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Controls over ecosystem functioning across spatial scales as derived from studies in drylands José M. Grünzweig Hebrew University of Jerusalem, Rehovot, Israel in colloboration with Marcelo Sternberg, Tel Aviv University, Israel Katja Tielbörger, University of Tübingen, Germany ClimMani & INTERFACE Workshop, Scaling climate change experiments across space and time: Challenges of informing large-scale models with small- scale experiments, Mikulov, Czech Republic, June 2013

Controls over ecosystem functioning across spatial scales as derived from studies in drylands

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Controls over ecosystem functioning across spatial scales as derived from studies in drylands. Jos é M . Grünzweig Hebrew University of Jerusalem, Rehovot , Israel in colloboration with Marcelo Sternberg, Tel Aviv University, Israel Katja Tielbörger , University of Tübingen, Germany. - PowerPoint PPT Presentation

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Page 1: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Controls over ecosystem functioning across spatial scales as derived from

studies in drylands

José M. Grünzweig Hebrew University of Jerusalem, Rehovot, Israel

in colloboration withMarcelo Sternberg, Tel Aviv University, Israel

Katja Tielbörger, University of Tübingen, Germany

ClimMani & INTERFACE Workshop, Scaling climate change experiments across space and time: Challenges of informing large-scale models with small-scale experiments, Mikulov, Czech Republic, June 2013

Page 2: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Climate anomalies, Europe, summer 2003

Ciais et al. 2005 Nature

Climate extremes in systems not adapted to those extremes

Page 3: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Global extent of drylands

Levant (SE Mediterranean)

Research in regions adapted to heat and/or drought

Page 4: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Climate

The physical properties of the Levant (SE Mediterranean)

Page 5: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Shrubland as spatially heterogeneous, mosaic-type ecosystem composed of different microsites

The physical properties of the Levant (SE Mediterranean)

Biomes/ecosystem types

Page 6: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Outline of questions

• Can we predict ecosystem functioning across a precipitation range with common biological and abiotic drivers?

• What processes control carbon pools and fluxes when it gets drier?

• Do climate-change experiments reveal tipping points in ecosystem structure and functioning?

• What can we learn from climate-extremes studies in drylands?

• Where are we going from here?

Page 7: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Rainfall manipulations along an aridity gradient

Aridity gradient – GLOWA Jordan River project

– South facing slopesshallow soil (Terra Rossa to lithosol) onsimilar bedrock

– Similar seasonal temperture range

– Eight-fold difference in mean annual rainfall

– Large difference in rainfall variability

Mediterranean: 540 mm, CV 30%

Semiarid: 300 mm, CV 37%

~ 24

5 km

Arid: 90 mm, CV 51%

Mesic Mediterranean: 780 mm, CV 22%Biomes/ecosystem types

Page 8: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

300 mmSemiarid

550 mmMediterranean

-30% +30%

Experimental rainfall manipulations

Control

Rainfall manipulations

Rainfall manipulations along an aridity gradient

Page 9: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Observed Rs (μmol m-2 s-1)

Pred

icte

d R s (

μmol

m-2

s-1)

r2 = 0.48

Talmon et al. 2011 GCB

Soil respiration at the herbaceous microsite during the growing season?

Prediction:Rs = soil respiration; Ts = soil temperature; θ = soil moisture

Site- and treatment- specific equations better fits

Overall inter-site and inter-treatment controls?

Can we predict ecosystem functioning across a precipitation range with common biological and abiotic drivers?

two sites, three climate-change treatments

Page 10: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Observed Rs (μmol m-2 s-1)

Pred

icte

d R s (

μmol

m-2

s-1)

r2 = 0.48

Ts , θ

Observed Rs (μmol m-2 s-1)

r2 = 0.73

Ts , θ , cover

Pred

icte

d R s (

μmol

m-2

s-1)

Vegetation cover is a factor that explains part of the inter-site and inter-treatment variation in soil respiration climate change modeling

Addition of vegetation cover as a driver of soil respiration

Prediction of ecosystem functioning with common biological and abiotic drivers?

Page 11: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Talmon et al. 2011 GCB

0 100 200 300 400 500 600 700 8000.0

0.5

1.0

1.5

2.0

2.5

3.0

Mean annual precipitation (mm)

Soi

l org

anic

C s

tock

(kg

m-2)

What processes control carbon pools and fluxes when it gets drier?

