forest ecosystems in a co2-rich world fileforest ecosystems in a co 2-rich world institute of botany...

Forest ecosystems in Forest ecosystems in a COa CO22--rich worldrich world

Institute of BotanyInstitute of BotanyUniversity of Basel, SwitzerlandUniversity of Basel, Switzerland

Christian KChristian Köörnerrner

ALTERALTER--Net Net SummerSummer--school, school, Peyresq, (F) 6 Sept 2008Peyresq, (F) 6 Sept 2008

Ch KCh Köörnerrner

Are these basic physiological functionsAre these basic physiological functionsdrivers or driven?drivers or driven?

Ass

imila

tion

Ass

imila

tion

COCO22 TT

Res

pira

tion

Res

pira

tion


Tenet ITenet I Assimilation drives growthAssimilation drives growth or or vice versavice versa??

AAssimilationssimilation GGrowthrowth(NPP)(NPP)

MMinerals etc.inerals etc.

COCO22 COCO22(R)(R) A or G first?A or G first?

•• Whenever M is limiting,Whenever M is limiting,G controls AG controls A•• Whenever COWhenever CO22 or light are or light are

limiting, A controls Glimiting, A controls G

•• The A G fine tuning is The A G fine tuning is masking cause and masking cause and consequenceconsequence

manipulative experimentsmanipulative experiments

Light and COLight and CO22 coco--control source activitycontrol source activity

Output is controlled Output is controlled by carbon inputby carbon input

(N input, water)(N input, water)plus ontogeny & temperatureplus ontogeny & temperature

coco--control sink activitycontrol sink activity

chicken or chicken or egg first?egg first?


In Geneva 200 years ago:In Geneva 200 years ago:

‘‘The primary plant food The primary plant food comes from aircomes from air‘‘

NicolasNicolas--ThThééodore de Saussure (1804)odore de Saussure (1804)Recherches chimiques sur la VRecherches chimiques sur la Vééggéétation.tation.Paris.Paris.

Ch Körner

Experiments that lack a naturalExperiments that lack a naturalplant plant -- rhizosphere rhizosphere -- soil linkagesoil linkageare fundamentally unsuitable forare fundamentally unsuitable formaking ecosystem scale inferences.making ecosystem scale inferences.


Tenet IITenet II Growth (productivity) drives CGrowth (productivity) drives C--stock formationstock formation

•• Carbon is never stocked Carbon is never stocked alone. alone.

CC--sequestration ties upsequestration ties upnutrients (slows thenutrients (slows thenutrient cycle)nutrient cycle)

R HyvR Hyvöönen nen et alet al (2007) New Phytol 173:463(2007) New Phytol 173:463

Stand age (years) Stand age (years)

NE

E (g

C m

NE

E (g

C m

-- 22aa--

11 ))Age and demography matter!Age and demography matter!

•• Young: high productivity Young: high productivity small Csmall C--poolpool

Old: low productivityOld: low productivitylarge Clarge C--poolpool

00 5050 100100 150150 200200--400400

--200200

200200

400400

600600

800800

00

C-stock(schematic)

Negative correlation between age Negative correlation between age (C(C--stocking) and the rate of Cstocking) and the rate of C--cycling.cycling.

cash flow (turnover)cash flow (turnover)is a poor predictor is a poor predictor of capitalof capital


Tenet IIITenet III Respiration follows temperatureRespiration follows temperature

•• R is largely a function of NPPR is largely a function of NPP•• NPP = f(soils, age, temperature, etc.)NPP = f(soils, age, temperature, etc.)•• R cannot be decoupled from NPP in the long runR cannot be decoupled from NPP in the long run

you can eat the lunch only onceyou can eat the lunch only once(but you may be eating it(but you may be eating itfaster or slower)faster or slower)


TimeTime

NPPNPP NEPNEPRR

Temporal shifts of Temporal shifts of RR should not be taken as should not be taken as evidence for increased or decreasedevidence for increased or decreased ΣΣRR


