Tropical Agroforestry

23 Pages·2013·1.1 MB·English

Tropical Agroforestry
Alain Atangana • Damase Khasa
Scott Chang • Ann Degrande
Tropical Agroforestry
1 3
Alain Atangana Scott Chang
Renewable Resources Renewable Resources
University of Alberta University of Alberta
Edmonton Edmonton
Canada Canada
Institute of Integrative Ann Degrande
and Systems Biology West and Central Africa Regional Program
Université Laval World Agroforestry Centre
2208 Pavillon C.-E. Marchand Yaounde
Quebec G1V 0A6 Cameroon
Canada
Damase Khasa
Forest and Wood Sciences
Université Laval
Quebec
Canada
ISBN 978-94-007-7722-4 ISBN 978-94-007-7723-1 (eBook)
DOI 10.1007/978-94-007-7723-1
Springer Dordrecht Heidelberg London New York
Library of Congress Control Number: 2013951527
© Springer Science+Business Media Dordrecht 2014
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Preface
Agroforestry, the deliberate introduction or retention of trees on farmlands, is wide-
ly recognized as a sustainable land-use management practice, including for tropi-
cal landscapes that are threatened as a result of non-sustainable land-use practices.
There is a need to promote environmentally friendly land management practices
and tropical ecosystems that provide local people with their everyday needs for
food, cash, shelter and medicine, among others. Agroforestry is a land-use prac-
tice that has come of age. Agroforestry techniques have been practiced traditionally
worldwide for millennia. Since the recognition of agroforestry as a discipline of
agricultural science, numerous institutions have been dedicated to agroforestry re-
search either on a global scale (e.g., the World Agroforestry Centre, formerly known
as the International Centre for Research in Agroforestry, ICRAF) or regionally. In
addition, agroforestry curricula have been developed for undergraduate and gradu-
ate trainings in many universities. Agroforestry practices have been particularly
popular in the tropics.
Despite rapid developments in agroforestry practices and improvements in agro-
forestry theory, textbooks on tropical agroforestry are lacking. The authoritative
textbook on agroforestry by Nair (1993) was published 20 years ago, and that was
before the advent of tree domestication, an important agroforestry practice today. In
addition, many other research activities and emerging issues, such as agroforestry
for integrated pest management, biofuel production, carbon sequestration, mitiga-
tion of climate change and REDD + (reducing emissions from deforestation and for-
est degradation, including conservation and sustainable management of forests and
the enhancement of forest carbon stocks) mechanism, have become prominent in
the agroforestry agenda of recent years. Therefore, there is an urgent need to de-
velop and make available up-to-date educational material on tropical agroforestry
for teaching agroforestry to students in agroforestry programs in general, and to
students in tropical regions in particular. This textbook strives to provide up-to-date
information on tropical agroforestry and, thus, to provide educational material spe-
cific to the tropical context.
This textbook is intended for agroforestry students, teachers and practitioners.
This textbook is divided into five main parts. Part I describes the tropical biomes
and the traditional land-use systems practiced in the tropics. It also highlights the
v
vi Preface
negative impact of non-sustainable land-use systems on land and forest resources.
This background is followed by an introduction to agroforestry, including the ra-
tionale, history and definition of agroforestry, and the description of major agro-
forestry systems that are found in the humid and semiarid tropics. Agroforestry
tree domestication in the tropics constitutes the fourth and last chapter of the first
part of the textbook. In Part II, the benefits and services of agroforestry systems,
including tree-crop interactions, nitrogen fixation and mycorrhizal associations, soil
conservation, carbon sequestration, biodiversity and integrated pest management in
agroforestry are discussed. Research methods in agroforestry, including diagnosing
methods, experimental design and on-farm research are covered in Part III. Part IV
deals with economic and cultural considerations in agroforestry. The last section,
Part V, provides an outlook on agroforestry in the 21st century. Lastly, this part cov-
ers biofuel production, phytoremediation, carbon markets, and modeling in tropical
agroforestry.
As this is the first edition of the textbook, errors and omissions are unavoid-
able. The authors would greatly appreciate feedback from readers, instructors,
and students who use this textbook for their agroforestry classes. Suggestions
and comments can be sent to any of the four authors: [email protected]
(ARA), [email protected] (DPK), [email protected] (SXC)
and [email protected] (AD).
The authors
Acknowledgments
The completion of this textbook was mainly supported by the International Office
of the Department of Foreign Affairs, Trade and Development Canada (former-
ly the Canadian International Development Agency (CIDA)) through a project
on training and management of natural resources in the Congo Basin (FOGRN).
