Carbon Storage in Northeast China As Estimated from Vegetation and Soil

Environmental Pollution 116 (2002) S157–S165 www.elsevier.com/locate/envpol

Carbon storage in northeast China as estimated from vegetation and soil inventories Shaoqiang Wanga,b,*, Chenghu Zhoub, Jiyuan Liub, Hanqin Tianb,c, Kerang Lib, Xiaomei Yangd aLaboratory of Remote Sensing Information Science, Institute of Remote Sensing Application, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China bThe State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, People’s Republic of China cThe Ecosystem Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA dEarth Observation Research Center, National Space Development Agency of Japan, Hamamatsu-cho, Minato-ku, Tokyo 105-8060, Japan ‘‘Capsule’’: Carbon stocks in soil and vegetation in China are 2.81 PgC and 26.43 PgC respectively with the eastern and northern regions showing the highest carbon storage potential.

Abstract We have estimated the stocks of carbon in vegetation and soil in northeast China based on data for 122 plots from the fourth national forest inventory, and for 388 soil profiles from the second national soil survey. The techniques of Geographic Information System (GIS) have been used to extrapolate site-specific estimates of vegetation and soil organic carbon to the entire area of northeast China. Our estimate indicates that the amount of carbon in vegetation and soil for the region are 2.81 PgC (1015g C) and 26.43 PgC, respectively, and that the area weighted average density of vegetation and soil organic carbon are 22.7 MgC/ha and 212.7 MgC/ha, respectively. The eastern and northern parts of the region show much higher carbon storage than the rest of the region. Substantial spatial variations in vegetation and soil organic carbon across northeast China suggest that regional estimates on carbon stocks and fluxes should take into account these spatial variations. We suggest that the methodology developed can be used for the entire nation of China as well as other regions of the world. # 2001 Published by Elsevier Science Ltd. All rights reserved. Keywords: Biomass; China; Soil organic carbon; Vegetation carbon; Terrestrial ecosystem

1. Introduction et al., 1998). Accurately estimating carbon storage and its dynamics in vegetation and soil is also important for Previous studies in the global carbon budget suggest predicting how terrestrial ecosystem carbon pools may that terrestrial ecosystems in the mid-latitudes of the change as climate and land use change in the future Northern Hemisphere act as a large carbon sink of (Melillo et al., 1996). atmospheric CO2 (Tans et al., 1990; Ciais et al., 1995). Terrestrial ecosystems in northeast China (>40 N) In particular, recent analyses based on atmospheric CO2 play an important role in the global carbon budget observations and models further indicate that North (Bousquest et al., 1999), and are especially susceptible to America acts as the largest carbon sink (Fan et al., future land-use change and projected climate change 1998), 1.7 PgC per year during 1988–1992. Other studies (Keeling et al., 1996; Tian et al., 2000). In this region, show that North America C sink for the same period the woodland area is about 57.63104 km2 and forest was small (Field and Fung, 1999; Houghton et al., 1999; cover area is about 30.35% of the whole region. Forests Tian et al., 1999; Schimel et al., 2000). On the other provide about 50% of the wood supply for China. hand, an analysis by Bousquest et al. (1999) suggests Major vegetation types include coniferous and broad- that a large carbon sink is located in northern Asia. To leaved deciduous forest, cropland, temperate steppe and reduce uncertainty in the carbon budget over the grassland. In the past decades, human activities includ- regions requires quantifying contemporary carbon sto- ing deforestation have signiﬁcantly altered the structure rage in terrestrial ecosystems (Brown et al., 1996; Tian and functioning of ecosystems in this region (Tian et al., 1995). These ecosystems also provide a good model for * Corresponding author. Fax: +86-10-6488-9630. understanding carbon cycling in human-modiﬁed eco- E-mail address: [email protected] (S. Wang). systems of other mid-latitude regions.