Soil organic carbon stocks at the herbaceous microsite along the aridity gradient

Page 12: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

0 100 200 300 400 500 600 700 8000

10

20

30

40

y=2.75x0.402

R2=0.968

Ann

ual l

itter

dec

ompo

sitio

n (%

)

Mean annual precipitation (mm)

2002-2005

0 100 200 300 400 500 600 700 8000

50

100

150

200

250

300

350

2003-2011

Abo

vegr

ound

NPP

(g m

-2 y

r-1)

Mean annual precipitation (mm)

y=0.0153x1.492

R2=0.998

0 100 200 300 400 500 600 700 8000.0

0.5

1.0

1.5

2.0

2.5

3.0

Mean annual precipitation (mm)

Soi

l org

anic

C s

tock

(kg

m-2)

What processes control carbon pools and fluxes when it gets drier?

Carbon loss

Carbon addition

Page 13: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Changes in plant strategies with increasing aridity

Mean annual precipitation (mm)

Unweighted community mean

2.0

3.0

4.0

Log

(spe

cific

leaf

are

a)

aab

b b

p<0.001 1030

50

Leaf

Nitr

ogen

(m

g g1) a

abc

bc

p<0.001

4.5

5.5

6.5

Log

(leaf

dry

mat

ter

cont

ent)

ns

-1.0

0.0

1.0

Log

(ten

sile

str

engt

h)ns

B L M Y

12

34

Log

(pla

nt h

eigh

t)

a

ab

b

b

p<0.05

B L M Y

-3-1

13

Log

(leaf

siz

e) ns

Unweighted community average of species leaf traits

Site

300 78055090300 78055090Mean annual precipitation (mm)

Sternberg & Lebrija

What processes control carbon pools and fluxes when it gets drier?

Page 14: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Alternative drivers of litter decay in the dry season

What processes control carbon pools and fluxes when it gets drier?

0 30 40 50 60 70 80 90 1000

10

20

30

40 Shrub Intershrub Lab

Moi

stur

e co

nten

t (%

)

Relative humidity (%)

y = 3.10 + 0.414 e0.0451x r2 = 0.998

Dirks et al. 2010 GCB

Dew Water vapor < saturation

Solar radiation

Page 15: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

To what extent is soil respiration along the aridity gradient directly controlled by changes in climatic variables and indirectly controlled by shifts in shrub cover?

0 300 600 9000

300

600

900

ecosystem

shrub microsite

Ann

ual s

oil r

espi

ratio

n (g

C m

-2 y

r-1)

Mean annual precipitation (mm)

herbaceous microsite

What processes control carbon pools and fluxes when it gets drier?

Page 16: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

0 200 400 600 8000

200

400

600

800

1000

Ann

ual s

oil r

espi

ratio

n (g

C m

-2 y

r-1)

Mean annual precipitation (mm)

0 200 400 600 8000

200

400

600

800

1000

-12%-15%

-20% -21%

-60%

Ann

ual s

oil r

espi

ratio

n (g

C m

-2 y

r-1)

Mean annual precipitation (mm)

assuming no change in shrub cover assuming change in shrub cover

-64%

13% 35% 55% 75%Shrub cover

-15%-12%

-21%-20%

-60%-64%

What processes control carbon pools and fluxes when it gets drier?

Page 17: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Kigel & Konsens

0 100 200 300 400 500 600 700 8000

50

100

150

200

250

300

350

2003-2011

Abo

vegr

ound

NPP

(g m

-2 y

r-1)

Mean annual precipitation (mm)

y=0.0153x1.492

R2=0.998

0 100 200 300 400 500 600 700 8000

50

100

150

200

250

300

350

Control Dry tmt. Wet tmt.

2003-2011

Abo

vegr

ound

NPP

(g m

-2 y

r-1)

Mean annual precipitation (mm)

y=0.0153x1.492

R2=0.998

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?

Page 18: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?

