Optimizar el funcionamentode un sistema agroforestal

Cultivos productivos en huertos

Christian DuprazUMR SYSTEM, Montpellier, Francia

20/03/2015

Segunda conferencia

2

Mixing trees ans crops ?m

on

ocu

ltu

re 1

mo

no

cult

ure

2

asso

ciat

ion

mo

no

cult

ure

1

mo

no

cult

ure

2

asso

ciat

ion

mo

no

cult

ure

1

mo

no

cult

ure

2

asso

ciat

ion

complémentarité compétition facilitation

Qu

anti

tyo

f re

sou

rce

cap

ture

d

capture espèce 2

perdu

capture espèce 1

Captured by plant 1Not usedCaptured by plant 2

Efficiency of the tree-crop associaton

To mix or not to mix …

1.2 to 1.6

Land Equivalent Ratio

Poplars winter cereals

14 years

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Prunus avium

Juglans hybrid

A 1.4 LER means

that an 100 ha agroforestry farm produces as much as a 140 ha farm where treesand crops are segregated

Improved efficiency of natural production factors (light, water, nitrogen)

Tree and crop plasticity in agroforestry systems

Poplar-cereal experiment

• 1996 – 2009 (14 years)

• Cereals and rape from 1996 to 2007

• Harvesting and selling the trees in december 2009

2000 2007

AF

AF

F

F

A

12

Plasticité des couronnes dans un système à base de peuplier

Unexpected canopy plasticityStrectched canopies with esat-west tree lines

CW = 14 m

CW = 11 m

Experimental 13 years old poplar-wheat agroforest

CW =

Crown Width

Unexpected root plasticity

Documenting the fine root distribution

15

0

10

20

30

40

50

00.5

11.5

22.5

3

soil d

ep

th (m

)

relative Lrv (%)

Agro

fore

stry

Fore

stry

8 ans après plantation14 ans après plantation

Pro

fon

de

ur

du

so

l (m

)

pourcentage de longueur de racines

Dupraz and Mulia, Plant and Soil, 2012

Agroforesterie

Témoinforestier

Agroforesterie

TémoinforestierForest control

AgroforestryAgroforestry

Years after plantation

Forest control

Agroforestry

Years after plantation

Root length (%)

Root phenology

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Germon et al, Plant & Soil, 2016

Unexpected phenology for walnut trees in agroforestry

Winter summer

Crop yield in Agroforestry

• With 50% of radiation, between50 and 100% of crop yield

• Light competition compensated by several processes

• Results obtained with numerical models

Treeplantation

Treeharvest

133 trees.ha-1

64 trees.ha-1

?

Relative irradiation

Relative

yeield

8 scenarii x 3 climate replications

Complementarity in ressource capture

Complementarity for light capture

20

15 year old trees

NoyersBléNon utilisé

02

04

06

08

01

00

% d

u r

ayo

nn

emen

t in

cid

ent

Janvier Avril Juillet Octobre

Light balance (40 ans)

21

Light captured in agroforestry:

Walnut : 0.73Wheat : 0.66

LER light = 1.39

0 10 20 30 40 0 10 20 30 400 10 20 30 40

020

40

60

80

100

Agriculture Agrofrestry Forest plantation

% d

u r

ayo

nn

emen

t in

cid

ent

AnnéeWalnutWheatNot used

What is the shape of the cumulated shade of a tree over a year?

A banana A flying cup A banana on a wheel

Nord

Nord

No : only on June 21 for direct beam

YESNo : only on 21 June for bothdirect and diffuse beams

A banana A flying cup A banana on a wheel

AGROFORESTRY AT ALL LATITUDES?

UNEXPECTED RESULTS ABOUT BEST DESIGNS TO ALLOW MORE LIGHT TO THE CROPS AT VARIOUS LATITUDE

Dupraz Christian, Lecomte Isabelle, Molto Quentin, Blitz-Frayret Céline, Gosme Marie

INRA, UMR-System, Montpellier

Latitude 52 °N (University of Leeds)

Path of the Sun over the celestial sphere through the course of the day at 56°N latitude.

