1. AGRICULTURAL
AND
FOREST
NETEOROLOGY
ELSEVIER 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 1996
Abstract
Forest plantations in the world total approximately 130 × 106 ha, and annual rates of establishment are about 10.5 × 106
ha. 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 integrates
information across latitudes to evaluate the potential of forest plantations to achieve these goals. For example, mean carbon
storage (MCS) in above- and below-ground phytomass of artificially established plantations generally increases from high to
low latitudes ranging from 47 to 81 t C ha -l. Over a 50-year period, harvests from these plantations are credited with
storing 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 today's distribution of plantations among the four zones of latitude and C storage values from this
analysis, the world's plantations can be credited with storing an area-weighted average of 91 t C ha-1 including MCS and
durable-wood products. Based upon these estimates, the world total C storage in forest plantations today is approximately
11.8 Pg C with an annual increase of 0.178 Pg C year- L
Keywords: Forest plantations; Carbon storage; Terrestrial ecology
1. 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 far
for: domestic products such as poles, fruit, etc.; back as the 6th Century BC (Levingston, 1984). In
industrial 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

2. 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 symposium
become mindful of the mitigating role of forests in on planted forests; and (3) a database on world
reducing 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 earth's terrestrial ecosystems in prein-
dustrial times to ~ 28% today (Sharma et al., 1992). 2.1. Extent o f world plantations
This 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 of
1993; 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. Data
forest 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 an
storage 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 forest
attributes, and their potential contribution toward data are based upon the best-available country-wide
global 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 by
2. 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 world's 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 for
Table 1
For 32 developed countries, the total natural forest in 1990 (FAO, 1995) and the planting rate per year during the early 1980s (WRI, 1992) a
Country Forest area (ha × 103) Country Forest area (ha × 103)
Total natural Planting year- l
rate Total natural Planting year-
rate
Albania 1046 2 Ireland 396 9
Austria 3877 21 Israel 102 2
Australia 39837 62 Italy 6750 l5
Belgium 620 19 Japan 24158 240
Bulgaria 3386 50 Netherlands 334 2
Canada 247164 720 New Zealand 7472 43
Cyprus 140 0 Norway 8697 79
Denmark 466 6 Poland 8672 106
Finland 20112 158 Portugal 2755 9
Former Czechoslovakia 4491 37 Romania 6190 3
Former Soviet Union 754958 2600 Spain 8388 92
Former Yugoslavia, SFR 8371 53 Sweden 24437 207
France 13110 51 Switzerland 1130 7
Germany 10490 62 Turkey 8856 82
Greece 2512 5 United Kingdom 2207 40
Hungary 1675 19 USA 209573 1094
a Planting rates for seven countires are the means for the decade of the 1980s: Albania, Cyprus, Denmark, Greece, Romania, and Former
Soviet Union (UN-ECE/FAO, 1992); USA (USDA FS, 1992).

3. a'.K. Winjum, P.E. Schroeder/Agricultural and Forest Meteorology 84 (1997) 153-167 155
Table 2
For 92 developing countries, the total existing plantation area in 1990 in ha x 1000, and the average annual increase in plantation area
during the period 1980 to 1990 (FAt, 1995) a
Country 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 increase
Algeria 485 18.3 Guyana 8 0.8 Panama 6 0.4
Angola 120 1.0 Haiti 8 0.8 Papua N. Guinea 30 1.5
Argentina 547 4.6 Honduras 3 0.3 Paraguay 9 0.7
Bangladesh 235 12.3 India 13230 1009.0 Peru 184 8.8
Benin 14 0.6 Indonesia 6125 331.8 Puerto Rico 3 0.1
Bhutan 4 0.2 lran 79 4.9 Reunion 7 0.1
Bolivia 28 1.0 Jamaica 15 0.6 Rwanda 88 4.3
Brazil 4900 195.4 Jordan 23 0.8 Samoa 9 0.5
Burkina Fast 20 1.1 Kenya 118 1.6 Senegal 112 10.3
Burundi 92 7.9 Korea, DPR 1470 77.0 Sierra Leone 6 0.2
Cameroon 16 1.2 Kuwait 5 0,5 Solomon Islands 16 0.3
Cape Verde 10 0.7 Laos 4 0,1 South Africa 965 15.5
Chad 4 0.2 Lesotho 7 0,6 Sri Lanka 139 6.0
Chile 1015 54.5 Liberia 6 0.1 Sudan 203 8.8
China 31831 1139.8 Libya 210 11.0 Suriname 8 0.2
Columbia 126 8.9 Madagascar 217 3.1 Swaziland 72 0.1
Congo 37 2.5 Malawi 126 7.0 Syria 127 9.9
Costa Rica 28 2.6 Malaysia 81 6.3 Tanzania 154 8.6
Cote d'Ivoire 63 3.2 Mali 14 1.3 Thailand 529 29.4
Ct. African Rep. 6 0.6 Mauritania 2 0.2 Togo 17 1.2
Cuba 245 13.5 Mauritius 9 0.1 Trinidad/Tobago 13 0.1
Dominican Rep. 7 0.3 Mexico 109 5.3 Tunisia 201 11.2
Ecuador 45 1.5 Morocco 321 9.6 Unit. Arab Emir. 60 5.9
Egypt 34 0.6 Mozambique 28 1.0 Uruguay 156 2.0
E1 Salvador 4 0.3 Myanmar 235 19.6 Vanuatu 7 0.4
Ethiopia 189 12.0 Nepal 56 4.3 Venuzuela 253 16.6
Fiji 78 5.0 N. Caledonia 9 0.4 Vietnam 1470 49.0
Gabon 21 0.8 Nicaragua 14 1.3 Zaire 42 2.6
Ghana 53 1.1 Niger 12 0.8 Zambia 48 2.1
Guatemala 28 1.8 Nigeria 151 3.7 Zimbabwe 84 1.4
Guinea 4 0.1 Pakistan 168 4.2
a 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 to
tically 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 d
w 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 these
that 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 r
time. 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 to
m 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 to
o 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 through
w 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.

