Impact of Deforestation on Biodiversity, Soil Carbon Stocks, Soil Quality, Runoff and Sediment Yield at Southwest Ethiopia’S Forest Frontier
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Impact of deforestation on biodiversity, soil carbon stocks, soil quality, runoff and sediment yield at southwest Ethiopia’s forest frontier Henok Kassa Tegegne Proefschrift voorgedragen tot het behalen van de graad van Doctor in de Wetenschappen Geografie Faculteit Wetenschappen Henok Kassa Tegegne Impact of deforestation on biodiversity, soil carbon stocks, soil quality, runoff and sediment yield at southwest Ethiopia’s forest frontier Proefschrift voorgelegd tot het behalen van de graad van Doctor in de Wetenschappen: Geografie 2016-2017 Copyright: Henok Kassa 2017 Published by: Department of Geography - Ghent University Krijgslaan 281 (S8), 9000 Gent (Belgium) (c) All rights reserved. ix x Promoter: Prof. Dr. Jan Nyssen, Department of Geography, Faculty of Sciences, Ghent University, Belgium Co-promoter: Prof. Dr. Jean Poesen, Department of Earth and Environmental Sciences, Section of Geography and Tourism, KU Leuven, Belgium Members of the Jury: Prof. Dr. Nico Vandeweghe, Department of Geography, Faculty of Sciences, Ghent University, Belgium (Chair) Dr. Denyse Snelder, Senior Advisor Natural Resources Management, VU Amsterdam, The Netherlands Prof. Dr. Stefaan Dondeyne, Department of Earth and Environmental Sciences, Section of Soil and Water Management, KU Leuven, Belgium Prof. Dr. Ann Verdoodt, Department of Soil Management, Faculty of Biosciences Engineering, Ghent University, Belgium Dr. Amaury Frankl, Department of Geography, Faculty of Sciences, Ghent University, Belgium (secretary) Dr. Miro Jacob, Department of Geography, Faculty of Sciences, Ghent University, Belgium Dean: Prof. Dr. Herwig Dejonghe Rector: Prof. Dr. Anne De Paepe xi xii Acknowledgements First and foremost, I thank the Almighty God for granting me the capability and patience to accomplish the study. Firstly, I would like to express my sincere gratitude to my promoters Prof. Dr. Jan Nyssen, and Prof. Dr. Jean Poesen for the continuous support, patience, motivation, immense knowledge sharing from the beginning to the current status of my PhD. Dr. Amaury Frankl and Prof. Dr. Stefaan Dondeyne have continuously supported my research. It is difficult to structure and organize my PhD thesis without the guidance and advice. I would like to appreciate and forward my special gratitude to my promoter Prof. Dr. Jan Nyssen, who always open the door to answer all my question during my PhD research work. I also wish to thank Prof. Dr. Nico Vandeweghe, Prof. Dr. Ann Verdoodt, Dr. Denyse Snelder, Dr. Miro Jacob, Dr. Amaury Frankl and Prof. Dr. Stefaan Dondeyne for accepting to be part of my PhD jury. This study was conducted in the framework of the STRONGBOW project, a cooperation between five Ethiopian Universities (including Mizan-Tepi University), the Horn of Africa Regional Environmental Centre, VU University Amsterdam (Netherlands), University of Leuven and Ghent University (Belgium), funded by NUFFIC (Netherlands). The project managers and staff are sincerely thanked for their cooperation. The Bench Maji, Semen Bench district and Debub Bench district agricultural offices and NTFPS provided valuable information and materials for this study, as well as Mekuria Argaw, Ashiber Berhie, Sisay Tomas, Abebe Abay, Girma Wolda, Getachew Mekuria, Solomon Getachew, Yassin Nurahmed, Solomon Getachew, Kebede Mengistu, Demelash Tessema, Julie Mahie, Bezabeh Banzi, Nardose Takele, Abiyot Dodeneya, Amare Dodeneya and Buzayew Geremew. In my daily work I have been blessed with a friendly and cheerful group in Ghent University. My appreciation goes to all staff members of Mizan-Tepi University College of Agriculture and Natural Resources. My sincere thanks goes to the staff members of Physical Geography of Ghent University; Dr. Sil Lanckriet, Dr. Miro Jacob, Abebech Abera, Hanne Hendrickx, Habenom Hailesilasse, Edo Beressa, Dr. Dereje Teklemariam, Dr. Biadglign Demissie, Zbelo Tesfamariam, Hanibal Lemma, Hailemariam Meaza, Etefa Guyassa for the stimulating discussions, fun and motivation during my research work. xiii I special thanks also to my data collector Alemayhu Nagite, Bezabe Banzi, Tamerate Mulen and Mengistu Beyene from Zemika village; Segude Diste and Robel Baybase from Fanika village; Alemayehu Titose and Lukase Ankate from Dakin and Oka village; Atrese Tile and Mesfine Bekele from Faketen village who potentially contribute for the success of this PhD work. Finally, I must express my very profound gratitude to my parents. There is nothing more precious than learning from a truly caring family and I heartily appreciate and thank my mother, Tenefe Zeleke and my father, Kassa Tegegne who passed away at the middle of my PhD work. They taught me compassion, dedication and hardworking throughout my life. Lastly, I would like to thank my loving and caring wife, Heregwine Tesfaye and my children as well as my brother Ferezer Fikadu, and my sisters Misrak Kassa, Ferhiwot Kassa, Mesert Seleshi, Zufan Mehari and Genete Kassa for their care and motivation. xiv Table of Contents Acknowledgements ................................................................................................................. xiii Table of Contents ..................................................................................................................... xv List of Tables ........................................................................................................................ xviii List of Figures ........................................................................................................................ xix List of Acronyms .................................................................................................................... xxi List of Publications .............................................................................................................. xxiii Chapter 1 General Introduction .......................................................................................25 1.1 Problem statement................................................................................................................ 26 1.2 The environmental degradation in southwestern Ethiopia ..................................................... 27 1.2.1. Drivers of land use change .................................................................................................... 31 1.2.2 Land use changes.................................................................................................................... 36 1.2.3 Consequences of forest degradation ..................................................................................... 38 1.2.4 Conservation efforts in southwest Ethiopia ........................................................................... 42 1.3 Study area ......................................................................................................................... 44 1.4 Thesis objectives and research questions ............................................................................... 50 1.5 Definitions ......................................................................................................................... 51 1.6 References ......................................................................................................................... 52 Chapter 2 Impact of deforestation on soil fertility, soil organic carbon and nitrogen stocks in southwest Ethiopia ...................................................................................63 2.1 Introduction ......................................................................................................................... 66 2.2 Materials and methods .......................................................................................................... 67 2.2.1 Study area ............................................................................................................................... 67 2.2.2 Data collection and analysis ................................................................................................... 69 2.3. Results ......................................................................................................................... 71 2.3.1 Contrasts between the three land-use types ......................................................................... 71 2.3.2 Soil physico-chemical characteristics ..................................................................................... 72 2.3.3 Soil carbon and nitrogen stocks in the three land use types ................................................. 79 2.4. Discussion ......................................................................................................................... 82 2.4.1 Factor analysis of soil characteristics ..................................................................................... 82 2.4.2 Soil physico-chemical characteristics ..................................................................................... 83 2.4.3 Soil organic carbon and nitrogen stocks ................................................................................ 85 xv 2.5.Conclusions ......................................................................................................................... 87 2.6. References ......................................................................................................................... 87 Chapter 3 The agro-ecological implications of forest and agroforestry conversion towards cereal-based farming systems: the case of the Gacheb catchment ......................93 3.1