j.g. pausas' blog

Hace unos días escribí una entrada (post) sobre los famosos “cipreses ignífugos” de Jérica (incendio de Andilla, Valencia, Julio/2012) argumentado que no habían ardido principalmente por la discontinuidad del combustible alrededor y dentro de la plantación, ayudado por la situación topográfica (en una pequeña vaguada), que limitaría la llegada de las llamas a los cipreses (ver De incendios y cipreses). Mucha gente ha mostrado estar de acuerdo con mi interpretación, pero también han habido personas que ha argumentado que la fotografía aérea que presentaba podía ser antigua, y por lo tanto, actualmente podría haber más vegetación (combustible) alrededor y dentro de la parcela. Para apoyar mi argumento, aquí muestro algunas fotografías tomadas ayer (6 de Octubre) donde se observan los detalles que yo mencionaba. La razón principal de que no ardieran es que no les llegaron las llamas.

Figura 1. Se aprecia la separación entre la zona forestal (a la izquierda) y la plantación de cipreses, a la derecha. Los cipreses presentan parte de la copa de color marrón debido al efecto del calor del incendio, pero las llamas no llegaron a ellos (foto JG Pausas, 6/10/2012).

Figura 2. Separación entre la zona forestal (a la derecha) y la plantación de cipreses, en otro de los lados de la plantación. Se observan matorrales verdes, no afectados por el fuego, y una carrasca sólo parcialmente afectada, evidenciando que el fuego no llegó a la plantación (foto JG Pausas, 6/10/2012).

Figura 3. El romero (Rosmarinus officinales) y la aulaga (Ulex parviflorus) son dos de las especies arbustivas más inflamables de nuestro territorio. En estas fotografías se aprecian en primer plano ejemplares de romero (foto izquierda) y aulaga (foto derecha) que no se quemaron porque no les llegaron las llamas, y mucho menos les llegaron a los cipreses de detrás. La coloración marrón indica que sí que llegó el calor del incendio al romero, a la aulaga, y a los cipreses más externos de la plantación. Las fotos también muestran la separación entre los cipreses, y la poca vegetación en el sotobosque, aspectos que impiden la propagación del fuego (fotos JG Pausas, 6/10/12).

Figura 4. Ejemplo de lo que puede pasar cuando llegan las llamas a los cipreses. Incendio del Alt Empordà, Julio 2012. (foto: L. Brotons).

Más información: De incendios y cipreses (1), jgpausas.blogs.uv.es, 19 Sep. 2012.

Este verano en España circularon unas fotos de una zona incendiada (incendio de Andilla, junio/julio 2012, Valencia) donde había una grupo de cipreses que no se había afectado por el incendio (ver figura 1). Eso llevó a que muchos medios de comunicación sacaran titulares como: “Los cipreses se comportan como escudos naturales contra el fuego“, “El enigma de los cipreses ignífugos“, “¿Y si los cipreses de Jérica nos estuvieran diciendo lo que hay que hacer?“, etc… Estas noticias han llevado a que se sugiera la plantación de cipreses para la “lucha contra incendios” y la “protección de viviendas”; incluso hay organismos que ya se han comprometido a realizar plantaciones con esos fines (“La Diputación de Valencia plantará cipreses para luchar contra los incendios“, “Cipreses contra el fuego“). Estas noticias sorprenden un poco a los especialistas, ya que se sabe que los cipreses no son ignífugos, arden como todas la plantas. Se conocen otras zonas afectadas por incendios en las que había cipreses y estos ardieron (p.e., incendio de las Useres, Castellón). Además, en algunos países, como en EEUU, está prohibida su plantación en jardines situados en zonas donde los incendios son frecuentes, precisamente por el peligro que conllevan. Los setos de cipreses alrededor de casas son especialmente peligrosos. Desde el punto de vista de la biodiversidad, los cipreses no son plantas autóctonas en España, y por lo tanto, no se aconseja su plantación en medios forestales, a no ser que la razón sea de mucho peso.

Figura 1. Fotografía difundida en los medios de comunicación donde se observan los cipreses no afectados por el incendio (Andilla, julio/julio 2012). Foto extraída de “El Pais”, 12/8/2012.

El 27 de septiembre se realizó en el Jardí Botànic de Valencia un seminario sobre los cipreses de Andilla, y quedó clara la razón por la que no ardieron. Básicamente, no ardieron porque se trata de una plantación mantenida (“limpia” y podada), de manera que no tiene sotobosque, los árboles están separados entre ellos, y al ser estrechos, a pesar de ser altos, las copas no se tocan (ver figura 2). Por lo tanto, el fuego no se puede propagar dentro de la plantación. Además, la plantación está rodeada de un camino, que impide que el fuego llegue a la mayoría de los cipreses. El fuego llegó a la plantación por el suroeste (flecha roja en la figura 2), donde hay un camino ancho que hizo de cortafuegos, de manera que disminuyó mucho la intensidad del fuego a la llegada de la plantación. Por otro lado, la plantación está situada en una pequeña vaguada, hecho que dificulta aún más que llegue el fuego de manera intensa.

Figura 2. Imagen aérea de la plantación de cipreses localizada en el término de Jérica que no se afectó por el incendio originado en Andilla (Junio/Julio 2012; imagen previa al incendio descargada de www.google.maps el 28/9/2012 [ver imagen en google]). La flecha roja indica la dirección del fuego (según Raúl Quílez, del Consorcio Provincial de Bomberos de Valencia). La orientación de la fotografía difundida en la prensa (figura 1) no permite ver que se trata de una plantación sin sotobosque, con árboles distanciados y con claras discontinuidades de combustible.

Por lo tanto, no se puede decir que los los cipreses sean ignífugos, sino que la discontinuidad de combustible que había dentro y alrededor de la plantación evitó que se afectaran por el fuego; una plantación de olivos, naranjos, algarrobos, etc.  hubiera tenido el mismo efecto. Un ejemplo de una plantación de pinos que no se vio afectada por un incendio se puede ver en la figura 3. Crear discontinuidades en el combustible constituye, de hecho, una manera de limitar los incendios;  esto resulta especialmente evidente con los cultivos (figura 4), por lo tanto, no es ninguna novedad. Lo ocurrido con estos cipreses es un ejemplo de cómo los medios de comunicación pueden desorientar a la población, e incluso influir en la gestión, sin ninguna base científica o técnica.

Figura 3: Plantación de pino piñonero (Pinus pinea) que sobrevivió a un incendio en Portugal; véase el bosque del fondo quemado (Foto: J. Climent).

Figura 4: Fotografía de una isla agrícola dentro de una zona forestal afectada por el incendio de Cortes de Pallás/Dos Aguas (Valencia, Junio/julio, 2012; foto: JG Pausas).

