european agroforestry federation | euraf - evidences and … · 2012-10-17 · meine van noordwijk...
TRANSCRIPT
Evidences and explanations for the unexpected high productivity of improved
temperate agroforestry systems
1rst EURAF Conference, 9 October 2012
Session 1
Christian Dupraz , Grégoire Talbot
INRA, Montpellier, France
Trees and Agriculture : a change of paradigm ?
Trees inside parcels
Trees around parcels
Around parcels
Inside parcels
5
Innovative Agroforestry
Dual approach : long-term experiments + models
Controlled Experiments
Agroforestry Agri-voltaism
8
2002 : Wageningen seminar
2005 End of SAFE project
2004 : Montpellier Seminar
The Hi-sAFe model : 2002-2011
2007
2011
Christian Dupraz (Inra) Grégoire Vincent (Ird)
Nick Jackson (Nerc) Harry Ozier-Lafontaine (Inra)
Hervé Sinoquet (Inra) Alain Fouéré (Inra)
Martina Mayus (Wageningen) François Bussière (Inra) Isabelle Lecomte (Inra)
Meine Van Noordwijk (Icraf) Betha Lusiana (Icraf)
Benoit Courbaud (Cemagref) Wopke van der Werf
(Wageningen) Hermann Van Keulen
(Wageningen) Gerry Lawson (Nerc)
Jean-Claude Poupa (Inra) François de Coligny (Inra)
Rachmat Mulia (Inra)
Objectives Hypotheses
Specifications
To mix or not to mix : trees and crops/animals…
Forest
Agroforestry
1 ha
Agriculture 0.8 ha
0.6 ha
LER = 1.4 ha
Land Equivalent Ratio (LER) (Mead and Willey, 1980)
Mixture Separation
1996
1997 2002
2005
2003
2009
2010
1.2 to 1.6 Land Equivalent Ratio
Poplars-winter cereals
14 years
A 1.4 LER means that a 100 ha agroforestry farms produces as much crop and tree products as a conventional 140 ha farm where trees and crops are separated
Part of a new green revolution Increased efficiency of natural production factors (light, water, natural nitrogen)
Measured LER for agrivoltaic systems with various densities of PV panels
1.3 to 1.7
Dupraz et al, 2011, Renewable Energy 36: 2725-2732
2003
2009
Solving the tree shade shape riddle
17
21 June
21 December 21 March / 21 September
Average irradiation under an isolated tree
Integrated irradiation under a tree stand
Light capture (40 years)
Light interception Land Equivalent Ratio : Walnut trees : 0.73 Winter wheat : 0.66 Light LER = 1.39
0 10 20 30 40 0 10 20 30 400 10 20 30 40
020
4060
8010
0 Pure crop Agroforestry Pure trees
% o
f inc
iden
t rad
iatio
n,
Year
Walnut trees Winter wheat Not captured
Water budget (40 years)
Water capture Land Equivalent Ratio : Walnuts : 0.71 Wheat : 0.84
Water LER = 1.55
Inputs: Rain Water table
Outputs Wheat transpiration Walnut transpiration Understorey transpiration Soil evaporation Drainage Run-off
A AF F
Wat
er fl
uxes
(mm
/yea
r)
0 20
0 40
0 60
0 80
0
A AF F
Inputs Outputs
22
Pure walnut grove Walnut wheat Agroforestry
Root profiles of 14 year old walnut trees (November 2009)
Experimental measures
Tree roots systems influenced by crop competition
23
Agroforestry tree
12 years
Forest tree
6 ans
Model predictions
0 10 20 30 40
02
46
8
0 10 20 30 40
02
46
8
Wheat yields predicted
Blé précoce Blé tardif
Année Année
Yiel
d (t
.ha-
1 )
• Pure wheat : high variability in yields
Témoin agricole
Model predictions
0 10 20 30 40
02
46
8
0 10 20 30 40
02
46
8
Wheat yields in agroforestry
AF Late walnut AF Early walnut
Témoin agricole
Année Année
• AF : yield and variability (more impact of early walnut)
Yiel
ds (
t.ha-
1 )
Early wheat Late wheat
Model predictions
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0 0.5 1 1.5 2Tree crowding index
Rel
ativ
e cr
op y
ield
Vézénobres_1996 Vézénobres_1997 Restinclières_East-West Restinclières_North-South
Research for action : guidelines for improved AF systems
Looking for the best tree density
Experimental measures
LER interpretation
• LERs can be simulated with process-based models • The simulations allow to decompose the LER in various
interacting effects • This is a way to hierarchy factors of success in agroforestry
and agrivoltaism
Talbot, 2011, Ph. D. thesis (Env. Model. Soft. In press)
LER interpretation for a walnut-wheat AF system
Land Equivalent Ratio : Walnuts : 0.76 Wheat : 0.52
LER = 1.28
Modelling the 3 options concurrently
7m 7m
4m 4m
1m
Pure crop Pure tree
Same soil Same climate
Same management 40 years
Spontaneous understorey
4m
9m 13m
1 m
Decomposing the LER
• LER= Rytree + Rycrop
• RY =π[relative indexes] • Exemple of decomposition :
• RY = Relative density x Size Memory x Light competition x Water competition x Harvest Index
Decomposing the relative yield of trees
