Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China

Transcription

1 Journal of Resources and Ecology Vol.1, No.2 J. Resour. Ecol (2) DOI: /j.issn x Article Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China YU Guirui 1 *, LI Xuanran 1,2,3, WANG Qiufeng 1 and LI Shenggong 1 1 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, CAS, Beijing , China; 2 Department of Environment and Resources Management, Chifeng University, Chifeng , China; 3 Graduate University of Chinese Academy of Sciences, Beijing , China Abstract:Process mechanisms of carbon storage and carbon cycle in earth system are the scientific foundation for analyzing the cause of climate change, forecasting the climate change trend, and making mitigation and adaptation countermeasures, which have attracted great attention from the scientific community and international community. Since the late 1980s, Chinese scientists have carried out a great deal of research on the terrestrial ecosystem carbon cycle, and have made great progress in many fields. In this paper, we review the history of the research on the terrestrial carbon cycle in China, summarize the results of the carbon storage in terrestrial ecosystems and its spatial patterns, evaluate the uncertainties of the research, and put forward important scientific issues which are needed to be addressed urgently. Overall, the research on the carbon cycle of terrestrial ecosystems in China consists of four stages of development, i.e., the early carbon cycle research, the comprehensive study on the carbon cycle at regional scale, the experimental research on the adaptation of ecosystem carbon cycle to climate change, and the coupling cycles of C-N-H 2O and the regional regulation and control. Most studies indicate that carbon storage of terrestrial ecosystems in China and its spatial pattern are controlled by temperature and precipitation. About Pg carbon is stored in soil, forest and grassland in China. Since the mid 1970s, many management measures such as afforestation and forest management, grassland protection, farming system reformation and conservation tillage, have played important roles in carbon sequestration. However, large uncertainty exists among the evaluation results with various methods. In the future we should focus on the integrated monitoring system of the dynamics of carbon storage and carbon sink, foresight studies on the coupling cycles of ecosystem C-N-H 2O and its regional regulation and control, quantitative assessment on the carbon budget and the potential of carbon sink of ecosystems in China, the evaluation of the economic benefit of various technologies for increasing carbon sink of typical ecosystems, and the measurable, reportable and verifiable scientific data and technical supports for establishing the policy framework of greenhouse gas management and carbon trading at national scale. Key words: carbon cycle; carbon storage; terrestrial ecosystems; global change 1 Introduction Due to fossil fuel burning, cement production, land use change and other human activities since the industrial revolution, organic and inorganic carbon originally sequestrated in lithosphere, terrestrial and marine ecosystems was activated again to participate in the carbon cycle of the earth system, which leads to continual increases of atmospheric CO 2, CH 4, N 2O and other greenhouse gas, and consequently, enhanced the greenhouse effect. Changes in earth s carbon cycle derived from human activities played an important role in global climate warming. Rising in global air temperature and sea surface temperature will result in the melting of the snow and glacier in a large area in the polar and alpine, and the rise of global sea level, which will threat to the sustainable development of human society (IPCC 2007). Process mechanisms of carbon storage and carbon cy- Received: Accepted: Foundation: this work was financially funded by Key Project of Chinese National Programs for Fundamental Research and Development (Grant No. 2010CB833500), National Natural Science Foundation of China (Grant No ), and Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX2-YW-432). * Corresponding author: YU Guirui. yugr@igsnrr.ac.cn.

2 98 cle in earth system are the scientific foundation for analyzing the causes of climate change, forecasting the climate change trend, and making mitigation and adaptation countermeasures, which have attracted great attention from the scientific community and international community (Yu et al. 2006; Yu et al. 2009). At present, scientists have basically mastered the size of each carbon pool (i.e. the atmosphere, ocean, soil, and vegetation) of globe and the cycle of carbon among them (such as fossil fuel combustion emissions, ocean uptake, vegetation photosynthesis, ecosystem respiration, etc.) (IPCC 2007). However, due to the complexity of various positive and negative feedback among each carbon pool, it is still a big challenge to reveal the mechanisms of terrestrial carbon cycle processes and the role in global climate change. Further quantitative assessments on the carbon storage of various types of ecosystems and the changing processes, the carbon source/ sink strength of ecosystem and its spatio-temporal variation, and the impact of ecosystem management on carbon cycle are still needed to be studied (Yu et al. 2006; Yu et al. 2009). Located in high latitudes of the Northern Hemisphere, China is a country with vast territory, complex natural conditions, diverse ecosystems, and unique geographical features. From north to south, it is 5500 km in length, spanning 49 degrees of latitude, including 9 climatic zones; from east to west, it is about 5200 km in width, across 62 degrees of longitude; including various natural and artificial ecosystems, such as forest, grassland, farmland, wetlands, deserts, urban, and water bodies. There are 46 different types of soil, 29 types of vegetation, and 48 types of land use. Thus, The research on the carbon cycle in China s terrestrial ecosystems and its pattern is not only an urgent need for assessing the regional carbon balance and effective management of greenhouse gases in China, but also of great importance in globe (Yu et al. 2006). Since the late 1980s, Chinese scientists have carried out a great deal of research on the ecosystem carbon cycle, and have made great progress in many fields. Based on reviewing about the research on carbon cycle in terrestrial ecosystems, this paper mainly focuses on summarizing the results of carbon storage in China s terrestrial ecosystems and its spatial patterns, evaluating the uncertainty of related researches, and putting forward