short and long term impacts of water deficits

Adaptation of perennial plants to episodic Adaptation of perennial plants to episodic drought: impact on ecosystems 6-8 Oktobdrought: impact on ecosystems 6-8 Oktober 2010er 2010

Short and long term Short and long term impacts of water deficits impacts of water deficits

and droughts on and droughts on perennial grasses in perennial grasses in

grasslandsgrasslands

Jean-Louis DurandJean-Louis Durand

Marc GhesquièreMarc Ghesquière

Jean-Paul SampouxJean-Paul Sampoux


Grasslands: Grasslands: a key for C global cycle 13 January 2010 – FAO Properly managed grasslands – even more than forests – could fight fight

climate change by absorbing and storing carbon dioxide,climate change by absorbing and storing carbon dioxide, according to a newly released report by the United Nations Food and Agriculture Organization (FAO).

The world’s nearly 3.4 billion hectares of grasslands store 30 per cent of store 30 per cent of global soil carbonglobal soil carbon in addition to the substantial amount of above-ground carbon held in trees, bushes, shrubs and grasses. They also account for 70 per cent of agricultural land.

In its report “Review of Evidence on Drylands Pastoral Systems and Climate Change,” FAO noted that grasslands could play a major role in supporting the adaptation and reducing the vulnerability to climate supporting the adaptation and reducing the vulnerability to climate change for the more than one billionchange for the more than one billion people who depend on livestock for a living.

The report also noted that grasslands help improve the soil’s water improve the soil’s water retention capacityretention capacity and thus can help its ability to withstand drought, and help safeguard biodiversity.

In addition, it cautioned that grasslands are particularly sensitivegrasslands are particularly sensitive to land degradation, which affects some 70 per cent of pastures as a result of overgrazing, salinization, acidification and other processes. Pressure on the land is also due to the need to meet fast-growing demand for meat and dairy products.


Projection of 2 French meteorological Projection of 2 French meteorological models for annual rainfalls in Amodels for annual rainfalls in A22 scenario scenario

(2000-2100)(2000-2100)

Livre blanc Escrime ed. 2009


Plant and population responses to Plant and population responses to drought or water deficitsdrought or water deficits

1.1. The plant (plasticity)The plant (plasticity)

2.2. The sward (from plasticity to The sward (from plasticity to evolution)evolution)

3.3. The community (from population The community (from population dynamics to speciation)dynamics to speciation)


1. The plant response to water deficits1. The plant response to water deficits

Potential volume growth rate * carbon costs (g mm-3d-1)

Roots Leavesstems

Absorbed PAR

LAI

Carbon demand

Partitioning according to environmentally

dependant hierarchy.

Photosynthesis-

Respiration

Carbon Carbon supplysupply

MORPHOGENESIS ENERGY ASSIMILATIONgenotype,genotype,

waterwater

genotype,genotype,waterwater


Adaptive responses to insure survival and competitionAdaptive responses to insure survival and competition

Leaf area

morphogenesis

Rooting depth

Plant water status

TA

MAXIMISE

MAXIMISE

MAXIMISE

MINIMISE

Trade off

ENERGYENERGY

WATERWATER



Expansion of leaf area Expansion of leaf area Expansion of roots.Expansion of roots. Anticipation - > Anticipation - >

• phenology, phenology, • stomatal conductance ?stomatal conductance ?



Festuca arundinaceaFestuca arundinacea

-.8 -0.6 -0.4 -0.2 0

Mean d (MPa)

0

0.2

0.4

0.6

0.8

1

LE

R re

lativ

e to

co

ntro

l (irrigate

d)

b

-0.8 -0.6 -0.4 -0.2 0

Mean d (MPa)

0

0.2

0.4

0.6

0.8

1.0

LE

R re

lativ

e to

irrigate

d c

on

trol

a

D’après Durand et al. 1997

Lolium perenneLolium perenne



Sensitivity of Sensitivity of tissue tissue expansionexpansion


Spollen et al. 1993


0 10 % 20 % 30 %Percentage of water consumption

180

150

120

90

60

30

0

Dep

th (

in c

m)

L. multiflorum: 19 mm L4F4: 35 mm

F. a. ssp. glauscescens: 45 mm

DURAND J.L., & al 1997 Eur. J. Agronomy 7: 99-107.

