How will climate change affect pasture plant species and their reserves?

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How will climate change affect pasture plant species and their reserves?

Jean-François Soussana, Florence Volaire, Frédérik Le Dily

To cite this version:

Jean-François Soussana, Florence Volaire, Frédérik Le Dily. How will climate change affect pasture plant species and their reserves?. ”Les réserves végétales et leur importance agronomique et sylvicole”, Institut National de Recherche Agronomique (INRA). UMR UMR INRA / Univ. Caen : Laboratoire de physiologie et biochimie végétales (0950)., Jun 2009, Caen, France. 66 p. �hal-02819471�

How will climate change affect

pasture plant species

and their reserves?

Jean-François Soussana

1

, Florence Volaire

2

and Frédérik Le Dily

3

1 : UR874 Grassland Ecosystem Research, INRA, Clermont, France 2 : UMR SYSTEM, INRA, Montpellier, France

Outlook

• Introduction: climate change

• 1° Plant types, reserves and climate

• 2° Elevated CO

₂

and incremental warming

effects on reserves

• 3° Drought and survival: the role of

reserves

What is climate change?

Increase in the main greenhouse gases

Carbon dioxide (CO

₂

)

Methane (CH

₄

)

Nitrous oxide (N

₂

O)

Changes in climate

Temperature

Precipitation

Extreme events

Global increase in anthropic greenhouse gas emissions

Global greenhouse gas emissions covered by the Kyoto protocol have increased by 70 % from 1970 to 2004

years BP ('000) 0 50 100 150 200 250 300 350 400 450 CO 2 160 180 200 220 240 260 280 300 320 340 360 380

Atmospheric CO

₂

in the past

The last 400‘000 years

today

Global warming since 1880

7

Projected droughting

of South Europe

Climate changes

(IPPC, 2007)

Predictions for Southern Europe



Increased frequency of severe droughts



Reduction of water availability

Climate models converge for

changes in rainfall in Europe

-Likely progression northwards of Mediterranean influence

- Frequency of severe summer droughts is likely to double

Impacts of climate variability and

extremes on grasslands

Interannual variability

Agricultural

Climate change: incremental warming

and increased variability

Years Climate variable

Variability

Incrementa l change

Growth

Reserves cycle

A synchronism exists between growth & dynamic

of reserves

Perennial Yr n-1 Yr n Yr n+1 … Storage : Fall - winter Mobilisation : Winter - spring Mi n i a ir tem p . N reserves Goulas et al. 2001 e.g. clover

Growth

Reserves cycle

A synchronism exists between growth & dynamic

of reserves

Sucro se in t ap roo t

Days after sowing

Le Dily et al. 1992 e.g. carota Bisannual Yr 1 Yr 2 Storage : Early fall Mobilisation : Winter - spring Yr 1 Yr 2 G R cycle

N per

plan

te

Annual

Storage :

Spring (leaf growth)

Mobilisation : Mid-spring (flowering)

e.g. oilseed rape

The synchronism between growth & dynamic of

reserves vary with phenology

Malagoli et al. 2005

Leaf development

G

Space for time analogy

• Which are the dominant pasture lifeforms in warmer/drier

climates?

– Perennials are dominant in temperate grasslands. However, earlier

flowering is documented at warmer/drier sites (e.g. Dactylis

glomerata, Volaire, 2001; Lolium perenne F. Balfourier,)

– Annuals become dominant in arid climates (below 300 mm)

– Geophytes (e.g. Poa bulbosa, Hordeum bulbosum; Dactylis ssp.

Hispanica cv. Kasbah) are located in semi-arid areas and are

summer dormant

• Can we keep perennials under climate change?

• Should we learn how to manage their C/N reserves?

• Would geophytes and annuals become useful?

• 2° Elevated CO

₂

and incremental warming

effects on reserves

Years Climate variable

Variability

Incrementa l change

Elevated CO

₂

and incremental

warming effects on reserves

Leaf proteins

Shoot structure

Roots

N reserve

C reserve

C subs

tra

te

N su

bs

tra

te

Respiration Photosynthesis NO ₃ - _uptake Root length Uptake capacity Leaf area &

vertical distribution Leaf N Structural mass Relative growth rate Daily radiative partitioning

Leaf proteins

Shoot structure

Roots

N reserve

C reserve

C subs

tra

te

N su

bs

tra

te

Respiration Photosynthesis NO ₃ - _uptake Root length Uptake capacity Leaf area &

vertical distribution Leaf N Structural mass Relative growth rate Daily radiative partitioning

+

+

+

Temperature

+

?

