Achim Röder Vom Fachbereich VI (Geographie/Geowissenschaften) der Universität Trier zur Erlangung des akademischen Grades Doktor der Naturwissenschaften (Dr. rer. nat.) genehmigte Dissertation A Remote Sensing Based Framework for Monitoring and Assessing Mediterranean Rangelands. Case Studies from Two Test Sites in Spain and Greece Betreuer: Univ.-Prof. Dr. Joachim Hill Berichterstatter: Univ.-Prof. Dr. Joachim Hill appl. Prof. Dr. Willy Werner Datum der wissenschaftlichen Aussprache: 7. 12. 2005 Trier, 2005 Acknowledgements Just as this work has been evolving and growing, so has the number of people who have helped to make it possible in one way or the other, by sharing their ideas, energy and time at work and – most importantly – beyond. To do them all justice is an impossible task; hence, a simple ‘Thank you!’ to all friends who accompanied me in these past years. Still, I owe particular words of gratitude to Prof. Dr. Joachim Hill, head of the Remote Sensing Department and my first supervisor, without whose scientific guidance and experience this work would not have been possible. My knowledge of Mediterranean processes and remote sensing concepts has vastly benefited from his expertise. Most importantly, I owe him the chance to work in a European research environment, for which I am very grateful; to Prof. Dr. Willy Werner, for accepting to act as the second supervisor for this work despite many other obligations. With his profound knowledge he complemented a remotely sensed view with a valuable ecological perspective; to Prof. Dr. Patrick Hostert, for his friendship and encouragement. He was a part of this pro- ject from the very beginning and shared long hours in the office and in field. My deepest gratitude for his support in the final phase – his ability to create time in a tight schedule was amazing. I am indebted to him for still answering the phone, and, not the least, to Viola Neukam for letting him; to the colleagues I had the pleasure to work with in GeoRange, who shared data and insight that are the basis of many analyses undertaken here, and who provided invaluable hours of Mediterranean hospitality: Prof. Dr. Vasilios Papanastasis, Dr. Mihailis Vrahnakis, Dimitrios Chouvardas and all the staff at the Aristotle University in Thessaloniki; Stefan Sommer and Wolfgang Mehl at the JRC/Ispra; Dr. Giuseppe Brundu at CFVA/Sardinia; Dr. Juan Puigdefabregas at EEZA/Almeria. In particular, my sincere gratefulness to Dr. Beatriz Duguy, Dr. Thomas Kemper, Dr. Gabriel del Barrio and Prof. Dr. Georgios Tsiourlis for making pro- ject work much more than a job; to all the student staff who contributed to the project in the past years: Silke Peine, Sebastian Mader, Markus Hampen, Henning Buddenbaum, and especially to Samuel Bärisch for his support in data processing and his talent to solve problems; special thanks are due to the stu- dents who supported the project and this work with excellent diploma theses: Björn Waske and Sebastian Schiefer for advancing the initial stages with their methodological works; finally, to Tobias Kümmerle, for his dedication and efforts in the last stage of the project and – most of all – for ‘quapping’ hours; to all colleagues at the Remote Sensing Department, from whose experience and knowledge I was privileged to benefit in the last years, and who make working in the department a pleasure; especially Dr. Thomas Udelhoven and Dr. Thomas Jarmer for help whenever needed; and not the least to Hermine Marx for sympathy, catering, and for ‘making things work’. to Martin Schlerf for sharing highs and lows of finishing a PhD and for ‘the carrot or the stick’ this takes; to my family, most of all to my parents, Inge and Horst Röder, and to my grandmother, Hedwig Kiefer; for their support and care throughout the years and generously accepting that visits were rare in the last months. The last and biggest ‘thank you’ goes to the person whose energy, endurance and belief dur- ing the last year has only made this possible: my partner Anja Brassel. Thanks a million for our years together and for being there! Achim Röder Trier, December 2005 Contents Contents............................................................................................................................ I List of Figures.................................................................................................................IV List of Tables..................................................................................................................IX 1 Introduction and scope of the work................................................................1 2 Land degradation in Mediterranean rangelands............................................4 2.1 Rangelands ...........................................................................................................4 2.2 Desertification and land degradation in the Mediterranean basin ........................5 2.3 Fire......................................................................................................................10 2.3.1 Historical perspective..........................................................................10 2.3.2 Fire risk................................................................................................11 2.3.3 Plant resilience and post-fire dynamics...............................................12 2.3.4 Fire as an agent of degradation............................................................13 2.4 Grazing ...............................................................................................................14 2.4.1 Historical perspective..........................................................................14 2.4.2 Grazing impact ....................................................................................15 2.4.3 Grazing management in rangelands ....................................................17 3 Remote sensing based monitoring of rangelands – conceptual considerations............................................................................20 3.1 Sensor systems and the question of scale ...........................................................20 3.2 Standardisation requirements .............................................................................22 3.2.1 Geometry .............................................................................................22 3.2.2 Radiometry ..........................................................................................23 3.3 Indicators ............................................................................................................24 3.4 Remote sensing of rangelands ............................................................................26 3.4.1 Derivation of vegetation-related information......................................26 3.4.2 Evaluation of processes in fire-affected rangelands............................28 3.4.3 Evaluation of processes in grazing-affected rangelands......................31 3.5 Elements of a remote sensing based rangeland monitoring and assessment framework........................................................................................33 4 Pilot areas .......................................................................................................35 4.1 The Ayora study area..........................................................................................35 4.1.1 Climate ................................................................................................38 4.1.2 Geology ...............................................................................................40 4.1.3 Soils .....................................................................................................41 4.1.4 Hydrology............................................................................................42 4.1.5 Vegetation............................................................................................44 4.2 The Lagadas study area ......................................................................................52 II 4.2.1 Climate ................................................................................................53 4.2.2 Geology ...............................................................................................55 4.2.3 Soils .....................................................................................................57 4.2.4 Hydrology............................................................................................58 4.2.5 Vegetation............................................................................................59 4.2.6 The grazing system..............................................................................65 5 Geometric data processing ...........................................................................68 5.1 Topography-induced distortions.........................................................................70 5.2 Ayora ..................................................................................................................71 5.3 Lagadas...............................................................................................................72 6 Radiometric processing ................................................................................75 6.1 Sensor calibration...............................................................................................75 6.2 Correction of atmospheric and topographic distortions .....................................78 6.2.1. Radiative transfer