4. 156 J.K. Winjum, P.E. Schroeder/ Agrtcultural and ForestMeteorology 84 (1999) 153-167
2.3. Potential plantation C storage el'ell~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 the
part 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 were
database 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 of
Table 3
Commonly cited ecological attributes of forest plantations
Attributes Selected references
Ecological positives
A. 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 negatives
A. 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)

5. J.K. Winjura, P.E. Schroeder /Agricultural and Forest Meteorology 84 (1997) 153-167 157
Table 4
Mean annual increment (MAI), mean annual biomass C (MABC), and rotation lengths for plantations in high, middle, and low (dry and
moist) latitudes of the world
Variables 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 of
the 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 is
tations within the four zones of latitude described
above (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 C
and 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 adapted
Specifically, MCS is the same as the average amount
from Brown and Lugo (1982) and Sedjo and
of 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 MABC
approach presented here may represent an upper MCS = ~ R (2)
bound, year= 1
Table 5
Calculated values for me~m carbon storage (MCS) for plantations of Table 4
Variables MCS (t C h a - 1)
Latitudes
High Middle Low-dry Low -moist
Q1 ~ Median Q3 Q1 Median Q3 Q1 Median Q3 Q1 Median Q3
Above-ground b 17 39 45 18 53 155 27 62 103 32 68 146
Below-ground c 3 8 9 4 11 31 6 12 21 6 13 29
Total 20 47 54 22 64 186 33 74 124 38 81 175
a 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).

6. 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 is
o 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 the
the 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 made
below-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, the
Table 6
Calculations leading to long-term storage of C in harvested wood at the end of each rotation
Variables Latitudes
High Middle Low-dry Low-moist
Q1 a Median Q3 Q1 Median Q3 Q1 Median Q3 Q1 Median Q3
Sternwood at harvest
Volume (m 3 ha- 1) b 82 184 216 82 247 724 121 283 476 138 306 668
Weight
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 72 157
Percent (%) of harvested wood used for: e
Fuel/charcoal 20 15 65 35
Paper products 40 45 25 40
Solidwood products 40 40 10 25
Allocation of harvested wood (t C ha - 1)
Fuel/charcoal 4 9 10 3 9 25 18 43 72 11 25 55
Paper 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 31
Solidwood 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 22
Long-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 16
Solidwood products i 4 9 10 4 12 35 1 4 6 4 9 20
Total 6 13 15 6 18 54 3 8 13 7 16 36
a 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 solidwood
products.
h Assumes 50% of the carbon in paper products remains in long-term products (e.g. books, discarded paper retained in landfills, etc.) for
several decades.
i Assumes 90% of the carbon in solidwood products remains in wood structures for several decades.

7. Table 7
Extent 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 ). --4
i Values are annual net increase (ha × 106 year- i ) × total C storage at 50 years (t C h a - l ).

8. 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
200 250 300
Fig. 1. For plantations in the high (a), middle (b), low-dry (c), and low-moist (d) latitudes, simulated trends of C storage in durable-wood
products for repeated rotations of 80, 25, 19, and 15 years, respectively. The saw-tooth peaks occur at the end of each rotation and the
downward-connecting-curved lines represent a 1% decay rate in diagrams (a) and (b) and 2% for diagrams (c) and (d). The dotted line from
50 years on the horizontal axes projected through the curved wood-product storage line to vertical axes gives an estimate of C storage credit
in 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 produced
SWC = 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

