Impact of host composition and shade tree spatial structure on pest infestation in cocoa agroforests

Cynthia Gidoingidoin@supagro.inra.fr

UR 106

Marie Ange Ngo Bieng, Christian Cilas, Rgis Babin, Martijn ten Hoopen, Leila Bagny Beilhe

18 August 2013 the 11th INTECOL Congress.

Montpellier FranceYaound, Cameroon

Ecosystem servicesMultispecies agroecosystems

Avelino et al. 2011 ; Ratnadass et al., 2012 ; Maleizeux et al., 20082

Cacao agroforests

Ecosystem servicesMultispecies agroecosystems

Complexvegetation structure

Avelino et al. 2011 ; Ratnadass et al., 2012 ; Maleizeux et al., 20083

Cacao agroforests

Ecosystem servicesMultispecies agroecosystems

Complexvegetation structure?

Avelino et al. 2011 ; Ratnadass et al., 2012 ; Maleizeux et al., 20084

Cacao agroforests

Ecosystem servicesMultispecies agroecosystems

Complexvegetation structure?

Pest

Avelino et al. 2011 ; Ratnadass et al., 2012 ; Maleizeux et al., 20085

Cacao agroforests

PestMirids

S. singularis

Chocolate

Pod

cacaoComplexvegetation structure

Crop

Ploetz 2007 ; Babin 20096

Ligneous

Vertical structure

Horizontalstructure

Multi strata Not regular

Crop

Cacao agroforests S. singularis

Pod

cacao

Chocolate

Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 20097

PestMirids

Pod

Microclimate Resource

Vertical structure

Horizontalstructure

Multi strata Not regular

Crop

Cacao agroforests S. singularis

Shade

- -

-

Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 20098

PestMirids

Ligneous spatial structure

Microclimate Resource

Vertical structure

Horizontalstructure

Multi strata Not regular

Cacao agroforests S. singularis

Shade

- -

Host composition

Pod

Crop

-

-

AbundanceDensity

Host composition

Stephens et al. 2012 ; Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 20099

PestMirids

Ligneous spatial structure

Microclimate Resource

Vertical structure

Horizontalstructure

Multi strata Not regular

Cacao agroforests S. singularis

Shade

- -

Host composition

Pod

Crop

-

-

AbundanceDensity

Host composition

Alternativehost

Cola spp.

+

+

Stephens et al. 2012 ; Malezieux et al., 2008 ; Schroth et al., 2004; Ploetz 2007 ; Babin 200910

PestMirids

Ligneous spatial structure

Microclimate Resource

Vertical structure

Horizontalstructure

Multi strata Not regular

Cacao agroforests S. singularis

Shade

- -

Host composition

Pod

Crop

-

-

AbundanceDensity

Host composition

Alternativehost

Cola spp.

+

+

1- What are the independent effects and relative importance of host composition and shade tree spatial structure in mirid density at the plot scale ?

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

Ligneous spatial structure

11

PestMirids

Yaound

Obala

Centre

7m

Sampling unit: 50 x 50 m

Plot (x 20)

Cacao

Fruit tree

Forest tree

Dcov %Fo HSfo HSfu

Plant spatial structure

Cacao agroforests

12

Dcov %Fo HSfo HSfu

7m

Plot (x 20)

Cacao

Fruit treeAggregated RandomLow density

Forest trees (HSfo)

Fruit trees (HSfu)

Low density/Random/Regular

Ripleys function Typology

Sampling unit: 50 x 50 m

Forest tree

Plant spatial structure

Cacao agroforests

Ripley 1977 ; Ngo Bieng et al., 201313

Dcov %Fo HSfo HSfuPlot (x 20)

Cacao 7 m

Sampling unit: 50 x 50 m

Cacao tree abundanceCacao tree densityCola spp. DensityProduction

Cola spp.

Plant spatial structure

Cacao agroforests

Host composition

Abca Dca Dcola Prod

14

Plot (x 20)

Cacao

Mirid density Cola spp.

x 80

2011 and 2012

Cacao tree abundanceCacao tree densityCola spp. DensityProduction

Cacao agroforests

Sampling unit: 50 x 50 m

Dcov %Fo HSfo HSfu

Plant spatial structureHost composition

Abca Dca Dcola Prod

15

Mirid density

Hierarchical partitionning

More causal factor explaining mirid density ?

