대기 중 CO2 변화에 따른 토양 CO2 방출량 변화
(DYNAMICS
OF
SOIL
CO2
EFFLUX
UNDER VARYING ATMOSPHERIC CO2 CONCENTRATIONS)
Dohyoung Kim
Duke University
July 19 2016
OUTLINE

Introduction

Materials and methods

Dynamics of soil CO2 efflux

Changes in carbon assimilation

Conclusion
INTRODUCTION
407.42 ppm (Apr. 2016)
Mean CO2 growth rate:
2 ppm/yr (2001-2010)
FREE AIR CO2 ENRICHMENT (FACE)





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
© Brookhaven National Laboratory
INTRODUCTION
PLANTS’ GENERAL RESPONSES
Increase of
Photosynthesis
 Leaf area
 Tree growth
 Soil moisture
 Soil respiration
 Fine-root biomass

Decrease of
Stomatal conductance
 Transpiration

INTRODUCTION
OBJECTIVES
1. To assess whether the
termination of eCO2 alters
the soil CO2 efflux in
previously eCO2 plots
2. To isolate the processes
influencing the amount of
CO2 returning to the
atmosphere from the forest
floor-soil system
© 2010 State of California
INTRODUCTION
weeks to months
days to weeks
Rhizosphere
microorganisms
exudation
FCO2
respiration
Atmospheric
CO2
Mycorrhizal
fungi
Root
photosynthesis
allocation
necromass
Labile SOM
Soil
microorganisms
decomposition
months to years
Recalcitrant SOM
decades to centuries
Leaf
MATERIALS 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)

MATERIALS AND METHODS
SITE HISTORY
1983
3-yr-old seedlings
were planted
1994-1995
Prototype
experiment
2005-2012
N fertilization
(11.2 g N m-2 yr-1)
1996
FACE started
(+200 ppm)
2010-2011
Final
harvest
2010
FACE ended
2011-2012
Relaxation
period
MATERIALS AND METHODS
MANIPULATION OF CO2 CONCENTRATION

Short-term
late Aug. to early Oct.
 5-day intervals
 five CO2 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

(Tor-ngern et al., 2014)
MATERIALS AND METHODS
AUTOMATED CARBON EFFLUX SYSTEM (ACES)
chamber-based
 multiport
 11 chambers per plot
 switched between two fixed
locations once a week

MATERIALS AND METHODS
AUTOMATED 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 CO2 concentration
air flow or CO2 concentration out of specific range
abnormal soil CO2 effluxes
periodic maintenance and recalibration
occasional power outage
failure of gas analyzer and tubing
MATERIALS AND METHODS
BAYESIAN STATE-SPACE MODEL
Ft-1
Ft
Ft+1
Data model
Rt-1
Rt
Rt+1
Process model
Xt-1
τ2
Xt
σ2
Xt+1
β
Parameter model
p (s 2 , t 2 , R, b | F )
µ N ( Ft | Rt , t 2 ) N ( Rt | Xt , s 2 ) IG (t 2 | t1, t2 ) IG (s 2 | s1, s2 ) N ( b | b0 ,Vb )
RESULTS
HYPOTHESES
Will soil CO2 efflux change with short- and longterm manipulation of CO2 concentration?
H1: Effect of five-day CO2 changes will be reflected in changes of
soil CO2 efflux (FCO2).
H2: FCO2 will decline to that of aCO2 within ~3 months and remain
at the level for the following two years.
RESULTS
MODEL PERFORMANCE
RESULTS
DAILY MEAN VALUES
RESULTS
SHORT-TERM MANIPULATION
RESULTS
ANNUAL INTEGRATED
FCO2
RESULTS
RESPONSE RATIO
~5 weeks after
~35%
RESULTS
RESPONSE RATIO
RESULTS
MONTHLY LEAF AREA AND
FCO2
CHANGES IN CARBON ASSIMILATION
Elevated
CO2
photosynthesis
A = GS × ca(1-ci/ca)
Root
allocation
Leaf
CHANGES IN CARBON ASSIMILATION
Will stomatal conductance respond to termination
of long-term CO2 enrichment?
STOMATAL CONDUCTANCE
Responses to eCO2
Direct: increase in ci  stomatal closure
Indirect: structural changes
RESULTS
Lower growing season T
in 2009
Growing season M was
lowest in 2010 and
highest in 2012
RESULTS
CHANGES IN LEAF AREA
Leaf area returned to
ambient level
+22%
+9%
+40%
RESULTS
MONTHLY MEAN
GS
GS of pine in previously eCO2 increased
Response of GS of sweetgum were not
particularly faster than pine
0.69  1.12
0.94  0.84
0.74  0.97
0.64  1.11
RESULTS
MONTHLY TRANSPIRATION
Canopy transpiration in
previously eCO2 maintained
RESULTS
CANOPY CONDUCTANCE
RESULTS
MONTHLY
C UPTAKE AND FCO2
CNPI = GC × [CO2] ratio
(canopy net photosynthesis index)
CONCLUSION