important scientific issues that are urgently needed to be addressed, which would provide valuable information for future research. Journal of Resources and Ecology Vol.1 No.2, Review of studies on carbon cycle of terrestrial ecosystem in China The global carbon cycle research began in the 1970s, which was promoted with the kick off of the International Geosphere-Biosphere Programme (IGBP) in The release of the first IPCC assessment report in 1990, the coming into force of the United Nations Framework Convention on Climate Change in 1992, particularly the signing of Kyoto Protocol in December 1997, had greatly stimulated the increase of scientific research investment in the carbon cycle research all over the world. In the following 20 years, it has always been the foresight research field in the ecosystem and global change science for fighting climate change,, and is also a hot topic with international concern, that the research on the mechanisms of carbon cycle processes of terrestrial and ocean ecosystems, the carbon budget of different types of ecosystem and different regions, the effect of climate change on carbon cycle and its feedback. Studies on the carbon cycle of terrestrial ecosystem in China began in the late 1980s, developed rapidly in the last 10 years. Various types of research projects were launched with the common scientific and technical issues which include: Information access technology for carbon pools of soil, vegetation and atmosphere, comprehensive evaluation of carbon pool of different types of ecosystem, and the spatio-temporal pattern of carbon storage in different types of pools and its influencing factors; Biogeographic mechanisms of carbon sink or source intensity, the spatio-temporal pattern, and the formation of carbon sink or source pattern of main types of terrestrial ecosystem and the uncertainty of evaluation; Simulation analysis of the historical process, enhancement potential of carbon sequestration, and future scenario of the strength of carbon pools and carbon sink or source in terrestrial ecosystems, introduction and development of process-based models and remote sensing models of the terrestrial carbon cycle; Mechanisms of natural and man-made regulation on the terrestrial carbon cycle, impacts of land use and land cover change, farmland management, watershed management, forest management and ecological engineering on carbon storage and carbon sequestration of terrestrial ecosystem; Mechanisms of the responses and adaptation of key biological processes in terrestrial ecosystem carbon cycle to climate change, approaches to ecosystem man-

3 YU Guirui, et al.: Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China 99 agement, quantitative authentification, sustainability, leakage and economy of man-made carbon sinks. So far, research on carbon cycle in terrestrial ecosystems in China has experienced 4 main development stages: early carbon cycle research, comprehensive study of ecosystem carbon cycle at regional scale, experimental research on the adaptation of ecosystem carbon cycle to climate change, and the coupling cycles of C-N-H 2O and the regional regulation and control. 2.1 Early carbon cycle research Research on carbon cycle in terrestrial ecosystems originated from the studies on the productivity of crops, grassland and forest, and the maintenance mechanisms of different types of soil fertility. Until the 1990s, such research began to serve for the climate change. Aiming to guide the distribution of agriculture, forestry and husbandry, research on carbon sequestration and emission in ecosystem was carried out from the aspects as assessment of ecosystem productivity, food, fodder and timber production, with focus on gross primary productivity (GPP), net primary productivity (NPP), and the potential of photosynthetic production of different types of plants in different regions, and the constraints of environmental factors such as water, heat, soil and fertilizer, (Zhu 1964; Li 1980; Deng et al. 1980; Chen et al. 1984; Hou et al. 1985). In addition, most research focus on the mechanism of the population production process, the yield increasing effect of population structure and environmental control measures, the theoretical basis and advanced technology for crops cultivation (Fei 1962; Zhang et al. 1964; Jia et al. 1988; Zhao 1989). From the late 1980s, some researchers began to carry out small-scale and sporadic research on plant biomass and carbon accumulation processes related to global change (Chen et al. 1984; Qiu et al. 1984; Jiang et al. 1985; Huang et al. 1988; Jin et al. 1990). Studies on carbon storage, carbon accumulation and carbon cycle of typical ecosystems teemed from the 1990s (Yang et al. 1991; Ding et al. 1991; Zhu 1991; Dang et al. 1992; Li, 1993; Hu et al. 1994; Wang et al. 1998). At regional scale, more and more attentions were paid to the integrated assessment of carbon storage of soil and vegetation and carbon sink function of ecosystems (Fang et al. 1996b; Luo et al. 1999; Wang et al. 1999), which lead the research on carbon cycle in China s terrestrial ecosystem to a new stage. 2.2 Comprehensive study on ecosystem carbon cycle at regional scale From the beginning of this century, research on carbon cycle of ecosystem in China entered into a stage of integration at regional scale. The Chinese Academy of Sciences launched a key research program Study on Carbon Budget of Terrestrial and Coastal Ecosystem in China in Synthesized research were carried out in the project, such as the spatio-temporal pattern of carbon budget in terrestrial and coastal ecosystems, processes of carbon cycle and models, technologies for increasing carbon sink and carbon mitigation (Yu 2003; Yu et al. 2008; Huang et al. 2008). In 2002, the Ministry of Science and Technology launched a National Key Basic Research Development Program (973 plan) project, Carbon Cycle and Driving Mechanisms in Chinese Terrestrial Ecosystem, made a evaluation on the historical processes, reality, trends and the potential for carbon sequestration of carbon sink or source in terrestrial ecosystems by combining top-down remote sensing models and bottom-up process-based models. Under the support of the above two projects, the Chinese Terrestrial Ecosystem Flux Research Network (ChinaFLUX) was established, which implements observation and experimental research on carbon flux and its main processes in major ecosystems in China (Yu et al. 2008). In 2007, the National Natural Science Foundation of China started two major international cooperation projects in the area of climate change, namely, CarboEastAsia: Capacity Building among