대기 중 CO 2 변화에 따른 토양 CO 2 방출량 변화 ( DYNAMICS OF SOIL CO 2 EFFLUX UNDER VARYING ATMOSPHERIC CO 2 CONCENTRATIONS ) Dohyoung Kim Duke University July

O UTLINE Introduction Materials and methods Dynamics of soil CO 2 efflux Changes in carbon assimilation Conclusion

I NTRODUCTION Mean CO 2 growth rate: 2 ppm/yr ( ) ppm (Apr. 2016)

F REE A IR CO 2 E NRICHMENT (FACE) © Brookhaven National Laboratory Overcome temporal and spatial limits of chamber experiments Allow investigation of undisturbed ecosystems Not modifying plant’s interaction with light, temperature, wind, precipitation, and other biological factors Allow integrated measurement of many processes Allow to study plants with extended period and space

I NTRODUCTION PLANTS ’ GENERAL RESPONSES Increase of Photosynthesis Leaf area Tree growth Soil moisture Soil respiration Fine-root biomass Decrease of Stomatal conductance Transpiration

I NTRODUCTION OBJECTIVES © 2010 State of California 1.To assess whether the termination of eCO 2 alters the soil CO 2 efflux in previously eCO 2 plots 2.To isolate the processes influencing the amount of CO 2 returning to the atmosphere from the forest floor-soil system

F CO2 Rhizosphere microorganisms Root Labile SOM Atmospheric CO 2 Mycorrhizal fungi Leaf Recalcitrant SOM Soil microorganisms necromass photosynthesis exudation respiration allocation decomposition I NTRODUCTION days to weeks weeks to months months to years decades to centuries

M ATERIALS AND METHODS SITE DESCRIPTION Duke FACE site Tree age: ~30 years Dominant species Loblolly pine ( Pinus taeda ) Major understory Sweetgum ( Liquidambar styraciflua ) Winged elm ( Ulmus alata ) Red maple ( Acer rubrum )

M ATERIALS AND METHODS SITE HISTORY yr-old seedlings were planted Prototype experiment 1996 FACE started (+200 ppm) N fertilization (11.2 g N m -2 yr -1 ) 2010 FACE ended Final harvest Relaxation period

M ATERIALS AND METHODS MANIPULATION OF CO 2 CONCENTRATION (Tor-ngern et al., 2014) Short-term late Aug. to early Oct. 5-day intervals five CO 2 levels (A, +100, +150, +200, +300) two moisture conditions (REW = 0.03, 0.78) Long-term terminated on Oct. 31, 2010 monitored for two years

M ATERIALS AND METHODS A UTOMATED CARBON EFFLUX SYSTEM (ACES) chamber-based multiport 11 chambers per plot switched between two fixed locations once a week

M ATERIALS AND METHODS A UTOMATED CARBON EFFLUX SYSTEM (ACES) Measurement: 10 minutes per chamber mean of last 3 minutes was used more than half available data per day per chamber Missing data unstable air flow or CO 2 concentration air flow or CO 2 concentration out of specific range abnormal soil CO 2 effluxes periodic maintenance and recalibration occasional power outage failure of gas analyzer and tubing

M ATERIALS AND METHODS B AYESIAN STATE - SPACE MODEL Parameter model Process model Data model R t-1 RtRt R t+1 F t-1 FtFt F t+1 X t-1 XtXt X t+1 τ2τ2 σ2σ2 β

R ESULTS HYPOTHESES Will soil CO 2 efflux change with short- and long- term manipulation of CO 2 concentration? H1: Effect of five-day CO 2 changes will be reflected in changes of soil CO 2 efflux (F CO2 ). H2: F CO2 will decline to that of aCO 2 within ~3 months and remain at the level for the following two years.

R ESULTS MODEL PERFORMANCE

R ESULTS DAILY MEAN VALUES

R ESULTS SHORT - TERM MANIPULATION

R ESULTS ANNUAL INTEGRATED F CO2

R ESULTS RESPONSE RATIO ~35% ~5 weeks after

R ESULTS RESPONSE RATIO

R ESULTS MONTHLY LEAF AREA AND F CO2

C HANGES IN CARBON ASSIMILATION A = G S × c a (1- c i / c a ) Root Elevated CO 2 Leaf photosynthesis allocation

C HANGES IN CARBON ASSIMILATION Will stomatal conductance respond to termination of long-term CO 2 enrichment?

S TOMATAL CONDUCTANCE Responses to eCO 2 Direct: increase in c i  stomatal closure Indirect: structural changes

R ESULTS Lower growing season T in 2009 Growing season M was lowest in 2010 and highest in 2012

R ESULTS CHANGES IN LEAF AREA Leaf area returned to ambient level +22% +9% +40%

R ESULTS MONTHLY MEAN G S 0.69     1.11 G S of pine in previously eCO 2 increased Response of G S of sweetgum were not particularly faster than pine

R ESULTS MONTHLY TRANSPIRATION Canopy transpiration in previously eCO 2 maintained

R ESULTS CANOPY CONDUCTANCE

R ESULTS MONTHLY C UPTAKE AND F CO2 CNPI = G C × [CO 2 ] ratio (canopy net photosynthesis index)

C ONCLUSION