Implementing fire history and fire ecology in fire risk assessment: the study case of Canton Ticino (southern Switzerland) Zur Erlangung des akademischen Grades eines DOKTORS DER NATURWISSENSCHAFTEN von der Fakultät für Bauingenieur-, Geo- und Umweltwissenschaften der Universität Fridericiana zu Karlsruhe (TH) genehmigte DISSERTATION von Dipl.-Forsting. ETH Marco Conedera aus Locarno (Schweiz) Tag der mündlichen Prüfung: 19. Mai 2009 Hauptreferent: Prof. Dr. Caroline Kramer Korreferent: Prof. Curt Beierkuhnlein Vorsitz: Prof. Dr. Dieter Burger Karlsruhe 2009 CONEDERA, M. (2009): Implementing fire history and fire ecology in fire risk assessment I Acknowledgments: I thank Prof. Caroline Kramer, Prof. Carl Beier- The fire management approach presented in this kuhnlein, Prof. Dieter Burger, Prof. Manfred Meurer work is based on the knowledge of fire history, fire and Dr. Christophe Neff for accepting and mentor- ecology, and fire suppression strategies acquired ing my PhD; the the WSL team in Bellinzona for the study area in the frame of the research (Marco Moretti, Patrik Krebs, Boris Pezzatti, Dami- efforts coordinated by the author at the WSL in ano Torriani, Daniela Furrer and Franco Fibbioli) Bellinzona. In the first chapter we present the for technical and psychological support; Marzio motivation and the objectives of the work. Chapter Giamboni of the Hazard Prevention Group, Federal 2 is devoted to the definition of the fire manage- Office for the Environment (FOEN) in Bern for ment related terms. In chapter 3 the study area providing us with the SilvaProtect-CH data; the (Canton Ticino) is presented. The chapters 4 to 6 colleagues of the Forest Fire Expert Group of represent an original synthesis of the results Canton Ticino (Gabriele Corti, Aron Ghiringhelli, achieved in the frame of different research projects Pietro Bomio, Daniele Ryser, Paolo Ambrosetti, (Swiss National Research Program 31 [Climate Tiziano Ponti) and Giancarlo Cesti (Nucleo Antin- changes and natural catastrophes], ONU decade cendi Boschivi della Valle d’Aosta in Quart, Italy) for natural disasters, EU-Prometheus s.v., EU Fire for advice during different stages of the present Paradox) and related publications (CONEDERA et al. study; Danielle Fuchs for the revision of the Eng- 1996; HOFMANN et al. 1998; CONEDERA et al. 1999; lish text; Jenny Sigot for the French abstract; the MARXER & CONEDERA 1999; CONEDERA et al. 2007b; WSL publication team (Ruth Landolt, Sandra PEZZATTI et al. 2009), the PhD works supervised by Gurzeler and Jacqueline Annen) for performing the the author (TINNER 1998; MORETTI 2003; MARXER layout of the present publication; and the colleagues 2003) and the many Master theses coordinated by of the Institut für Geographie und Geoökologie of the WSL in Bellinzona. The chapters 7 and 8 repre- the University of Karlsruhe (Alexander Scheid, sent the core of the present work consisting in an André Hohmann, Anna Mai and Anja Müller) for the original methodology for assessing fire danger, interesting discussions during common seminars. vulnerability to fire and fire risk. Bellinzona, May 2009 Marco Conedera CONEDERA, M. (2009): Implementing fire history and fire ecology in fire risk assessment III Contents Acknowledgements I Contents III Index figures V Index tables VIII Abbreviations and acronyms IX 1 Introduction 1 2 Defining some key concepts and activities related to fire management 3 2.1 Problems related to the fire management terminology 3 2.2 Fire management 3 2.3 Fire management related terminology 3 2.4 Fire risk related terminology 3 2.5 Fire regime 4 3 The study area 5 3.1 Criteria for selecting the study area 5 3.2 Main historical, political and economic characteristics 5 3.3 Geography, geology and climate 6 3.4 Forest cover 8 4 Forest fire history 14 4.1 Methodological approach 14 4.2 Long-term fire history 15 4.3 From the Middle Age to the modern times 17 4.4 Wildland fires in the last century 18 4.5 Present fire regime 20 4.6 Concluding remarks 22 5 Forest fire selectivity and ecology 23 5.1 Methodological approach 23 5.2 Fire selectivity 25 5.3 Post-fire vegetation response 28 5.4 Post-fire response of invertebrates 28 5.5 Fire adapted species 31 5.6 Post-fire effects on soil 33 5.7 Concluding remarks 34 6 Fire management history 35 6.1 Methodological approach 35 6.2 Fire prevention 35 6.3 Fire fighting organization 41 6.4 Concluding remarks 44 7 Assessing relative fire danger 46 7.1 Methodological approach 46 7.2 Logical outline for evaluating the fire danger 46 7.3 Results of the Monte Carlo simulations 47 7.4 Fire danger indexes 51 IV CONEDERA, M. (2009): Implementing fire history and fire ecology in fire risk assessment 8 Assessing relative fire risk 57 8.1 Methodological approach 57 8.2 Assessing the fire ecological effects 57 8.3 Assessing the fire impact on resources 58 8.4 Assessing the vulnerability to fire 59 8.5 Implementing the relative fire risk 59 9 Conclusions 64 10 Abstract 65 11 Zusammenfassung 67 12 Riassunto 69 13 Résumé 71 14 References 73 15 Glossar 81 CONEDERA, M. (2009): Implementing fire history and fire ecology in fire risk assessment V Index Figures Fig. 1.1 Schematic representation of the driving forces asking for a shift from the fire control to the fire management approach. 