ChinaFlux, JapanFlux and KoFlux to Cope with Climate Change Protocols by Synthesizing Measurement, Theory and Modeling in Quantifying and Understanding of Carbon Fluxes and Storages in East Asia, and Quantifying and Predicting Terrestrial Carbon Sequestration in East Asia: Toward a Network of Climate Change Research. Scientists in East Asia come together to research observations and modeling of regional carbon budget. Thus, research on carbon cycle in China s terrestrial ecosystem has come into a new stage of continental cooperation. Chinese scientists have adopted and improved a number of carbon cycle models of terrestrial ecosystems in recent years, such as CEVSA (Tao et al. 2003), BEPS (Wang et al. 2004), BIOME3 and BIOME-BGC (Dong et al. 2008), GLO-PEM (Gao et al. 2004; Liu et al. 2007; Jiang et al. 2008), EALCO (Mi et al. 2007), SIB2 (Zhou et al. 2008). Furthermore, Chinese scientists have developed the FORCCHN model (Yan et al. 2007), Agro-C model (Huang et al. 2009) and DCTEM (Huang et al. 2008) for carbon budget simulation of forest, cropland, and grassland ecosystem, respectively. Also, the atmosphere-vegetation interaction models (AVIM and AVIM2) based on the transfer processes of energy, water and carbon in soil-vegetation-atmosphere system, coupling with vegeta-

4 100 tion dynamics and soil organic carbon turnover, have been developed (Ji et al. 1999; Huang et al. 2008). All the above development of models provides a tool for evaluating ecosystem productivity and carbon balance in China. ChinaFLUX provides advanced observation and experiment platform for the carbon cycle research in terrestrial ecosystem. Taken eddy covariance techniques as the main methods, ChinaFLUX established more than 20 flux observation towers in forest, grassland, farmland and wetlands at 3 levels as typical ecosystems (sites), terrestrial transect of global change study, and the region of China, which composed a long-term observation network of ecosystem C and H2O flux and processes (Fig. 1). ChinaFLUX has established a research platform by combining multiple processes (biological, physical, and chemical processes), multiple scales (sites, transects, region), and multiple technologies (meteorological, ecological, and isotopic). An e-science environment for observation-data quality control-integration of multi-source data and its conformity with model simulation, a platform for field observa- Journal of Resources and Ecology Vol.1 No.2, 2010 tion, model simulation, and data sharing have been come into being by combination of ecological, meteorological, and isotopic techniques system for observation of C-H2O-N fluxes and its process in typical ecosystems (ChinaFLUX-EMI, Fig. 1a), a carbon flux and storage observation technology system of ecosystem flux observation-transect investigation-remote sensing (ChinaFLUX-FTR, Fig. 1b), and a model-data fusion system for carbon cycle modeling and evaluation in China (ChinaFLUX-MDFS, Fig. 1c) have been developed, which could provide service for research on regional carbon cycle and carbon budget evaluation. 2.3 Experimental study on adaptation of ecosystem carbon cycle process to climate change It is an important field in global change research to study the response and adaptation of ecosystem to global change. Warming, precipitation change, CO2 enrichment, and N deposition increase are 4 main forms of global change resulted from human activities. In order to study

5 YU Guirui, et al.: Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China 101 the response of ecosystem carbon cycle to environmental factors, warming and precipitation control experiments have been conducted in the grassland of Qinghai-Tibet Plateau and Inner Mongolia in China. In recent years, experiments of N deposition and precipitation alteration, effect of CO 2 concentration on growth of forest plants with Open-top chamber (OTC) were conducted in major types of forest in eastern China, and a FACE experiment was also conducted in a farmland ecosystem in Jiangdu City of Jiangsu Province. In addition, Chinese scientists also conducted a series of research on the response and adaptation of ecosystems to global change based on the platform of the Northeast China Transect (NECT), (Zhang et al. 1995), the North South Transect of Eastern China (NSTEC) (Teng et al. 2000), and the China Grassland Transect (CGT) (Yu 2003). The National Natural Science Foundation of China launched a key project Transect study on the response and adaptation of typical terrestrial ecosystem to global change in China in 2006, and organized a experimental study on response and adaptation of carbon cycle in terrestrial ecosystems to climate change at multi-site, which symbolized that the carbon cycle research of terrestrial ecosystem in China has entered a stage of experiment study on adaptation of ecosystem carbon cycle to climate change. In recent years, some scientists have dedicated to promoting the integration of the Euro-Asian Continental Eastern Edge Transect (EACEET), the Euro-Asian Continental Grassland Transect (EACGT), and the regional flux network in Asia (Yu et al. 2008), developing a platform for field comprehensive studying on ecosystems and global change in Asia, and organizing a program of united carbon flux observation and research in China, Japan, and South Korea (CarbonEastAsia), which have made a series of important progress (Fu et al. 2009; Fang et al. 2010; Wen et al. 2010; Zhang et al. 2010). 2.4 Coupling cycles of C-N-H 2O of ecosystem and its regional regulation and management How warming, CO 2 concentration enrichment, precipitation pattern change, N deposition increase will affect the spatio-temporal variation of carbon sink function of terrestrial ecosystem is a frontier scientific issue in the study of ecosystem carbon cycle and global change in recent years. However, understanding of the equilibrium relation of C, N, and H 2O cycles and its response to climate C and H 2O fluxes observation Integrating data from previous research Field experiment Inventory Model Remote sensing C-N-H 2O fluxes Stable isotope N deposition Micrometeorology Ecosystem flux observation platform ChinaFLUX Temperature Precipitation Nitrogen input Grazing Observation network Research platform ChinaFLUX-CN Control experiment C-N-H 2O coupling model Model-RS-Data fusion Equilibration relation of C, N, and H 2O and its environmental impact mechanism Estimation of C, N, and H 2O fluxes in China Response and adaptation of C, N, and H 2O cycles processes to global change Fig. 2 Strategy for studying the coupling cycles of C-N-H 2O of ecosystem and its regional regulation and management.

