Trophic interactions of ants, birds and bats affecting crop yield along shade gradients in tropical

168 Pages·2015·8.64 MB·English

by  Pierre Gras

Trophic interactions of ants, birds and bats affecting crop yield
along shade gradients in tropical agroforestry

Dissertation
zur Erlangung des Doktorgrades
der Mathematisch-Naturwissenschaftlichen Fakultäten
der Georg-August-Universität Göttingen

im Promotionsprogramm
Biologische Diversität und Ökologie

vorgelegt von
Pierre Gras
geboren in Peine
Göttingen, November 2014

Promotionsausschuss:
Prof. Dr. Teja Tscharntke (Agrarökologie, Georg-August-Universität Göttingen)
PD Dr. Yann Clough (Centre for Environmental and Climate Research, Lund University)
Prof. Dr. Stefan Vidal (Agrarentomologie, Georg-August-Universität Göttingen)

Tag der mündlichen Prüfung: 10.12.2014

Contents
Chapter 1: The value of tropical agroforestry for ecosystem service provision,
nature conservation and agricultural productivity ........................................... 9
Introduction ............................................................................................................................................ 11
Chapter outline ....................................................................................................................................... 16
References ............................................................................................................................................... 19
Chapter 2: How ants, birds and bats affect crop yield along shade gradients
in tropical agroforestry ................................................................................... 23
Summary ................................................................................................................................................. 25
Introduction ............................................................................................................................................ 26
Material and methods ............................................................................................................................ 27
Site selection and gradients .............................................................................................................. 27
Exclusion treatments ........................................................................................................................ 28
Sampling and surveying methods ................................................................................................... 28
Statistical analyses .............................................................................................................................. 30
Results...................................................................................................................................................... 31
Effects of predator exclusion, canopy cover and distance to forest on cacao yield ................ 31
Ant exclusion ..................................................................................................................................... 32
Bird exclusion .................................................................................................................................... 33
Bat exclusion ...................................................................................................................................... 33
Ant and bird diversity along the canopy cover and forest distance gradient ........................... 35
Discussion ............................................................................................................................................... 37
Canopy-cover dependent effects of ants ....................................................................................... 37
Bird exclusions can decrease or increase yields depending on canopy cover ........................... 38
Bats ...................................................................................................................................................... 39
Study limitations and caveats ........................................................................................................... 39
Management recommendations ...................................................................................................... 40
Acknowledgements ................................................................................................................................ 40
References ............................................................................................................................................... 41
Supporting information - Chapter 2 ................................................................................................... 45
Fig. S1. Schematic experimental design. ........................................................................................ 46
Table S2. Non-crop tree species within chemical application free area. ................................... 47
Table S3. Herbal plant species. ........................................................................................................ 50
Table S4. Discovered ant species. ................................................................................................... 53
Table S5. Discovered bird species. ................................................................................................. 55
Table S6. Ant and bird community. ............................................................................................... 57
Fig S7. Open bat exclusion. ............................................................................................................. 58
Fig. S8. Conical-shaped ant exclusion rings (without insect glue). ............................................ 59
Table S9. Potentially yield influencing variables (additional to the predator exclusion). ........ 60
Table S10. Characteristics of experimental trees and plantations at treatment level. .............. 63
Table S11. Fruit development categories. ...................................................................................... 67
Table S12. Pest and disease categories. .......................................................................................... 67
S13 ANOVA Tables ......................................................................................................................... 68
Fig. S14. RDA – Management, landscape, and predator access manipulation influences on the
ant community composition (morpho species level). .................................................................. 86
Figure A: canopy cover:.................................................................................................................... 86
Fig. S15. RDA – Management and landscape effects on the bird community (species level).
.............................................................................................................................................................. 87
Fig. S16. Visualization of bird and ant community composition related to shade cover and
forest distance. ................................................................................................................................... 88
Table S17. Bat species ....................................................................................................................... 89
Table S18 Agroforest description ................................................................................................... 91
Chapter 3: Resource distribution changes species-specific trophic positions
and ecosystem service provision of omnivorous ants .................................... 93
Summary ................................................................................................................................................. 95
Introduction ............................................................................................................................................ 95
Material and methods ............................................................................................................................ 96
Study sites and ant colony establishment. ...................................................................................... 96
Sampling and survey methodology ................................................................................................. 97
Statistical analyses ............................................................................................................................ 100
Results.................................................................................................................................................... 101
Discussion ............................................................................................................................................. 105
Acknowledgements .............................................................................................................................. 109
References ............................................................................................................................................. 110
Supporting information - Chapter 3 ................................................................................................. 115
List S1 Present plant species (all plantations).............................................................................. 116
Table S2 Fruit phenology categories. ........................................................................................... 117
Table S3 Ant colony size. ............................................................................................................... 118
Description S4 Pre-experiment life cycle D. thoracicus and P. cf. cordata .................................. 118
Chapter 4: Multi-scale intensification changes trophic position of omnivores
in tropical agroforestry .................................................................................. 119
Summary ............................................................................................................................................... 121
Introduction .......................................................................................................................................... 122
Material and methods .......................................................................................................................... 123
Study sites ......................................................................................................................................... 123
Sampling and analysing methods .................................................................................................. 124
Statistical analyses ............................................................................................................................ 125
Results.................................................................................................................................................... 127
Discussion ............................................................................................................................................. 130
Conclusion ............................................................................................................................................ 133
Acknowledgements .............................................................................................................................. 133
References ............................................................................................................................................. 134
Supporting information ...................................................................................................................... 139
Supporting information - Chapter 4 ................................................................................................. 140
Fig. S1. Unstandardized δ15N values of all ant (morpho-) species. ........................................ 141
Fig. S2. Unstandardized δ13C values of all ant (morpho-) species. ......................................... 142
Chapter 5: Intra-specific plasticity in dietary resource-use maintains inter-
specific complementarity in natural ant communities ................................. 145
Summary ............................................................................................................................................... 147
Introduction .......................................................................................................................................... 147
Material and methods .......................................................................................................................... 148
Study sites ......................................................................................................................................... 148
Sampling and analysing methods .................................................................................................. 149
Statistical analyses ............................................................................................................................ 150
Results.................................................................................................................................................... 150
Discussion ............................................................................................................................................. 153
Acknowledgments ............................................................................................................................... 155
References ............................................................................................................................................. 155
Supporting information - Chapter 5 ................................................................................................. 157
Thesis summary ............................................................................................. 159
Danksagung ................................................................................................... 163
Curriculum vitae ............................................................................................ 165
Thesis declarations ........................................................................................ 167
8 / 168
Chapter 1: The value of tropical agroforestry for ecosystem service
provision, nature conservation and agricultural productivity

The Palolo valley harbours a hilly, agroforestry-dominated landscape with large paddy fields in the
flat areas.

9 / 168
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