Forest Ecology and Management 256 (2008) 246–255 Contents lists available at ScienceDirect Forest Ecology and Management journal homepage: www.elsevier.com/locate/foreco Review Fire resistance of European pines Paulo M. Fernandes a,*, Jose´ A. Vega b, Enrique Jime´nez b, Eric Rigolot c a Centro de Investigac¸a˜o e de Tecnologias Agro-Ambientais e Tecnolo´gicas and Departamento Florestal, Universidade de Tra´s-os-Montes e Alto Douro, Apartado 1013, 5001-801 Vila Real, Portugal b Centro de Investigacio´n e Informacio´n Ambiental de Galicia, Consellerı´a de Medio Ambiente e Desenvolvemento Sostible, Xunta de Galicia, P.O. Box 127, 36080 Pontevedra, Spain c INRA, UR 629 Mediterranean Forest Ecology Research Unit, Domaine Saint Paul, Site Agroparc, 84914 Avignon Cedex 9, France ARTICLE INFO ABSTRACT Article history: Pine resistance to low- to moderate-intensity fire arises from traits (namely related to tissue insulation Received 8 January 2008 from heat) that enable tree survival. Predictive models of the likelihood of tree mortality after fire are Received in revised form 13 April 2008 quite valuable to assist decision-making after wildfire and to plan prescribed burning. Data and models Accepted 14 April 2008 pertaining to the survival of European pines following fire are reviewed. The type and quality of the current information on fire resistance of the various European species is quite variable. Data from low- Keywords: intensity fire experiments or regimes is comparatively abundant for Pinus pinaster and Pinus sylvestris, Fire ecology while tree survival after wildfire has been modelled for Pinus pinea and Pinus halepensis. P. pinaster and P. Fire regime Pinus pinea, and Pinus canariensis in special, are better equipped to survive fire, but low-intensity fire is Prescribed burning tolerated even by species often referred to as fire-sensitive (P. halepensis and Pinus radiata). The relative Surface fire fire resistance of European pine species is assessed on the basis of (i) morphological and experimental Tree mortality data, and (ii) mortality modelling that considers fire behaviour. Limitations of these approaches to rate fire resistance are discussed, and the current knowledge gaps are indicated. ß 2008 Elsevier B.V. All rights reserved. Contents 1. Introduction . 246 2. Fire survival data and models for European pine species . 247 2.1. Pinus halepensis and Pinus brutia ............................................................................... 247 2.2. Pinus radiata ............................................................................................... 248 2.3. Pinus pinea ................................................................................................ 248 2.4. Pinus pinaster .............................................................................................. 249 2.5. Pinus canariensis ............................................................................................ 249 2.6. Pinus nigra ................................................................................................ 249 2.7. Pinus sylvestris ............................................................................................. 249 3. The relative fire resistance of European pine species. 251 4. Conclusion . 253 Acknowledgements. 253 References...................................................................................................... 253 1. Introduction Disturbance by wildland fire plays a prominent role in the ecology of pine ecosystems. Pine strategies to cope with fire can assist either species persistence (by sexual reproduction) or * Corresponding author. Tel.: +351 259350885; fax: +351 259350480. individual survival (Keeley and Zedler, 1998). Agee (1998) E-mail address: [email protected] (P.M. Fernandes). combined the fire severity concept with life-history characteristics 0378-1127/$ – see front matter ß 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.foreco.2008.04.032 P.M. Fernandes et al. / Forest Ecology and Management 256 (2008) 246–255 247 (Rowe, 1983) to categorize and describe the range of plant removal, salvage logging, reforestation, wildlife habitat and responses in fire-prone environments. Pines under a low-severity watershed quality (Brown et al., 2003). Also, knowledge on tree fire regime are typically fire resisters, possessing traits that enable resistance to low- to moderate-intensity fire is critical to the sound survival to low- to moderate-intensity fire: tissue insulation from use of fire in forest management. However, and in spite of its lethal temperature provided by thick bark, large and protected potential contribution to management decisions conducive to buds, relatively thick needles, deep rooting habit, and a crown more resilient pine forests, research on fire resistance