6 102 change is limited. Meanwhile, there is a great uncertainty in some preliminary understanding and forecast since both climate change and anthropogenic activities drive the C, N, and H 2O cycles, and the complexity of the coupling mechanisms among three cycles, Therefore, Chinese government kicked off a 973 project, i.e. Equilibration Relation of Terrestrial C, N, and H 2O Fluxes and Its Response Mechanisms to Environment in China in 2010, which symbolized the study on ecosystem carbon cycle in China has come to a new stage focusing on the coupling cycles of C-N-H 2O of ecosystem and its regional regulation and management. To study the equilibration relation of terrestrial C, N, and H 2O fluxes and its response mechanisms to environment in China is not only an urgent demand for China s confronting global climate change, but also a need to improve ecosystem management and ensure ecological security in China. The objective of the project is to establish a scientific research platform for studying C, N, and H 2O cycles of terrestrial ecosystems in China, named as China- FLUX-CN; to conduct a long-term observation network and a multiple factor experiment network; to develop a new process-based model coupled with remote sensing for C-N-H 2O cycles; and to quantify the ecological stoichiometry characteristics of C, N, and H 2O fluxes and their responses to climate change, based on previous studies on NSTEC and CGT, Chinese National Ecosystem Observation and Research Network (CNERN), and China- FLUX (Fig. 2). The project will take the coupling processes of C, N, and H 2O cycles of terrestrial ecosystems in China and its response and adaptation to climate change as the main line, using eddy covariance techniques, static chamber/ gas chromatogram methods, stable isotope techniques, and plant eco-physiological methods, to operate an integrated network observation, network control experiments of multi-factor, to develop a model system of the coupling cycles of C, N, and H 2O fused with multi-source observation data at multiple scales, and to analyze synthetically the relation of C-N-H 2O fluxes and its environmental impact mechanism. 3 Soil carbon stock and its spatial patterns in China 3.1 Storage and distribution of soil organic carbon in China Soil organic carbon (SOC) refers to the C stored in the soil in soil organic matter (SOM), which consists of tissues from dead plants and animals, products produced as Journal of Resources and Ecology Vol.1 No.2, 2010 these decompose and the soil microbial biomass. SOC has great effects on the physical, chemical and biological characteristics of soil. The capacity of soil holding water and fertilizer, the soil biodiversity, and the plant productivity, are also influenced by SOC. The amount of organic carbon stored in soil in 1m depth is about Pg (1 Pg = g) globally, which is 2 to 3 times as that stored in plant (Post et al., 1982; Jobbágy & Jackson, 2000), and more than 2 times as that stored in atmosphere (Davidson et al. 2000). Therefore, SOC plays an important role in the terrestrial carbon cycle. Broad-scale soil organic carbon stock can be estimated based on soil survey data or modeling approach (Yu 2003). When estimating based on soil survey data, different SOC density calculating methods may make the estimation of SOC stock different (Wang et al, 2003; Yu et al. 2005). Besides, some other factors, such as the spatial resolution of digital soil map, the source of survey data, the number of soil profiles, soil depths and so on, can also contribute to the difference among estimations. The estimations of soil carbon storage in China are listed in Table 1. Various estimates ranged from 44.5 Pg (Pan 1999) to 180± Pg (Fang et al. 1996a), with a large variation among different studies. The estimation of Fang et al. (1996a) is the largest, partly because the selected soil profiles covered only one third of the soil profiles of the Second State Soil Survey. Pan s (1999) result is rather small when compared to others, mainly because the constant soil bulk density ( kg m 3 ) is used in this study, and the area covered by certain type of soil is from Soil Species Record of China,which contains only the overall soil species area information and maybe not specific enough. The difference among other estimates is also significant, ranged from 69.1 Pg (Yang et al. 2007) to Pg (Wang et al. 1999). The part of the reason is different soil areas were used. The resolution of soil map used in Yu et al. (2005) is higher than that in others, and the number of polygons in the map (more than ) is also larger, so we take the soil area from Yu et al. (2005) as the true value of soil area in China. Based on this area and the SOC density in previous studies, the SOC stock in China is Pg, with an average of 87.78±9.98 Pg (The values with a light color in Table 1 are not included). The distribution of SOC storage in China showed an obvious zonal pattern (Wang et al. 2000; Xie et al. 2004; Yu et al. 2005; Yu et al. 2007b). Among all the Chinese Soil Taxonomy orders, the mean SOC density of Histosols was the highest, followed by Spodosols, and Primosols showed the lowest SOC density (Yu et al. 2007b).

7 YU Guirui, et al.: Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China 103 Resolution of soil map Data Sources Number of profiles Area (10 4 km 2 ) SOC storage (Pg C) SOC density (kg m 2 ) Soil depth (cm) References 1:10M ± Fang et al. 1996a 1:4M Profile depth Wang & Zhou 1999 > Profile depth Pan :4M Profile depth Wang et al :4M ± Wang et al :4M Profile depth Wu et al :4M Profile depth Wu et al :4M Xie et al :1M Min(100, Profile depth) Yu et al. 2005, 2007a, 2007b 1:4M Profile depth Xie et al :4M Li et al :4M Yanget al 2007 OBM model Not mentioned Peng & Apps 1997 BIOME Not mentioned Ni 2001 CEVSA Not mentioned Li et al This Study ± ±1.08 Among the great administrative regions, Southwest of China stored the largest amount of soil carbon, and the higher mean SOC density was found in northeast of China, east of Tibetan plateau and Yunnan-Guizhou Plateau. The lower value of mean SOC density was found in Tarim Basin, Junggar Basin, Alxa Plateau and other places in Gansu, Qinghai provinces and Ningxia Autonomous Region (Xie et al. 2004; Yu et al. 2007). The distribution of SOC is controlled by climate, vegetation, parent material, soil texture and other factors. Under natural conditions, more precipitation will benefit the growth of plant, thus result in an increase of carbon input to soil. Higher temperature, on the contrary, will accelerate the decomposition of soil organic matter (Wang et al. 2000, 2001; Xie et al. 2004; Yu et al. 2007b). So the SOC storage increases with the increase of mean annual precipitation, and decreases with the increase of mean annual temperature at a regional scale. Soil in the deciduous conifer forests (mainly distributed in northeast of China) showed the highest SOC density is related to the abundant precipitation and lower temperature. SOC density in desert steppe less than 1.5 kg m 2 is caused by the lower precipitation and scarce of vegetation (Yu et al. 2007b). 