00 100100 200200 300300 400400 500500 600600

200200

400400

600600

800800

10001000

12001200

14001400

16001600

00

Litterfall carbon (g mLitterfall carbon (g m--22 aa--11))

Soi

l res

pira

tion

(g m

Soi

l res

pira

tion

(g m

-- 22aa--

11 ) )

Raich JW, Nadelhoffer KJ (1989) Ecology 70:1346Raich JW, Nadelhoffer KJ (1989) Ecology 70:1346

Warming and soil respiration

from Alaska from Alaska to Amazoniato Amazonia


Message 1Message 1Photosynthesis (A) and growth (G) are in a finePhotosynthesis (A) and growth (G) are in a fine--tuned balance tuned balance so that the hierarchy of action remains masked. Most commonly so that the hierarchy of action remains masked. Most commonly the sink activity (meristems) is driving the sink activity (meristems) is driving source activity source activity (photosynthesis). Low light is the most likely condition in natu(photosynthesis). Low light is the most likely condition in nature re where A drives G and where elevated COwhere A drives G and where elevated CO22 is stimulating A+G.is stimulating A+G.

Message 2Message 2Higher carbon stocks require longer carbon residence time. Higher carbon stocks require longer carbon residence time. Since carbon is never stocked alone, but needs mineral Since carbon is never stocked alone, but needs mineral nutrients for stocking, larger carbon residence time removes nutrients for stocking, larger carbon residence time removes nutrients from the nutrient cycle and thus slows growth.nutrients from the nutrient cycle and thus slows growth.

Message 3Message 3Respiration cannot be decoupled from NPP, in the long run.Respiration cannot be decoupled from NPP, in the long run.

examples from Flakaliden, Havard forestexamples from Flakaliden, Havard forest Ch KCh Köörnerrner

Rates (productivity, growth) Rates (productivity, growth) versusversusPools (biomass, CPools (biomass, C--storage)storage)

00

100100

Bio

mas

s C

Bio

mas

s C

-- poo

l (%

)po

ol (%

)

5050

00 100100Time (years)Time (years)

BB

Fast turnoverFast turnover

CC

00 100100

Slow turnoverSlow turnover

Mean CMean C--poolpool

Time (years)Time (years)

AA

A growth stimulation (experiments) should never be A growth stimulation (experiments) should never be confused with landscapeconfused with landscape--wide carbon sequestrationwide carbon sequestration

Ch KCh Köörner (2006) New Phytol 172:393 rner (2006) New Phytol 172:393 Ch KCh Köörnerrner

Years before presentYears before present

CO

CO

22--co

ncen

tratio

n (

conc

entra

tion

( ppmpp

m))

17501750

200200

240240

280280

320320

360360

160160

400400

00100'000100'000200'000200'000300'000300'000400'000400'000500'000500'000600'000600'000

Siegenthaler U Siegenthaler U et et alal.. (2005)(2005) ScienceScience 310:1313310:1313Petit JR Petit JR et et alal.. (1999)(1999) NatureNature 399:429399:429

20082008

CurrentlyCurrently385 ppm385 ppm

Rat

e of

net

R

ate

of n

et

phot

osyn

thes

isph

otos

ynth

esis

COCO22--concentration (ppm)concentration (ppm)00 400400 800800

COCO22--saturationsaturation


linking the two

linking the two

180180 280280 380380 580 ppm CO580 ppm CO22

Atmospheric COAtmospheric CO22

Climate effectsClimate effects Direct biological effectsDirect biological effects

Indirect effectsIndirect effects Ch KCh Köörnerrner

Two direct biological effects of elevated COTwo direct biological effects of elevated CO22 are are known for >100 years:known for >100 years:

(1) Stimulation of (1) Stimulation of leaf photosynthesis leaf photosynthesis (more photo(more photo--

assimilates)assimilates)

(2) Reduction of (2) Reduction of stomatal aperture stomatal aperture (water savings)(water savings)

1 + 2 1 + 2 potential stimulation of plant growthpotential stimulation of plant growth Ch KCh Köörnerrner