2 Fig. 2.1 Structure and major components of the Wildland fire risk. 4 Fig. 3.1 Geographical and political location of the Canton Ticino. 5 Fig. 3.2 Evolution of the population of Canton Ticino 1850–2005. 6 Fig. 3.3 Evolution of livestock breeding in Canton Ticino 1865–2005. 6 Fig. 3.4 Evolution of the land cover in Canton Ticino 1912–2005. 6 Fig. 3.5 Distribution of the urbanized area in Canton Ticino. 7 Fig. 3.6 Elevation map of Canton Ticino. 7 Fig. 3.7 Geologic map of Canton Ticino. 7 Fig. 3.8 Climatic diagrams of Lugano, Locarno-Monti and Comprovasco for the period 1971–2000. 7 Fig. 3.9 Distribution maps of the main forest cover classes in Canton Ticino. 9 Fig. 3.10 Box-plot distributions of elevation, slope and aspect for the main forest cover classes. 12 Fig. 4.1 Coring sites in the study area for the reconstruction of the long term fire history. 14 Fig. 4.2 Long-term fire history in Sottoceneri (Ticino). 16 Fig. 4.3 Selected anthropogenic indicators and long term fire history at Lago di Origlio. 16 Fig. 4.4 Evidence of pasture fires for the period 1870–2000 in Canton Ticino. 17 Fig. 4.5 Place names referring to pasture fires (brüsada, Schwändi). 18 Fig. 4.6 Annual precipitation, charcoal influx Origlio, number of fires, and burnt area in Canton Ticino for the period 1900–2006. 18 Fig. 4.7 Annual precipitation, number of fires, forest area, cattle, and number of farmers in Canton Ticino for the period 1900–2006. 19 Fig. 4.8 Monthly distribution of forest fires in Canton Ticino. 20 Fig. 4.9 Percentage distribution of the ignition causes according to the fire season and to the period. 20 Fig. 4.10 Geographic distribution of the forest fires starting points in Canton Ticino. 21 Fig. 4.11 Different elevation, slope, and duration of lightning-ignited and anthropogenic fires in the summer season. 21 Fig. 5.1 Correlograms of charcoal influx, pollen percentages and diversity from Lago di Origlio. 29 Fig. 5.2 Schematic representation of the short and long term effects of different fire frequencies on the species diversity in Canton Ticino. 30 Fig. 5.3 Schematic representation of the short and long term effects of different fire frequencies on R-, N- and H-values in Canton Ticino. 30 Fig. 5.4 Overall biodiversity in terms of number of species and number of individuals trapped in differently burned chestnut stands in Canton Ticino. 31 Fig. 5.5 Distribution area of Cistus salviifolius in Canton Ticino. 31 Fig. 5.6 Specimens of Aradus lugubris FALLEN 1807 collected in the frame of the fire experiment of March 28th 1998 in S. Antonino (Canton Ticino). 32 Fig. 5.7 Rate of water infiltration in burned and unburned soil in Ronco s./Ascona. 33 Fig. 5.8 Runoff in burned and unburned areas. 33 Fig. 5.9 Erosion in burned and unburned areas. 34 Fig. 6.1 Annual precipitation, number of fires, trend, and legislation related to fire prevention in Canton Ticino for the period 1900–2006. 36 VI CONEDERA, M. (2009): Implementing fire history and fire ecology in fire risk assessment Fig. 6.2 Box-plot distribution of the number of forest fires in the periods 1980–1989 and 1990–1999 in Canton Ticino and in Canton of Grisons. 36 Fig. 6.3 Effect of pre-suppression measures on number of fires and burnt area ignited by the railways in Canton Ticino for the period 1900–2006. 36 Fig. 6.4 Effect of pre-suppression measures on number of fires and burnt area ignited by the army in Canton Ticino for the period 1900–2006. 36 Fig. 6.5 Water points available for water supply during aerial fire fighting. 41 Fig. 6.6 Stands originated from plantations in Canton Ticino. 41 Fig. 6.7 Cumulative percentage of the forest fire events according to their size and to different seasons. 42 Fig. 6.8 Annual precipitation, burnt area, trend, fire brigades reorganisations, technical improvements, and aerial fire fighting in Canton Ticino for the period 1900–2006. 42 Fig. 6.9 Running means over 11 years of mean, median and maximal annual fire sizes of winter and summer forest fires in Canton Ticino for the period 1900–2006. 43 Fig. 6.10 Cumulative percentage of number of fires and burnt area for the periods 1969–1989 and 1990–2007 and for winter and summer fires.