3.2 Storage and distribution of soil inorganic carbon in China - Soil inorganic carbon (SIC) is composed of HCO 3 in the soil solution, CO 2 in the soil air, and CaCO 3 and MgCO 3 precipitated from soil solution. SIC storage down to 1m depth is about 940 Pg at the global scale (Eswaran et al., 2000), being the most common form of C in arid and semiarid climate regions. Estimation of SIC pool in China are mainly based on the national soil survey database (Li et al., 2007; Mi et al., 2008), which is rather less when compared with the SOC research. An attempt was made to estimate the SIC pool in China by Pan (1999) based on the basic information in Soil Species Record of China, whose result showed that SIC storage in China is about 60 Pg. Li et al. (2007) found that SIC storage down to 1m depth in China was 77.9 Pg based on approximately 2500 soil profile data and 1:4M soil map. The SIC storage estimated by Mi et al. (2008) is 47.1 Pg in the depth of 1m and 53.3 Pg in the depth of 2m. Wu et al. (2009) used the actual soil profile depth when calculating the profile C density, and obtained the SIC stock in China was 55.3 Pg. The discrepancy among those estimates may be related to three factors: the number of profiles, the soil area and the soil depth. Here we also use the soil area of km 2 from Yu et al. (2005) to estimate the SIC storage in China, and get a SIC pool of ± Pg in China (Values with a light color in Table 2 are not included). 4 Vegetation carbon stock and its spatial patterns in China 4.1 Forest carbon stock and its dynamics Forests are major contributors of terrestrial ecosystem car-

8 104 Journal of Resources and Ecology Vol.1 No.2, 2010 Table 2 Estimation of soil inorganic carbon storage in China. Number of profiles Resolution of soil map Number of profiles Area (10 4 km 2 ) SIC storage (Pg C) SIC density (kg m 2 ) > Pan :4M Li et al :1M ± Mi et al :4M ± ±1.2 Profile depth Wu et al This study ± Soil depth (cm) References bon pools, and are thus crucial components for assessing the global carbon budget. The carbon density in forest ecosystems is also larger when compared with other terrestrial ecosystems. Most of the forest carbon storage studies are based on either inventory data or modeling methods. Six times of forest resources inventories have been conducted in China since 1973, and a lot of studies were carried out based on these data. Here we take the middle year of each inventory as a symbol, and average the estimation of each inventory obtained by different studies. The dynamics of forest carbon stock, carbon density and planting area are shown in Fig. 3. The carbon density did not change a lot since 1980s, with an average of 3.96±0.14 kg C m 2. The planting area and carbon storage, however, were increasing gradually. The carbon storage increased from 4.02±0.35Pg (in the second forest resources inventory, ) to 5.68 ± 0.24 Pg (in the sixth forest resources inventory, ), which increased about Pg C (Fig. 3). Forest carbon storage was mainly distributed in northeast and southwest of China, where the vegetation type was dominated by dark coniferous forest, and the dominant species are spruce and fir. About 28.7% of the total forest biomass in China was stored in Liaoning, Jilin and Heilongjiang provinces, and about 34.3% was stored in Sichuan, Yunnan, Guizhou, Tibet and Guangxi provinces/autonomous regions (Fang et al. 1996a). The region with the largest forest biomass was in the Great Canyon Region of Yalungzangbo River, the plain and hilly regions in east and southeast of China, and the arid region in north and northwest of China stored less carbon compared to other regions (Wang et al. 2001a, 2001b; Zhao et al. 2004). Among all the forests, oak and deciduous pine forests stored more carbon than other forests (Wanget al. 2000; Wang et al. 2001a). 4.2 Carbon stocks in grasslands and the distribution Carbon stocks in grasslands of China played an important role in the global grasslands pools (Fan et al. 2003), and the size of the carbon pool was about 8% of the global grasslands carbon stocks (Ni 2001). Ni (2002) and Fan et al. (2008) showed that the carbon storage in grasslands of China was Pg C based on the carbon density method. The estimate derived from grassland resource inventory data was about 1.15 Pg C (Fang et al. 2007). The study based on the relationship between grassland re-

9 YU Guirui, et al.: Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China 105 Table 3 Estimation of carbon storage of grassland and shrub land in China. Vegetation types Area (10 4 km 2 ) Carbon storage (Pg C) Carbon density (kg m 2 ) References Ni Ni Fang et al Fan et al Grasslands Piao et al Peng et al Li et al Piao et al This study ± ±0.077 Hu et al Shrub land Li et al This study source inventory data and NDVI data showed that carbon storage in China s grassland increased about Tg C from the early 1980s to the late 1990s (Piao et al. 2007). The area of shrub land in China is about 1/5 of the total land area in China. Based on published biomass data and 1: digital vegetation map of China, carbon storage of major shrub land in China was estimated using a mean biomass carbon density method by Hu et al. (2006). The result showed that the carbon storage of six shrub land in China is 1.68 ± 0.12 Pg C, with a total area of km 2 (Table 3). Vegetation carbon storage in the biomass of the grasslands was mainly distributed in the grasslands of the Tibet-Qinghai plateau and northern temperate grasslands, with 56.4% contained in the former and 17.9% in the latter (Fan et al. 2008). Shrub land in Yunnan, Guizhou and Sichuan in Southwest China occupies 23.5% of the total area and contributes to approximately one-third of the total carbon storage of six shrub land types in China (Hu et al. 2006). 5 Carbon storage in China s terrestrial ecosystems and its spatial pattern The methodologies adopted in previous studies on carbon Table 4 The estimates on vegetation and soil carbon storage in China s terrestrial ecosystems (Pg C). Vegetation carbon Soil carbon orage (Pg) storage (Pg) Total (Pg) References Fang et al. 1996a Peng et al Wang et al. 2000, Ni Wu et al Li et al Wang et al Xie et al Huang et al Li et al Xie et al Yu et al. 2005, 2007a, 2007b 84.8 Mi et al Ji et al ± ± This study

