storage is significant.
162 J.K. Winjum, P.E. Schroeder /Agricultural and Forest Meteorology 84 (1997) 153-1673.1. Plantation extent A total of 124 countries out of about 200 coun- tries and territories in the world are reported to have Across all latitudinal regions in 1990, about 130 an annual projects of plantation establishment equal × 106 ha of plantations exist in the world (Allan and to or greater than 100 ha (WRI, 1992; FAO, 1995)Lanly, 1991). The distribution by latitudinal region is (Tables 1 and 2). Useful trends are seen in theseapproximately: high, 14%; middle, 63%; low-dry, data. For developed countries, a log-log diagram14%; and low-moist, 9% (UN-ECE/FAO, 1992; shows that the greater the area of natural forestFAO, 1993). within a country (x axis), the higher the annual Annual rates of plantation establishment in the plantation rate (y axis; Fig. 2). The proportions ofworld during the early 1980s were estimated to be new plantations established for reforestation, af-10.5 X 10 6 ha year- 1 (WRI, 1992). Exact figures are forestation, or agroforestry are unknown.not available, but this rate in the late 1980s may have For developing countries, annual rates of planta-slowed to about 8.5 × 106 ha year- ~ (Sharma, 1992; tion establishment are not given in the 1990 assess-UN-ECE/FAO, 1992; FAO, 1993). Estimates by ment by FAO (1995). Instead, the average annuallatitudinal region are: high, 27%; middle, 63%; and increase in plantation area is presented and tends tolow-dry plus moist, 10% (WRI, 1992; FAO, 1993). be higher within countries with larger areas of exist-It is unknown what portions of the new plantations ing plantations (Fig. 3). That is, for 88 developingare replacing harvested forests (natural or older plan- countries with an average annual plantation increasetations) or are the result of afforestation or agro- equal to or greater than 100 ha, a log-log diagramforestry projects. However, in 1965, existing planta- shows that the more plantations that countries havetions in the world were estimated to cover 81 × 106 in place (x axis), the more the net increase inha compared with the 130 × l 0 6 ha in 1990 (Allan plantation area each year (y axis). For this diagram-and Lanly, 1991). The average annual net gain in matic analysis, the four super-size countries of Brazil,plantations for that 25 years, therefore, is assumed to China, India, and Indonesia were omitted becausebe 1.96 × 106 ha year- 1 the size of their forests and average annual plantation 10000 1000. >, o 0 i00 • 0 •-~ ° ° 0 ~ 10 < 1 10"5 10**6 10**7 10**8 10**9 Existing n a t u r a l f o r e s t s (ha; log scale)Fig. 2. For 32 developed countries (Table 1), a log-log scatter digram showing the trend for increased level of annual plantationestablishment during the 1980s (WRI, 1992) when plotted against the area of existing natural forests in each country during 1990 (FAO,1995).
J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167 163increases relative to the other 88 countries inordi- period, harvests from these plantations are creditednately dominated the analysis (Table 2). with storing C at median values of 10, 34, 15, and 37 t C ha -1 in wood products in the high, middle,3.2. Ecological poshives and negatives of planta- low-dry, and low-moist latitudes, respectively (Fig.tions 1). (Interquartile values (Q1 and Q3) for all medians are given in Table 7.) Summary documents coveting the wide-spread The sum of the respective medians give the totaluse of forest plantations in the world point to many C credit in t C ha -1 for plantations in the fourecological attribute,,;, both positive and negative, latitudinal regions, i.e. high, 57; middle, 98; low-dry,Some attributes apply to specific locations, but a 89; and low-moist, l l8 (Table 7). The area-weightednumber are applicable to most forest regions of the median for C storage credited to all plantations is 91world (Table 3). Attributes suggested since UNCED t C ha -1 (Q1 = 39 and Q3 = 217 t C ha-l).are generally consistent with those published prior to Multiplying the total C credits per ha times the1992 (Boyle et al., 1997). One additional positive 1990 areas of existing plantations provides estimatesattribute noted was the role of plantations to protect of the amount of C stored in each region. Medianwatersheds (Buckman, 1997), and negatively, the values are 1.0, 8.0, 1.6, and 1.4 Pg C for the high,risk of exotic planted trees to invade adjacent ecosys- middle, low-dry, and low-wet latitudes, respec-tems (Bliss, 1997). tively (Table 7). The total C storage that can be credited to global forest plantations today, therefore,3.3. Potential C storage per ha is an estimated 11.8 Pg C (Q1 = 5.0 and Q3 = 28.2 Pg C). Mean carbon storage (MCS) in above- and Similarly, the product of the annual increase inbelow-ground phytomass of plantations generally in- plantation area for the period leading up to 1990 andcreases from high to low latitudes ranging in medi- the C credits gives an estimate of the annual uptakeans from 47 to 81 t C ha-1 (Table 5). Over a 50-year in C for world plantations. Median values are 0.015, 100.0 2 I i0.0 ": • ." : . ¢~ , *° O * O • O o• o 10 • •e ,~ I l l 01 . . . . . • = i0 I00 I000 i0000 Existing plantaLions (i000 ha; log scale)Fig. 3. For 88 developing countries (Table 2), a log-log scatter diagram showing the trend for greater average annual increase in plantationarea in each country with larger amounts of existing plantations during the period 1980-1990 (FAO, 1995). Data for the coutnries of Brazil,China, India and Indonesia are omitted because values are inordinately large compared with these 88 countries (Table 2).