Bibliografía

– Libro: Incendios forestales
– Incendios forestales en Valencia, Junio 2012: ¿Por qué? ¿Cómo evitarlos?
– Life 15 days after the large fires in Valencia

Actualización:

De incendios y cipreses (1), jgpausas.blogs.uv.es 29/9/2012
De incendios y cipreses (2), jgpausas.blogs.uv.es 7/10/2012
De incendios y cipreses (3), jgpausas.blogs.uv.es 22/6/2013
De incendios y cipreses (4), jgpausas.blogs.uv.es 31/8/2015
De incendios y cipreses (5), jgpausas.blogs.uv.es 11/10/2016
De incendios y cipreses (y 6), jgpausas.blogs.uv.es 3/13/2017

“Cerrado” are neotropical savannas from Brazil. As in most savannas, fire is very frequent in cerrado, and fires has been occurring in these ecosystems during the last few millions years. Consequently, cerrado communities are strongly filtered by fire and are composed by species capable of succeed under frequent fires (e.g., resprouters, with very thick bark, etc). A recent study [1] comparing zones with different fire regimes (annual fires, biennial fires, and protected from fires) within the cerrado (in Emas National Park) suggests that most plant trait variability is found within species (intraspecific) and little trait variability is due to changes in species composition (interspecific) between fire regimes. Thus, at community scale, fire act more as an filter, preventing some of the species from outside cerrado to colonize the cerrado (e.g., from nearby non-flammable forests), than as an internal factor structuring species composition in the already filtered cerrado communities with different fire regimes. However, fire acts as an important factor generating intraspecific variability. These results support the hypothesis of the prominent importance of intraspecific variability in strongly fire-filtered communities [2,3].

Figure: The rhea (emas in Portuguese; Rhea americana) are a flightless birds that give the name to the Emas National Park (Parque Nacional das Emas), a World Natural Heritage site located in the Brazilian Central Plateau (Photo: JG Pausas, 2009, during the field sampling [1]).

References

[1] Dantas V.L., Pausas J.G., Batalha M.A., Loiola P.P. & Cianciaruso M.V. 2013. The role of fire in structuring trait variability in Neotropical savannas. Oecologia, 171: 487-494. [doi | pdf]

[2] Moreira B., Tavsanoglu Ç. & Pausas J.G. 2012. Local versus regional intraspecific variability in regeneration traits. Oecologia, 168, 671-677. [doi | pdf | post]

[3] Pausas J.G., Alessio G., Moreira B. & Corcobado G. 2012. Fires enhance flammability in Ulex parviflorus. New Phytologist 193: 18-23. [doi | wiley | pdf]

Many pines species are fire adapted. In 1998, JE Keeley & PH Zedler provided a seminal paper showing the various fire adaptations of pines, and the relation between the different adaptations and the different fire regimes [1]. Recent phylogenetic [2,3] and conceptual [4,5] advances in fire ecology have allowed to better understand the evolutionary role of fire in plants, and specifically in pines [2-6]. In a recent paper, JE Keeley provides a new review on the ecology and evolution of pine life histories [7]. Pinus originated ~150 Ma in the mid-Mesozoic Era and radiated across the northern continent of Laurasia during the Cretaceous period, when fire activity was high [3]. Pines have followed two evolutionary strategies interpreted as responses to competition by the newly emerging angiosperms: 1) The Strobus lineage mostly has radiated into stressful sites of low nutrient soils and extremes in cold or heat; ans 2) The Pinus (subgenus) lineage has radiated into fire-prone landscapes with diverse fire regimes. Based on the life history traits associated to fire, JE Keeley define four pine syndromes [7]: fire-avoiders (no fire-adapted; with thin bark), fire-toleraters (adapted to surface fires; with thick bark and self-pruning of dead branches; tall pines), fire-embracers (adapted to crown fires; with retention of dead branches and serotinous cones), and fire-refugia (with marked metapopulation dynamics) strategies.

Figure: Basal fire scar (a) and cross-section of pine with previous fires delineated (b) demonstrating fire survival after recurrent fires. Photos by JE Keeley from [7].

References
[1] Keeley J.E. & Zedler P.H. 1998. Evolution of life histories in Pinus. In: Ecology and biogeography of Pinus (ed. Richardson DM). Cambridge University Press Cambridge (UK), pp. 219-250.

[2] Schwilk D.W. & Ackerly D.D. 2001. Flammability and serotiny as strategies: correlated evolution in pines. Oikos, 94, 326-336. [doi]

[3] He T., Pausas J.G., Belcher C.M., Schwilk D.W. & Lamont B.B. 2012. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytol., 194, 751-759. [doi | wiley | pdf ]

[4] Pausas, J. G. and J. E. Keeley. 2009. A burning story: The role of fire in the history of life. Bioscience 59: 593-601. [doi | jstor | pdf]

[5] Keeley, J. E., J. G. Pausas, P. W. Rundel, W. J. Bond, and R. A. Bradstock. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Sci. 16:406-411.  [doi | pdf]

[6] Pausas J.G. & Schwilk D.W. 2012. Fire and plant evolution. New Phytol., 193, 301-303.  [doi | wiley | pdf]

[7] Keeley J.E. 2012. Ecology and evolution of pine life histories. Ann. For. Sci., 69, 445–453. [doi]

Traditionally, Australian aboriginal people set fires in their landscape to facilitate hunting. A recent study has compared the landscape and fire history from two regions, one where aboriginal people live in a traditional way and the other where fires are “natural” and caused by lightning [1]. The results show that aborigines generate many small fires that are climate-independent, while lightning generates few large climate-driven fires. Anthropogenic fires are smaller even when climatic conditions cause huge fire in the lightning region. The authors suggest that this climate-buffering effects of aboriginal fires has likely been important for many species that benefit both from fine-grained mosaics of alternating resources and from enhanced protection from large catastrophic fires and the predators that hunt within them. This may explain the coincident decline of many small- to medium-sized mammals in the arid regions of Australia with the cessation of aboriginal hunting and burning. That is, the extinction of the aboriginal life style shifted fire regimes from small fires to large climate-driven fires, in a similar manner to the extinction of rural life styles in the Mediterranean Europe [2], and this shift promoted the extinciton of Australian mammals.

Fire Dreaming, by Malcolm Maloney Jagamarra [from www.aboriginalartcoop.com.au]

References

[1] Bird R.B., Codding B.F., Kauhanen P.G. & Bird D.W. (2012). Aboriginal hunting buffers climate-driven fire-size variability in Australia’s spinifex grasslands. PNAS, 109, 10287-10292. [pnas]

[2] Pausas J.G. & Fernández-Muñoz S. (2012). Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Clim. Change, 110, 215-226.  [doi | springer | pdf]

Few days ago two simultaneously large fires occurred very near to Valencia city [1]: The first affecting Dos Aguas and surroundings (ca. 29000 ha burned), and the second in Andilla and surroundings (ca. 19000 ha burned). The fires burned under extreme fire whether conditions (strong drought, high temperature and strong dry wind [Foehn type wind]). 15 days after the fire, I visited area burned around Dos Aguas and took these pictures showing the postfire life activity; several species already started to resprout and pines were dispersing their seeds. In addition I saw several lizards, different birds and a fox, all in the middle of the recently burned area, quite far from the edge of the fire.

