Spatial and Temporal Patterns of Carbon Exchanges between

Spatial and Temporal Patterns of Carbon Exchanges between the Atmosphere and Terrestrial Ecosystems of China Hanqin Tian Ecosystem and Regional Studies Group Auburn University, AL 36849, USA & NASA IDS Project Participants*

*The NASA IDS Project Participants: • Jerry M. Melillo, David Kicklighter, Ben Felzer, The Ecosystem Center, Marine Biological Laboratory, Woods Hole, USA. • Steven Running, Maosheng Zhao, Qiaozhen Mu, University of Montana, Missoula, USA. • Jiyuan Liu, Guoyui Yu, Aifeng Lv, Chaoqun Lv, Wei Ren, Xiaofeng Xu, IGSNRR, Chinese Academy of Sciences, Beijing, 100101, China. • Ranga Myneni, Yuri Knyazikhin, Nikolay Shabanov, Boston University, Boston, USA. • Mingliang Liu, Shufen Pan, Hua Chen, Siqing Chen, Guangsheng Chen, Chi Zhang, Auburn University.

IPCC TAR (Prentice et al. 2001): both North America and Eurasia served as carbon sinks during the 1990 s, suggesting a net sink of 1 -2. 5 Pg C yr-1 that is distributed relatively evenly between North America and Eurasia. – The US carbon sink: Forest inventory, bookkeeping model--land use change, and inverse model (Birdsey and Health, 1995, Houghton et al. 1999, Capersen et al. 2000, Pacala et al. 2001) (0. 3 -0. 58 Pg/yr). – The Eurasian carbon sink has received less attention. From both scientific and policy perspectives, it is of critical importance to quantify regional carbon budget and mechanisms controlling the carbon cycle.

We haven’t succeeded in answering all problems. The answers we have found only serve to raise a whole set of new questions. In some ways, we feel we are as confused as ever, but we believe we are confused on a higher level and about more important things.

Everything about China, good or bad, is BIG! China is the world’s third largest country, the most rapidly developing nation and home to 1. 3 billion people. Since the early 1980 s, the unprecedented combination of economic and population growth has led to a dramatic land transformation across the nation. China is “Natural Laboratory” for studying dynamics of coupled natural and human systems as well as the carbon cycle.

Total Population: 1, 306, 313, 812 (July 2005 est. )

0– 2 2 -5 5 -10 10 -30 30 -50 50 -80 80 -100 100 -200 200 -300 300 -400 400 -500 500 -600 600 -700 700 -800 800 -900 900 -1000 -1100 -1200 -1300 -1400 -1500 -1600 -1700 -1800 -1900 -2000 -2200 > 2200 Population distribution of 2000 in China (cell size = 1 km, Unit: persons per km 2)

Chinese Population urbanized (%) Rapid urbanization in China 60 35 37 27 17 18 1970 1978 13 1950 1990 2002 2020

Large-scale land transformation estimated with satellite data Liu, J. , H. Q. Tian, M. Liu, D. Zhuang, J. M. Melillo and Z. Zhang (2005). Geophys. Res. Lett. , 32, L 02405, doi: 10. 1029/2004 GL 021649.

OBJECTIVES: Our study will be organized by two linked questions: Q 1 - HOW HAVE PRIMARY PRODUCTION AND CARBON STORAGE CHANGED IN CHINA OVER THE PAST TWO DECADES? Q 2 - WHAT MECHANISMS HAVE HAD MAJOR EFFECTS ON CHANGES IN THESE FLUXES AND STOCKS? We will consider the relative roles of: (a) climate variability, (b) changes in land cover and use, (c) changes in fire disturbance, (d) changes in the chemistry of precipitation (particularly nitrogen), and (e) changes in the composition of the atmosphere (carbon dioxide, ozone).

APPROACHES: Here we try to combine remote-sensing data (MODIS, AVHRR, Landsat-TM/ETM) and a set of biogeochemical simulation models (TEM, Biome-BGC and A new model) to quantify the consequences of land transformations and other environmental changes on productivity in forests and other “natural” ecosystems and carbon sequestration.

The Integrated Approach Quantifying Regional C Dynamics Modeling Measuring Flask Data Satellite Data Eddy Flux Synthesis Ecosystem Experiments

BIOME-BGC

The Terrestrial Ecosystem Model (TEM)

A New Model of Coupled Biogeochemical Cycles

Data Development • • • Climate Land use history O 3 CO 2 Other data: elevation, soil texture, potential vegetation

1700 1800 1900 2000 Historical Cropland & Urban area distribution (10 X 10 km)

1961 -2000 Annual mean temperature (0. 1℃) 1961 -2000 Average annual precipitation (0. 1 mm)

Mean annual N deposition in 1990 s in China (mg N/m 2)

Mean surface O 3 concentration in 1990 s in China (Unit: D 40)

2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988

Simulation Experiments 1. 2. 3. 4. 5. 6. 7. 8. Climate Only CO 2 only Land use only O 3 only Climate + Land use Climate + CO 2 + Land Use Climate + CO 2 + O 3 + Land use

Vegetation Carbon Soil Organic Carbon g. C/m 2 TEM-based estimate on vegetation and soil carbon in 2000 (Climate_CO 2_LUCC_O 3)

1980 -2000 1860 -2000 Change in total carbon storage (g. C/m 2)

Mean annual Net Carbon Exchange (1981 -1990) (g. C/m 2/yr) Mean annual Net Carbon Exchange (1991 -2000) (g. C/m 2/yr)

Ozone effect on carbon storage during 1860 -2000 (g. C/m 2)

Annual Net Carbon Exchange (Pg. C/yr)

Cumulative Net Carbon Exchange (Pg C)

Relative contribution of CO 2, climate, land use and O 3 to carbon fluxes during 1981 -2000 (Pg C/yr)

NPP RH NEP NEE Annual NPP, HR, NEP and NEE trends during 1961 -2000 derived from Biome-BGC.

Decadal variations in carbon emission induced by forest fires across China

a. b. c. d. a) Mean AVHRR NPP from 1982 -2000 b) NPP trend from 19822000 c) Mean MODIS NPP d) Mean NPP as estimated by a new model.

CH 4 emission from cropland derived from a new coupled biogeochemical model 1980 2000

Summary • The combined effect of climate, CO 2, land use and O 3 on net carbon exchange show that terrestrial China acted as a small carbon sink ( 64 Tg C per year) during 1980 -2000, but showing substantial year-to-year variation. • For the time period from 1980 to 2000, both land use and CO 2 resulted in carbon uptake while climate and O 3 led to carbon release. During 1860 -2000, however, landuse change resulted in a large release of carbon to the atmosphere (about 12 Pg C). • CH 4 emission from agricultural land varied from 6 to 16 Tg C per year. Fireinduced carbon emission is about 11. 3 Tg C per year. • In any year over the period 1980 -2000, net carbon exchange can be very large in one location but very small or negative in another location because of the spatial heterogeneity of vegetation, soils and climate. • Additional factors needed to be considered include N deposition, Forest management and agronomic practices. • In the future, Model intercomparison needs to be done. Also modeled results need to be evaluated against field data.

ACKNOWLEDGMENT This study is supported by NASA Interdisciplinary Science Program (NNG 04 GM 39 C).