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''Composition, Degradation and Stabilization of Soil Organic Matter ‘‘Composition, degradation and stabilization of soil organic matter along an elevation gradient of Mount Kilimanjaro” Dissertation Submitted to obtain Doctoral Degree of Philosophy (Ph.D.) within the doctoral degree program at the Faculty of Forest Science and Forest Ecology, Georg- August University of Gottingen, Germany Presented by Emanueli Mathayo Ndossi Born in Arusha, Tanzania Gottingen, December, 2020 Thesis committee members (Supervisors) 1. Professor Dr. Michaela Dippold Department of Biogeochemistry of Agroecosystems University of Gottingen 2. Professor Dr. Sandra Spielvogel Department of Soil Science, Christian-Albrechts-University Kiel, Germany 3. Dr. Joscha N. Becker Institute of Soil Science, CEN Center for Earth System Research and Sustainability, Universität Hamburg, Allende-Platz 2, 20146 Hamburg, Germany 4. Dr. Matthias Gube Department of Soil Science of Temperate Ecosystems, University of Gottingen, Germany Thesis examination date: 20.12.2019 Table of contents Table of contents ......................................................................................................................... i i. List of Tables ..................................................................................................................... iii ii. List of Figures .................................................................................................................... iii iii. Abbreviations ..................................................................................................................... vi iv. Summary ........................................................................................................................... vii 1. Extended summary ................................................................................................................. 1 1.1. General introduction ........................................................................................................ 1 1.1.1. Tropical Afromontane ecosystems ............................................................... 1 1.1.2. Impacts of land-use intensification in Kilimanjaro. ......................................................... 2 1.1.3. Relationship between Soil organic matter, enzymes and soil aggregate. ......................... 3 1.2. Objectives ........................................................................................................................ 4 1.3. Hypothesis ....................................................................................................................... 5 1.4. Materials and Methods ................................................................................................ 5 1.4.1. Study area description ................................................................................... 5 1.4.2. Soils of Kilimanjaro ...................................................................................... 5 1.4.3. Land-use and climatic zonation .................................................................... 6 1.4.4. Climatic condition ......................................................................................... 6 1.5. Research design ........................................................................................................... 8 1.5.1. Soil lignin and sugar composition study-sampling ....................................... 9 1.5.2. Enzymes kinetics .......................................................................................... 9 1.5.3. Soil aggregate distribution ............................................................................ 9 1.6. Analytical methods .................................................................................................... 10 1.6.1. Lignin and sugar analysis ............................................................................ 10 1.6.2. Analysis of enzyme activities and kinetics ................................................. 10 1.6.3. Analysis of stability and aggregate size distribution .................................. 11 1.7. Results and discussion ............................................................................................... 11 1.7.1. Effects of land-use change on SOM, enzymes and soil aggregates ............ 11 1.7.2. Effects of elevation on the SOM, enzymes and soil aggregate size ........... 13 1.7.3. Summary of objectives, main conclusions of the studies ........................... 15 1.9. Conclusions ............................................................................................................... 18 1.9.1. Contribution to studies ................................................................................ 18 1.9. 2. References ................................................................................................................. 20 2. Publications and Manuscripts ............................................................................................... 36 i 2.1. Study 1: Soil lignin and sugar composition along a 3300 m elevation gradient of Mount Kilimanjaro ............................................................................................................................... 36 2.1.1. Abstract ....................................................................................................................... 36 2.1.2. Introduction ................................................................................................................ 37 2.2. Methods ............................................................................................................................. 39 2.3. Results ............................................................................................................................... 42 2.3.2. Effects of elevation gradient on lignin contents and composition .............................. 43 2.4. Discussion ......................................................................................................................... 47 2.5. Conclusions ............................................................................................................... 50 2.6. Acknowledgments ..................................................................................................... 51 2.7. References ................................................................................................................. 51 2.8. Appendix A ................................................................................................................ 66 3. Study 2: Effects of land-use and elevation on the functional characteristics of soil enzymes at Mt. Kilimanjaro .................................................................................................................... 67 3.1. Abstract .......................................................................................................................... 67 3.2. Introduction ................................................................................................................... 68 3. 3. Material and method ......................................................................................................... 71 3.3.1. Study area ................................................................................................................... 71 3.3.2. Soil sampling and preparation for experimentation ................................................... 73 3.3.3 Enzyme Kinetics .......................................................................................................... 74 3.3.4. Calculations and statistical analyses ........................................................................... 75 3.4. Results ............................................................................................................................... 75 3.4.1. Effect of land use and depth on enzyme activity (Vmax) ............................................. 75 3.4.2. Effect of depth and land use on catalytic properties (Km and Ka) .............................. 78 3.4. 3. Response of enzyme kinetics to elevation ................................................................. 81 3.5. Discussion ...................................................................................................................... 82 3.6. Conclusions ................................................................................................................... 86 3.7. Acknowledgment s ........................................................................................................ 87 3.8. References ..................................................................................................................... 87 3.9. Supplementary ............................................................................................................... 97 4. Study 3: Effects of land-use change and elevation gradient on soil aggregate size distribution on Mount Kilimanjaro .......................................................................................... 98 4.1. Abstract .......................................................................................................................... 98 4.2. Introduction ................................................................................................................... 99 4.2. Materials and methods ................................................................................................. 101 4.2.1. Study area ................................................................................................................. 101 4.2.2.
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