A. Chamaerops humilis (en: Mediterranean dwarf Palm, es: palmito, cat: margalló)

B. Resprout of Quercus coccifera (en: Kermes oak, es: coscoja, cat: garric, coscoll)

C. Resprout of Daphe gnidium (en: flax-leaved daphne, es: torvisco, cat: matapoll). The high intensity of the fire is clear from the thick remaining branch.

D. Post-fire seed dispersal of the serotinous cones of Pinus halepensis (en: Aleppo Pine , es: pino carrsco; cat: pi blanc).

[1] Incendios forestales en Valencia, Junio 2012, jgpausas.blogs.uv.es, 4/Julio/2012.

Cork oak (Quercus suber) is a strong fire-resistant tree species thank to is very thick and insulating corky bark [1-4]. In fact it is the only European tree with the capacity to resprout from epicormic buds in the canopy after an intense crown-fire [1]. However, the bark of the cork oak is periodically harvested for cork production (mainly for bottle tops but also for other uses, [2]) and thus bark harvesting increases the vulnerability of the tree to fire. In a recent paper we quantified the response of cork oak (tree mortality, stem mortality, and crown recovery) after fire [5]. The results showed that fire vulnerability was higher for trees with thin bark (young or recently debarked individuals) and decreased with increasing bark thickness until cork was 3–4 cm thick. This bark thickness corresponds to the moment when exploited trees are debarked again, meaning that exploited trees are vulnerable to fire during a long period. Exploited trees were also more likely to be top-killed than never-debarked trees, even for the same bark thickness. Additionally, vulnerability to fire increased with burn severity and with tree diameter, and was higher in trees burned in early summer or located in drier south-facing aspects. All these aspects need to be considered when managing cork oak woodlands specially nowadays that fire activity is increased [6]. Increasing the length of the cork harvesting cycle would increase the time during which the trees have a thicker bark and are better protected against fire injury. Since cork is the main economical income from these forests, stopping bark exploitation might be unrealistic in most cases. However, in fire-prone areas where conservation and tourism are the main objectives, stopping bark explotation would likely be the most effective option to increase ecosystem resilience to fire. The valorisation of many other services provided by cork oak forests [7] could create economic incentives to decrease the bark-exploitation dependency of these systems in the future.

Foto: Cork oak  resprouting from epicormic buds (By F. Catry)

References

[1] Pausas, J.G. 1997. Resprouting of Quercus suber in NE Spain after fire. J. Veg. Sci. 8: 703-706. [doi | pdf]

[2] Aronson, J., J. S. Pereira, and J. G. Pausas (eds). 2009. Cork Oak Woodlands on the Edge: Ecology, Adaptive Management, and Restoration. Island Press, Washington, DC. [web of the book]

[3] Pausas J.G. 2009. Convergent evolution. jgpausas.blogs.uv.es, 8/Nov/2009. [link]

[4] Pausas J.G. 2011. Bark thickness: a world record? jgpausas.blogs.uv.es, 3/Jan/201. [link]

[5] Catry F., Moreira F., Pausas J.G., Fernandes P.M., Rego F., Cardillo E. & Curt T. 2012. Cork Oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors. PLoS ONE 7: e39810. [doi | pdf ]

[6] Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. [doi | springer | pdf]

[7] Bugalho M.N., Caldeira M.C., Pereira J.S., Aronson J., & Pausas J.G. 2011. Mediterranean Cork oak savannas require human use to sustain biodiversity and ecosystem services. Frontiers in Ecology and the Environment 9: 278-286. [doi | pdf | blog]

¿Por qué se dan estos incendios?

• El incremento de población urbana en el paisaje rural (chalets, urbanizaciones, actividades de fin de semana, etc…) aumenta la probabilidad de igniciones. Esto es debido a que muchas actividades humanas generan chispas o igniciones, tanto de manera accidental (vehículos, soldaduras, cocinas, cigarros, cableados, barbacoas, …) como intencionada (malhechores y pirómanos).
• La disminución de la población rural (reducción del pastoreo, agricultura, recolección de leña, etc..) durante las últimas décadas conlleva un incremento de la cantidad de vegetación (combustible) en el paisaje. De manera que si se da un incendio, es más probable que sea de mayor tamaño e intensidad que anteriormente cuando el uso del monte era intenso.
• La elevada sequía y las elevadas temperaturas hacen que la vegetación sea muy inflamable, y una fuente de ignición (chispa, etc.) pueda ser fuente de un incendio. El cambio climático aumenta la frecuencia de estas situaciones.
• Los vientos de poniente en Valencia son muy secos, cálidos y relativamente fuertes. Si hay un incendio en estas condiciones, el fuego se propaga rápidamente y es prácticamente imposible detenerlo, hasta que no cambian las condiciones del viento.

Los días 28 al 30 de Junio de 2012 en Valencia se dieron todos estos factores. Las condiciones climáticas eran extremas, con temperaturas elevadas  (las máximas rondando 40 grados) y humedad muy baja (hacía al menos 2 meses que no llovía); en esas condiciones, las chispas prenden fácilmente. Además, hubo tres días seguidos de vientos secos y sin cambio de dirección (el poniente), que facilitó la rápida propagación del fuego. Los dos incendios que se dieron esos días afectaron aproximadamente a un total de 50000 ha. Los incendios se controlaron cuando el poniente calmó.

¿Qué podemos hacer para evitarlos?

No es fácil, y se requiere una política a largo plazo. La simple extinción no es suficiente, tal como hemos visto en muchas ocasiones, tanto en nuestro país como en otros (incluidos países tecnológicamente más avanzados y ricos). Aquí algunas ideas:

• Disminuir la población urbana que vive en los paisajes inflamables, es decir, disminuir los chalets y urbanizaciones que tenemos en nuestros montes, reducir la interfaz urbano-forestal. En general las urbanizaciones en el medio natural son: 1) potenciales puntos de ignición; 2) puntos de desastre cuando se da un incendio (a menudo los incendios no son perjudiciales para la vegetación, que se regenera, pero causan problemas a los habitantes que viven en el monte); 3) son en sí mismos un problema para la biodiversidad, independientemente de los incendios (destrozan parte del paisaje y de la naturaleza, incrementan las especies invasoras, etc…).
• Incentivar la vida rural y el uso sostenible de los montes. Introducir o facilitar a la presencia de herbívoros autóctonos (y sus depredadores).
• Reducir el cambio climático, es decir, reducir las emisiones de gases efecto invernadero y cumplir con los protocolos de Kyoto sobre el cambio climático. Reducir el uso de energías contaminantes, etc.
• Aceptar que siempre habrá incendios en nuestros montes mediterráneos, y aprender a vivir con ello. Diseñar con detalle las zonas donde se puede construir y donde no; limitar fuertemente el paso en los caminos rurales, especialmente en épocas propensas a incendios; regular las construcciones y sus alrededores considerando los incendios como parte del paisaje.