Elevated CO

₂

and incremental

Elevated CO

₂

effects

(Free Air Carbon dioxide Enrichment)

CO₂ released into the

ambient airstream Wind

Consistent increase in leaf photosynthesis

All studies: +58% (Drake et al., 1997)

FACE studies: +35 % (Ainsworth and Long, 2005)

Response to elevated CO

₂

of maximal

carboxylation capacity

Nitrogen, leaf area and biomass allometry

in

Lolium perenne

(Soussana et al., 1996; Casella & Soussana, 1997; Calvet & Soussana, 2001)

Leaf area per unit root+shoot mass declines under elevated CO

_2.

This decline correlates with that in shoot N content

Ambient CO₂

C-N fluxes in elevated CO

₂

with

L. perenne

N Min Water soluble carbohydrates +

Photosynthesis

Rhizo-deposition

C:N

Respiration

SOIL

N immobilisation

N uptake

C yield

+

+

+

Organic C +

+

-

-

+

-

-

+

Negative feedback on yield, because of an increased soil N immobilization and increased allocation of C below-ground

Negative

feedback

(Soussana et al., 1996; Loiseau & Soussana, 2000)

WSC pools in laminae and sheath of perennial

ryegrass monocultures (mean of two N supplies)

(Casella and Soussana, 1997, J. Exp. Bot.)

Ambient Elevated CO₂ +3°C Elevated CO₂ 350 700 700+ m g g -1 DM 0 50 100 150 200 250

Lamina (Hex. Sucr) Lamina (Fructans) Sheath (Hex. Sucr.) Sheath (Fructans) a A B _B b b

Transplant experiment with a semi-natural grassland

(mini-FACE system, INRA Clermont)

Water soluble carbohydrate contents of

laminae (L) and stems (S) of plant community

at two cutting frequencies (C-, C+)

(Picon-Cochard et al., 2004, EJA)

Ambient Elevated CO₂ 2D Graph 8 '350 '600 m g g -1 DM 0 20 40 60 80 100 120 140 160 Laminae Cut- Laminae Cut+ Stems Cut- Stems Cut+ a a A A b b A A

'350 '600 mg g -1 D M 0 20 40 60 80 100 120 140 Grasses Cut- Grasses Cut+ Forbes Cut- Forbes Cut+

Water soluble carbohydrate contents of

grasses and forbes at two cutting frequencies

(Teyssonneyre et al., 2002 GCB; Picon-Cochard et al., 2004, EJA)

Ambient Elevated CO₂

a a

A A

b b

A A

At leaf level

Farquhar’s photosynthetic model Stomatal regulation

Coordination of leaf N content Leaf N distribution vs. light Acclimation to temperature, CO2

Morphogenesis Architecture

Plasticity for some traits …

At root level NO3-, NH4+ uptake vs.

acquisition in function

of N in plant/ soil concentration Morphogenesis Architecture Acclimatation to Temperature … At soil level Inorganic N balance

SOM dynamics (four SOM pools)

Microbial turnover (two decomposer types)

At plant axis level

Assimilate partitioning

Functional balance between roots & shoots Reserve dynamics

Substrate dynamics

Root, shoot structure & shoot proteins dynamics …

At population level

Self thining

Axis density dynamics

Density dependent recruitment Mortality

…

At community level

Radiative balance (Kubelka-Munk equations) Inorganic N balance (diffusion driven competition) Community dynamics

At ecosystem level

Primary productivity C and N cycles

Grassland Ecosystem Model with Individual

centred Interactions (GEMINI)

Modelling reserve and substrate dynamics

Same dynamics for N substrate and reserve

(Soussana et al., 2000, Soussana & Oliveira Machado, 2001)

Simulated CO

₂

response ratio of substrate

and reserve dynamics

(Festuca arundinacea, cut-, N+, 10 yrs simulation)

Days since start of simulation

0 1000 2000 3000 4000 CO 2 r esponse rat io 700 /350 0 1 2 3 4 Substrate C Labile reserve C Slow reserve C