Interception light: • a : interception capacity • i : competition
Conversion into biomass: • p : leaf aging • w : water stress
Harvest ratio • ha : ABG/BG allocation • hs : Trunk allocation
yind a i p w ha hs
Relative Yield per tree
-0.4 0.0 0.4 0.8
Decomposing the relative yield of trees
yind a i p w ha hs
Relative Yield per tree
-0.4 0.0 0.4 0.8
Decomposing the relative yield of trees
19 m x 19 m 19 m x 11 m 11 m x 9 m 11 m x 5 m 7 m x 7 m
yind a i p w ha hs
-0.4 0.0 0.4 0.8
Interception capacity (leaf area, leaf duration)
Decomposing the relative yield of trees
19 m x 19 m 19 m x 11 m 11 m x 9 m 11 m x 5 m 7 m x 7 m
yind a i p w ha hs
-0.4 0.0 0.4 0.8
Light competition • On the tree line space essential
19 m x 19 m 19 m x 11 m 11 m x 9 m 11 m x 5 m 7 m x 7 m
Decomposing the relative yield of trees
yind a i p w ha hs
-0.4 0.0 0.4 0.8
C Allocation to trunk: • Negative • Large canopies -> C allocated to branches
Decomposing the relative yield of trees
19 m x 19 m 19 m x 11 m 11 m x 9 m 11 m x 5 m 7 m x 7 m
Decomposing the crop yield
Light Interception : • a : interception capacity • i : competition by trees
Conversion to biomass : • p : phenology • n : nitrogen stress • s : light saturation • t : temperature stress • w : water stress
Harvest index • g : grain filling duration • u : thermal stress • f : grain number
-40 -30 -20 -10 0 10
y a i p n w s t g u f
0.0 0.5 1.0 1.5 2.0 2.5 3.0
-1.0
-0.5
0.0
0.5
1.0
1.5
Log(
Ren
dem
ent r
elat
if)
LAI peuplement noyers (m2.m-2)
Relative yield
Decomposing the crop yield
Relative Yield
0.0 0.5 1.0 1.5 2.0 2.5 3.0-1
.0-0
.50.
00.
51.
01.
5Lo
g(R
ende
men
t rel
atif)
LAI peuplement noyers (m2.m-2)
-40 -30 -20 -10 0 10
Walnut Early Late
Whe
at
Late
Ear
ly
y a i p n w s t g u f
Decomposing the crop yield
Light Competition : • Major and negative effect • Strong under early walnut
0.0 0.5 1.0 1.5 2.0 2.5 3.0
-1.0
-0.8
-0.6
-0.4
-0.2
0.0
LAI peuplement noyers (m2.m-2)
Log(
i) 44
-40 -30 -20 -10 0 10
y a i p n w s t g u f
Decomposing the crop yield Walnut
Early Late
Whe
at
Late
Ear
ly
Water Stress Thermal Stress during grain filling
-40 -30 -20 -10 0 10
y a i p n w s t g u f
Decomposing the crop yield Walnut
Early Late
Whe
at
Late
Ear
ly
Interception capacity • Delayed senescence
TA
AF
-40 -30 -20 -10 0
y a i p n w s t g u f
Decomposing the crop yield Walnut
Early Late
Whe
at
Late
Ear
ly
Number of grains
-40 -30 -20 -10 0 10
y a i p n w s t g u f
Decomposing the crop yield Walnut
Early Late
Whe
at
Late
Ear
ly
If the model is right…
Advantages in AF Drawbacks in AF Neutral
Trees Larger canopies
Less light competition
Few trees
Invest C in roots
Water stress
WinterCrops
Reduced water stress
Longer life of leaves
Reduced N stress
Reduced heat stress
Reduced cropped area
Less light
Harvest index (?)
Integrated over 40 years
But what dynamics during the 40 years?
0,0
0,3
0,5
0,8
1,0
1,3
1,5
1,8
2,0
0 5 10 15 20 25 30 35 40Years
Land
Equ
ival
ent R
atio
AnnualIntegrated
Association type Plant Cycles Soil depth
Root segre-gation
Water body in summer
Probable LER
Walnut-cereal on plains with a water table
Almost complementary
Deep High Yes 1.5
Sorbus-wheat Lagged Medium Intermediate No 1.4
Prunus-Medicago Close Deep Intermediate No 1.3
Prunus-sunflower Synchronous Shallow Poor No 1.2
Populus-maize Synchronous Poor No Yes 1.1
Evergreen tree and summer crop
Superposed Any Variable No 1.0
Never demonstrated so far <1.0
A synthesis of probable LERs of temperate AFs
Conclusions
• LERs of AFs may be extremely high (part of a second green revolution?)
• Process-based models can help in interpreting productivity results of AF systems at various time steps.
• Winter crops better in AF (temperate latitudes-specific)
Pending : more virtual experiments
11 m x 9 m 100 stems/ha
11 m x 5 m 180 stems/ha
7 m x 7 m 200 tiges/ha (forest control) 19 m x 11 m
50 stems/ha
19 m x 19 m 30 stems/ha
Tree density and plantation design
Pending : more virtual experiments
AF and Climate change : are crops in AF protected against climate change hazards ?
Pending : System management optimisation assisted by modelling
Tree line orientation North-South / East-West
133 trees.ha-1 64 trees.ha-1
10 10
10
10
6
6 6
6
NS NS EW EW
Pruning height : 10 m versus 6 m
Tree density
Pending : Designing enhanced and innovative agroforestry systems
Biomass production in agroforestry Various tree managements (pollarding, root trenching, precision fertilisation…) Mixtures of tree species
Merci