Terrestrial ecosystems carbon balance in China during 1980s and 1990s Tao Wang, Shilong Piao, Philippe Ciais Oct. 1 2012

Partial absorption of CO2 at Mauna Loa Land and ocean carbon sinks offset climate change Levin (2012) from Nature 1/30

+ Fate of Anthropogenic CO2 Emissions (2000-2008) 45% 29% 26% 1.4 Pg C y-1 + 7.7 Pg C y-1 3.0 Pg C y-1 29% 4.1 Pg C y-1 45% 26% 2.3 Pg C y-1 Le Quéré et al. 2009, Nature-geoscience; Canadell et al. 2007, PNAS, updated 2/30

Why do we need regional C budget estimates? Link regional fluxes to the global increase in CO2 Understand regional processes by comparison between regions Better predict the future impacts of humans and climate on the C cycle Help define mitigation policies 3/30

It is of critical importance to quantify China’s carbon budget Large C emissions 2000 China 1600 USA 1200 Carbon Emissions per year (tons x 1,000,000) 800 India Russian Fed. 400 Japan 1990 03 05 07 99 01 03 05 2008 Time Global Carbon Project 2009; Data: Gregg Marland, CDIAC 2009 4/30

Afforestation/reforestation projects China contributed about one quarter of the global plantation area. Forest plantation benefit net carbon uptake Kauppi et al., (2006) 5/30

Rapid Urbanization Carbon loss from new urban settlements Carbon gain since movement of rural population to cities have diminished the collection of fuel wood, accelerating the recovery of vegetation 1950 1970 1978 1990 2000 2002 2020 Chinese Population urbanized (%) Tian et al., (2005) 6/30 3/30

Pronounced warming trend in China 7/30

Dryer in the North, wetter in the South 8/30

Significant change in Atmospheric composition Nitrogen deposition enhances the net carbon fixation Atmospheric O3 pollution cause a decrease in C storage Magnani et al. 2007, Nature Sitch et al. 2007, Nature 9/30

Grassland Shrub How do vegetation activity and carbon storage respond to these climate and human disturbance? Forest Crop 10/30

Ensemble Approach Remote-sensing Ecosystem modeling Atmospheric inverse modeling Inventory (biomass and soil carbon) 11/30

Method 1: Inventory + Satellite Datasets 1. Forest inventories and field biomass data ~200,000 permanent and temporary sample plots, 5 periods: 1977-81, 1984-88, 1989-93, 1994-98, 1999-2004 2. Shrub and Grassland biomass inventory data 3. Cropland SOC survey data, statistics for crop yield, area, and others 4. GIMMS-NDVI dataset 8 km resolution; 15-day; 1981-1999. 12/30

Method 1: Inventory + Satellite Forest biomass densitity change We estimate forest biomass density from timber volume using BEF (Biomass expansion factor), the ratio of biomass to timber volume, expressed as a function of stem volume (x), BEF = a + b/x 13/30 4/30

Method 1: Inventory + Satellite Shrub biomass change We estimate biomass C of shrubs using relationship between aboveground biomass and seasonal NDVI at 34 shrub sites. 14/30

Method 1: Inventory + Satellite Grassland biomass change We estimate biomass C of grasslands using relationship between aboveground biomass and seasonal NDVI. The difference of biomass C density between the late 1990s and early 1980s 15/30

Method 1: Inventory + Satellite Soil carbon storage change Assumption: trends in litter input can be inferred from trends in NDVI, and that changes in decomposition of SOC are driven by temperature and precipitation. 16/30

Method 1: Inventory + Satellite Limitations Not included wetland; trees out forests (four-side trees and individual tress) Large uncertainties.... 17/30

Method 2: Atmospheric inversion Prior flux information LMDZ transport model observations Optimized fluxes 18/30 4/30

Method 2: Atmospheric inversion Limitations Limited observing sites Only measure net CO2 flux，and thus need further validation Uncertainties from human CO2 emissions Uncertainties from transport model 19/30

convection de chaleur sèche Method 3: Ecosystem model Température convection de chaleur sèche de la surface Interception par la canopée Infiltration, stockage, drainage ruissellement de surface Evapotranspiration Humidité de l’air Précipitation Solaire et infra-rouge Rayonnement Photosynthèse nette Respiration de croissance & maintenance Allocation des assimilats litière Bilan de carbone et de nutriments Flux de CO2 Concentration en CO2 Vitesse du vent Turbulence de l’air 20/30

Method 3: Ecosystem model Limitations Uncertainties due to model parameterizations Uncertainties from climate driving Not consider land use change… To overcome these (Trendy Project) The same climate forcing 10 ecosystem models HyLand, Lund–Potsdam–Jena DGVM, ORCHIDEE, Sheffield–DGVM, TRIFFID, LPJ-GUESS, NCAR-CLM4CN, OCN, VEGAS and VISIT 21/30

Method 1: Inventory- and satellite- based estimation Result Method 1: Inventory- and satellite- based estimation Forest Grassland Crop Shrub 75±35 Tg C/yr 7±3 Tg C/yr 13±1 Tg C/yr 22±10 Tg C/yr vegetation 4±4 Tg C/yr 6±1 Tg C/yr 26±11 Tg C/yr 39±9 Tg C/yr Soil Wood products Fire Bamboo ? 9 Tg C/yr - 3 Tg C/yr 1±1 Tg C/yr 22/30

Method 1: Inventory- and satellite- based estimation Result Method 1: Inventory- and satellite- based estimation Forest Grassland Crop Shrub 75±35 Tg C/yr 7±3 Tg C/yr 13±1 Tg C/yr 22±10 Tg C/yr vegetation 4±4 Tg C/yr 6±1 Tg C/yr 26±11 Tg C/yr 39±9 Tg C/yr Soil Wood products Fire Bamboo 186±73 Tg C/yr 9 Tg C/yr - 3 Tg C/yr 1±1 Tg C/yr 22/30

Method 2: Atmosphere inversion estimation Prior flux information LMDZ transport model observations The mean result of the inversion ensemble over the period 1996-2004 is a net CO2 uptake of 350 Tg C/yr. Optimized fluxes 23/30 4/30

Chinese terrestrial carbon balance from Method 2 261Tg C/yr 24/30

Method 3: Ecosystem model estimation Climate change + Rising CO2 Only Climate change 25/30

Updated ecosystem carbon balance by ecosystem models (in East Asia) Different factors’ (climate, climate +CO2, nitrogen deposition, land-use change, O3 pollution, agricultural management, fire and biofuels) contributions to the carbon balance of terrestrial ecosystems in East Asia. 26/30

Comparison of C balance in different regions 27/30

Spatial distribution of C balance in China 28/30

Conclusions Offsets ≈ 28-37% of emissions over 1980-2000 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 1980-2000 Offsets ≈ 16-22% of emissions over 2001-2005 50% 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 active, and shrubland recovery. Recent trends in agricultural practice also cause an increase in carbon sequestration. 29/30

Thank you! 30/30