Days since start of simulation

0 1000 2000 3000 4000 CO 2 r esponse rat io 700 /350 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Substrate N Labile reserve N Slow reserve N Carbon Nitrogen

Gradual saturation in C reserves Initial decline in N reserves,

Simulated CO

₂

response ratio of leaf

proteins, shoot structures and roots

(Festuca arundinacea, cut-, N+)

Days since start of simulation

0 1000 2000 3000 4000 CO 2 r esponse rat io (700 /350 ) 0 1 2 3 4 5 6 Leaf proteins Shoot structures Roots

Role of reserves under incremental

warming and elevated CO

₂

Increasing demands on the buffering capacity in plants:

Between increased supply (CO

₂

) and increased demand (warming) of

carbohydrates,

Between increased C assimilation and reduced soil N supply,

Which strategies for managing carbohydrate (and

storage proteins) under climate change?

Increased buffering capacity to avoid down-regulation of leaf photosynthesis under elevated CO₂ ?

Which plant parts for storage? e.g. breeding for tap roots, rhizomes, stolons.. Which forms of storage? Fructans, VSP, starch...

• 3° Drought and survival: the role of

reserves

Years

Variability

& extremes

Incrementa l change

34

Increased importance of drought resistance

in forage grasses

Drought survival

Autumn recovery

Perenniality

Sustainability of agro-ecological functions

Stability production

Autumn/winter/spring

Stability soil cover

35

Stages of plant responses

of perennial grasses under a standard climatic scenario

June July August September _{Increasing water} deficit

Green Progressive senescence Total senescence

STAGE1 STAGE 2 STAGE 3

---SURVIVAL PERIOD ---Rehydration Survival/Mortaliy Recovery Leaf Development & growth Root growth Mature lamina

STAGE 1: Transpiration & assimilation unaffected – Growth modulation STAGE 2: Transpiration & assimilation reduced – Growth reduced & stopped

STAGE 3: Transpiration (cuticular) – progressive senescence progressive (Blum, 1989)

Surviving organs Meristems

? ?

Main research areas (litterature) Research questions

36

Drought survival

of aerial meristems - surviving organs

=

combination of adaptations  3 strategies



Dehydration delay



Increase of water uptake

(root system)



Reduction of water loss

(lamina senescence)



Dehydration tolerance

 Sugars: fructans + Proteins: dehydrins



cell membrane stability

37

Dehydration tolerance



No discriminating differences

in

le

thal hydration of

meristematic tissues

Lethal hydration of meristems in dactylis = 35 % to 45%

 much lower than lethal hydration of lamina

BUT



Discriminating differences

in

duration of survival at low

hydration

38

 Accumulation of

water soluble

carbohydrates

(Julander, 1945; Suzuki & Nass, 1988…)

 Accumulation of

dehydrins -

LEA

Proteins associated with desiccation & osmotic stress Abundant in dormant embryos and resurrection plants (Bartels et al., 1996; Close, 1996, 1997)

Factors

contributing

to dehydration

tolerance of

meristems ?

Dehydration tolerance

39

Water soluble carbohydrates

Dehydration tolerance

Total WSC High-DP fructans Low-DP fructans Sucrose Osmotic adjustment (-4 to –7 MPa) Monosaccharides 80 days 8 days Drought recovery Rehydration

40

Accumulation of highly polymerised fructans

Sensitive populations Resistant populations

Water soluble carbohydrates:

Discriminating adaptation

Dehydration tolerance

Volaire & Gandoin (1996) Volaire & Lelièvre (1997) Volaire et al. (1998b)

41

Accumulation of highly polymerised fructans

Sensitive populations Resistant populations

Water soluble carbohydrates:

Discriminating adaptation

Dehydration tolerance

Volaire & Gandoin (1996) Volaire & Lelièvre (1997) Volaire et al. (1998b)

Fructans DP >3

Carbon reserves (regrowth after rehydration)

Stabilisation lipidic layers of cell walls

Crowe et al. (1987); Demel et al. (1998); Hincha et al. (2002, 2007); Vereyken et al. (2003)

42

Dehydration tolerance

Water soluble carbohydrates:

Interaction with

management

Severe defoliation in Spring Depletion of Carbon reserves

Low summer survival + Low autumn recovery

Volaire (1994)

Spring intensity of defoliation affects autumn recovery after drought through fructan accumulation in meristems in Summer