 Valencia, 30 Junio 2012.

Para más información:

Libro: Incendios forestales, Ed. Catarata-CSIC [enlace]

Incendios de ayer, de hoy y de mañana, Crónica Popular 6/7/2012  [enlace | pdf]

Pausas J.G. & Paula S. 2012. Fuel shapes the fire-climate relationship: evidence from Mediterranean ecosystems.  Global Ecol. Biogeogr. [doi | pdf | post]

Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. [doi | pdf | post]

Pausas, J.G. 2004. Changes in fire and climate in the eastern Iberian Peninsula (Mediterranean basin). Climatic Change 63: 337-350. [doi | pdf]

Pausas, J.G., Vallejo R. 2008. Bases ecológicas para convivir con los incendios forestales en la Región Mediterránea – decálogo Ecosistemas, 17(2): 128-129 (5/2008). [link | pdf]

Urban planning for fire management [link]

Book: Fire in mediterranean ecosystem [link]

The answer is blowing in the wind [link]

Nuevo libro: Se acaba de publicar un libro que pretende ser una introducción a la ecología del fuego: Incendios forestales, Editorial Catarata-CSIC.

Para más información ver aquí.

Comprar en: www.catarata.org, editorial.csic, Amazon, Fnac, CasaDelLibro, etc. | distribuidores
Precio: 12 euros

We recently analyzed the fire-climate relationship in the Iberian Peninsula (western Mediterranean Basin) [1], and found that climate shapes fire activity on a temporal scale by modifying fuel flammability (i.e., more fire during dry years; left figure below) and on a spatial scale by affecting fuel structure (i.e., more fire in productive Iberian regions). On the temporal scale, fire and climate are not linearly related, but there is a critical aridity level (i.e., the aridity threshold) above which fuels become highly flammable and area burnt increases sharply (left figure below). This aridity threshold is not universal, but rather intrinsic to each ecosystem (i.e., to its landscape structure). The drier the region, the higher the dryness level needed for switching from non-flammable to flammable conditions (right figure below), suggesting that the aridity threshold is mediated by fuel. In productive regions, an ignition may lead to a fire under relatively high moisture conditions (compared to drier regions) due to the high fuel load and connectivity. On the contrary, in dry regions, wildfires are more fuel-limited, so more extreme climatic conditions (higher aridity than in more mesic regions) are needed for fires to successfully spread. The fact that the aridity threshold is intrinsic to the ecosystem emphasizes the importance of landscape structure in determining fire-climate relationship.

Fuel structure does not depend exclusively on environmental conditions (e.g., aridity/productivity); shifts in fire activity have also been related to changes in land-use [2,3] and fire-suppression policies. Gradual historical shifts in land-use may produce abrupt changes in fuel structure across landscapes and thus, in fire activity [3]. Therefore, the fire-climate relationship changes not only with climatic conditions, but also  in response to different land uses and management practices (and often in an abrupt way).

Figure: [left:] Relation between area burnt and monthly aridity ( (PET-AET)/PET) in one of the 13 Iberian regions considered (temporal scale); vertical line indicates the location of the aridity threshold. [Right:] Relationship between the the aridity threshold and the aridity of the region, for 13 Iberian regions (Pausas & Paula, 2012 [1]).

References
[1] Pausas J.G. & Paula S. 2012. Fuel shapes the fire-climate relationship: evidence from Mediterranean ecosystems. Global Ecology and Biogeography 21: 1074-1082 [doi | pdf | supp]

[2] Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226. [doi | springer | pdf | post]

[3] Pausas, J.G. 2004. Changes in fire and climate in the eastern Iberian Peninsula (Mediterranean basin). Climatic Change 63: 337-350. [doi | springer | pdf]

Fire are often considered disasters when they destroy infrastructure and lives (independently of the ecological effects); this is specially important in mediterranean-type climate regions where there is a high density of houses in the wildland-urban interface. The most common management action to avoid these disasters are based of fuel reduction (fuel breaks, prescribed fires, etc). However, these actions do not seems to be very successful, at least in crowded regions and where fire occur in extreme weather situations. For instant, in southern California nearly 1000 homes per year have been destroyed by wildfires since 2000, despite their fire management plans. In addition, strong fuel reduction actions have negative biodiversity implications (vegetation degradation, alien invasion, etc.). In a recent paper, Syphard et al. [1] suggest that urban planning could be more efficient in reducing disasters and property losses from fire than fuel management. They found that at the regional scale, fuelbased maps did not predict property loss as well as maps developed using a combination of factors that included housing arrangement and location. Consequently land use planning and housing development policies should be important components of fire risk management plans for the wildland-urban interface.

[1] Syphard A.D., Keeley J.E., Massada A.B., Brennan T.J. & Radeloff V.C. (2012). Housing arrangement and location determine the likelihood of housing loss due to wildfire. PLoS ONE, 7, e33954.

Finally the new fire ecology book by Keeley et al. (2012) has been published:

For more information, table of contents, etc, see here.

Cambridge UP (uk | usa | au), Amazon (uk | usa | jp), eBooks

How old are wildfires? Probably as old as terrestrial ecosystems [1]. The origin of fire is tied to the origin of land plants, which are responsible for two of the three elements essential to the existence of fire: oxygen and fuel. The third element, a heat source, has probably been available throughout the history of the planet (mainly through lightning). There is charcoal evidencs of fires already in the Silurian (440 Ma). However, the existence of fire does not necessarily mean that fire was playing an evolutionary role at that time. So when did fire start to play an evolutionary role generating fire adaptations [2, 3]? By mapping fire adaptation onto a dated phylogeny of Pinaceae, we recently demonstrated [4] that at least, and for this family, fire was an agent of natural selection since about 90-125 Ma! This is far back from what was known until now [4]. At this time, fire-protective thick barks were originated in Pinus species as response to surface fires. With increasing fire intensity, thicker barks and serotiny appeared by 70-90 Ma. These innovations appear at the same time as the Earth’s paleoatmosphere experienced elevated oxygen levels that led to high burn probabilities (mid-Cretaceous). That is, the fiery environments of the Cretaceous strongly influenced trait evolution in Pinus. Whether fire had an evolutionary role prior to this is a challance for future research.

