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CARBON SEQUESTRATION POTENTIAL OF AGROFORESTRY SYSTEMS

IN THE WEST AFRICAN SAHEL:

AN ASSESSMENT OF BIOLOGICAL AND SOCIOECONOMIC FEASIBILITY

By

ASAKO TAKIMOTO

A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL

OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT

OF THE REQUIREMENTS FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA

2007

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2007 Asako Takimoto

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To my parents and grandmother

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ACKNOWLEDGMENTS

I am indebted and grateful for many individuals and organizations who contributed to this

study and my doctoral program. I thank my chair, Dr. P.K. Nair, for his dedication and guidance

throughout this process, and my committee, Dr. Nick Comerford, Dr. Janaki Alavalapati, Dr.

Tim Martin, Dr. Ted Schuur, and Dr. V.D. Nair, for their support and encouragement.

I recognize and express my sincere gratitude to the individuals and their institutions that

supported me during my doctoral studies: the School of Forest Resources and Conservation

(Cherie Arias, Sherry Tucker, Dr. Tim White), University of Florida International Center (Debby

Anderson), the Center for Tropical Conservation and Development of UF, the World

Agroforestry Centre (especially Dr. Bocary Kaya), the Fulbright Program, and the Joint

Japan/World Bank Graduate Scholarship Program (JJ/WBGSP).

At the fieldwork in Sgou, Mali, I received tremendous support and cooperation from the

farmers, field officers, and other collaborators. It was one of the most challenging times of my

life, and I could not go through without them. Thank you to Nicole Demers, Bayo Mounkoro,

Keita, Samake, and other officers in ICRAF Sgou office, Kayo Sakaguchi, Takako Uchida, Mr.

Kiyoshi Sakai, and all the farmers in Sgou who let me use their fields for data collections and

participated the survey.

I have greatly benefited from my friendship with colleagues in the agroforestry lab at UF.

I thank Solomon Haile, Alyson Dagang, Julie Clingerman, Sam Allen, Eddie Ellis, Brian Becker,

Joyce Leptu, David Howlett, Wendy Francesconi, Subrajit Saha, Shinjiro Sato, and Masaaki

Yamada, for the discussions and supports.

To my precious friends who have been an integral part of the many years of this process,

thank you Gogce Kayihan, Brian Daley, Elli Sugita, Mike Bannister, Jason and Karen Hupp,

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Charlotte Skov, Chrysa Mitraki, Rania Habib, Maitreyi Mandal, Trina Hofreiter, Troy Thomas,

and my fianc, Nick Georgelis.

Last but not least, I express my most profound gratitude to my mother Ayuko Takimoto,

whose endless love and confidence in me made me come this far.

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TABLE OF CONTENTS

page

ACKNOWLEDGMENTS ...............................................................................................................4

LIST OF TABLES .........................................................................................................................10

LIST OF FIGURES .......................................................................................................................11

ABSTRACT ...................................................................................................................................13

CHAPTER

1 INTRODUCTION ..................................................................................................................15

Background .............................................................................................................................15

Rationale and Significance .....................................................................................................16

Research Questions and Objectives ........................................................................................17

Dissertation Overview ............................................................................................................18

2 THE WEST AFRICAN SAHEL: GENERAL LAND-USE AND AGROFORESTRY ........20

Description of the Region .......................................................................................................20

Climate ............................................................................................................................20

Vegetation ........................................................................................................................21

Soil ...................................................................................................................................22

Traditional Farming Systems and Agroforestry in the WAS .................................................24

Traditional Agroforestry Practices ..................................................................................25

Bush fallow/shifting cultivation ...............................................................................25

Parkland system ........................................................................................................25

Improved Agroforestry Practices ....................................................................................26

3 LITERATURE REVIEW: CARBON SEQUESTRATION POTENTIAL OF

AGROFORESTRY SYSTEMS IN THE WEST AFRICAN SAHEL (WAS) .......................36

Overview .................................................................................................................................36

C Sequestration as a Climate-Change-Mitigation Activity .............................................36

Agroforestry for C sequestration .....................................................................................37

Methodologies for C Sequestration Measurements ................................................................39

Direct On-site Measurement ............................................................................................39

Inventory ..................................................................................................................40

Conversion and estimation .......................................................................................40

Indirect Remote Sensing Techniques ..............................................................................42

Modeling ..........................................................................................................................43

Default Values for Land/Activity Based Practices ..........................................................44

Accounting Methods ...............................................................................................................44

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Approaches to Assessing C Sequestration Performance .................................................45

Fluxes of C and flow summation .............................................................................45

Average changes in the stocks of C .........................................................................45

Cumulative C storage ...............................................................................................46

Other accounting methods ........................................................................................46

Technical Problems and Uncertainties ............................................................................47

Biomass C Sequestration ........................................................................................................48

Studies in Various Ecoregions .........................................................................................48

Studies in West Africa .....................................................................................................48

Soil C Sequestration ...............................................................................................................50

Studies of Soil C Stock and Dynamics ............................................................................50

Soil C in the WAS ...........................................................................................................52

Socioeconomic Implications ...................................................................................................54

Economic Models ............................................................................................................54

National/global scale ................................................................................................54

Micro/site-specific scale ...........................................................................................55

Feasibility in West Africa ................................................................................................56

4 ABOVEGROUND AND BELOWGROUND CARBON STOCKS IN TRADITIONAL

AND IMPROVED AGROFORESTRY SYSTEMS IN MALI, WEST AFRICA .................61

Introduction .............................................................................................................................61

Materials and Methods ...........................................................................................................62

Study Area .......................................................................................................................62