Fructan concentration in meristems in July -drought (mg / g DM)

0 100 200 300 400 Recov ery A ut um n biom ass (g/ m²) 0 50 100 150 200 250 Resistant Dactylis Sensitive Dactylis LOW LOW MEDIUM MEDIUM HIGH HIGH

43

Dehydration tolerance

Dehydrins :

Non discriminating differences

– Dactylis - resistant ++ Dactylis - sensitive + Volaire et al. (2001), Volaire (2002) – Barley - resistant +++ Barley - sensitive +++ Volaire (2003)

– Fescue - resistant ++ Fescue - sensitive +++ Norton et al. (2006)



Correlated with water content of tissues

(maximum when WC < 50 %)



Not correlated with levels of dehydration tolerance

Dehydrins : Hydrophilic proteins  stabilisation of cell walls

Hoekstra et al. (2001); Goyal et al. (2005); Tompa et al. (2006)

Interaction with fructans

44

Conclusion - Strategies of perennial grasses under drought

Leaf growth Leaf senescence Photosynthesis Carbon Reserves Lamina turgescence Root growth WHOLE PLANT MERISTEMS

none low moderate high severe INCREASING DROUGHT

STRATEGIES 100 0 Growth maintainance Dehydration delay Dehydration tolerance Desiccation tolerance 0 0 0 Lamina mortality Tissue hydration Carbon reserves Dehydrins Membrane stability Tiller mortality 0 0 0 0

Conclusions (1/3)

• Basic knowledge of reserve dynamics in plants

needs to be extended and applied to climate

change adaptation.

• Which ideotypes for optimal C-N reserve

dynamics in a future climate?

– Increased reserve levels (insurance hypothesis)?

– Increased share of specialized organs (e.g. rhizomes,

bulbs, stolons, tap roots)?

– Are fructans and VSP preferable to other reserve types

(water stress tolerance)?

Conclusions (2/3)

• Adapting plant material

– Take advantage and increase Genetic variability ;

Genotype x Environment interactions;

– Breed genotypes with high plasticity; use populations?

– Use mixtures rather than monocultures?

– Breed for adapted plant reserve dynamics

• Adapting pasture management

– Avoid excess reserve depletion (e.g. frequent cutting,

severe grazing)

Conclusions : research needs

• Modelling

• Improve formalisms for: mortality, high temperatures etc..

• Observations

• Climatic gradient (e.g. Morocco—South of France)

• Experiments

• Impacts of extreme climatic events

• Biotic interactions

• Competition (weeds)

• Pests and pathogens

VALIDATE : expérience

avec extrêmes

Expérience in-situ à l’air libre combinant

sécheresse et

réchauffement de 3°C (scénario 2050)

avec ou sans extrêmes Un événement extrême appliqué en été 2009

de magnitude égale à celle de 2003 ou à celle projetée en 2050

Exclusion de pluie : rideaux automatisés Réchauffement : émetteurs infra-rouge

Exclusion de pluie Chauffage infra-rouge Lusignan 12 °C (ORE) Prairie temporaire Theix 9°C (ORE) Prairie permanente Mauguio 15°C Prairie temporaire Lautaret 2°C (CNRS) Alpage Lusignan 12 °C (ORE) Prairie temporaire Theix 9°C (ORE) Prairie permanente Mauguio 15°C Prairie temporaire Lautaret 2°C (CNRS) Alpage

ECOTRON CEFE-CNRS

Macrocosmes : monolithes de prairie (5 m2_{) prélevés à Theix}

Scénario 2050 : réchauffement, pluviométrie

Un événement extrême est appliqué. Suivi des bilans C et eau, avec ou sans enrichissement en CO₂

Expérience avec/sans extrêmes (chaleur, sécheresse) avec

ou sans enrichissement en CO

₂

Atelier de Réflexion Prospective

ADAGE

ADaptation de l’AGriculture et des Ecosystèmes

anthropisés au changement climatique

A. Approche générique

1.Traitement de l’incertitude dans les études d’adaptation 2. Traitement de la biodiversité et de la santé 3. Traitement de l’innovation 4. Traitement de l’adaptabilité et de la vulnérabilité B. Approche matricielle