Fotos: In many pines, the thick bark and the discontinuity between the canopy and the understory (self-pruning) allows survival after surface fires (left: Pinus nigra, eastern Spain). Serotinous cones allow a quick seed regeneation after crown fire (right: P. halepensis, eastern Spain). Photos: JG Pausas

References
[1] Pausas, J. G. and J. E. Keeley. 2009. A burning story: The role of fire in the history of life. Bioscience 59: 593-601. [doi | jstor | BioOne | pdf]

[2] Keeley, J. E., J. G. Pausas, P. W. Rundel, W. J. Bond, and R. A. Bradstock. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16:406-411. [doi | trends | pdf] | For managers]

[3] Pausas, J. G. and D. W. Schwilk. 2012. Fire and plant evolution. New Phytologist 193:301-303. [doi | wiley | pdf]

[4] He T., Pausas J.G., Belcher C.M., Schwilk D.W., Lamont B.B. (2012). Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytologist 194: 751-759 [doi | wiley | pdf]

Resprouting is a mechanism that allows individual plants to persist in disturbance-prone ecosystems. It is often considered a binary trait, defining species as resprouters or non-resprouters [1]. Although this dichotomous classification accounts for a high proportion of the interspecific variability in resprouting, it does not account for the intraspecific variability, as not all individuals of resprouting species successfully resprout [2], even if they are subject to a similar disturbance. In a recent paper, we proposed a conceptual model that disaggregates the process of resprouting into three sequential steps: initial ability to resprout, resprouting vigour and post-resprouting survival [3]. Intraspecific variability in resprouting supported the importance of: a) the pre-disturbance state of the plant (i.e. plant size and stored resources) on the initial ability to resprout and on the resprouting vigour, and b) the initial post-disturbance capacity to acquire resources (i.e., resprouting vigour) on the post-resprouting survival. The proposed three-step model of resprouting provides a mechanistic description of the factors driving intraspecific variability in resprouting.

Figure: Probability of initiating resprouting (as a function of starch concentration in roots), resprouting vigor (as a function of pre-disturbance plant size), and survival (as a function of the resprouting vigor), for Linum suffruticosum [see pictures] in the Valencia (eastern Spain). From Moreira et al. (2012) [2]

References

[1] Pausas, J.G., Bradstock, R.A., Keith, D.A., Keeley, J.E. & GCTE Fire Network. 2004. Plant functional traits in relation to fire in crown-fire ecosystems. Ecology 85: 1085-1100. [jstor | pdf]

[2] Catry F.X., Rego F., Moreira F., Fernandes F.M., Pausas J.G. 2010. Post-fire tree mortality in mixed forests of central Portugal. For. Ecol. Manage. 206: 1184-1192. [doi | pdf | post]

[3] Moreira B., Tormo J, Pausas J.G. 2012. To resprout or not to resprout: factors driving intraspecific variability in resprouting. Oikos [doi | pdf]

Considering fire as evolutionary pressure driving evolution has traditional been neglected, and only now is becoming a topic of research [1-3]. The role of fire as an evolutionary pressure can be elucidated using both macro- and micro-evolutionary approaches. While the micro-evolutionary approach searches for trait divergences in different current selective environments, the macro-evolutionary approach uses dated phylogenies to trace the evolution of traits over long time scales (My). In a previous post [3] we mentioned an example of the macro-evolutionary approach. In a recent paper, S. Goméz-Gonzalez and collaborators [5] provided, for the first time, a clear example of the micro-evolutionary approach to demonstrate natural selection driven by fire.  They presented compelling evidence that the novel anthropogenic fires affecting the Chilean matorral shaped seed traits on a native annual plants (Helenium aromaticum). By studying populations growing on sites with different recent fire histories, they showed that increasing fire frequency selects for increasing seed pubescence (directional selection): a trait that was proven to be heritable and that increased fitness under experimental heat treatments. This paper was also presented in a special session at the MEDECOS Conference [3].

Figure: Habitat of Helenium aromaticum in central Chile [5]

References
[1] Pausas J.G. & Keeley J.E. 2009. A Burning Story: The role of fire in the history of life. BioScience 59: 593-601. [doi | pdf | post]

Keeley J.E., Pausas J.G., Rundel P.W., Bond W.J., Bradstock R.A. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16: 406-411 [doi | trends |pdf]

[3] Pausas, J. G. and D. W. Schwilk. 2012. Fire and plant evolution. New Phytologist 193: [pdf]

[4] Pausas J.G. 2011. Australia born to burn – phylogenetic evidences. URL: jgpausas.blogs.uv.es, 18/03/2011

[5] Gómez-González S, Torres-Díaz C, Bustos-Schindler C, Gianoli E, 2011. Anthropogenic fire drives the evolution of seed traits. PNAS 108: 18743-18747. [doi]

It is know that the germination of some species from Mediterranean fire-prone ecosystems is triggered by combustion chemicals which appear in the smoke and the charred wood (for simplicity, we use the term “smoke-stimulate germination”). This smoke-stimulated germination is now known from many post-fire recruiting species in South Africa, Australia, California and the Mediterranean Basin [e.g., 1-4]. Certain nitrogen oxides (NOx) induce germination in a limited number post-fire species [3], but this does not apply to most the smoke-stimulated species. In 2004 two independent studies isolated the active organic compound from the smoke that stimulates germination [5,6]: butanolide (also named karrikinolide). Because this compound is a derived from the combustion of cellulose it was thought to be universal germination cue in all smoke-stimulated plants. However, the fact that smoke-induced germination appears in very distant regions and in species from very different lineages, suggest that unrelated species could had evolve mechanisms that are triggered by different components from the smoke [7]. Later it was demonstrated that some species with smoke-stimulated germination did not responded to butanolide, supporting the idea that could be multiple mechanisms to stimulate germination by smoke [8]. A recent paper has found a new smoke-stimulation mechanism from which burning plant material produces cyanide that stimulate the germination of some species [9]. Little by little we are learning on the role of fire in plant ecology and evolution [7, 10].

Figure:  Germination percentage (mean+s.e.) in relation to time since sowing (days) for Cistus monspeliensis after different heat treatments (A), and for Lavandula stoechas after different smoke treatments (B). From Moreira et al. (2010) [4]

References:
[1] Brown, N. A. C. 1993. Promotion of germination of fynbos seeds by plant-derived smoke. New Phytologist 123:575-584.

[2] Dixon, K. W., S. Roche, and J. S. Pate. 1995. The promotive effect of smoke derived from burnt native vegetation on seed germination of Western Australian plants. Oecologia 101:185-192.

[3] Keeley, J. E. and C. J. Fotheringham. 2000. Role of fire in regeneration from seeds. Pages 311-330 in M. Fenner, editor. Seeds: The ecology of regeneration in plant communities. CAB International, Wallingford, UK.

[4] Moreira, B., J. Tormo, E. Estrelles, and J. G. Pausas. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Annals of Botany 105:627-635. [doi | pdf | post]

[5] Van Staden, J., A. Jäger, M. Light, and B. Burger. 2004. Isolation of the major germination cue from plant-derived smoke. South African Journal of Botany 70:654-659.

[6] Flematti, G. R., E. L. Ghisalberti, K. W. Dixon, and R. D. Trengove. 2004. A compound from smoke that promotes seed germination. Science 305:977.

[7] Pausas, J. G. and J. E. Keeley. 2009. A burning story: The role of fire in the history of life. Bioscience 59:593-601. [doi | pdf | post]

[8] Downes, K. S., B. B. Lamont, M. E. Light, and J. van Staden. 2010. The fire ephemeral Tersonia cyathiflora (Gyrostemonaceae) germinates in response to smoke but not the butenolide 3-methyl-2H-furol[2,3-c]pyran-2-one. Annals of Botany 106:381-384.