Some previous studies indicate that changing climate profiles consist of geographical location, soil depth, and atmospheric composition could significantly influ- organic carbon concentration, altitude, color, con- ence the evolution of terrestrial ecosystems and biogeo- sistency, texture, structure, vegetation, terrain position, chemical cycling in China (Yan et al., 2000). Under a parent material, land-use pattern, meteorological index doubled CO2 climate change scenario using GCMs and and bulk density. The collected data were integrated and Forest Gap Models (Deng et al., 2000; Yan et al., 2000), analyzed by employing Geographical Information Sys- some coniferous forest species would be replaced by tem (GIS) technology to determine the quantity and broadleaved forest species and the future warming rate spatial distribution of carbon in vegetation biomass would determine the succession of broadleaved Pinus and soil storage of the region. A digital version of the koraiensis forest. However, little is known about the 1:4,000,000 vegetation and soil maps of China was used carbon storage in terrestrial ecosystems of northeast as the base map to display the spatial distribution of soil China, which has limited our capacity of evaluating the carbon extent (Figs. 2 and 3). In this region the area of carbon budget and predicting ecosystem response to cropland is about 30.6104 km2, or 24.7% of the total climate change. The goals of this study are: (1) to esti- (Fig. 3; Table 1). mate carbon storage in northeast China based on data from vegetation and soil inventories; (2) to analyze the 2.2. Estimation of vegetation carbon spatial variation in vegetation carbon and soil organic carbon; and (3) to identify the key gaps in quantifying a We estimated vegetation carbon over the region by regional carbon budget. multiplying the area of each vegetation type by vegetation carbon density. We determine the area of vegetation from vegetation maps and statistical records 2. Materials and method (Fig. 4). The estimation of vegetation carbon density is mainly based on the standing biomass data observed in 2.1. Study region and materials the field. Standing aboveground biomass data for each vegetation type was obtained from various published The study area covers about 124104 km2 in North- reports or papers. Carbon content varies among vege- east China (115370–13550 E and 38430–53340 N; tation types, and changes from season-to-season (Li et Fig. 1). In this area, major vegetation types on hills and al., 1996; Wu et al., 1997). Carbon conversion coeffi- mountains are temperate broadleaved deciduous and cients are different, considering species, age, formation needle-leaved evergreen forest. The dominated vegeta- and community structure of vegetation types, from 0.45 tion types in the west parts of the region are semi-arid to 0.55 (Olson et al., 1983; Fang et al., 1996a). In this shrubs, grass and temperate steppe. The area of crop- study, we used a carbon conversion coefficient of vege- land is about 20% of the whole region. The climate of tation biomass of 50% (Brown and Lugo, 1984). most of northeast China is classified as temperate monsoon climate in a majority of region, but the north over 2.3. Estimation of soil organic carbon 50N is classified as cold temperate monsoon climate. Main soil types include the dark-brown earths, brown The quantity of soil organic carbon was calculated by coniferous forest soils, gleyed meadow soils, and calcic using carbon density estimated from soil samples and chernozems. The long history of agricultural coloniza- the total soil area (Post et al., 1982, 1990; Sampson et tion coupled with increasing population density and al., 1993; Fang et al., 1996b). In this research, we are economic development has led to significant modifica- able to take advantage of the large number of sampled tion of land-cover types. Northeast China has abundant soil profiles by considering the physical and chemical natural resources including land resource, which can play properties of every soil stratum. The laboratory analy- an important role in regional economic development. sis on the 388 soil samples provides reliable estimations To estimate vegetation carbon, we used biomass data on organic matter concentration, measured soil depth from 122 plots of the fourth national forest inventory, and bulk density for each soil type. The corresponding and other published data in China, official documents soil organic carbon is subsequently converted from soil or technical reports (Fang et al., 1996a,b; Li et al., 1996, organic content by using the conversion coefficient of 1998; Wu et al., 1997; Wang et al., 1998a,b, 1999). To 0.58 suggested by Fang et al. (1996b). Based on this estimate soil organic carbon, we used data on physical strategy, we firstly calculated the carbon content of and chemical variables for every soil stratum from 388 different soil depths in the same soil profile. Then, we soil profiles of the second national soil survey (National used the depth of each horizon as weighting coefficient Soil Survey Office, 1995, 1998). Properties of vegetation to derive the average physical and chemical properties samples include geographical location, vegetation type, of the soil profiles. The average value of profiles was soil type, forest age, land-use pattern, meteorological further aggregated by classifying profiles into different index, and biomass. And properties of typical soil soil subtypes. Using the area of soil subtypes, and the S. Wang et al. / Environmental Pollution 116 (2002) S157–S165 S159