5. Définition de la matrice utilisée et recensement des études nationales 6. Biome cultures – filières alimentaires ou

non

7. Biome prairies-savanes ; filière élevage 8. Biome forêts ; filière bois et fibres 9. Biome hydrosystèmes continentaux et

océaniques ; filière pêche 10. Agriculture de subsistance 11. Zones protégées et corridors de

biodiversité

C. Approche systémique

12. Interactions entre adaptation, atténuation et utilisations non alimentaires de la

biomasse

13. Adaptation et ressources en eau et en sols 14. Adaptation sécurité alimentaire et

compétitivité des filières 15. Adaptation et territoires

D. Coordination & Synthèse 16. Gestion de l’information et des connaissances 17. Coordination et gestion de l’ARP

A. Approche générique

1.Traitement de l’incertitude dans les études d’adaptation 2. Traitement de la biodiversité et de la santé 3. Traitement de l’innovation 4. Traitement de l’adaptabilité et de la vulnérabilité B. Approche matricielle

5. Définition de la matrice utilisée et recensement des études nationales 6. Biome cultures – filières alimentaires ou

non

7. Biome prairies-savanes ; filière élevage 8. Biome forêts ; filière bois et fibres 9. Biome hydrosystèmes continentaux et

océaniques ; filière pêche 10. Agriculture de subsistance 11. Zones protégées et corridors de

biodiversité

C. Approche systémique

12. Interactions entre adaptation, atténuation et utilisations non alimentaires de la

biomasse

13. Adaptation et ressources en eau et en sols 14. Adaptation sécurité alimentaire et

compétitivité des filières 15. Adaptation et territoires

D. Coordination & Synthèse 16. Gestion de l’information et des connaissances 17. Coordination et gestion de l’ARP

•

species and cultivar

•

soil properties

•

(re)distribution of pests and pathogens

•

direct effects of elevated CO

₂

(photosynthesis)

•

interactions between CO

₂

- air temp - water stress – mineral

nutrition…

•

and adaptive responses of plants…

Crop yield responses to climate change depend upon

53

Influence of global changes on plant

growth and survival and

sustainability of perennial grasses

54

Plan

I.

Background - Objectives

II.

The main drought survival strategies

in grasses

55

Importance of drought

Mediterranean areas :

Chronic summer droughts



severe water stress



Summer water deficit

• 300 – 1000 mm

• 45 - 30° latitude

Diagramme ombrothermique Montpellier (1970 - 2000) Mois 1 2 3 4 5 6 7 8 9 10 11 12 Pré cipitation s (mm) Te mpé ratur es x 2 (° C) 0 20 40 60 80 100 Drought Diagramme ombrothermique Rabat - maroc (1970 - 2000) Mois 1 2 3 4 5 6 7 8 9 10 11 12 Pré cipitation s (mm ) Te mp ér atur es x 2 (° C ) 0 20 40 60 80 100 Drought Montpellier (1970 –2000) Drought 3 months Rabat (1970 –2000) Drought 5 months P <2T

Mediterranean areas

Relevant field-research environment

to analyse plant responses

under

increasing summer aridity

predicted for larger areas

under climate change

63

Methodological key-points



Comparison of species and genotypes with

contrasting resistance

Dactylis glomerata

(orchardgrass), Lolium arundinaceum (tall

fescue), Lolium perenne (ray-grass), Phalaris tuberosa

(phalaris), Poa bulbosa



Realistic conditions

– Whole plant (well developed plants)

–

Realistic water deficits

(progression – intensity)  plant

64

Agronomical consequences

Strategies of perennial forage grasses to survive severe drought

(Volaire, 2008)

Dactylis Mediterranean +++ +++ ++ +++ Temperate ++ ++ - ++ Tall Fescue Mediterranean ++++ ++ + +++ Temperate +++ + - ++ Lucerne ++++ + + +++

Red fescue-turf - - - -

Dehydration

Delay Tolerance

Drought survival

65

Importance of the summer dormancy trait

Drought survival strategies in perennial forage grasses

(Volaire, 2008)

Dactylis Semi-arid +++ +++ ++++ ++++ Mediterranean +++ +++ ++ +++ Temperate ++ ++ - ++ Tall Fescue Semi-arid +++ +++ ++ ++ ++++ Mediterranean ++++ ++ + +++ Temperate +++ + - ++ Lucerne ++++ + + +++

Red fescue-turf - - - -

Dehydration Summer

Delay Tolerance Dormancy

Drought survival