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Sun path at the summer solstice (dashed), equinox (solid) and winter solstice (dotted-dashed) for latitude 65° (left) and 25°(right) as seen from the center of the alley

Summer solstice

Equinox

Winter solstice

North-South tree line

East-West tree line

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Sun path during the summer solstice at 25° and 65° of latitude North

Poplar alley cropping system with tree lines spaced 16 m and tree height 20 m

North-South tree line

East-West tree line

From the center of the alley

South and close from the tree

The sky as the crop « sees » it

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Extraterrestrial irradiation throughout the year at different Northern latitudes

50 cm DBH trees, 84 trees/hectare

Relative irradiation of the crop in March, June, September and December

North-South better

Low impact of latitude

East-West better

Heterogeneity of relative crop irradiation

84 trees/ha (17m wide alleys)

East-West tree lines North-South tree lines

Month of June

Increase light

availability

Reduce light

heterogeneity

Increase tree

growth

Best

compromise

Low latitudes

(<35° Tropics)

East-West

+++

North-South

+

North-South

+

East-West

++

Temperate latitudes

(35°-50°)Equal

North-South

++

North-South

+

North-South

+

High latitudes

(>50° Boreal/Austral)

North-South

+++Equal Equal North-South

Looking for the best compromise for tree row orientation

Complementarity for light

• Impact of tree and crop phenology

36

0 10 20 30 40

02

46

8

0 10 20 30 40

02

46

8

Late leafing walnutEarly leafing walnut

Monocrop

Année Année

Ren

dem

en

t (

t.h

a-1)

Winter wheat long cycle Winter wheat short cycle

Complementarity for water

• Less important in irrigated systems

• Example : Wheat system water balance

– Rain : 750 mm

– Soil evaporation : 250 mm

– Crop transpiration : 300 mm

– Leaks (runoff + drainage) : 200 mm - > rivers, water tables

• Transpiration of mature walnut trees : 150 mm

37

Water balance (40 years)

38

Water capture:Walnut : 0.71Wheat : 0.84

LER water = 1.55

Inputs :RainWater table

OutputsWheat transpirationWalnut transpirationUnderstory forest transpirationSoil evaporationdrainageRunoff

A AF F

(mm

/an)

0200

400

600

800

A AF F

Entrées Sorties

Yield of crops in agroforestry

39

What yield components are modified and when?

Increased light capture• Delayed senescence

A

AF

40

-40 -30 -20 -10 0 10

Noyer

Prec Tard

Blé

Tard

Pre

cEffect

y

ai

pnwst

guf

Explanation

LAI walnutsPhénology walnutPhénology wheat

0 40 8020 60 100

Yield of crops in agroforestry

Complémentarité pour l’azote

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Nitrogen capture in an agroforestry system

Complémentarité pour l’azote• Safety net for nitrate leaks

– Capture of leached nitrate in depths and recycling by the trees

42

AgricultureAgroforestry Forestry

N loss

Looking for facilitation

Mecanisms triggered by trees for facilitation

• Nutrients pump

• Hydraulic lift

• Microclimate change : reduction of soil evaporation, reduction of windspeed, reduction of crop temperature

44

Optimizing AF system with simulation models

The Hi-sAFe model (2005-2017)

• 3D process-based

• Competition for light, water and nitrogen

• Day time step, decades run

• STICS crop model embedded and replicatedon each cell

• Toric symmetry allowing infinite stands

• 3D tree root systems

4m

9m

13m

Scène réelleScène virtuelle Scène virtuelle

First results of simulation runs

• Impact of climate change with IPCC predictions

Montpellier, Restinclières,

Longitude 3° 5' E, Latitude 43° 7' N, Elevation 62 m

Tree pruning, tree row orientation, tree density

Tree line orientationNorth-South / East-West

133 trees.ha-1 64 trees.ha-1

10

10

10

10

6

66

6

NS NSEO EO

Pruning height: 10 / 6 m

Tree density

Root plasticity of trees

52

+ 33% explained by :

• total PAR intercepted : +12 %

• light use efficiency : +19 %

Above ground biomass

+23 %

Below ground biomass

+100 %

Total growth (Kg C)

Opportunistic tree roots as a

key success factor for tree

growth

Resilience to climate change

Assessing the adaptation to climate change of agroforestry systems by field experiments and numerical simulations.