Fig. 1. The location of Northeast China (left) and the spatial distribution of soil samples (right).

Fig. 2. The spatial distribution of vegetation types in Northeast China. S160 S. Wang et al. / Environmental Pollution 116 (2002) S157–S165

Fig. 3. The spatial distribution of soil types in Northeast China.

aggregated average depth, organic matter concentra- bon density of microphyllous deciduous woodland in tion and bulk density of diﬀerent soil subtypes, the temperate zone is the lowest, about 45.5 MgC/ha. The total carbon quantity of a given soil type can be carbon density of cold temperate and temperate forests calculated as: is relatively high because most of these forests are mature (Fang et al. 1996a,b). Among non-forest vege- Cj ¼ 0:58SjHjOjWj ð1Þ tation types, the carbon density of broadleaved deciduous scrub in temperate zone is the highest, about 10.4 where j denotes the given soil type, C is the carbon sto- MgC/ha and that of temperate needlegrass steppe is the rage, S is the distribution area, H is the average depth, lowest, about 0.5 MgC/ha. O is the average organic matter concentration, W is the The carbon storage of needle-leaved deciduous forest average bulk density. in cold-temperate or on mountains in temperate zone is the highest, about 0.94 Pg C, but carbon storage of needle evergreen forest in temperate zone is the lowest, 3. Result and discussion about 0.04 Pg C because of its smallest area (Table 2). The vegetation carbon in forests is 2.19 Pg C, or about 3.1. Stocks of vegetation and soil organic carbon 77.9% of total vegetation carbon pool in northeast China. The area of agriculture is about 24.71104 km2, Vegetation carbon in northeast China is 2.81 Pg C, which is 19.9% of the total land area, however, crop- while the average vegetation carbon density is 22.7 lands store only 0.29 Pg C and represents only about MgC/ha. The carbon density in forests is higher than 10% of total vegetation carbon. Although the area of that of steppes, deserts, meadow and crops (Table 2). steppe and meadow occupies the largest area Among forest vegetation types, the carbon density in (35.55104 km2), the vegetation carbon is only 0.07 Pg needle-leaved evergreen forest on mountains in tempe- C, or about 2.5%. This indicates that forests are the rate is the highest, about 110.2 MgC/ha, while the car- main component of vegetation carbon in northeast S. Wang et al. / Environmental Pollution 116 (2002) S157–S165 S161

Table 1 Vegetation biomass in northeast China

Vegetation type Area (104 km2) Carbon density (MgC/ha) Carbon stock (1015gC)