The CIDA-funded project was a collaborative effort led by Université Laval with the
aim of strengthening forestry and agroforestry training in three countries most rep-
resentative of the Congo Basin: Democratic Republic of Congo (DRC), Cameroon
and Gabon. Project partners were the University of Alberta, Centre d’enseignement
et de recherche en foresterie (CERFO), Oxfam-Québec (Canada), and eight insti-
tutions in the Congo Basin: University of Dschang and École nationale des eaux
et forêts-ENEF (Cameroon); École nationale des eaux et forêts-ENEF (Gabon);
the Institut supérieur d’études agronomiques (ISÉA) de Tshéla, Institut supérieur
agro-véterinaire (ISAV) Kimwenza, Université de Kinshasa, and the École régio-
nale d’aménagement intégré des forêts et territoires tropicaux-ERAIFT (DRC); and
the Réseau des institutions de formation forestière et environnementale d’Afrique
centrale-RIFFEAC (Cameroon). We are indebted to CIDA for funding this project.
We also acknowledge the Natural Sciences and Engineering Research Council of
Canada (NSERC) for partially supporting this work through funding to the Univer-
sity of Alberta (SXC) and Université Laval (DPK).
Many people provided photos for this textbook. We thank Prof. Roger Leakey,
Drs. Serge Bobo Kadiri (University of Dschang), Jules Bayala (ICRAF), and Pierre-
Marie Mapongmetsem (University of Ngaoundéré, Cameroon) for their support. We
also thank Dr. Bill Parsons (Centre for Forest Research, University of Sherbrooke,
Canada) and Ms. Kether Hayden for providing language editing of earlier drafts
of this textbook. Dr. Estelle Campagnac (IBIS, Université Laval) provided useful
comments on an earlier draft of the eightieth chapter of this textbook. Dr. Julie
Godbout provided drawings for this textbook.
The authors
vii
Table of Contents
Part I Tropical Biomes, Land Use Issues and Introduction to
Agroforestry Systems
1 Tropical Biomes: Their Classification, Description and Importance .... 3
1.1 Tropical biomes: Classification and Description .............................. 3
1.1.1 Classification of Biomes Based on Climate ......................... 4
1.1.2 Other Classification Systems of Biomes .............................. 8
1.1.3 Main Tropical Humid and Semiarid Biomes ........................ 12
1.2 T he Importance of Tropical Forest and Semiarid Ecosystems ......... 18
Bibliography .............................................................................................. 20
2 Major Land Use Issues in the Tropics, and the History
of Agroforestry ........................................................................................... 23
2.1 Introduction ...................................................................................... 23
2.1.1 Impacts of Traditional Natural Resource Use on
Tropical Ecosystems ............................................................. 24
2.1.2 History of Agroforestry ........................................................ 27
Bibliography .............................................................................................. 31
3 Definitions and Classification of Agroforestry Systems ......................... 35
3.1 Introduction ....................................................................................... 35
3.1.1 Definition of Agroforestry .................................................... 35
3.1.2 Some Basic Concepts in Agroforestry .................................. 37
3.1.3 Classification of Agroforestry Systems ................................ 38
Bibliography .............................................................................................. 47
4 Major Agroforestry Systems of the Humid Tropics ................................ 49
4.1 Introduction ...................................................................................... 49
4.2 Homegardens .................................................................................... 55
4.2.1 Intensive Small-Scale Farming Systems .............................. 61
4.3 Perennial Crop Based Agroforestry Systems ................................... 63
4.3.1 Jungle Rubbers (Rubber Agroforests) .................................. 69
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4.4 Farm Woodlots ................................................................................. 70
4.5 Annual or Biennial Food Crop Farms: S lash-and-Burn Agriculture .... 71
4.5.1 A lley Cropping/Intercropping Systems ................................ 73
4.6 Improved Fallows and Rotational Tree Fallows .............................. 82
4.6.1 Improved Fallows with Herbaceous Legumes:
the Case of Cajanus cajan .................................................... 83
Bibliography .............................................................................................. 88
5 Major Agroforestry Systems of the Semiarid Tropics .......................... 95
5.1 Introduction ...................................................................................... 95
5.2 Annual or Biannual Food Crop Farms in the Semiarid
Tropics: Shifting Cultivation ............................................................ 96
5.3 Multipurpose Trees on Farmlands: Agroforestry Parklands ............. 97
5.4 Silvopastures ..................................................................................... 99
5.4.1 Fodder Trees and Shrubs .................................................... 100
5.5 Windbreaks ..................................................................................... 100
5.5.1 Trees Used as Windbreaks .................................................. 106
5.6 Live Fences ..................................................................................... 106
5.7 Buffer Strips .................................................................................... 107
Bibliography ............................................................................................ 108
6 Participatory Domestication of New Crops
using Agroforestry Techniques ............................................................. 111
6.1 Introduction .................................................................................... 111
6.1.1 History of the Participatory Domestication
of Agroforestry Species ...................................................... 112
6.1.2 Participatory Domestication as Implemented
by ICRAF and its Partners .................................................. 114
6.1.3 Priority Species for Domestication .................................... 121
Bibliography ............................................................................................ 140
Part II The Benefits and Services of Agroforestry Systems
7 Ecological Interactions and Productivity
in Agroforestry Systems ........................................................................ 151
7.1 Introduction .................................................................................... 151
7.2 Interactions of Components in Agroforestry Systems .................... 151
7.2.1 Positive Interactions ........................................................... 153
7.2.2 Negative Interactions ......................................................... 154
7.2.3 Neutral Interactions ............................................................ 156
7.3 Soil Productivity in Agroforestry .................................................... 157