10 106 Journal of Resources and Ecology Vol.1 No.2, 2010 Table 5 Carbon density and carbon storage for different type of vegetations. Ecosystems Area (10 4 km 2 ) Vegetation carbon density (kg m 2 ) Vegetation carbon storage (Pg C) Soil carbon density (kg m 2 ) Soil carbon storage (Pg C) Ecosystem carbon storage (Pg C) Forest ± ± Grassland ± ± Shrub land ± ± Cropland ± ± Desert ± ± Wetland ± ± Total Note: the areas for forest, grassland, cropland and shrub land are from Fang et al. (2007), and the area for desert and wetland are from Fang et al. (1996a). storage in China s terrestrial ecosystems are mainly focused on two categories. One is based on the resources inventory data and vegetation area, the other is using modeling methods. The estimation of terrestrial ecosystems carbon storage based on forests and grasslands resources inventory data indicated that the carbon storage in China for all vegetations was about Pg C (Fang et al. 1996a). The results estimated by the Atmospheric-Vegetation Interaction Model (AVIM2) and the Carbon Exchange between Vegetation, Soil and Atmosphere (CEV- SA) model showed that the mean vegetation carbon storage in China was Pg C during the period of (Li et al. 2003; Huang et al. 2006), the soil carbon storage was Pg (Li et al. 2003), and the vegetation carbon density was kg m -2 (Li et al. 2003; Huang et al. 2006; Ji et al. 2008). Among all the vegetation carbon pools, the forest was of the largest carbon pool, which was about 5 times as that stored in grasslands (Li et al. 2003). Table 4 presents the studies and the estimates on vegetation and soil carbon storages in China s terrestrial ecosystems. If the boldface results (which are not so acceptable, as analyzed above) are neglected and average the rest, then the soil carbon storage is 84.24±5.56 Pg, vegetation carbon storage is 13.71±0.35Pg, and the carbon storage in China s terrestrial ecosystems is Pg C. We selected the estimates concerning the carbon storage on different type of ecosystems and the corresponding soil carbon storage, then averaged the carbon density derived from carbon storage and the corresponding area after quality controlling, and get the vegetation carbon density and soil carbon density as listed in Table 5. The soil carbon storage and the vegetation carbon storage were then calculated, which were Pg C and Pg C, respectively. Although the vegetation carbon stock estimation was nearly of the same in Table 4 and Table 5, the soil carbon storage in Table 5 was larger than that described in Table 1 and Table 4, and the ecosystem carbon stock was also larger in Table 5. One of the reasons for the discrepancy is that the studies for some ecosystems were fairly rare, and the standard error for carbon density is larger. So when the carbon storage is estimated based on the mean carbon density, the uncertainty incurred. China is dominated by monsoon climate. There is an obvious temperature gradient from south to north, and an obvious precipitation gradient from east to west. The study of Zhao & Zhou (2006) showed that vegetation carbon storage in China s temperate forests and subtropical forests is about % and % of the same climatic zone in the world, respectively. The carbon storage in China s grasslands is 7.74% of the global grassland carbon storage (Fan et al. 2003; Zhong et al. 2005). Temperature and precipitation are the dominant factors in controlling the distribution of vegetation carbon density. In the regions with suitable water and energy conditions, the plants grow faster, so the accumulated biomass and vegetation carbon density is higher. The spatial pattern of carbon density for forest, grassland, shrub land and cropland showed a significant positive relationship with soil moisture, annual precipitation and mean annual temperature (Huang et al. 2006). For grassland ecosystems, carbon storage is controlled by precipitation (Huang et al. 2006). For forests, temperature is more important (Zhao et al. 2004). 6 Conclusion and prospects The global carbon cycle and climate change are closely related. Process mechanisms of carbon storage and carbon

11 YU Guirui, et al.: Carbon Storage and Its Spatial Pattern of Terrestrial Ecosystem in China 107 cycle in earth system are the scientific foundation for analyzing the cause of climate change, for forecasting the trend, and for making mitigation and adaptation countermeasures. Research on global carbon cycle of ecosystem began in 1970s, while related studies started in 1980s in China, which experienced 4 main stages: the early carbon cycle research, the comprehensive study of ecosystem carbon cycle at regional scale, the experiment research on the adaptation of ecosystem carbon cycle to climate change, and the coupling cycles of C-N-H 2O and the regional regulation and control. Overall, the studies on carbon storage and its distribution in China can be concluded as follows: (1) The mean SOC density in China is 9.46±1.08 kg m 2 in a depth of 1 m, the SOC storage is about 87.78±9.98 Pg C, and the SIC storage is about 61.16±16.45 Pg C. (2) The forest area and carbon storage are increasing since 1980s, while the carbon density does not change a lot, with an average of 3.96±0.14 kg C m 2. The carbon storage increases from 4.02±0.35Pg (in the second forest resources inventory, ) to 5.68±0.24 Pg (in the sixth