and post- structure favourable to heat dissipation and hence less crown burn mortality has been limited in Europe, presumably because of scorch. Self-pruning and lower branch shedding due to competi- the prevalence of stand-replacement fire and the incipient tion or fire contribute to crown fire avoidance. High-severity fire development of prescribed burning. Several authors (Agee, regimes are characterized by stand-replacement events, and the 1998; Keeley and Zedler, 1998; Climent et al., 2004; Tapias corresponding pine species are fire evaders that store a canopy et al., 2004; Fernandes and Rigolot, 2007) describe the fire-related seed bank in serotinous cones, or fire endurers that recover after traits, strategies or fire regimes of European pines, including the disturbance by sprouting. Moderate or mixed-severity (Brown, explicit comparisons with other pine species. Here we will focus on 2000) fire regimes correspond to diverse or combined fire response the resistance of European Pinus to fire, by reviewing the existing strategies. quantitative knowledge on the ability to survive fire, and then Tree mortality can directly arise from various amounts of fire- rating the fire resistance of each species. caused injury to crown (foliage and buds), vascular or root tissues, either solely or in combination. Tree size can exert an important 2. Fire survival data and models for European pine species influence on the likelihood of tree death after fire. Larger trees should be able to survive more intense fires (Ryan and Reinhardt, 2.1. Pinus halepensis and Pinus brutia 1988; Beverly and Martell, 2003; Kobziar et al., 2006) mainly because of thicker bark and higher position of the foliage. Tree P. halepensis is a typical fire evader that forms highly flammable mortality modelling combines morphological descriptors of the stands and as a rule is killed by wildfire (Agee, 1998; Ne’eman et al., trees with fire damage measurements, indirectly by considering 2004). This possibly explains the scarcity of literature on the fire variables related to fire behaviour or directly by observing tissue resistance of P. halepensis (and of the closely related P. brutia) damage (Fowler and Sieg, 2004). Because tree mortality is a binary versus the wealth of post-fire regeneration studies. variable (trees either live or die) it is well suited to be modelled as a The first experimentation with prescribed burning in the probability by using logistic regression analysis. The extent of Mediterranean Basin was conducted by Liacos (1974) in P. crown scorch, crown consumption, or both, is included as an halepensis and P. brutia in Greece. The author considered these independent variable in most tree mortality models, in relation species amenable to treatment with prescribed fire at an age of 30 either to crown volume (Ryan et al., 1988; McHugh and Kolb, 2003) years – when bark accumulation is sufficient to hamper cambium or to crown length (Wyant et al., 1986). The height, percentage or injury – and went on to develop an underburning prescription severity of bole charring are often adopted as model surrogates for (Liacos, 1986), thereby showing how to minimize fire-induced tree cambium death (Ryan, 1982; Sieg et al., 2006). Fire characteristics mortality. such as fire intensity (Beverly and Martell, 2003; Kobziar et al., Aravanopoulos et al. (2004) refers to a surface wildfire in Greece 2006) or forest floor consumption (Stephens and Finney, 2002; that did not result in P. brutia mortality. In NE Spain after a wildfire Varner et al., 2007) are less often employed as tree mortality of varying severity in a stand (DBH = 10.2 Æ 7.5 cm; basal predictors. area = 21.6 m2 haÀ1) composed of 20-year-old regeneration plus Pines are an important component of European forest vegeta- trees that had survived the previous fire, P. halepensis individuals tion, especially in nutrient-limited or disturbed habitats (Richard- with more than 20% of green foliage were alive less than 1 year after son and Rundel, 1998). The biogeography of the 13 species of the fire (Pausas et al., 2003). In a naturally regenerated and open P. native European pines is described in Barbe´ro et al. (1998) and halepensis stand in SE France, Trabaud and Valina (1998) describe tree Willis et al. (1998), respectively for the Mediterranean Basin and mortality 1 year after a surface wildfire ranging in flame height from for the rest of Europe. Southern Europe pines can be divided in low- 0.5 to 2.5 m. Fire damage descriptors were not measured but tree to mid-elevation species occurring predominantly along the coast survival increased with size: all individuals with less than 5 cm and in islands (Pinus halepensis Mill., Pinus brutia Ten., Pinus pinea ground line diameter died; 37% and 66% of the trees were alive in the L.,