This study found that shade trees increased the light use efficiency (LUE) of coffee plants by 57% despite decreasing available photosynthetically active radiation (aPAR) by 41%. The 3D light and gas exchange model MAESPA found that the increased LUE under shade trees could only be partially explained by the increase in diffuse light, with changes to microclimate also playing a role. Surprisingly, the net primary productivity of coffee resprouts did not differ between light environments, suggesting a nearly total compensation of productivity despite large reductions in aPAR under shade trees. This level of compensation is rarely observed in other studies but may be possible due to coffee's natural shade tolerance.

1. STRONG SPATIAL VARIABILITY OF LIGHT USE EFFICIENCY IN A COFFEE
AFS, HIGHLIGHTED BY 3D LIGHT AND GAS EXCHANGE MODEL
Fabien Charbonnier1,2,3,4,*, Olivier Roupsard1,4, Fernando Casanoves4, Louise Audebert5,
Elsa Defresnet6, Aurélie Cambou7, Clémentine Alline8, Bruno Rapidel8, Jacques Avelino9,4,
Karel Van den Meersche1,4, Jean-Michel Harmand1, Christophe Jourdan1, Philippe Vaast1,10,
Alejandra Barquero11, Patricia Leandro4 & Erwin Dreyer2,3
1CIRAD,
UMR Eco&Sols (Ecologie Fonctionnelle & Biogéochimie des Sols et des Agro-écosystèmes), 34060 Montpellier Cedex 2, France; 2Université de
Lorraine, UMR 1137 “Ecologie et Ecophysiologie Forestières, F 54500 Vandoeuvre, France; 3INRA, UMR 1137 “Ecologie et Ecophysiologie Forestières”,
F54280 Champenoux, France; 4CATIE (Centro Agronómico Tropical de Investigación y Enseñanza), 7170 Turrialba, Costa Rica; 5Faculté des Sciences,
Université de Lorraine, F 54500 Vandoeuvre, France; 6AGROCAMPUS OUEST, Centre de Rennes, 35042, Rennes Cedex, France; 7ENSAIA, Ecole
Nationale Supérieure d’Agronomie et des Industries Alimentaires, Nancy, France; 8CIRAD, UMR System, 34060 Montpellier, France; 9CIRAD, UPR
Bioagresseurs, F-34398 Montpellier, France; 10ICRAF, United Nations, Avenue Gigiri, PO Box 30677-00100, Nairobi, Kenya; 11Cafetalera Aquiares S.A.,
PO Box 362-7150 Turrialba, Costa Rica

2. Tree/Crop interactions in AFS
SHADE TREES
CROP
ENERGY
???
Ressources
CO2
H20
Nutrients
Conversion
Light Use
efficiency
Efficiency
Species, phenology,
microclimate, plant
architecture, leaf traits…
COMPETITION
COMPLEMENTARITY/FACILITATION
By-products
Respiration
Net Primary
Production

3. LUE, NPP and aPAR
gC resprout-1 year-1
gC MJaPAR-1
LUENPP
NPP
aPAR
NPP = Net Primary Productivity; G = Growth;
L = Litter production; Ex = Exportation
MJaPAR resprout-1 year-1
3
Poorter et al. (2002), Hunt et al. (2001)
3
MAESPA model (Duursma & Medlyn , 2013; Charbonnier et al., 2013)

4. M&M: experimental design
4 YO
4 YO
5 YO
5 YO
3 YO
5 YO
3m
•60 coffee resprouts / 6 age classes / 2 light environments / 5 blocks
•Design of branch, leaf and fruit level allometric relationships
•One biometric measurement every 2 months
• Litter harvest every 15 days
• Coffee fruit harvesting every year
• Monitored during 2 years
• Analyzed with Linear Mixed Models
Modeled light environment in MAESPA (transmittance+aPAR)
Charbonnier et al., Agric. For. Meteorol. (2013)
4

5. NPP of coffee resprouts
NPP - 2 years average
Fruit NPP
NPP (gC resprout-1 Y-1)
600
Leaf NPP
Branch NPP
197
400
157
24
77
0
215
65
119
109
165
162
148
51
15
25
200
On a 2 year basis:
208
230
203
264
213
162
41
42
29
34
108
123
151
155
179
179
82
101
178
83
0
0
1
1
2
2
3
3
4
4
5
5
• Strong age effect on
resprout NPP
• Surprisingly, no effect
of shade on resprout
NPP
On a year to year basis
• Strong biennial bearing under sun
• No biennial bearing under shade
• Shade tree transmittance not
explanatory
5

6. NPPLA & LUENPP of resprouts
Coefficients
NPPLA ( R22=0.24)
Resprout age
Shade tree transmittance
LUENPP (R22=0.37)
Resprout age
Shade tree transmittance
F-value
p-value
109
-0.72
df
5.16
0.0003
NS
90
90
6.43
8.80
0.0001
<0.0039
Example for resprouts
of 4 years old:
6

7. What happened under Shade Trees?
SHADE TREES
+30% diffuse radiation
CROP
-40% aPAR ENERGY
EXPLAINS 20% of the LUE increase
Source: Photosynthesis model in MAESPA
+57%
Ressources
CO2
H20
Nutrients
No significant change
Above-ground
Net Primary
NPP
Production
Below-ground
NPP
Light Use
Efficiency
Specie, microclimates, pheno
•Leaf traits change? Not significant
logy, plant architecture, leaf
•Change in microclimate? Shade trees
traits…
buffer highest temperatures
i.e: -3°C under large Inga densiflora (Siles et al. 2010)
By-products
Respiration
-25% ???
Not significant
Source:Sequential Coring

8. What does the litterature say?
-
Increased LUE is an important phenomenon in AFS
Few studies on LUE because of the difficulty in characterizing aPAR
The nearly total compensation was rarely observed in the litterature:
 +26% for groundnut with a decrease of transmitted light of 50% (Monteith
et al., 1991);
 +27% for millet with a decrease of transmitted light of 50% (Monteith et
al., 1991);
 + 20% for lettuce with a decrease of transmitted light of 33% (Dapoigny et
al., 2000)
 +57% in our study for a 41% decrease of irradiance
-
Our study on LUE is one of the first working with large shade trees prone to
affect significantly local temperatures
-
May be coffee plants are more prone to such behavior because it is a shade
tolerant specie: more efficient photosynthesis at low incident light (Ong et
al., 1991).
8

9. THANK YOU !
THIS EXPERIMENT WAS CONDUCTED WITHIN
FLUXNET/COFFEE-FLUX OBSERVATORY
charbonnier.fabien@gmail.com