ChloroplastChloroplaststarchstarch

LeafLeaf StemStem ReproRepro--ductionduction RootsRoots Soil Soil

microbesmicrobesMycorMycor--rhizarhiza

VolatilesVolatiles

Net cNet carbon assimiliationarbon assimiliation

PhotoassimilatesPhotoassimilates

COCO22

Conceptual model of plant growthConceptual model of plant growth

SOURCESOURCE

SINKSINK

HeteroHeterotrophic respirationtrophic respiration

DOCDOC

Autotrophic respirationAutotrophic respiration

Litter or HerbivoresLitter or HerbivoresDetrivoresDetrivores

Sugar loading to phloemSugar loading to phloemand allocationand allocation

Dem

and

Dem

and

Sup

ply

Sup

ply

SLA, LAR, LAISLA, LAR, LAI

ClimateClimatecontrolcontrol

Sink Sink control control

Leaf area feedbackLeaf area feedback

Water,Water,nutrientsnutrients

Soil feedbackSoil feedback

feedfeed--backback

COCO22

COCO22

COCO22

COCO22

CC--storagestorageCC--reservesreserves

Structural Structural growthgrowth MetabolismMetabolism ExportExport

Ch KCh Köörner (2006) New Phytol 172:393rner (2006) New Phytol 172:393

C

h K

Ch

K öörn

errn

er


Carbon Carbon cyclecycle

Mineral Mineral nutrient nutrient cyclecycle

CC

Mineral Mineral nutrientsnutrients

COCO22

The ecosystem carbon cycle is driven by the The ecosystem carbon cycle is driven by the nutrient cycle and other growth nutrient cycle and other growth ‘‘facilitatorsfacilitators‘‘

couplingcoupling

Ch Körner

41.6 %41.6 %14.1 %14.1 %13.0 %13.0 %11.4 %11.4 %

9.5 %9.5 %3.2 %3.2 %2.7 %2.7 %

1.6 %1.6 %0.8 %0.8 %0.8 %0.8 %0.7 %0.7 %

0.3 %0.3 %

00 5050 100100 150150 200200 250 Mrd t C250 Mrd t C

Tropical rainforestTropical rainforest

Subtropical forestSubtropical forest

Boreal forestBoreal forestTemperate deciduous forestTemperate deciduous forestTemperate evergreen forestTemperate evergreen forestSavannaSavannaShrublandShrubland

WetlandsWetlandsTemperate grasslandTemperate grasslandFarmlandFarmlandSemidesertsSemideserts

TundraTundra

ForestForestNonNon--forestforest

100 % = 650 Mrd t C100 % = 650 Mrd t C


For CFor C--storage storage in biomass only in biomass only trees matter trees matter (>86 %)(>86 %)

Plant growth in elevated COPlant growth in elevated CO22

Decoupled Decoupled systemssystems

(horticulture)(horticulture)

Expanding Expanding systems systems

(in transition)(in transition)

Coupled Coupled systems,systems,

steady state steady state nutrient cyclenutrient cycle

Ch KCh Köörner (2006) Tansley Review, New Phytol 172:393rner (2006) Tansley Review, New Phytol 172:393


Methods Methods go from go from open topopen topchambers chambers to ...to ...



Duke FACE: Duke FACE: stems respondingstems responding

Pinus taedaPinus taeda

Oak Ridge FACE: Oak Ridge FACE: roots respondingroots responding

Liquidambar styracifluaLiquidambar styraciflua

Gas control Gas control

Gas Gas analysisanalysis

CO

CO

22

webweb--FACE at the Swiss Canopy Crane siteFACE at the Swiss Canopy Crane site

COCO22 + + 1313C tracer C tracer Ch KCh Köörnerrner

Growth of 100 year old Growth of 100 year old trees in elevated COtrees in elevated CO22,,Swiss webSwiss web--FACE FACE

Ch KCh Köörner rner et al.et al. (2005) (2005) Science 309:1360 Science 309:1360 and new dataand new data