Y ~ Xi Ri : total variance explained

Ri = Ii + Ji

I : Independent contributionJ : Joint contribution

Xi collinearity

Y

Xi : Host composition

Abca Dca Dcola Prod Dcov %Fo HSfo HSfu

Plant spatial structure

Mac Nally 2000

1- What are the independent effects and relative importance of host composition and shade tree spatial structure in mirid density at the plot scale ?

16

56.38 %

Hierarchical partitionning

15

10

5

0

13.9%

Dcov %Fo HSfo HSfu

Plant spatial structure

Mirid density% variance explained

21 % 79 %

Host composition

49%12.0%

IndependentJoint

Abca Dca Dcola Prod

1- What are the independent effects and relative importance of host composition and shade tree spatial structure in mirid density at the plot scale ?

17

56.38 %

12.0%

13.4%

Dcov %Fo HSfo HSfu

Hierarchical partitionning

-Mirid density% variance explained

Plant spatial structure

R2 = 0.22

Plant spatial structureVertical structure

%Fo

Log(

Dm

ir)

00 100%Fo

F = 10.8**

4

2

Forest ratherthan fruit trees

18

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

Forest ratherthan fruit trees 56.38 %

12.0%

13.4%

Dcov %Fo HSfo HSfu

Hierarchical partitionning

Plant spatial structure

R2 = 0.22

Plant spatial structureVertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Aggregated RandomLow density

Log(

Dm

ir)Lo

g(D

mir)

00 100%Fo

F = 10.8**

4

2

Mirid density% variance explained

F = 3.9* Randomrather thanaggregated

R2 = 0.17

-

19

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

Hierarchical partitionning

R2 = 0.22

Plant spatial structureVertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Aggregated RandomLow density

R2 = 0.17

Log(

Dm

ir) F = 3.9*

Log(

Dm

ir)

00 100%Fo

F = 10.8**

4

2

Babin et al., 2010

- Homogeneous shadeForest rather

than fruit trees

Randomrather thanaggregated

20

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

%trans.light

Mirid/cacao

Hierarchical partitionning

R2 = 0.22

Plant spatial structureVertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Aggregated RandomLow density

Log(

Dm

ir)Lo

g(D

mir)

00 100%Fo

F = 10.8**

4

2

- Homogeneous shade

Architectural characteristics

Our data

Babin, 2009

R2 = 0.17

F = 3.9*

Forest ratherthan fruit trees

Randomrather thanaggregated

Fu

Fo

20

5Cro

wn

heig

ht(m

)21

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

Hierarchical partitionning

R2 = 0.22

Plant spatial structureVertical structure

Horizontal structure

%Fo

HSfo

ab b

3,5 2,7 2,1

a

Aggregated RandomLow density

Log(

Dm

ir)Lo

g(D

mir)

00 100%Fo

F = 10.8**

4

2

- Homogeneous shade

% light variance reduction

Martens, 2009

40%

3

16

80%Canopy cover

2- What is the vegetation structure of agroforest to promote in order to reduce the mirid density at the plot scale.

R2 = 0.17

F = 3.9*

Forest ratherthan fruit trees

Randomrather thanaggregated

Architectural characteristics

Our data

Babin, 2009

Fu

Fo

20

5Cro

wn

heig

ht(m

)

PA

R v

aria

nce

(.10

6 )

22

Host composition

Microclimate

Mirids pest

Ligneous spatial structure

Resource

Vertical structure

Horizontalstructure

Crop

AbundanceDensity

Amount

cacao

Shade

-

Alternativehost

Cola spp.Forest ratherthan fruit trees

Random ratherthan aggregated

79%21%

ConclusionSignificance of the study: Mirid density is more explained by shade tree spatial structure than by host composition. Promoting forest trees randomly distributed.

23

Pod

Host composition

Microclimate

Mirids pest

Ligneous spat