Bibliography ............................................................................................ 168
Table of Contents xi
8 Biological Nitrogen Fixation and Mycorrhizal Associations
in Agroforestry ....................................................................................... 173
8.1 Introduction .................................................................................... 173
8.2 Plant Species Forming Associations with Rhizobium or
Mycorrhizal Fungi .......................................................................... 174
8.2.1 Acacia Sensu Lato .............................................................. 177
8.2.2 Albizia ................................................................................ 179
8.2.3 Calliandra calothyrsus ....................................................... 180
8.2.4 Erythrina ............................................................................. 180
8.2.5 Gliricidia sepium ............................................................... 181
8.2.6 Inga edulis ........................................................................... 183
8.2.7 Leucaena leucocephala ...................................................... 183
8.2.8 Mimosa ............................................................................... 185
8.2.9 Sesbania .............................................................................. 186
8.3 A ctinomycorrhizal Plants ............................................................... 186
8.3.1 Alnus acuminata (syn. Alnus jorullensis) .......................... 187
8.3.2 Casuarinaceae ..................................................................... 187
8.3.3 Coriaria ............................................................................... 187
8.4 Quantification of Nitrogen Fixation ............................................... 188
8.4.1 Total Nitrogen Difference .................................................. 188
8.4.2 Acetylene Reduction Assay ................................................ 188
8.4.3 1 5N Enrichment ................................................................... 189
8.4.4 Natural Abundance in 15N .................................................. 189
8.4.5 Sap Nitrogen Solute Analysis ............................................. 189
8.5 Technologies for the Exploitation of Nitrogen-Fixing
Mycorrhizal Plants in Agroforestry ................................................ 190
8.5.1 Selecting Species and Provenances of Nitrogen-
Fixing Trees ........................................................................ 191
8.6 Areas of Research Concerning Nitrogen Fixation
and Mycorrhizae in Agroforestry .................................................... 193
Bibliography ............................................................................................ 194
9 Agroforestry for Soil Conservation ...................................................... 203
9.1 Introduction .................................................................................... 203
9.2 Concepts and Trends in Soil Conservation .................................... 204
9.3 Measurement of Soil Erosion ......................................................... 204
9.4 Erosion Control Using Agroforestry Practices ............................... 207
9.5 Effects of Agroforestry Practices on Erosion Factors ..................... 208
9.5.1 Soil erodibility .................................................................... 209
9.5.2 Runoff reduction: ................................................................ 209
9.5.3 Soil cover ............................................................................ 209
9.6 Erosion Rates in Agroforestry Systems .......................................... 210
9.7 W indbreaks for Erosion Control ..................................................... 211
9.8 Anticipated Costs and Benefits of Windbreaks
for Soil Conservation ...................................................................... 214
Bibliography ............................................................................................ 214
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10 Carbon Sequestration in Agroforestry Systems .................................. 217
10.1 Introduction .................................................................................. 217
10.2 T he Potential for C Sequestration in Agroforestry Systems ......... 218
10.3 Agroforestry and REDD ............................................................... 222
Bibliography ............................................................................................ 224
11 Agroforestry and Biodiversity Conservation
in Tropical Landscapes ........................................................................... 227
11.1 Introduction .................................................................................. 227
11.2 T he Agroforestry and Deforestation Hypothesis .......................... 228
11.3 The Agroforestry—Habitat Hypothesis ........................................ 229
11.4 The Agroforestry-Matrix Hypothesis ........................................... 231
Bibliography ............................................................................................ 232
12 Integrated Pest Management in Tropical Agroforestry ...................... 233
12.1 Pests in Tropical Agroforestry Systems ........................................ 233
12.2 Agroforestry Practices for Pest Management ............................... 237
12.3 Research Areas on Pest Management Using Agrofor-
estry Techniques ........................................................................... 238
Bibliography ............................................................................................ 240
Part III Research Methods in Agroforestry
13 Diagnosis and Design (D & D) Approach and Participatory
Rural Appraisal (PRA) .......................................................................... 243
13.1 Introduction .................................................................................. 243
13.2 T he D & D method ....................................................................... 244
13.3 Main Concepts and Procedures of the D & D Method ................ 246
13.4 Scales of D & D ........................................................................... 246
13.5 Participatory Rural Appraisal in Agroforestry .............................. 249
13.6 Evaluating Agroforestry Technologies ......................................... 251
Bibliography ............................................................................................ 255
14 Experimental Design in Agroforestry .................................................. 259
14.1 Agroforestry Research .................................................................. 259
14.2 Experimentation in the Field ........................................................ 262
14.3 Particularities of Agroforestry Experiments ................................. 263
14.3.1 S ize and Arrangement of the Plot ................................... 264
14.3.2 E xperimental Designs .................................................... 264
14.4 On-going Field Agroforestry Experiments in the Tropics ............ 270
14.4.1 S creening and MPTS Selection Tests ............................ 271
14.4.2 E xperiments on Management of Systems and
Components ................................................................... 272