Addis Ababa University School of Graduate Studies
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ADDIS ABABA UNIVERSITY SCHOOL OF GRADUATE STUDIES WOODY SPECIES ENCROACHMENT AND RELATED ECOLOGICAL CONDITIONS IN THE GRASS PLAIN OF NECHSAR NATIONAL PARK By HASAN YUSUF MOHAMMAD A THESIS SUBMITTED TO THE SCHOOL OF GRADUATE STUDIES ADDIS ABABA UNIVERSITY IN PARTIAL FULFILLMENT OF THE REQUIREMENTS OF THE DEGREE OF MASTER OF SCIENCE IN BIOLOGY (BOTANICAL SCIENCES) June 2008 ADDIS ABABA ACKNOWLEDGEMENTS The writing of this thesis is obviously not possible without the personal and practical support of numerous people. First, I would like to thank Allaha/God almighty for the strength that He supplied to me for finalizing this work. This thesis would not have been possible without the expert guidance of my esteemed Supervisors, Professor Sebsebe Demissew and Professor Zerhun Woldu. I wish to express my deep gratitude to them for their follow up and encouragement throughout my study period. I would like to thank the cooperation of Wellaga University for handling of all the administrative matters during my study period. I am especially grateful to Professor Fekadu Beyene, the president of Wellaga University for his encouragement and unreserved support. I would also like to thank Addis Ababa University Herbarium workers w/t Shewa, Melaku, and Assefa for their provision of all necessary materials required for the study and assistance during plant species identification work. The field research was conducted in Nechsar National Park. I am thankful also, for African Parks Foundation-Ethiopia(APF plc) for initiating this demand driven research, and assist me in all research activities, and I would love to thank Dr.Assefa Meberate, Ato Matios Ersado,Mr.Derik Clark, Ato Girema Timer, Ato Aramdie, Ato Olani, Park Scouts Ato Ademasu, Ato Hasan,and Ato Jarso where I received all kind of support. I am particularly thankful to my friends Juhar Yasin, Juhar Jibril, Kamil Ahmed, Zeinu Ahmed, Tofik Shukur, Deresse Teshome, Fite Getanhe, Ayantu Mekonon, Jibril Mamo, Siraj Mamo, Sintayehu Shuri, Teshome Takale for their assistance and encouragement in various ways during my course of studies. I would like to thank my parents for their prayers, encouragement, support, sacrifice and advice ever since my youth. Words can not express my feelings, which I have for my family, my dear mother, Makiya Abdurhaman, I am very much thankful for her love, encouragement and support. Special thanks for my dear sisters Keriya Yusuf and her family, Fate Ali and her family and dear brothers Nasir Yusuf, Imam Yusuf, Kasim Yusuf, Amdihun Yusuf, Mohamud Yusuf, Kedir and Anuwar Yusuf for the courage and love they gave me during my study. Miss you Dad. 1 CONTENTS Page Acknowledgement iii Contents iv List of tables vi List of figures vii List of Appendices viii Abstract ix 1. INTRODUCTION............................................................Error! Bookmark not defined. 2. LITERATURE REVIEW...................................................................................................4 2.1 Ecology of savanna ecosystem............................................................................. 4 2.2 Human influence in savanna.................................................................................5 2.3 Dynamics of savanna ecosystem.......................................................................... 6 2.3.1 Causes of bush encroachment.........................................................................6 2.3.2 The ecological models.................................................................................... 6 2.3.2.1 The equilibrium model.................................................................................7 3.2.2 The non-equilibrium model............................................................................ 8 2.3.2.3 Patch-dynamic models...............................................................................9 2.3.2.4 Disturbance models................................................................................. 11 2.4 Multivariate Techniques for Vegetation Analysis..............................................15 2.4.1 Classification................................................................................................ 15 2.4.2 Measure of Species Diversity....................................................................... 17 3. MATERIALS AND METHODS.................................................................................... 19 3.1 Description of the study area.............................................................................. 19 3.1.1 Location........................................................................................................ 19 3.1.2. Climate.........................................................................................................22 3.1.4 Geology and Soil.......................................................................................... 23 3.1.5 Topography and Hydrology..........................................................................24 3.1.6. Socioeconomics........................................................................................... 26 3.1.3 Biological and Habitat diversity................................................................... 27 3.2 Sampling techniques.............................................................................................33 3.3 Data Collection..................................................................................................... 34 3.4. Plant species identification.................................................................................. 35 3.5. Data Analysis.......................................................................................................35 3.6 Diversity Indices...................................................................................................36 3.7 Other statistical tests.............................................................................................36 4. RESULT.......................................................................................................................... 37 4.1 Floristic composition............................................................................................. 37 4.2 Description of community types............................................................................40 4.3 Plant diversity........................................................................................................ 46 4.4 Density of woody plants........................................................................................ 47 4.5 Cover of woody plants and ecosystem structure................................................... 48 4.6 Population structure of woody tree species........................................................... 55 4.7 Impact of woody plants on herbaceous cover and ecological conditions..............57 5. DISCUSSION..................................................................................................................58 2 5.1 Floristic composition and diversity....................................................................... 58 5.2. Disturbance, environmental variables and patterns of vegetation distribution 63 5.3 Popuation structure and spatial distribution pattern of bush species......................66 5.4 Invassive bush density and cover........................................................................... 68 5.5 Impacts of encroachment of woody species on ecosystem.................................... 70 6 CONCLUSION.................................................................................................................76 7. REFERENCES.................................................................................................................80 3 LIST OF FIGURES Figure 1.Location Map of the study area............................................................................. 20 Figure 2 Location map of Nechsar grass plain with transects............................................. 21 Figure 3 Climatic Diagram of Nechisar Park (Data Obtained from Arba Minch University Metrological Station)............................................................................................. 22 Figure 4 Topography and hydrology of the study area (APC, 2006)...................................25 Figure 5 Some flora of the grass plain of Nechsar National Park.......................................30 Figure 6 Wild life distribution in the grass plain of Nechsar National Park (APF, 2006)...33 Figure 7 Dstribution of plant life forms in the grass plain of Nechsar Nationa Park.......... 38 Figure 8 Frequency distribution of plant species in the grass pain of Nechsar National Park ..............................................................................................................................................39 Figure 9 Whittaker plot of species - abundance data for the plant species recorded in Nechsar National Park...........................................................................................39 Figure 10 Dendrogram showing the classification of the releves in the grass plain of Nechsar National Park Using Syntax similarity ratio........................................... 40 Figure 11 The Over all ecosystem structure of the grass plain of Nechsar National Park. 49 Figure 12 The Variablity in the structure of woody tree species across community types in the grass plain of Nechsar National Park.......................................................51 Figure 13 The structure of woody tree species in the grass plain