[9] Flematti, G. R., D. J. Merritt, M. J. Piggott, R. D. Trengove, S. M. Smith, K. W. Dixon, and E. L. Ghisalberti. 2011. Burning vegetation produces cyanohydrins that liberate cyanide and stimulate seed germination. Nature Comm. 2:360.

[10] Keeley, J. E., J. G. Pausas, P. W. Rundel, W. J. Bond, and R. A. Bradstock. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16:406-411. [doi | pdf | post]

Mediterranean Ecosystem (MEDECOS) conferences are held every 3–5 yrs, rotating venues through all five Mediterranean-type climate (MTC) regions of the world. The first meeting was held in Valdivia (Chile) in 1971. The last MEDECOS was held in Los Angeles (University of California, September 6-9, 2011, [1]), and about 300 scientist from the different MTC regions got together and presented their research on the different aspects of the ecology in mediterranean ecosystems. In this MEDECOS, fire was an important topic, it was explicit in the title at least in the following 5 special sessions:

– Fire as an evolutionary pressure shaping plant traits (6th Sept, Pausas & Schwilk)
– Fire management at the wildland-urban interface (7th Sept, Keeley)
– Global change and fire (7th Sept, van Mantgem)
– Fire ecology in Mediterranean woodlands ans shrublands (8th Sept, O’Leary)
– Fire management (9th Sept, Fotheringham)

Dylan Schwilk and I organised the first one which highlighted several key aspects on the role of fire in plant evolution: First, there is good evidence for vegetation-fire regime feedbacks at different spatial and temporal scales, in such a way that plant flammability is a major driver of plant evolution and vegetation distribution. Second, the evidence that fire acts as a selective force is apparent on both micro- and macro-evolutionary scales, suggesting that fire shapes plant traits and generates fire adaptations. And third, that fire is a complex selective pressure – plants adapt to (and, in turn, influence) particular fire regimes rather than fire in the abstract. This is an exciting time for fire ecologists, as fire is now recognized as fundamental for many ecological and evolutionary processes; the coming macro- and micro- evolutionary studies will certainly reinforce many of the ideas drawn during the meeting [2]. The details of this session, including slides of the talks and a summary of the session [2], are now available here .

[1 ] MEDECOS 2011:  web | program | abstracts | final resolution [2] Pausas, J. G. and D. W. Schwilk. 2012. Fire and plant evolution. New Phytologist 193 (2). [doi | pdf]

Recurrent fires are a strong evolutionary pressure shaping plants [1,2]. It has been hypothesized that in fire prone-ecosystems, natural selection has favoured the development of traits that enhance flammability [3]. Consistent with this idea, in a recent study [4] we found that Ulex parviflorus (Fabaceae) populations that inhabit in recurrently burn areas (HiFi populations) are more flammable than populations of this species growing in old-fields where the recruitment was independent of fire (NoFi populations). That is, HiFi plants ignite quicker, burn slower, release more heat and have higher bulk density than NoFi plants. Thus, it appears that repeated fires select for individuals with higher flammability, and thus driving trait divergence among populations living in different fire regimes. These results provide some field support for the ‘kill thy neighbour’ hypothesis [3], but they also highlighted the need for heritability studies to unambiguously demonstrate natural selection driven by fire. This study together with other studies recently commented in this blog [5, 6] are placing flammability as a fundamental trait in plant evolution.

Figure: Flammability experiments using an epiradiator [4].

References

[1] Keeley, J. E., J. G. Pausas, P. W. Rundel, W. J. Bond, and R. A. Bradstock. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16:406-411. [doi | pdf]

[2] Pausas J.G. & Keeley J.E. 2009. A burning story: The role of fire in the history of life. BioScience [doi | jstore | pdf]

[3] Bond, W. J. and J. J. Midgley. 1995. Kill thy neighbour: an individualistic argument for the evolution of flammability. Oikos 73:79-85.

[4] Pausas J.G., Alessio G., Moreira B., Corcobado G. 2012. Fires enhance flammability in Ulex parviflorus. New Phytologist 193:18-23 [doi | pdf]

[4′] Pausas J.G. & Moreira B. 2012. Flammability as a biological concept. New Phytologist 194: 610-613. [doi | pdf]

[5] Pausas JG. 2011. Australia born-to-burn: a phylogenetic approach. jgpausas.blogs.uv.es, 18/March/2011 [link]

[6] Pausas JG. 2011. Fire and evolution: Cretaceous fires and the spread of angiosperms. jgpausas.blogs.uv.es, 9/Sept/2011 [link]

Resprouting is a very important process in plants living in disturbance-prone ecosystems, and the December issue of the journal Plant Ecology is going to be dedicated to this topic (Ecology of plant resprouting in fire-prone ecosystems). During the recent years, and starting from the PERSIST project, we have been comparing functional traits between resprouters and non-resprouters in Mediterranean fire-prone ecosystems, and the last comparison (physiological traits [5]), is included in this special issue. Resprouters and non-resprouters are two plant syndromes in Mediterranean ecosystems that also differ in their evolutionary history [1]. Resprouters tend to exhibit a deeper root-system than non-resprouters that inverse less resources on roots. So one could think that resprouters are better adapted to drought. However, both resprouters and non resprouters coexist, and non-resprouters counteract their lower root allocation by different traits that confer higher drought resistance [2]. Non-resprouters have higher drought resistance at leave level because they have higher water use efficiency (WUE) and higher leaf mass per area (LMA; i.e., higher sclerophylly, lower SLA) [3]. The seedling root structure of non-resprouters also allows them to more efficiently explore the upper soil layer [4]. A recent paper also shows that, when water is non-limiting, non-resprouters showed a better performance of leaf gas exchange traits (higher assimilation, stomatal conductance and transpiration) than resprouters [5]; that is non-resprouters have higher efficiency in resource capture, and thus a better capacity to take advantage of water when it is freely available. In addition, resprouters and non-resprouters also differ in their post-fire germination, as non-resprouters tend to have a greater capacity to both (i) persist after fire by means of recruiting (greater heat-tolerance) and (ii) increase their population after fire (greater heat-stimulated germination), than resprouters [4]. All these results suggest that resprouters and non-resprouters are two contrasted syndromes or functional types in the Mediterranean Basin [6].

Figure: Arbutus unedo resprouting after a fire.

References:

[1] Pausas J.G. & Verdú M. 2005. Plant persistence traits in fire-prone ecosystems of the Mediterranean Basin: A phylogenetic approach. Oikos 109: 196-202. [pdf |doi]

[2] Pausas J.G. 2010. Fire, drought, resprouting: leaf and root traits. URL: jgpausas.blogs.uv.es, 22/Oct/2010.