forest resources inventory, ), which increases about Pg C. (3) Carbon storage in grasslands and shrub land is about 2.72Pg C and 0.96 Pg C, respectively. The shrub land carbon storage is still uncertain due to the lack of studies. (4) The vegetation carbon storage in China is about Pg (based on vegetation-scale estimates) or Pg (based on ecosystem-scale estimates). The soil carbon storage is not the same when different scale methods are used. Consequently, the estimation based on ecosystem-scale studies is larger than that based on vegetation-scale studies. Since the mid 1970s, many management measures, such as afforestation and forest management, grassland protection, farming system reformation and conservation tillage, play an important role in carbon sequestration. Large uncertainty exists among the evaluation derived from various methods, mainly from the uncertainty of the evaluation of carbon storage. Focuses of future research are to establish an integrated monitoring system of the dynamics of carbon storage and carbon sink, conduct foresight studies on coupling cycles of ecosystem C-N-H 2O and its regional regulation and control, quantitatively assess the carbon budget and the potential of carbon sink increase of ecosystem in China, evaluate the economic benefit of various technologies for increasing carbon sink of typical ecosystem, and to provide measurable, reportable, verifiable scientific data and technical supports for establishing the policy framework for greenhouse gas management and carbon trading at national scale. References Chen L Z, Ren J K, Bao X C, et al Studies on the sociological characteristic and biomass of pine plantation on Xishan in Beijing. Acta Phytoecologica et Geobotanica Sinica, 8(3): (in Chinese) Chen M R, Long S Y Attempt on the climatic productivity division in China. Natural Resources, 3: (in Chinese) Dang C L, Wu Z L Studies on the biomass for Castanopsis Echidnocarpa community of monsson evergreen broad-leaved forest. Journal of Yunnan University, 14(2): (in Chinese) Davidson E A, S E Trumbore, R Amundson Soil warming and organic carbon content. Nature, 408: Deng G Y, Feng X H Energy, temperature resources and climatic productivity in China. Natural Resources, 4: (in Chinese) Ding S Y, Peng J A study on biomass of Castanopsis Orthacantha sprouted shrub community in Kunming region. Journal of Southwest Forestry College, 11(1): (in Chinese) Dong M W, Yu M Simulation analysis on net primary productivity of grassland communities along a water gradient and their responses to climate change. Journal of Plant Ecology, 32(3): (in Chinese) Eswaran H, P F Reich, J M Kimble Global carbon stocks. In: Lal R, J M Kimble, H Eswaran, B A Stewart (eds.). Global climate change and pedogenic carbonates. Boca Raton, USA: CRC Press. Fan J W, Zhong H P, Harris W, et al Carbon storage in the grasslands of China based on field measurements of above- and below-ground biomass. Climatic Change, 86: Fan J W, Zhong H P, Liang B, et al Carbon stock in grassland ecosystem and its affecting factors. Grassland of China, 25(6): Fang H J, Yu G R, Cheng S L, et al Effects of multiple environmental factors on CO2 emission and CH4 uptake from old-growth forest soils. Biogeosciences, 7(1): Fang J Y, Guo Z D, Piao S L, et al Terrestrial vegetation carbon sinks in China, Science in China (Series D), 37(6): Fang J Y, Liu G H, Xu S L. 1996a. Carbon pools in terrestrial ecosystems in China. In: Wang G C, Wen Y P (eds.). Monitoring and Relevant Process of Greenhouse Gas Concentration and Emission. Beijing: China Environmental Science Press, (in Chinese) Fang J Y, Liu G H, Xu S L. 1996b. Biomass and net production of forest vegetation in China. Acta Ecologica Sinica, 16(5): (in Chinese) Fei J X Increasing yield effect of adding nitrogen fertilizer at soybean first flowering period. Acta Agronomica Sinica, 1(2): (in Chinese) Fu Y, Zheng Z, Yu G, et al Environmental influences on carbon dioxide fluxes over three grassland ecosystems in China. Biogeosciences, 6 (12): Gao Z Q, Liu J Y, Cao M K, et al Impacts of land use and climate change on regional net primary productivity. Acta Geographica Sinica, 59 (4): (in Chinese) Hou G L, Liu Y F Climatic productivity in China and its distribution. Natural Resources, 3: (in Chinese) Hu H F, Wang Z H, Liu G H, et al Vegetation carbon storage of major shrublands in China. Journal of Plant Ecology, 30(4): (in Chinese) Hu Z Z, Sun J X, Li Y, et al The characteristics of biomass and conversion efficiency of solar radiation for principal types of alpine grasslands in Tianzhu, Gansu province, China. Acta Phytoecologica Sinica, 18 (2): (in Chinese) Huang D H, Chen Z Z, Zhang H F Comparison of belowground biomass among Stipa baicalensis steppe, S. krylovii steppe and Filitolium sibiricum steppe. Research on grassland ecosystems, 2nd. Beijing: Science Press. (in Chinese) Huang M, Ji J J, Cao M K, et al Modeling study of vegetation shoot and root biomass in China. Acta Ecologica Sinica, 26(12): (in Chinese)

12 108 Huang M, Ji J J, Peng L L The response of vegetation net productivity to climate change during in the Tibetan Plateau. Climatic and Environmental Research, 13(5): (in Chinese) Huang Y, Yu Y Q, Zhang W, et al Agro-C: A biogeophysical model for simulating the carbon budget of agroecosystems. Agricultural and Forest Meteorology, 149(1): Huang Y, Zhou G S, Wu J S, et al Terrestrial ecosystem carbon budget model in China. Beijing: Science Press. IPCC Summary for Policymakers of Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge: Cambridge University Press. Ji J J, Hu Y C A multi-level canopy model including physical transfer and physiological growth processes. Climatic and Environmental Research, 4(2): (in Chinese) Ji J J, Huang M, Li K R Prediction of carbon exchanges between China terrestrial ecosystem and atmosphere in 21st century. Science in China (Series D: Earth Sciences), 51(6): Jia Z H, Li Y, Jiang Z Y Studies on effect of fertilizer application to the formation in yield and quality of winter wheat. Journal of Beijing Agricultural College, 3(2): (in Chinese) Jiang Q O, Deng X Z, Zhan J Y, et al Impacts of cultivated land conversion on the vegetation carbon storagein the Huang-Huai-Hai Plain. Geographical