Mass fruitingMass fruitingMMElevated COElevated CO22

Ambient COAmbient CO22

Annu

al tr

ee b

asal

are

a in

crem

ent (

stan

d. b

y pr

eAn

nual

tree

bas

al a

rea

incr

emen

t (st

and.

by

pre --

treat

m. m

ean)

treat

m. m

ean)

+ CO+ CO22


0.00.00.50.51.01.01.51.52.02.02.52.53.03.0

0.00.0

0.50.5

1.01.0

1.51.5

0.00.0

0.50.5

1.01.0

1.51.5Carpinus betulusCarpinus betulus

Fagus sylvaticaFagus sylvatica

Quercus petraeaQuercus petraea

****

MM MMMMMM

MM

n = 14n = 14 n = 3n = 3

±± sese

MM

MM

n = 7n = 7n = 3n = 3

n = 5n = 5n = 3n = 3

PretreatmentPretreatment Elevated COElevated CO22

19961996 19981998 20002000 20022002 20042004 20062006

n = 10n = 10

All trees All trees (+ (+ TiliaTilia))

DroughtDroughtn = 29n = 29

19961996 19981998 20002000 20022002 20042004 20062006

MM

MM

MM

00

1010

2020

3030

4040R

elat

ive

biom

ass

or N

PP

incr

emen

t (E

/A, %

)R

elat

ive

biom

ass

or N

PP

incr

emen

t (E

/A, %

)

Swiss mixed decid. forestSwiss mixed decid. forestd d (n = 1)(n = 1)Oak RidgeOak Ridgec c (n = 2)(n = 2), , LiquidambarLiquidambar

Duke I + II (n = 2+1), Duke I + II (n = 2+1), PinusPinus

Duke IIDuke IIb b (n = 3)(n = 3), , PinusPinus

Duke IDuke Ia a (n = 1)(n = 1), , PinusPinus

Years of treatmentYears of treatment00 11 22 33 44 55 aa R Oren R Oren et alet al (2001)(2001)

bb KVR SchKVR Schääfer fer et alet al (2003)(2003)cc RJ Norby RJ Norby et alet al (2004)(2004)dd Ch KCh Köörner rner et alet al (2005)(2005)

Effect of elevated COEffect of elevated CO22 on tree growthon tree growth

Duke I + II (n = 3+1)Duke I + II (n = 3+1), , PinusPinus

Ch KCh Köörner (2006) New Phytol 172:393rner (2006) New Phytol 172:393 Ch KCh Köörnerrner

Rel

ativ

eR

elat

ive

diffe

renc

e of

diffe

renc

e of

tree

ring

wid

thtre

e rin

g w

idth

(( mea

nm

ean±±

se)

se)

--0.50.5

0.00.0

0.50.5

1.01.0

1.51.5

Tree ageTree age (a)(a)

Natural CONatural CO22--spring,spring,Rapolano, ItalyRapolano, Italy

COCO22 effects on growth effects on growth decline with time ...decline with time ...

SS HHäättenschwilerttenschwiler etet alal. . (1997)(1997) Glob Change BiolGlob Change Biol 33: 463: 463

00 55 1010 1515 2020 2525 3030 3535 4040

rr22 = 0.457, P < 0.001= 0.457, P < 0.001y = 0.791 y = 0.791 -- 0.024 x0.024 x

Transition from Transition from expanding expanding system to steady system to steady state systemstate system


Since more carbon is taken up per unit Since more carbon is taken up per unit leaf area, where does the carbon go?leaf area, where does the carbon go?