Sternberg & Navon

0 100 200 300 400 500 600 700 8000

10

20

30

40

y=2.75x0.402

R2=0.968

Ann

ual l

itter

dec

ompo

sitio

n (%

)

Mean annual precipitation (mm)

2002-2005

0 100 200 300 400 500 600 700 8000

10

20

30

40

50

y=2.75x0.402

R2=0.968

Ann

ual l

itter

dec

ompo

sitio

n (%

)

Mean annual precipitation (mm)

2002-2005

Control Dry tmt. Wet tmt.

Page 19: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Talmon et al. 2011 GCB

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?

Page 20: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Rainfall manipulations had no significant effect on species diversity at the semiarid site (same for the Mediterranean site)

Kigel et al., unpublished

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20110.8

1

1.2

1.4

1.6

1.8

2

Species diversityDry Control Irrig

Shan

non

inde

x

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 20112

3

4

5

Species diversityDry Control Irrig

Sim

pson

reci

proc

al in

dex

Year

Year*** Treatment NS

T x Y*

Year*** Treatment NS

T x Y*

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?

Page 21: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Spe

cies

rich

ness

Spe

cies

eve

nnes

s (J

’)

Mediter.

arid

mesic Mediter.

semiarid

2001 2002 2003 2004 2005 2006 2007 2008 20090

10

20

30

40

50Station *** Year *** S x Y ***

2001 2002 2003 2004 2005 2006 2007 2008 20090

0.5

1

1.5

2

2.5

3

3.5

4Station *** Year *** S x Y **

2001 2002 2003 2004 2005 2006 2007 2008 20090

0.10.20.30.40.50.60.70.80.9

1

Station *** Year *** SxY **

Spe

cies

div

ersi

ty (H

’)

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?

Species diversity along the aridity gradient

Page 22: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

What can we learn from climate-extremes studies in drylands?

Rs = soil respiration; Ts = soil temperature; θ = soil moisture; PPFD = photon flux density

Moist season:Dry season:

R s

Grünzweig et al. 2009 JGR

Page 23: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

R s

Testing extreme conditions: irrigation during the hot summer

Rs = soil respiration; Ts = soil temperature; θ = soil water content; PPFD = photon flux density

PredictionsIrrigation:Control:

Grünzweig et al. 2009 JGR

Page 24: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Final ConferenceLimassol, Cyprus, 2011 Katja Geissler, Martin Köchy, Florian Jeltsch, Dan Malkinson

Scaling of output: the model Wadiscape

topographic and

Spatial information

GIS

slopes (DEM)

MAP

(characterization of region by mean

annual precipitation )

1.0 km

geographic variation

•Experiments (GLOWA)•Surveys (GLOWA)•Literature•Experts (GLOWA)

global circulation

models

pattern (GLOWA)

Modeling (semi-) natural vegetation

Page 25: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Final ConferenceLimassol, Cyprus, 2011 Katja Geissler, Martin Köchy, Florian Jeltsch

Modeling (semi-) natural vegetation

(Over)grazed vegetation is highly vulnerable to climate change

climate changeclimate change, moderate grazing

climate change, current grazing

Page 26: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Summary

Vegetation cover is a driver of soil respiration together with climatic drivers.

The relative distribution of vegetation types has a small impact on ecosystem-scale soil respiration under a drier climate; the decrease in soil respiration is mainly driven by the decline in biological activity.

The decrease in soil organic carbon storage with increased aridity is related to greatly reduced productivity and less drastically reduced decomposition; alternative drivers start to become important under drier conditions.

Climate change studies might reveal tipping points in species richness.

Page 27: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Where are we going from here?

• Climate-change studies in systems adapted to drought provide better understanding of ecosystem functioning under more realistic conditions• Climate-extremes studies, even unrealistic ones, can teach us about processes and potentially about thresholds and tipping points

Page 28: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Funding sourcesInternational Arid Lands Consortium(IALC) Climate Change and Impact Research: the Mediterranean Environment (CIRCE) (EU FP6)German Federal Ministry of Education and Research (BMBF)Israeli Ministry of Science and Technology (MOST)

CollaboratorsHebrew University Tel Aviv University Haifa UniversityJaime Kigel Yael Navon Dan MalkinsonYiftach Talmon Edwin LebrijaIrit KonsensRita Dumbur

Acknowledgements

Page 29: Controls over ecosystem functioning across  spatial  scales as derived from studies in drylands

Thank you for your attention!