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Agroecology:modellingtheresilienceofagro-ecosystems.Cours2CorinneRobert(INRA,ENS)andDavidClaessen(ENS)

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Characteris9csofnaturalecosystems,tradi9onalandmodernagriculture

2Malézieux,2012

Whatisbiodiversity?

GENES

SPECIES

FUNCTIONS

Diversityof:

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SoilferClity

Waterquality

Nutrientcycling

CarbonsequestraCon

Pathogentransmission

PollinisaCon

Fossileenergy

Naturalresources

Pharmacology

Epidemicrisk

TrophicinteracCons

PrimaryproducCon

Watercycle

Geochemistry

Solstability

Airquality

AgriculturalproducCon

ClimateregulaCon

ResistancetoinvasionofexoCcspecies

Ecosystem“func9ons”and“services”

GENES

SPECIES

FUNCTIONS

“FUNCTIONS”

“SERVICES”

Diversityof:

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Agroecology:modellingtheresilienceofagro-ecosystemsCorinneRobert(INRA,ENS)andDavidClaessen(ENS)

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Whatisagroecology?•  Asocialmovement

–  Focusontropicalcountries–  Smallscale,tradiConalagriculture–  FocusonsocialjusCce,roleofmulCnaConalsinworldinequaliCes,peasantindependence

–  ConservaConofbiodiversity,culturaldiversity–  AlternaCveeconomical,societalsystem,humanwellbeing

•  AnagriculturalproducConsystem–  UsecologicalprocessestoimproveproducConandreducedependenceonpesCcidesandferClizers

•  AscienCficdiscipline–  Howtodesignsustainableagriculturalsystemsusingecologicalprinciplesandknowledge?

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Whatarethescien9ficprinciplesunderlyingagroecology?

•  Useecologicalprocessestoimproveagriculturalperformancewhilereducingenvironmentalimpact

•  Biodiversity:insteadofusingmonocultures,usemixturesofspeciesandvarieCes

•  UseecologicalinteracConsbetweenspeciestoregulatepests

•  UseecologicalprocessestoimprovesoilcharacerisCcs

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Diversity,complexity,recycling,self-regulaCon(resilience?)

“Agroecology”Naturalecosystem Modernagriculture

Bohanetal2013•  Mimicryofnaturalecosystems:

–  notexpectedtoprovidetheyieldsobtainedinmodernagriculture,

–  Keyecologicalconceptsinnaturalsystems•  resilience,stabilityandcapacityforself-organizaCon

–  notnecessarilyreadilytransferableorrelevanttoagroecosystems(Malézieux,2011).

•  Somekeyecologicalprinciplesshouldholdinagroecosystems–  maintainingdiversecomplementaryfuncConaltraitsinspeciesassemblages,

–  forsustainingthe‘predictable’assemblyofcommuniCesofspeciesaroundacrop

–  forthemanagementofthemicrobial,plantandanimalspeciesnaturallypresentinthesystem.

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Biologicalcontrol

•  NaturalenemiesofagriculturalpestsmaybeusedtolimitpestdensiCesbeloweconomicthresholds(Costanzaetal.,1997).

•  SuchregulaConshouldallowpesCcideinputstobereducedandsystemresilienceandsustainabilitytobeenhanced.

•  UnderwhatcondiConsdoweexpectbiologicalcontroltobeeffecCve,andinwhattypeofnetworkstructure?

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Commonprinciplesinagroecology

•  Highbiodiversity(polyculture)

•  Combininganimalhusbandryandcrops

•  SCmulateacCve,alivesoils

•  OpCmizespaCalorganizaCon(landscape)

-  OpCmaluseofsoilnutrients-  PosiCveeffectonhydrology-  Bufferagainstunfavorable

condiCons

-  FerClizaCon-  Weedcontrol-  Herbivorecontrol

-  NitrogenfixaCon-  Nutrientrecycling-  Favorablehydrology

-  Reducepestanddiseasedispersal-  Reducewinddamage-  Reducesoilerosion

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“Tradi9onal”vs“Agroecological”view

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Examplesofagroecologialsystems

MiguelAlCeri 13

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Achievinggoodweedsuppressionwithcovercropmixtures.

ThelegumesredcloverandAustrianwinterpeaareslowertoestablishinthefallandcanallowweedstogetafoothold(A,B).

Undernitrogen-deficientcondiCons,canolagrowthislimited(C),reducingitsweedsuppressioncomparedtocanolawithsufficientnitrogenavailable(G).

Amixtureofslow-growinglegumes(D)willbenobeieratsuppressingweedsthanaslow-growinglegumemonoculture.

Grasseslikeoatsandryeareexcellentweedsuppressors(E,F)butevenasmallgapbetweendrillpassescancreateaspotforweedstotakeroot(F).

Adiversemixturethatincludesafewfast-growingspecieswillprovideweedsuppressionwhileallowingforbenefitssuchasnitrogenfixa9onandfloralresourcesfromtheotherspecies(H).

CharlesWhiteetal(2016)16

Complementarygrowthforms:-  cerealryeandcanolatransiConfromshortdensecanopiestotallopen

canopiesinthelatespring,-  Austrianwinterpeaisvining,andredcloverremainsshortanddense.

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Agroecology:modellingtheresilienceofagro-ecosystemsCorinneRobert(INRA,ENS)andDavidClaessen(ENS)

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Ecologicalnetworktheory

•  Bohanetal2013–  eveniftheprovisionofaspecificecosystemservicesmaybemaximizedthroughtheabundanceoffuncConallyimportantspecies(Gaston,2010),suchashoneybeesaspollinators(Calderone,2012;Hagenetal.,2012),

–  widersystemresilienceandecosystemserviceprovisionreliesdirectlyonspeciesdiversityandfuncConing(Naeemetal.,2009).

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“Resilience”thoughbiodiversity(1)

•  “AresilientagroecosystemwillconCnuetoprovideavitalservicesuchasfoodproducConifchallengedbyseveredroughtorbyalargereducConinrainfall”

•  TheroleofdiversityinagroecosystemstofuncConalcapacityandresilience(Vandermeerandcolleagues1998):–  BiodiversityenhancesecosystemfuncConbecausedifferentspeciesor

genotypesperformslightlydifferentrolesandthereforeoccupydifferentniches

–  BiodiversityisneutralornegaCveinthattherearemanymorespeciesthantherearefuncCons;thus,redundancyisbuiltintothesystem.

–  BiodiversityenhancesecosystemfuncConbecausethosecomponentsthatappearredundantatonepointinCmemaybecomeimportantwhensomeenvironmentalchangeoccurs.

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“Resilience”thoughbiodiversity(2)

•  Thekeyhereisthatwhenenvironmentalchangeoccurs,theredundanciesofthesystemallowforconCnuedecosystemfuncConingandprovisioningofservices.

•  Theinsurancehypothesis(YachiandLoreau1999),whichproposesthatbiodiversityprovidesaninsurance,orabuffer,againstenvironmentalfluctuaConsbecausedifferentspeciesresponddifferentlytochange,leadingtomorepredictableaggregatecommunityorecosystemproperCes.

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