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Fire and Its Effects on Vegetation in the Okavango Delta.Pdf MICHAEL HEINL Fire and its effects on vegetation in the Okavango Delta, Botswana Feuer und sein Einfluss auf die Vegetation im Okavango Delta, Botswana supported by Fire and its effects on vegetation in the Okavango Delta, Botswana Feuer und sein Einfluss auf die Vegetation im Okavango Delta, Botswana Diplomarbeit am Lehrstuhl für Vegetationsökologie Technische Universität München Freising-Weihenstephan Prof. Dr. Jörg Pfadenhauer - 25. August 2001 - Autor: Michael Heinl ([email protected]) Betreuer: Dr. Jan Sliva ([email protected]) Prof. Jörg Pfadenhauer Dr. E. Veenendaal supported by PREFACE II Fire and its effects on vegetation in the Okavango Delta, BoBotttswanaswana Preface The present MSc-Thesis (Diplomarbeit) describes the results of a one-year project about the effects of fire on vegetation, with special focus on the Okavango Delta region, Botswana. The study is based on a new initiated research co-operation between Harry Oppenheimer Okavango Research Centre (HOORC) in Maun, Botswana, part of University of Botswana and the Chair of Vegetation Ecology of the Technische Universität München (TUM), Germany funded by Stifterverband für die Deutsche Wissenschaft within their programme “Forschung für Naturräume“ for young scientists. Under the topic “Elements in Conflict - Anthropogenic fires in the RAMSAR-wetland Okavango-Delta (Botswana)”, prerequisites were set for future co- operative research projects between HOORC and TUM during August 2000 to August 2001. Besides the theoretical introduction to the ecology of the study area ‘Okavango Delta’, this period was primarily used to gain first practical experience on the vegetation and the fire ecology of the Okavango Delta during the stays in Botswana in October 2000 and March/April/Mai 2001. These were further used for getting in contacting with local and international researchers, NGOs and the authorities. The study can be used as a scientific basis for further research on fire ecology in southern African savannas, especially in the Okavango Delta region and was admitted to the international research initiative SAFARI 2000. The structure of the present study describes indirectly the temporal development of the project. As a first step, a precise introduction to the study area Okavango Delta in Bot- swana was developed (part A). Because of the spatial and also the thematic distance to Central Europe, detailed studies were necessary both on large-scale relations and on local characteristics for getting an overall view of the ecology for this area. The understanding of ecological interactions is the basis for developing useful hypotheses for studies and interpretations of gained results. Therefore, part A deals besides climate, geology, vegetation and soil primarily with explanations on the hydrographic system of the Okavango Delta, which is probably the key for understanding ecological relations in this vast wetland. Unfortunately, this section is presented on German language omly, because at the time of its elaboration it was still unsure in which context this study will be used. An afterwards translation of this chapter would have meant to sacrifice the field-work, because of the time-limit of this study. Therefore, it is kindly asked to excuse the missing international understanding of this chapter. Part B of the present study describes the focus of the ecological research in the Okavango Delta on the topic fire and its effects on vegetation. Here again, a detailed evaluation of the present scientific knowledge was necessary to derive an ecological overview about fire, for interpretations of causes and consequences of fire on vegetation. PREFACE III Part C describes the utilisation of the gained theoretical knowledge in the course of a field-study in April 2001, concerning the effects of fire on the vegetation in the Okavango Delta. But because of missing baseline-data, mainly about fire-events of the last years, the study is based on a simplified question (effects of the 2000/01 fires on vegetation). Besides, the vegetation surveys were used for developing and evaluating useful methods and approaches, as well as for gaining experience on the logistics. A kind of weakness of the results, as a consequence thereof, was expected and accepted in advance. Nevertheless some interesting ecological and methodical aspects referring to effects of fire on southern African savanna vegetation could be derived. VORBEMERKUNGEN IV Feuer und sein Einfluss auf die Vegetation im Okavango Delta, Botswana Vorbemerkungen Die vorliegende Diplomarbeit dokumentiert die Resultate einer einjährigen Studie über den Einfluss von Feuer auf die Vegetation, im Speziellen für das Gebiet des Okavango Deltas in Botswana. Die Arbeit basiert auf einer neu initiierten