Needle-leaved deciduous forest in cold-temperate or on mountains in 11.82 79.3 0.94 temperate zone Needle-leaved evergreen forest on mountains in temperate zone 1.10 110.2 0.12 Needle-leaved evergreen forest in temperate zone 0.60 60 0.04 Mixed broad-leaved deciduous and needle-leaved evergreen forest in 3.36 71.4 0.24 temperate zone Broad-leaved deciduous forest in temperate and subtropical zone 11.05 51.4 0.57 Microphyllous deciduous forest in temperate and subtropical zone 3.43 62.5 0.21 Microphyllous deciduous woodland in temperate zone 1.61 45.5 0.07 Broad-leaved deciduous scrub in temperate or subtropical zone 24.66 10.4 0.26 Tundra with evergreen dwarf-shrub and moss on high mountains in 0.16 2.4 0.0004 temperate zone Temperate forb-grass steppe and xeromesophytic meadow 16.90 3.3 0.06 Temperate needlegrass steppe 3.33 0.5 0.002 Temperate meadow 10.62 1 0.01 Alpine and subalpine meadow 0.06 1.8 0.0001 Temperate graminoid swamp 4.63 0.5 0.003 One crop annually, cold-resistant economic crops 24.71 99 0.24 Two crops annually or three crops in 2 years, and warm temperate 5.89 82.3 0.05 economic forest, deciduous orchard Total 124 22.7 2.81

Fig. 4. The spatial distribution of vegetation carbon density in Northeast China (MgC/ha). S162 S. Wang et al. / Environmental Pollution 116 (2002) S157–S165

Table 2 Soil organic carbon storage in northeast China

Soil subtype Area Carbon density Carbon stock (104 km2) (MgC/ha) (1015gC)

Paddy soils 0.90 73.6 0.07 Weakly developed brown earths 1.45 103.5 0.15 Aquic brown earths 0.79 100.2 0.08 Yellow-cinnamon soils 1.08 57.6 0.06 Grey fluvo-aquic soils 2.30 69.3 0.16 Salinized fluvo-aquic soils 0.54 62 0.03 Wet fluvo-aquic soils 0.55 77.4 0.04 Brown earths 5.83 119.5 0.70 Cinnamon soils 1.24 97.3 0.12 Leached cinnamon soils 1.76 101 0.18 Calcic cinnamon soils 0.26 87.9 0.02 Dark-brown earths 26.38 202.4 5.34 Albic dark-brown earths 2.04 127.5 0.26 Meadow dark-brown earths 6.10 223.3 1.36 Gleyed dark-brown earths 0.11 198 0.02 Brown coniferous forest soils 10.28 498.8 5.13 Dark gray forest soils 1.62 69.8 0.11 Gray forest soils 0.28 153.4 0.04 Black soils 0.75 165.9 0.12 Albic black soils 0.75 139.1 0.10 Meadow black soils 0.05 203.3 0.01 Bleached beijiang soils 1.14 126 0.14 Meadow bleached beijiang soils 3.15 171.2 0.54 Chernozems 5.98 186.7 1.12 Calcic chernozems 8.05 237.9 1.92 Leached chernozems 0.08 219.8 0.02 Meadow chernozems 3.87 154.9 0.60 Alkalized chernozems 0.09 105.0 0.01 Castanozems 2.32 93.7 0.22 Dark castanozems 5.09 136.1 0.69 Meadow castanozems 0.67 128.3 0.09 Brown caliche soils 0.08 52 0.004 Meadow soils 1.34 174.8 0.23 Albic meadow soils 4.75 21.51 1.02 Salinized meadow soils 1.40 84.1 0.12 Gleyed meadow soils 8.17 177.5 1.45 Meadow bog soils 1.10 203.9 0.22 Mucky bog soils 0.53 294.3 0.16 Peaty bog soils 3.79 925.5 3.51 Coastal tideland solonchaks 0.23 80.4 0.02 Meadow solonchaks 0.06 42.1 0.002 Alkalinzed solonchaks 0.14 70.4 0.01 Desert aeolian soils 0.86 24.1 0.02 Steppe aeolian soils 3.51 27 0.09 Meadow aeolian soils 3.05 36.6 0.11