•• More storage reserves (NSC)More storage reserves (NSC)yes, but very little, species specificyes, but very little, species specific

•• More export More export (soil microbes + fungi)(soil microbes + fungi)yes, at the beyes, at the beginning, little sustainedginning, little sustained

•• Counterbalancing LAI?Counterbalancing LAI?no (constant litter production)no (constant litter production)


IsotopeIsotope signals in fungal sporocarpssignals in fungal sporocarpsunder COunder CO22--enriched forest treesenriched forest trees

S Keel S Keel et alet al (2006) New Phytol 172:319 and new data(2006) New Phytol 172:319 and new data

44 33 88 441313 88 1111 77 66 1414 88 881313 2323 1919 1717

--3030

--2828

--2626

--2424

--222220012001 20032003 20042004 20052005 20012001 20032003 20042004 20052005

MycorrhizalMycorrhizal SaprobicSaprobic

Fung

al

Fung

al δδ

1313C

(C

( ‰‰))

n = n =

Ambient Ambient COCO22

Elevated COElevated CO22

****** ****** **** ******

**


S Keel S Keel et alet al (2006) New Phytol 172:319 and new data(2006) New Phytol 172:319 and new data

Seasonal variation of Seasonal variation of δδ1313C tracer signal C tracer signal in soilin soil air at 3air at 3--11 cm depth11 cm depth

--3232

--3030

--2828

--2626

--2424

20022002 20032003 20042004 2005200520012001

δδ1313

C o

f soi

l air

(C

of s

oil a

ir ( ‰‰

))

Ambient Ambient COCO22


Gro

win

g se

ason

Gro

win

g se

ason


Ch KCh Köörner rner et al.et al. (2005) Science 309:1360(2005) Science 309:1360

IsoIso--metermeter

00

11

22

33

44

55

66

77

19991999 20012001 20022002 20032003 20042004YearYear

Wood Wood Roots (< 1 mm)Roots (< 1 mm)LeavesLeaves

00

5050

100100

% o

f C4

iso

% o

f C4

iso --

met

er re

adin

gsm

eter

read

ings

Fate of new carbonFate of new carbonδδ

1313C

(am

bien

t CO

C (a

mbi

ent C

O22

min

us e

leva

ted

CO

min

us e

leva

ted

CO

22, , ‰‰

))


70 % of all continental 70 % of all continental evaporation passes evaporation passes through stomata poresthrough stomata pores


QuercusQuercus FagusFagus CarpinusCarpinus

Stomatal response to elevated COStomatal response to elevated CO22

Leaf

con

duct

ance

Leaf

con

duct

ance

(( mm

olm

mol

mm-- 22

s s -- 11

))

--7%7%--2 %2 % --22 %22 %

•• WeakWeak•• NoneNone •• StrongStrong

S Keel S Keel et alet al (2007) Trees 21:151(2007) Trees 21:151©© Ch KCh Köörnerrner

Swiss webSwiss web--FACEFACE

COCO22

+ C

O+

CO

22

100100

200200

300300

400400

00

1

0.10.1

0.20.2

0.30.3

Sap

flux

(arb

itrar

y un

its)

Sap

flux

(arb

itrar

y un

its)

0.00.0

0.20.2

0.40.4

0.60.6

0.80.8

1.01.0S

oil m

oist

ure

(vol

%)

Soi

l moi

stur

e (v

ol %

)

Day in July/August 2005Day in July/August 2005

Elevated COElevated CO22 reduces forest water loss to the atmospherereduces forest water loss to the atmosphere



S Leuzinger & Ch KS Leuzinger & Ch Köörner (2007)rner (2007)Glob Change Biol 13:2498Glob Change Biol 13:2498

33 44 55 66 77 88 99 1010 111111 2231312828 2929 30302222 2323 2424 2525 2626 27272020 212100

1010

2020

3030

Pre

cipi

tatio

n (m

m)

Pre

cipi

tatio

n (m

m)

A A

EE


PP

Soil layer 1Soil layer 1


Canopy Canopy + litter+ litter

= Interception= Interception

EvaporationEvaporation

RunoffRunoff

PrecipitationPrecipitation

TranspirationTranspiration

A bucket model to simulate A bucket model to simulate runoff under elevated COrunoff under elevated CO22

•• daily resolutiondaily resolution

•• driven with 104 yrs driven with 104 yrs of climate dataof climate data

•• transpiration transpiration modelled based on modelled based on experimental data*experimental data*

