1 The carbon balance of terrestrial ecosystems in China during the 1980s and 1990s Shilong Piao, Jingyun Fang, Philippe Ciais, Philippe Peylin, Yao Huang, Stephen Sitch, Tao Wang April 2009

2  in 1998, a very controversial study by Fan et al. finds a huge NA sink ‘seen from the atmosphere’ (1.7 Pg C / yr)  in 2001, Pacala et al. estimate C budget in USA ( Pg C / yr)  in 2003, Janssen et al. estimate C budget in Europe ( PgC/yr)  in 2007, Stephens et al. Estimate a NH sink of 1.5 ± 1.5 Pg C / yr much smaller than in prevous inversions studies -> this call for an assessment using bottom up data  China? Regional C budget (hi)story

3 Spatial distribution climae Mean annual temperature Annual Precipitaion

4 Distribution of vegetation types in China

5 Distribution of NPP in China NPP (gC / m2 / yr)

6 -China contributed about one quarter of the global plantation area. -Forest plantation benefit net carbon uptake Kauppi et al., (2006) Afforestation/reforestation projects

7 Temperature change - During the past two decades, mean annual temperature over China increased by more than 0.5 ºC/decade. - Warmer-dryer in the North and warmer-wetter in the South where most productive ecosystems are distributed. Significant climate change Precipitation change Based on CRU climate data (Mitchell et al., 2003)

8 Crop HOW DID CARBON STORAGE RESPOND TO CLIMATE AND HUMAN DISTURBANCE OVER THE PAST 20-YEARS? Forest Grassland Shrub

9 dm ha 10 km 1000 km Downscaling Verification Upscaling Prediction + Integration by modeling ( Moses-Triffid; LPJ; Sheffield-DGVM; Hyland; ORCHIDEE ) Atmospheric inverse Model Methods used in this study

10 1. Forest inventories and field biomass data ~200,000 permanent and temporary sample plots, 5 periods: , , , , Grassland biomass inventory data 3. Cropland SOC survey data, statistics for crop yield, area, and others 4. NDVI datasets The NDVI data were from the GIMMS (Global Inventory Monitoring and Modeling Study) group derived from NOAA/AVHRR land dataset, with 8 km resolution for each 15 days from 1981 to Datasets

11 6±1 Tg C/yr4±4 Tg C/yr Forest Grassland CropShrub 22±10 Tg C/yr 75±35 Tg C/yr 7±3 Tg C/yr - 3 Tg C/yr Soil Inventory and satellite based estimation BambooFire 1±1 Tg C/yr 13±1 Tg C/yr vegetation 26±11 Tg C/yr39±9 Tg C/yr Total net C balance (?)

12 6±1 Tg C/yr4±4 Tg C/yr Forest Grassland CropShrub 22±10 Tg C/yr 75±35 Tg C/yr 7±3 Tg C/yr - 3 Tg C/yr Soil Inventory and satellite based estimation BambooFire 1±1 Tg C/yr vegetation 26±11 Tg C/yr39±9 Tg C/yr Limitations: Not included wetland; trees out forests (four-side trees and individual tress) 177±73 Tg C/yr = 13±1 Tg C/yr

13 Prior flux information observations LMDZ transport model The mean result of the inversion ensemble over the period 1996 – 2004 is a net CO2 uptake of 0.35 Pg C/yr. Atmospheric inversion estimation Limitations: scarce atmospheric netwrork (only 9 sites in North Asia) and uncertainty from transport model Optimized fluxes

14 The link between inventory and atmospheric inversion estimation

15 Carbon balance of Chinese terrestrial ecosystems

16 Spatial distribution of the C balance in China

17 Comparison of C balance in different regions

18 Raupach et al., (2007) NEP vs. fossile fule CO2 emission

19 ● large-scale reforestation ● changes of energy consumption structure and vegetation recovery ● intensive agriculture practices ● regional climate changes Why large C sinks?

20 % of total global plantation area Countries with the largest proportion of the world’s forest plantations, 2000 ▲ FAO (2001) China is the largest country with planted forests, about 1/4 of total global plantations (FAO, 2001) (i) Reforestation and afforestation

21 In the last 30 yrs, firewood, charcoals, and crop straws that had been used as major energy sources in the most rural areas have been steadily replaced with fossil fuels. This on the one hand has increased the consumption of fossil fuels, but it accelerated the recovery of vegetation, especially of scrubs. Movement of rural residents to cities reduced pressure to nature. (ii) Change of energy consumption strucure and recovery of vegetation

22 expansion of straw incorporation, shallow plowing, irrigation, and no-till farming have increased C sequestration in agricultural soils. (iii) Intensive agriculture practices

23 Inter-annual changes in seasonal precipitation Summer Autumn Spring Despite no significant change in annual rainfall, summer precipitation in China has significantly increased by 2.5 mm each year over the last 2 decades. (iv) Regional climate changes

24 Comprehensive estimate of Chinese ecosystems carbon budget A carbon sink of 0.19 to 0.26 Pg C / yr Offsets ≈ 28-37% of emissions over Offsets ≈ 16-22% of emissions over % forest; up to 30% in shrublands More than 65% of the sinks are distributed in southern China owing to regional climate change, reforestation and afforestatioin programmes acive, and shrubland recovery. Recent trends in agricultural practice also cause an increase in carbon sequestration. Conclusions

25 References Janssens IA. et al. (2003), Europe's terrestrial biosphere absorbs 7 to 12% of European anthropogenic CO2 emissions. Science, 300, Kauppi PE, Ausuble JH, Fang JY, Mather A, Sedjo RA, Waggoner PE (2006), Returning forest analyzed with the forest identity. PNAS, 103, Mitchell TD, Jones PD (2005), An improved method of constructing a database of monthly climate observations and associated high-resolution grids. Int. J. Climatol, 25, Pacala SW et al. (2001), Consistent land- and atmosphere-based US carbon sink estimates. Science, 292, Piao SL, Fang JY, Ciais P, Peylin P, Huang Y, Sitch S, Wang T (2009), The Carbon balance of terrestrial ecosystems in China. Nature, doil: /nature07944 [in press] Raupach MR, Marland G, Ciais P, LeQuere C, Canadell JG, Klepper G, Field CB (2007), Global and regional drivers of accelarating CO2 emissions. PNAS, 104,

26 Thank you!