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Controls over ecosystem functioning across Controls over ecosystem functioning across

Controls over ecosystem functioning across - PowerPoint Presentation

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Controls over ecosystem functioning across - PPT Presentation

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 ID: 715296

soil climate ecosystem change climate soil change ecosystem functioning carbon drier experiments respiration control processes points tipping aridity reveal

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Slide1

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, IsraelKatja 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 2013Slide2

Climate anomalies, Europe, summer 2003

Ciais et al. 2005 Nature

Climate extremes in systems not adapted to those extremesSlide3

Global extent of drylands

Levant (SE Mediterranean)

Research in regions adapted to heat and/or droughtSlide4

Climate

The physical properties of the Levant (SE Mediterranean)Slide5

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

The physical properties of the Levant (SE Mediterranean)

Biomes/ecosystem typesSlide6

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?Slide7

Rainfall manipulations along an aridity gradient

Aridity gradient – GLOWA Jordan River project

South facing slopesshallow soil (Terra Rossa to lithosol) onsimilar bedrockSimilar seasonal temperture rangeEight-fold difference in mean annual rainfallLarge difference in rainfall variability

Mediterranean: 540 mm,

CV 30%

Semiarid: 300 mm,

CV 37%

~ 245 km

Arid: 90 mm,

CV 51%

Mesic Mediterranean: 780 mm,

CV 22%

Biomes/ecosystem typesSlide8

300 mm

Semiarid

550 mmMediterranean

-30

%

+30

%

Experimental rainfall manipulations

Control

Rainfall manipulations

Rainfall manipulations along an aridity gradientSlide9

Observed

R

s (μmol m-2 s-1)Predicted Rs (μmol m-2 s-1)r2 = 0.48Talmon et al. 2011 GCB

Soil respiration at the herbaceous

microsite

during the growing season?

Prediction:

R

s

= soil respiration;

T

s

= 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

treatmentsSlide10

Observed

R

s (μmol m-2 s-1)Predicted Rs (μmol m-2 s-1)r2 = 0.48Ts

,

θ

Observed

R

s

(

μ

mol

m

-2

s

-1

)

r

2

= 0.73

T

s

,

θ

, cover

Predicted

R

s

(

μ

mol 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 modelingAddition of vegetation cover as a driver of soil respirationPrediction of ecosystem functioning with common biological and abiotic drivers?Slide11

Talmon

et al. 2011 GCB

What processes control carbon pools and fluxes when it gets drier?Soil organic carbon stocks at the herbaceous microsite along the aridity gradientSlide12

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

Carbon loss

Carbon additionSlide13

Changes in plant strategies

with increasing aridity

Mean annual precipitation (mm)Unweighted community mean

300

780

550

90

300

780

550

90

Mean annual precipitation (mm)

Sternberg &

Lebrija

What processes control carbon pools and fluxes when it gets drier?Slide14

Alternative drivers of litter decay in the dry season

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

Dirks et al. 2010 GCB

Dew

Water

vapor

< saturation

Solar radiationSlide15

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?

What processes control carbon pools and fluxes when it gets drier?Slide16

13% 35%

55% 75%

Shrub

cover

-15%

-12%

-21%

-20%

-60%

-64%

What processes control carbon pools and fluxes when it gets drier?Slide17

Kigel

& Konsens

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?Slide18

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

Sternberg &

NavonSlide19

Talmon

et al.

2011 GCBDo climate-change experiments reveal tipping points in ecosystem structure and functioning?Slide20

Rainfall manipulations had

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

Kigel et al., unpublishedYearYear ***

Treatment NS

T x Y *

Year ***

Treatment NS

T x Y *

Do climate-change experiments reveal tipping points in ecosystem structure and functioning?Slide21

Species richness

Species evenness (J’)

Mediter.

arid

mesic Mediter.

semiarid

Station *** Year ***

S x Y

***

Station *** Year ***

S x Y **

Station *** Year ***

SxY

**

Species diversity (H’)

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

Species diversity along the aridity gradientSlide22

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 JGRSlide23

R

s

Testing extreme conditions: irrigation during the hot summerRs = soil respiration; Ts = soil temperature;

θ

= soil water content;

PPFD

= photon flux density

Predictions

Irrigation:

Control:

Grünzweig et al. 2009 JGRSlide24

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 vegetationSlide25

Katja Geissler, Martin Köchy, Florian Jeltsch

Modeling (semi-) natural vegetation

(Over)grazed vegetation is highly vulnerable to climate change

climate change

climate change, moderate grazing

climate change, current grazingSlide26

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

.Slide27

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 pointsSlide28

Funding sources

International 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

AcknowledgementsSlide29

Thank you for your attention!