**Leuzinger Leuzinger et alet al (2005) (2005) Tree Physiol 25:641Tree Physiol 25:641

Leuzinger & KLeuzinger & Köörner (2007) rner (2007) Glob Change Biol 13:2489Glob Change Biol 13:2489


00

2020

4040

6060

8080

Wat

er c

olum

n (m

m)

Wat

er c

olum

n (m

m)

00

100100

200200

Accumulated Runoff


Acc

um. r

unof

f (m

m)

Acc

um. r

unof

f (m

m)

JJ FF MM MMAA JJ JJ AA SS OO NN DD



00

2020

4040

6060

Pre

cipi

tatio

n P

(mm

) P

reci

pita

tion

P (m

m)

PP

Month in 1902Month in 1902

Increased runoff = 8 mm (4.2 %)


Average year (1902)

Results of 104 years model runResults of 104 years model run


Betts Betts et alet al (2007) Nature 448:1037(2007) Nature 448:1037--1041:1041:direct climate change effects direct climate change effects + 11%+ 11%indirect effects via plant responses + 6 % globallyindirect effects via plant responses + 6 % globally

•• ca. 5.5 mm per year (2.9 %) increased runoff over ca. 5.5 mm per year (2.9 %) increased runoff over all years under elevated COall years under elevated CO22

•• 1 out of 17 years produces a CO1 out of 17 years produces a CO22--signal in runoff signal in runoff larger than 20 mm per year larger than 20 mm per year

•• the effect mostly depends on 2the effect mostly depends on 2--7 events per year7 events per year

•• Maximum signal 1901Maximum signal 1901--2004, 46 mm per year 2004, 46 mm per year (1938)(1938)

Species differ in their responsesSpecies differ in their responses

Biodiversity effectsBiodiversity effects(winners and losers, new assemblages)(winners and losers, new assemblages)

Ecosystem effectsEcosystem effects(water loss, carbon and nutrient cycle)(water loss, carbon and nutrient cycle)


Gonolobus viridiflorusGonolobus viridiflorus(Asclepiadaceae)(Asclepiadaceae)

COCO22 concentration (ppm) concentration (ppm)

Pla

nt b

iom

ass

per i

ndiv

idua

l (g)

Pla

nt b

iom

ass

per i

ndiv

idua

l (g)

Ceratophytum tetragonolobumCeratophytum tetragonolobum(Bignoniaceae)(Bignoniaceae)

+164 %+164 %****+62 %+62 %

--11 %11 %

280280 420420 560560 700700 J Granados & Ch KJ Granados & Ch Köörner (2002) GCB 8:1109rner (2002) GCB 8:1109

+130 %+130 %****

******+41 %+41 %

--61 %61 %

00

22

11

33

00

22

44

11

33

55Lianas Lianas are are gaininggaining

Ch KCh Köörner (2003) Phil Trans R Soc Lond A 361:2023rner (2003) Phil Trans R Soc Lond A 361:2023



The fate of these landscapes

in a T, CO2 world

= f (water, nutrients, biodiversity, demography, seasonality)in which C-sink activity controls C-source activity

•• Elevated COElevated CO22 may enhance productivity, provided may enhance productivity, provided nutrient supply permits. However nutrient supply permits. However more dynamicmore dynamicforests commonly store forests commonly store lessless carboncarbon..

•• First principle responses (e.g. photosynthetic or First principle responses (e.g. photosynthetic or stomatal COstomatal CO22--response) might become overrun by response) might become overrun by biodiversity effectsbiodiversity effects in the long run.in the long run.

•• Elevated atmospheric COElevated atmospheric CO22 is unlikely to cause ais unlikely to cause asustainedsustained increase of increase of carbon storagecarbon storage in biomass, in biomass, but may enhance but may enhance carbon turnovercarbon turnover..

•• Experimental data are confounded by water effects. Experimental data are confounded by water effects. The actual influence on hydrology is minute.The actual influence on hydrology is minute.

Summary COSummary CO22 effectseffects


forest ecosystems in a co2-rich world fileforest ecosystems in a co 2-rich world institute of botany...

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