164 J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-1670.122, 0.024, and 0.021 Pg C year-1 for the four 1993). These human constraints and adverse impacts,latitudinal regions from high to low-moist, respec- however, can be and have been overcome as evi-tively (Table 7). The global total estimate is 0.178 denced by the above statistics. This indicates thatPg C year -l (Q1 = 0.076 and Q3 = 0.425 Pg C plantation programs will likely continue as long asyear-l), ecological constraints do not exist that make the practice unreasonable or forbidding. Furthermore, the positive attributes indicate4. Diseussion strongly that plantation programs can contribute to environmental quality and forest productivity (Table Support for forest plantations establishment ap- 3). Recent advances in forest technology have greatlypears ongoing in the world today. This is strongly contributed to such projects. Examples are improvedevident by the 124 countries (over half of the world s knowledge of forest ecology relative to more species,200 countries and territories) engaged in some form particularly in the their regeneration phases; and aof plantation establishment totaling between 8.5 and half century of research and operations in forest10.5 × 106 ha year-~. The net gain in area is about genetics have greatly increased the capability of2 × 10 6 ha year -1 plantations to grow more vigorously with increased There appears to be momentum toward plantation resistance to pests and pathogens (Talbert et al.,establishment within countries having existing forests 1985; Gadgil and Bain, 1997).and plantations. That is in the developed countries, At the same time, the negative attributes arethe more natural forest area they have, the greater the seemingly forbidding (Table 3). In careful reading ofannual rate of plantation establishment (Fig. 2). In the technical literature on these attributes, however,the developing countries, the data show that the more authors consistently describe these negative at-area they have in existing plantations, the higher tributes more as warnings to be heeded before imple-their net annual increase in planting area (Fig. 3). At menting plantation programs (Sedjo, 1983; Mather,first glance these results seem self-evident, but it also 1993). In that context, people who favor plantationindicates that the more forests countries have or the establishment generally feel that with careful plan-more experienced they are with plantations, the ning, implementation, and follow-up measures, thegreater is the propensity to establish new plantations, threat of the ecological negatives can be held to an Thus globally, plantations continue to be used. acceptable minimum (Savill and Evans, 1986;Indeed, continuing and perhaps expanding forest Kanowski et al., 1992).plantations was urged in 1992 within UNCEDs Assuming then that forest plantations will be anAgenda 21 and the Forest Principles (Keating, 1993). ongoing activity in the world for the foreseeable Yet the purpose in considering the ecological future, it is of interest to estimate their contributionattributes of plantations was to determine if any to an increasingly important attribute, C storage.critical new ecological evidence has arisen for not Estimates here show that the world plantations incontinuing this forest practice. Human constraints to 1990 can be credited with storing approximately 11.8plantation establishment are widely known. Included Pg C with Q1 = 5.0 Pg C and Q3 = 28.2 Pg Care many combinations of factors such as limitation (Table 7). The median value is less than one percentof land tenure systems, insufficient capital, lack of of the 1500 to 2000 Pg C estimated to be stored byknowledge about some species, poorly understood all the worlds forests (Smith et al., 1993).site conditions, unavailability of trained labor and The annual increase, however, in stored C cred-supervisors, and inconsistent commitments by forest ited to plantations is a median of 0.178 Pg C year-management organizations, both public and private (Q1 = 0.076 and Q3 = 0.425 Pg C year-l). This(Wiersum, 1984). Adverse effects of plantations on median is about 11% of 1.6 Pg C year -! that washumans are sometimes cited. Examples are: high risk the estimated net annual gain of C in the atmosphereof scarce capital; an excuse to clear mature forests ( _ 1.0 Pg C year -~) in the 1980s (Houghton et al.,thereby reducing biodiversity; and displacement of 1993). Such a contribution is important consideringindigenous people (Kanowski et al., 1992; Mather, that studies of global mitigating options to the prob-
J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167 165lem of C O 2 buildup in the atmosphere have not Referencesshown to date any single solution. Rather, a varietyof small contributions a r o u n d 10% is the probable Adlard, P.G., 1979. Tropical forests - comparisons and contrasts.solution to reducing atmospheric CO 2 (Schneider, In: E.D. Ford, D.C. Malcolm and J. Atterson (Editors), The1989). Further, studies have shown that there is Ecology of Even-Age Forest Plantations, Proceedings of the Meeting of Division I, International Union of Forestry Re-enough suitable and available land in the world to search Organizations, Edinburgh. Institute of Terrestrial Ecol-more than double the net annual increase in planta- ogy, Cambridge, UK, pp. 505-526.tion area of 1.96 X 10 6 ha year -1 in the next several Allan, T. and Lanly, J.P., 1991. Overview of status and trends ofdecades (Grainger, 1991; Trexler, 1991; V o l z et al., world forests. In: D. 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