Forschungskooperation zwischen dem Harry Oppenheimer Okavango Research Centre (HOORC) in Maun, Botswana, einer Außenstelle der University of Botswana und des Lehrstuhls für Vegetationsökologie der Technischen Universität München, unterstützt durch das Nachwuchsförderungsprogramm 2000 „Forschung für Naturräume“ des Stifterver- band für die Deutsche Wissenschaft. Unter dem Thema “Elemente im Konflikt - anthropogene Feuer im RAMSAR-Feuchtgebiet Okavango Delta (Botswana)“ wurden während des Zeitraums August 2000 bis August 2001 primär die Grundlagen für weiterführende wissenschaftliche Arbeiten in Kooperation mit dem HOORC geschaffen. Dabei standen neben der theoretischen Einarbeitung in den aktuellen Forschungsstand zur Ökologie des Okavango Deltas vorwiegend die Aufenthalte vor Ort im Oktober 2000 und im März/April/Mai 2001 im Vordergrund, die die ersten Erfahrungen mit der Vegetation und der Feuerökologie ermöglichten. Sie wurden außerdem zur Knüpfung von Kontakten zu lokalen und internationalen Wissenschaft- lern, Behörden und NGOs genutzt. Die Studie soll als wissenschaftliche Basis für weiterführende Forschungen im Bereich der Feuerökologie der südafrikanischen Savannen, im Speziellen des Okavango Delta dienen und wurde in die internationale Forschungsinitiative SAFARI 2000 aufgenommen. Die Struktur der vorliegenden Arbeit beschreibt indirekt den zeitlichen Ablauf und die Entwicklung des Projekts. Dabei bestand der erste Schritt zunächst in einer detaillierten Einarbeitung und Beschreibung des Untersuchungsgebiets Okavango Delta in Botswana (Teil A). Aufgrund der räumlichen und auch thematischen Distanz des Projekts zu Mitteleuropa waren ausführliche Studien nötig, um großräumige Zusammenhänge aber auch lokale Besonderheiten zu verstehen und in einen ökologischen Gesamtkontext stellen zu können. Das ökologischen Verständnis eines Raumes bildet die Grundlage für die Erstellung sinnvoller Arbeitshypothesen und die Interpretation der Ergebnisse. Teil A beschäftigt sich daher neben Klima, Geologie, Vegetation und Boden primär mit dem hydrographischen System des Okavango Deltas, dessen Verständnis als der Schlüssel zur Ökologie diese weiträumigen Feuchtgebiets angesehen werden kann. Leider liegt dieser Abschnitt nur in einer deutschen Fassung vor, da zum Zeitpunkt der Erstellung noch nicht abzusehen war, in welchem Rahmen die Diplomarbeit Verwendung finden soll. Einer nachträglichen Übersetzung wären aufgrund der zeitlichen Beschränkung der Diplomarbeit die Geländeuntersuchungen zum Opfer gefallen und so sei an dieser Stelle angesichts der fehlenden internationalen Verständlichkeit um Verzeihung gebeten. VORBEMERKUNGEN V Teil B der Arbeit beschreibt die Konkretisierung der ökologischen Forschung im Okavango Delta auf das Thema Feuer und seinen Einfluss auf die Vegetation. Auch hier bedingt die thematische Distanz der Savannenbrände zu Mitteleuropa eine detaillierte Auseinandersetzung mit den bestehenden wissenschaftlichen Erkenntnis- sen, ebenfalls zur Erlangung eines ökologischen Überblicks, der es erlaubt, Ursachen und Folgen von Feuer auf die Vegetation abschätzen und interpretieren zu können. Teil C beschreibt die Anwendung der gewonnenen Erkenntnisse im Zuge einer Geländeuntersuchung im April 2001 zum Einfluss von Feuer auf die Vegetation des Okavango Deltas. Aufgrund fehlender Grundlagendaten, vorwiegend zu Feuerereignis- sen der letzten Jahre, liegt dieser Studie allerdings nur eine vereinfachte Fragestellung zugrunde (Einfluss der Feuer von 2000/01 auf die Vegetation). Parallel dienten die vegetationskundlichen Untersuchungen der Ausarbeitung und Evaluierung geeigneter Methoden und Ansätze sowie der Gewinnung logistischer Erfahrungen zur Vorberei- tung weiterführender Studien. Eine damit verbundene geringere Aussagekraft der Ergebnisse wurde bewusst in Kauf genommen. Nichtsdestotrotz konnte mit der vorliegenden Arbeit der Bogen von der Ökologie des Okavango Deltas über die Feuer in den Savannen des südlichen Afrika hin zu einer verbindenden Geländeuntersuchung gespannt werden und auch einige interessante Aspekte zum Einfluss von Feuer auf die Vegetation des Okavango Delta abgeleitet werden. INHALT / CONTENTS VI Erklärung I Preface II Vorbemerkungen IV Contents/Inhalt A Das Okavango Delta - Lage, UmweltfaktorenUmweltfaktoren und Ökologie 1 1 Das ‚Okavango Delta‘ - Eine geographische Kurzeinführung 2 2 Klima 6 2.1 Die großklimatische Lage Botswanas 6 2.2 Das regionale Klima in Botswana 7 3 Geologie 10 3.1 Geologische Formationen 10 3.2 Tektonik und Oberflächenstruktur 12 3.3 Geologische Aktivitäten und landschaftliche Veränderungen im späten Quartär 14 4 Hydrographisches System 16 4.1 Das zeitliche Zusammenspiel von Niederschlag und Flut 16 4.2 Die räumliche Verteilung der Flut innerhalb des Okavango Deltas 21 4.3 Typisierung der ‚channels‘
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