9. 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 above
their proportions among latitudes are only approxi- from Tables 4 and 6 were entered into a simulation
mations that represent a mix of wood removals from routine that determines the declining amount of C
both 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 so
pools of forest C following harvest of plantations at that the upward trend approaches a horizontal line
a 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 lines
paper and solidwood products, conversion efficien- from the saw-tooth peaks at the end of each harvest
cies must be considered. Here, it is assumed that the represents the C stored, on average, throughout each
average yield from the harvested wood allocated for rotation. The curve connecting these midpoints takes
paper products is 50% (Briggs, 1994). Also used is the form of an ascending curve that approaches an
an average conversion efficiency for sawn or peeled upper limit asymptotically (Fig. 1). Differences
roundwood logs frora plantations of 1.75 units of among the curves represent differences in: (1) C
harvested 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) rotation
torate General of Forest Utilization, DGFU, 1989; length. To determine the product C credit for a
Sedjo and Lyon, 1991); Harmon et al., 1990; Briggs, 50-year period (i.e. closer to the period of concern
1994). for mitigating increasing atmospheric CO2), a point
Other assumptions were that 90% of the solid- on the vertical axis was also projected from the
wood 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 per
decades, e.g. wood-flame houses and other durable- hectare for the plantations was determined simply by
wood products (Row and Phelps, 1992). Also half of summing the C above-ground, below-ground, and in
the 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 the
ucts 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 and
needed that can be added to the MCS in biomass, solidwood products with portions in long-term C
The amount of C in wood products credited to such storage (Table 7).
plantations was calculated in the computer simula-
tion described below. Simulations were conducted
for plantations in each of the four latitudinal zones
(Fig. 1). Input value:~ were rotation ages (Table 4),
3. Results
the 'total' values (medians, Q1, and Q3 values) for C
in durable-wood products at harvest (Table 6), and a
decay 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 among
high and middle latitudes, a relatively cooler climate, countries in all latitudinal regions; ecologically, there
is 1% annually and fi~r the warmer low latitudes, 2% are strong positives as well as cautions to be heeded
annually. The rates are assumptions that reflect the from the negatives; and estimates show that the
latitudinal zone where a predominant amount of the potential for plantation C storage is significant.

10. 162 J.K. Winjum, P.E. Schroeder /Agricultural and Forest Meteorology 84 (1997) 153-167
3.1. 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 these
approximately: high, 14%; middle, 63%; low-dry, data. For developed countries, a log-log diagram
14%; and low-moist, 9% (UN-ECE/FAO, 1992; shows that the greater the area of natural forest
FAO, 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 of
world 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 annual
latitudinal region are: high, 27%; middle, 63%; and increase in plantation area is presented and tends to
low-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 developing
are replacing harvested forests (natural or older plan- countries with an average annual plantation increase
tations) or are the result of afforestation or agro- equal to or greater than 100 ha, a log-log diagram
forestry projects. However, in 1965, existing planta- shows that the more plantations that countries have
tions in the world were estimated to cover 81 × 106 in place (x axis), the more the net increase in
ha 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 because
be 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 plantation
establishment during the 1980s (WRI, 1992) when plotted against the area of existing natural forests in each country during 1990 (FAO,
1995).

11. J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167 163
increases relative to the other 88 countries inordi- period, harvests from these plantations are credited
nately 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 total
use of forest plantations in the world point to many C credit in t C ha -1 for plantations in the four
ecological 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-weighted
number are applicable to most forest regions of the median for C storage credited to all plantations is 91
world (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 the
1992 (Boyle et al., 1997). One additional positive 1990 areas of existing plantations provides estimates
attribute noted was the role of plantations to protect of the amount of C stored in each region. Median
watersheds (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 in
below-ground phytomass of plantations generally in- plantation area for the period leading up to 1990 and
creases from high to low latitudes ranging in medi- the C credits gives an estimate of the annual uptake
ans 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 plantation
area 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).

12. 164 J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167
0.122, 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 that
Pg C year -l (Q1 = 0.076 and Q3 = 0.425 Pg C plantation programs will likely continue as long as
year-l), ecological constraints do not exist that make the
practice unreasonable or forbidding.
Furthermore, the positive attributes indicate
4. 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 greatly
pears ongoing in the world today. This is strongly contributed to such projects. Examples are improved
evident 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 a
of plantation establishment totaling between 8.5 and half century of research and operations in forest
10.5 × 106 ha year-~. The net gain in area is about genetics have greatly increased the capability of
2 × 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 are
the more natural forest area they have, the greater the seemingly forbidding (Table 3). In careful reading of
annual 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 plantation
indicates 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, the
greater 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 UNCED's Assuming then that forest plantations will be an
Agenda 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 contribution
attributes 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 in
continuing this forest practice. Human constraints to 1990 can be credited with storing approximately 11.8
plantation establishment are widely known. Included Pg C with Q1 = 5.0 Pg C and Q3 = 28.2 Pg C
are many combinations of factors such as limitation (Table 7). The median value is less than one percent
of land tenure systems, insufficient capital, lack of of the 1500 to 2000 Pg C estimated to be stored by
knowledge about some species, poorly understood all the world's 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 was
humans are sometimes cited. Examples are: high risk the estimated net annual gain of C in the atmosphere
of 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 considering
indigenous people (Kanowski et al., 1992; Mather, that studies of global mitigating options to the prob-

13. J.K. Winjum, P.E. Schroeder / Agricultural and Forest Meteorology 84 (1997) 153-167 165
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