[3] Paula S. & Pausas J.G. 2006. Leaf traits and resprouting ability in the Mediterranean basin. Functional Ecology 20: 941-947. [pdf | [doi]

[4] Paula S. & Pausas J.G. 2011. Root traits explain different foraging strategies between resprouting life histories. Oecologia 165:321-331. [doi | pdf | blog]

[5] Hernández E.I., Pausas J.G. & Vilagrosa A. 2011. Leaf physiological traits in relation to resprouter ability in the Mediterranean Basin. Plant Ecology 212:1959-1966 [doi| pdf]

[4] Paula S. & Pausas J.G. 2008. Burning seeds: Germinative response to heat treatments in relation to resprouting ability. Journal of Ecology 96 (3): 543 – 552. [pdf | doi]

[6] Pausas, J.G., Bradstock, R.A., Keith, D.A., Keeley, J.E. & GCTE Fire Network. 2004. Plant functional traits in relation to fire in crown-fire ecosystems. Ecology 85: 1085-1100. [pdf | jstor] [Ecological Archives E085-029]

Variability is a fundamental characteristic of life and the raw material for natural selection, driving speciation and diversification processes. Traditional biogeographical theory would predict that plants in populations that are close each other (e.g., few km) should be more similar among them, than plants in distant populations (e.g., 100s or 1000s km). This is because biogeographical processes such as migration, glacial/interglacial climatic fluctuations and isolation should cause distant plant populations to diverge, and thus enhance intraspecific variability at large scales, while gene flow through close populations should reduce divergences. In contrast, in a recent paper we suggest that in fire prone-ecosystems, where fire may generate local heterogeneity, local variability in traits related to regeneration are quite large, overriding the variability at the larger scale [1]. Studying post-fire regeneration traits in Cistus salviifolius and Lavandula stoechas, in eastern Iberia (IB, Spain) and in south-western Anatolia (AN, Turkey), we found that the trait variability within each region is larger than between regions (separated by about 2600 km, with the sea in the middle). The traits studied were seed size, seed dormancy and germination stimulation by head and by smoke. The two studied species exhibited germination stimulated by the fire-related cues; and independently of the region, the different populations of each species had a similar pattern of response. That is, Cistus salviifolius was stimulated by heat and Lavandula stoechas was mainly stimulated by smoke, although heat also exhibited a positive effect on the latter species (see also [2] for more details on heat- and smoke- stimulated germination). All these results supports the prominent role of fire as an ecological and evolutionary process across the Mediterranean Basin, producing trait variability and shaping biodiversity [3, 4].

References

[1] Moreira B., Tavsanoglu Ç., Pausas J.G. 2012. Local vs regional intraspecific variability in regeneration traits. Oecologia 168: 671-677 [doi | pdf]

[2] Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Annals of Botany 105: 627-635.[pdf| doi | blog]

[3] Pausas J.G. & Keeley J.E. 2009. A burning story: The role of fire in the history of life. BioScience 59: 593-601 [doi | pdf | post]

[4] Keeley J.E., Pausas J.G., Rundel P.W., Bond W.J., Bradstock R.A. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16(8): 406-411. [doi | pdf | For managers]

There are still people believing that wildfires are a catastrophic disturbance to ecosystems, and that are the product of humans. However there is an increasing evidence from paleoecological records and from phylogenetic analyzes suggesting that fire is a very old process in the history of life, dating back to the origin of land plants [1, 2, 3]. As a consequence many plants have evolved in the presence of recurrent wildfires and acquired adaptive traits to persist and reproduce in those conditions. Examples of these traits are the resprouting ability, germination by head or smoke, and serotiny; all of these confer fitness advantage in fire-prone ecosystems. However, plants are not adapted to fire per se but to fire regimes. Species that exhibit traits adaptive under a particular fire regime can be threatened when that regime changes, like the recent human-induced fire regime changes (e.g., increasing or decreasing fire frequency or severity in relation to the historic fire regime).

In a recent paper, Keeley et al. [4] proposed five scenarios of change in a trait state (Figure 1). An adaptive trait might not change through time regardless of the selective environment (scenarios 1 and 2 in Figure 1). Such traits cannot be described as adaptations to the current selective (fire-prone) environment as there is no evidence that natural selection shaped this trait. Other adaptive traits that were shaped by natural selection under a previous evolutionary pressure, but not under the current (fire-prone) environment (scenario 3 in Figure 1) would be adaptations to previous evolutionary pressures and exaptations to the current (fire) environment [4, 5]. Fire adaptations are those adaptive traits in which natural selection is acting under the current fire-prone environment to shape the trait, and it is independent of how long this pressure has been present (scenarios 4 and 5 in Figure 1). For instance, there are clear examples of lineages that resprout after fire, but their origin and evolution is hardly liked to fire. However the most plausible scenario of lineages that resprouting from lignotubers is the number 4 in Fig. 1 (old origin of resprouting reshaped by current recurrent fires). Similarly serotiny and thick barks are traits that has been reshaped by natural selection under the framework of recurrent fires and thus they also fit under the concept of adaptation to fire (scenario 4 or 5 in Fig. 1).

References
[1] Pausas J.G. & Keeley J.E. 2009. A Burning Story: The role of fire in the history of life. BioScience 59: 593-601. [doi | pdf | post | slides]

[2] Pausas J.G. 2011. Australia born to burn – phylogenetic evidences. URL: jgpausas.blogs.uv.es, 18/03/2011.

[3] Pausas J.G. 2010. Fire and evolution: Cretaceous fires and the spread of angiosperms. URL: jgpausas.blogs.uv.es, 9/Sep/2010.

[4] Keeley J.E., Pausas J.G., Rundel P.W., Bond W.J., Bradstock R.A. 2011. Fire as an evolutionary pressure shaping plant traits. Trends in Plant Science 16: 406-411 [doi | trends | pdf]

[5] Endler J.A. (1986) Natural selection in the wild. Princeton University Press.

Figure. 1. Five possible evolutionary scenarios of change in a trait state along the evolutionary time (simplified). For each scenario, different line types are periods under different dominant evolutionary pressures (e.g., the continuous line represents a period in which fire acted as an evolutionary pressure; dashed line the period with a different previous selective environment). The scenarios are:
1) and 2) No change along the time axis and no sign of natural selection (no adaptation to fire);
3) trait shaped during the first evolutionary pressure, but no change (with persistence of the state of the trait) during the second evolutionary pressure; natural selection acted during the first period only (no adaptation to fire, but exaptation);
4) and 5) Trait shaped during the whole period; natural selection acts during the whole period even if the dominant evolutionary pressure changed (adaptation to fire).
From Keeley et al. (2011, [4]).