Research, 27(4): (in Chinese) Jiang S, Qi Q H, Kong D Z Comparison of community biomass between Leymus Chinensis steppe and Stipa Grandies Steppe. Research on grassland ecosystems, 2nd. Beijing: Science Press. (in Chinese) Jin X H, Liu H G, Song Y C A study on the productivity of secondary shrub thicket and shrub-grassland inyixian county, Anhui province. Acta Phytoecologica et Geobotanica Sinica, 14(3): (in Chinese) Jobbágy E G, R B Jackson The vertical distribution of soil organic carbon and its relation to climate and vegetation. Ecological Application, 10: Li J Y Photosynthetic productivity of crops in different regeion of China. Journal of Agricultural Meteorology, 4: (in Chinese) Li K R, Wang S Q, Cao M K Vegetation and soil carbon storage in China. Science in China (Series D: Earth Sciences), 33(1): Li Y D Comparative analysis for biomass measurement of tropical mountain rain forest in Hainan Island, China. Acta Ecologica Sinica, 13 (4): (in Chinese) Li Z P, Han F X, Su Y, et al Assessment of soil organic and carbonate carbon storage in China. Geoderma, 138: Liu H G, Tang X L, Zhou G Y, et al Spatial and temporal patterns of net primary productivity in the duration of in Guangdong, China. Acta Ecologica Sinica, 27(10): (in Chinese) Luo T X, Li W H, Luo J, et al A comparative study on biological production of major vegetation types on the Tibetan Plateau. Acta Ecologica Sinica, 19(6): (in Chinese) Mi N, Wang S Q, Liu J Y et al Soil inorganic carbon storage pattern in China. Global Change Biology, 14:1 8. Mi N, Yu G R, Wang P X, et al Modeling seasonal variation of CO2 flux in a subtropical coniferous forest using the EALCO model. Journal of Plant Ecology, 31(6): (in Chinese) Ni J Carbon storage in terrestrial ecosystems of China: Estimates at different spatial resolutions and their responses to climate change. Climatic Change, 49(3): Ni J Carbon storage in grasslands of China. Journal of Arid Environments, 50: Pan G X Study on carbon reservoir in soils of China. Bulletin of Science and Technology, 15(5): (in Chinese) Peng C H, M J Apps Contribution of China to the global carbon cycle since the last glacial maximum. Tellus, 49B: Piao S L, Fang J Y, He J S, et al Spatial distribution of grassland biomass in China. Acta Phytoecologica Sinica, 28(4): (in Chinese) Piao S L, Fang J Y, Zhou L M, et al Changes in biomass carbon stocks in China s grasslands between 1982 and Global Biogeochemical Cycles, 21, GB2002, doi: /2005gb Post W M, W R Emanuel, P J Zinke, et al Soil carbon pools and world Journal of Resources and Ecology Vol.1 No.2, 2010 life zones. Nature, 298: Qiu X Z, Xie S C, Jing G F A preliminary study on biomass of Lighocarpus Xylocarpus forest in Xujiaba region, Ailao Mts., Yunnan. Acta Botanica Yunnanica, 6(1): (in Chinese) Tao B, Li K R, Shao X M et al The temporal and spatial patterns of terrestrial net primary productivity in China. Journal of Geographical Sciences, 13(2): Teng L, Ren H, Peng S L The natural situation of North South Transect of eastern China. Ecologic Science, 19(4): (in Chinese) Wang Q F, Niu D, Yu G R, et al Simulating the exchanges of carbon dioxide, water vapor and heat over Changbai Mountains temperate broadleaved Korean pine mixed forest ecosystem. Science in China (Series D: Earth Sciences), 48(S1): Wang S Q, Liu J Y, YU G R Error analysis of estimating terrestrial soil organic carbon storage in China. Chinese Journal of Applied Ecology, 14(5): (in Chinese) Wang S Q, Zhou C H, Li K R, et al Analysis on spatial distribution characteristics of soil organic carbon reservoir in China. Acta Geographica Sinica, 55(5): (in Chinese) Wang S Q, Zhou C H, Li K R, et al Study on spatial distribution character analysis of the soil organic carbon reservior in China. Journal of Geographical Sciences, 11(1): Wang S Q, Zhou C H, Luo C W Studying carbon storage spatial distribution of terrestrial natural vegetation in China. Progress in Geography, 18 (3): (in Chinese) Wang S Q, Zhou C H Estimating soil carbon reservoir of terrestrial ecosystem in China. Geographical Research, 18(4): (in Chinese) Wang X K, Feng Z W, Ouyang Z Y. 2001a. Vegetation carbon storage and density of forest ecosystems in China. Chinese Journal of Applied Ecology, 12 (1): (in Chinese) Wang X K, Feng Z W, Ouyang Z Y. 2001b. The impact of human disturbance on vegetative carbon storage in forest ecosystems in China. Forest Ecology and Management, 148: Wang X K, Feng Z W The potential to sequester atmospheric carbon through forest ecosystems in China. Chinese Journal of Ecology, 19(4): (in Chinese) Wang Y F, Chen Z Z, T Larry Distribution of soil organic carbon in the major grasslands of Xilinguole, Inner Mongolia, China. Acta Phytoecologica Sinica, 22 (6): (in Chinese) Wen X F, Wang H M, Wang J L, et al Ecosystem carbon exchanges of a subtropical evergreen coniferous plantation subjected to seasonal drought, Biogeosciences, 7(1): Wu H B, Guo Z T, Gao Q et al Distribution of soil inorganic carbon storage and its changes due to agricultural land use activity in China. Agriculture, Ecosystems and Environment, 129: Wu H B, Guo Z T, Peng C H Land use induced changes of organic carbon storage in soils of China. Global Change Biology, 9: Xie X L, Sun B, Zhou H Z, et al Organic carbon density and storage in soils of China and spatial analysis. Acta Pedologica Sinica, 41(1): (in Chinese) Xie Z B, Zhu J G, Liu G, et al Soil organic carbon stocks in China and changes from 1980s to 2000s. Global Change Biology, 13(9): Yan X D, Zhao J F Establishing and validation individual-based carbon budget model FORCCHN of forest ecosystems in China. Acta Ecologica Sinica, 27(7): (in Chinese) Yang H K, Cheng S Z Study on biomass of the karst forest community in Maolan, Guizhou province. Acta Ecologica Sinica, 11(4): (in Chinese) Yang Y H, Mohammat A, Feng J M et al Storage, patterns and environmental controls of soil organic carbon in China. Biogeochemistry, 84 (2): Yu D S, Shi X Z, Sun W X, et al Estimation of China soil organic carbon storage and density based on 1: soil database. Chinese Journal of Applied Ecology, 16(12): (in Chinese) Yu D S, Shi X Z, Wang H J, et al. 2007a. National scale analysis of soil organic carbon storage in China based on Chinese soil taxonomy. Pedo-