Dupraz Christian, Reyes Francesco, Inurreta Daniel,

Dufour Lydie, Lecomte Isabelle,

Gosme Marie

INRA, SYSTEM,

University of Montpellier, France

• Climate change is a threat to many crops and forests in Europe.

• For crops : thermal and water stresses occur more and more frequently and are considered as a main limit to crop yield increase in Europe.

• For trees : Rain reduction and temperature increase may induced water stresses with impacts on growth and health

Brisson N et al. 2010. Why are wheat yields stagnating in Europe? A comprehensive data analysis for France. Field Crops Research 119: 201-212.

Yields of major crops in Europe stagnate since 15 years, and climate change is largely responsible for this

Agroforestry systems have the potential to modify the microclimate of crops grown in agroforestry alleys.

Effet protecteur contreles fortes températures en été

Farmer Henri Breton: « Some years we miss 10% because of tree competition, but other dry and hot years, trees microclimate increase yield by 0.5-1 tonne per hectare as compared to monocrops »

But what about crops ?

Likely impact of trees on crops

• Reduced incoming radiation (shade)– Reduced biomass

– Reduced yield

– Reduced crop temperature and delayed crop phenology

• Shade and sky mask result in a different climate– Reduced daily air temperature range

– Delayed soil warming in spring and cooling in automn

– Reduced soil evaporation and PET

– Reduced radiative frost and dew

• Impact on wind less easy to predict– Reduced average speed

– Possible venturi effect under the pruned trees

– Depends on tree line orientation and wind direction

Likeky impacts of crops on trees

Tillage, fertilisation, weeding, N-fixation by the crops, irrigation may benefit to the trees

But out of the forest, trees are strongly coupled to the atmosphere(transpiration is enhanced)

Subjected to strong mechanical constraints (wind)

Crops may induce contrasted microclimate conditions for treesAir humidity increased by crop transpiration (eg irrigated maize vs dry cereal stubbles)

Soil moisture reduced in the top soil inducing deep rooting

Dual approach :

Field Experiment Numerical modelShort term (5 years) Allow long term studies (100 years)

Imposed rain reductionand temperature increase

Following IPCC predictions

Restinclières farm Hi-sAFe model

IPCC Assessment Report 5scenario RCP85 adjusted to our experimental location

(Clipick sampling tool developped by Palma et al, Agforward project)

Surprise : No significant total annualrainfall change

As expected : 3° increase in maximumdaily temperatures

The LER of AF increases with climate change

Trees behave better in AF than in F with climate change

No significant change for the average RY of crops

Final LER :

PAST : 1.28

PRESENT : 1.32

FUTURE : 1.39

How can we explain crop relative yields in AF?

Small trees Large mature trees

Crop temperature in Monocropping (M) and Agroforestry (AF).

• We need to document the frequency of eventsaffecting crop yields in the past, present and future

Crop stage Stresses

Flower initiation Light reduction, water stress, high temperature

Grain filling Water stress, high temperature

Can we try?

No experiment so far in agroforestry systems, especially mechanized systems.

How to do it?

How to reduce rain?

How to increase temperature?

Rain reduction experiments on forests 2

Eucalypts (Brazil, Itatinga,)Reduction of 30% of the rainfall with permanent guttersSignificant impact on trees

We set up a mobile rain capture device in a mature walnut-wheat agroforestry system in South France. This is a unique experiment so far in Europe.

The system is entirely supported by the trees and is open before each rain that we want to capture. Area : 50 m x 26 m (two alleys)

Vielen Dank für Ihre Aufmerksamkeit

According to the model :

With Climate Change, AF is better

AF trees take advantage of CC, F trees did not

AF crops have more stable yields than monocrops

But we now need the field experiment !

A final word : new research needs

• New varieties adapted to shade

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Gracias por su atención