Depth of water extraction, as a quantitative trait

Lm

LmFg (4x)

Fg



gS

T A

0SdGTA

d


Transpiration use efficiency as an integrated estimate of water status and resource acquisition


Three levels of changesThree levels of changes





How do populations change under How do populations change under dry conditions on the longer term?dry conditions on the longer term?

Under high competition, high water and nitrogen status, the frequency of individuals exhibiting vegetative growth is enhanced in a plot sawn 20 years before.


The The EFESTEFEST design (Genetic design (Genetic EEvolution of volution of FestFestulolium ulolium populations under summer water deficit)populations under summer water deficit)

March 2005 June 2006 Sept. 2006 June 2007

Sowing Seed harvest Plant sampling Seed harvest

rain fed

rain fed

4x- BC1 pop.

Amphi. pop.


Delta Delta 1818O soil water profiles in the O soil water profiles in the spaced-plant spaced-plant trial trial for clonal assessment (sampled for clonal assessment (sampled vsvs initial initial

plants)plants)

soil water 18O (o/oo)

-8 -6 -4 -2 0 2

So

il de

pth

(cm

)

-100

-80

-60

-40

-20

0

d1 vs profondeur d2 vs profondeur d3 vs profondeur


population

Lm LmFg INITIAL LmFG FINAL Fg

Me

an

18 O

of

stu

bb

le w

ate

r (o / oo)

-5,5

-5,0

-4,5

-4,0

-3,5

-3,0

1818O plant water in O plant water in spaced-plant trialspaced-plant trial with response of with response of plants sampled in sward compared to the initial seed plants sampled in sward compared to the initial seed

batch of the batch of the FestuloliumFestulolium population population

Lolium FestucaInitial Sampled


Estimation of plant selection within the Estimation of plant selection within the FestuloliumFestulolium population in sward because population in sward because

of droughtof drought

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0 -0.6 -1.2 -1.8 -2.4 -3 -3.6 -4.2 -4.8 -5.4 -6

Delta O18 in sward 2006

plants sam pled in thedroughted sward

hypotheticaldis tribution at sowing

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

0 -0.6 -1.2 -1.8 -2.4 -3 -3.6 -4.2 -4.8 -5.4 -6

Delta O18 in nursery 2008

plants from the initial seed batchplants sam pled in the droughted sward

δ18O in the plants sampled in the rain fed sward has shifted by 0.4 phenotypic standard deviation of the initial population as if 10 % of the least deeply rooted plants (δ18O > - 0.10 o/oo) disappeared because of drought


Three levels of changesThree levels of changes





3. Long term evolution and speciation3. Long term evolution and speciation

Biogeography of water deficit tolerance: fine-Biogeography of water deficit tolerance: fine-leaved fescues leaved fescues

Sampoux and Huyghe 2010


Festuca nigrescens

Festuca rubra ssp fallax

Festuca ovina



Modelled ecological probability of presence of Festuca nigrescens (Sampoux and Badeau, 2009)



Conclusions / 1Conclusions / 1 Fast responses of plants to water deficit: some Fast responses of plants to water deficit: some

adaptive, most of them mere passive reactions to adaptive, most of them mere passive reactions to low water supply. low water supply.

Plant structures produced Plant structures produced previousprevious to drought to drought and mantained ability of plants and mantained ability of plants following following drought drought are importantare important

Drought is hence a selection pressure at the scale Drought is hence a selection pressure at the scale of the sward. of the sward.

Dense canopies and competition for water and Dense canopies and competition for water and light need be considered together.light need be considered together.

Adaptation to drought tolerance seems to drive Adaptation to drought tolerance seems to drive spatial distribution of tightly related (fine-leaved) spatial distribution of tightly related (fine-leaved) fescue speciesfescue species


Conclusions: / questions Conclusions: / questions

What are the adaptative characters involved in What are the adaptative characters involved in drought survival in closely related grass drought survival in closely related grass populations ?populations ?• Depth of rooting ?Depth of rooting ?• Transpiration use efficiency ?Transpiration use efficiency ?• Nitrogen status ?Nitrogen status ?• Morphogenesis ?Morphogenesis ?• Phenology ?Phenology ?

How closely linked are the various traits ?How closely linked are the various traits ?


Thank you for your attention

short and long term impacts of water deficits

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