Total 124 212.7 26.43

China. Clearly, change in the area of forests could result As expected, the carbon density of peaty bog soils is in larger impacts on atmospheric CO2 concentration the highest, containing about 925.5 MgC/ha, while the than that of steppes, scrubs, crops, swamp and meadow. carbon density of desert aeolian soils is the lowest, For soils in northeast China, the soil organic pool is about 24.1 MgC/m2 (Table 2). Among soil types, the 26.43 Pg C, with an average soil carbon density of 212.7 carbon pool of dark-brown earths is the highest, con- MgC/ha. The land area in northeast China is about taining 5.34 Pg C, while the carbon pool of meadow 12.94% of the nation, but its soil carbon pool is about solonchaks is the lowest, containing 0.002 Pg C mainly 28.59% of the national soil carbon pool (Wang et al., because of its least area. Seven soil types that carbon 2000). The carbon stored in soil is almost 10 times the density is above of the average soil carbon density total in live vegetation in northeast China. (Table 2), occupying about 33.58104 km2 (about S. Wang et al. / Environmental Pollution 116 (2002) S157–S165 S163

Fig. 5. The spatial distribution of soil organic carbon density in Northeast China (MgC/ha).

27.2% of total area), store 13.11 Pg C, or about 49.6% Carbon density of forest soils and bog soils is very of total carbon storage in northeast China. high. For example, brown coniferous forest soils, dark- brown earths and gray forest soils (northeast), and 3.2. Spatial distribution of carbon stocks peaty bog soils, meadow dark-brown earths have a higher organic carbon density than that of other soils. Vegetation carbon density is highest in the north and In northeast China, the humid temperate climate and southeast areas of the region, where forests are located, less-intensive human activities make it favorable for the and lowest in west, east and central regions, where growth of temperate forests. Organic matter enters into crops, scrubs, steppe and meadow are located (Fig. 4). soil mainly as deadwood and litterfall, so that the The vegetation carbon density increases as mean annual extensive accumulation is observed in the upper soil temperature decreases from south to north, and increases proﬁle. Low temperature and common surface water- as annual precipitation increases from temperate steppe logging slows decomposition in these forests, resulting and swamp in the west to needle-leaved evergreen forest in high organic carbon content remaining in the soil on mountains in temperate in the east. proﬁle. Soil carbon density is the highest in the north in the Daxinganling and Xiaoxinganling mountains (Fig. 5). Low temperature in the cold temperate conifer forest 4. Conclusions zone leads to slow decomposition of soil carbon and low soil respiration rate, thus soil carbon has accumulated This study shows that the total amount of vegetation (Rozhkov et al., 1996). Soil carbon density is low in the carbon and soil organic carbon is 2.81 and 26.43 Pg C, southwest and central area where steppe and crops are respectively, and the average carbon density is 22.7 and located. Soil carbon density is higher in the east forest 212.7 MgC/m2, respectively. From the spatial distribu- region than in west grassland region. tion of vegetation carbon and soil organic carbon, it is S164 S. Wang et al. / Environmental Pollution 116 (2002) S157–S165 revealed that the carbon storage is high in eastern and Field, C., Fung, I.Y., 1999. The not-so-big US carbon sink. Science northern region in northeast China, where forests are 285, 544–545. located. Our GIS-based spatial analysis further suggests Houghton, R.A., Hackler, J.L., Lawrence, K.T., 1999. The US carbon budget: contributions from land-use change. Science 285, 574–578. that the regional carbon budget estimate should take Keeling, C.D., Chin, J.F.S., Whorf, T.P., 1996. Increased activity of into account spatial heterogeneity in vegetation carbon northern vegetation inferred from atmospheric CO2 measurements. and soil organic carbon. Results drawn from this study Nature 382, 146–149. provide useful information for policy-making to control Li, M., Yu, M., Chen, Q., Chang, J., Pan, X., 1996. Dynamics of car- CO emission in China. And the methodology devel- bon in the evergreen broadleaved forest dominated by Cyclobala- 2 nopsis glauca in south-east China. Acta Ecologica Sinica 16 (6), oped from this study can be used for the entire nation as 643–651. well as the other regions of the world. Li, Y., Wu, Z., Zeng, Q., Zhou, G., Chen, B., 1998. Estimation of

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