We have compiled the longest fire history for a region in the Mediterranean Basin, from contemporary fire statistics plus old newspapers and old forest administration dossiers in Valencia (Spain) [1]. With this information we statistically demonstrated that fire regime has changed during the 1970’s, in such a way that fires increased in annual frequency (doubled), fire size, and area burned (by an order of magnitude). The main driver of this shift was the increase in fuel amount and continuity due to rural depopulation (vegetation and fuel build-up after farm abandonment) suggesting that fires were fuel-limited during the pre-1970s period. Climatic conditions were poorly related to pre-1970s fires and strongly related to post-1970s fires, suggesting that fire are currently less fuel limited and more drought-driven than before the 1970s. Thus, the fire regime shift implies also a shift in the main driver for fire activity. In conclusion, the collapse of the rural lifestyle shifted fire regimes from being fuel-limited to be drought-driven, and this may have consequences in an world where droughts are increasing in frequency [2]. The same process occurred in all the European Mediterranean region, and the large fires in Greece during the 2007 heat wave [link] are a good example of a system drought-driven. Interestingly, simultaneously to our study, a similar work has just been published demonstrating that the collapse of the Soviet Union lead to a reduction in grazing pressure and a subsequent increase in area burned [3].

[1] Pausas J.G. & Fernández-Muñoz S. 2012. Fire regime changes in the Western Mediterranean Basin: from fuel-limited to drought-driven fire regime. Climatic Change 110: 215-226 [doi | pdf]

[2] Pausas, J.G. 2004. Changes in fire and climate in the eastern Iberian Peninsula (Mediterranean basin). Climatic Change 63: 337-350. [doi | pdf]

[3] Dubinin M., Luschekina A. & Radeloff V.C. 2011. Climate, livestock, and vegetation: What drives fire increase in the arid ecosystems of southern Russia? Ecosystems, doi:10.1007/s10021-011-9427-9

Fig. 1. The abandonment of agriculture and livestock, and the change in the domestic energetic sources (from wood to others) modified the landscape from a mosaic (top image) to an homogeneous fuel bed of flammable vegetation (bottom image). These changes drove the increased fire activity since the 70’s (see Fig. 2 below).

Fig. 2. Annual area burnt (ha × 1000, vertical lines, left axis) for 1873 to 2006 and the rural population density (inhabitants/ha, dotted line, right axis), in Valencia (Spain). From Pausas & Fernández-Muñoz (2011).

Traditionally wildfires were considered a disturbance linked to the recent history of the Quaternary, and specially linked to the humans. However, evidence are accumulating about the ancient role of wildfires in terrestrial ecosystems [1]. In Australia, the flammable continent, the current believe is that fires started to be important during the onset of seasonal aridity in the Miocene (25 Ma). However, two recent and independent papers demonstrate, using phylogenetic techniques, that fire-dependent traits appeared about 60 Ma ago (early Paleocene), implying that fire was already an effective agent of selection by then. Crisp et al [2] studied the Myrtaceae family and showed that post-fire epicormic resprouting (typical of many eucalypts) is an ancient trait linked to the flammable sclerophyll biomes originated about 60-62 Ma. He et al. [3] studied the Banksia genus (Proteaceae) and showed that serotiny (fire dependent dispersal; figure below) and dead floret retention around the cones (enhanced flammability around serotinous cones) co-originate with the first appearance of Banksia 60.8 Ma ago. The coincidence of the two independent papers, using two different taxa (Myrtaceae and Banksia) is amazing, and clearly suggests that fire was a selective force in Australia during the Paleocene.  These papers are part of the accumulating research on the prominent and ancient role of fire in shaping plant species and biodiversity [1, 4 ].

References
[1] Pausas J.G. & Keeley J.E. 2009. A Burning Story: The role of fire in the history of life. BioScience 59: 593-601. [doi | pdf | post | slides]

[2] Crisp MD, Burrows GE, Cook LG, Thornhill AH, Bowman DMJS. 2011. Flammable biomes dominated by eucalypts originated at the Cretaceous-Palaeogene boundary. Nature Communications 2: 193. [doi]

[3] He T, Lamont BB, Downes KS. 2011. Banksia born to burn. New Phytol. [doi]

[4] Bond, W. J. and Scott, A. C. 2010. Fire and the spread of flowering plants in the Cretaceous. New Phytol. 188: 1137–1150 [post]

Figure: Banksia cone opened by the fire to release seeds (serotiny).

The thickness of the bark is a trait of paramount importance in trees living in ecosystems with frequent surface (understory) fires (e.g., some coniferous forests, savanna woodlands, etc.). This is because the bark is a good insulator protecting vital tissues from the heat of the fire. Having a bark few millimeter thicker provide an advantage in such fire-prone ecosystems. Thus there has been a selection for thick barks in surface fire ecosystems [1]. A prominent example of a tree with a very thick and insulating bark is the Cork oak (Quercus suber) that growth in the western part of the Mediterranean Basin [2]. In such species the thicker is the bark, the better is the response after fire [3, 4]. This bark is so thick and insulating that it is used not only as bottle tops, but also as insulating material in many industrial applications. However the Mediterranean Basin has been densely populated from long ago and it is very difficult (if possible) to find Cork oak woodlands in “natural” conditions, and thus it is not easy to know how thick the bark of Cork oak could attain in natural conditions. Most trees are frequently debarked for obtaining cork (frequencies ranging from every 9 to every 12 years, depending of the site conditions).

Few days ago I visited an ethnographic museum in Aggius (Sardinia) and found a piece of Cork oak bark of about 22 cm thick (see picture below), which is pretty thick. I only know of one record of a thicker bark: 27 cm in a 140 years-old Cork oak that was never debarked [5]. Do you know of any tree (of the same or another species) in the world with a thicker bark? Is Cork oak the world record on bark thickness?

Figure: Piece of bark from a Cork oak (Quercus suber), in the ethnographic museum of Aggius (Sardinia).

References:

[1] Pausas J.G. 2009. Convergent evolution. jgpausas.blogs.uv.es, 8/Nov/2009. [link]

[2] Aronson J., Pereira J.S., Pausas J.G. (eds). 2009. Cork Oak Woodlands on the Edge: conservation, adaptive management, and restoration. Island Press, Washington DC.  [link]

[3] Pausas, J.G. 1997. Resprouting of Quercus suber in NE Spain after fire. J. Veg. Sci. 8: 703-706. [doi | pdf]

[4] Catry F.X., Rego F., Moreira F., Fernandes F.M., Pausas J.G. 2010. Post-fire tree mortality in mixed forests of central Portugal. Forest Ecology & Management 206: 1184-1192. [doi | pdf]

[5] Natividade J.V. 1950. Subericultura. Direçao Geral dos Serviços Florestais e Aquícolas Lisbon, Portugal.

In Mediterranean Basin ecosystems, fires are frequent, and post-fire regeneration is tipically based on native species, that is, there is no invasion of alien species after fire. However, this is not the case in the other Mediterranean climatic regions, where fire frequencies higher than their natural (historic) fire regime favors the invasion of alien plants. This is specially the case in the Mediterranean ecosystems of Chile, where recurrent fires play a little role on the evolutionary history. In Chile, fires appeared with the indigenous settlements, and increased exponentially since the time of the Spanish invasion (1536). This increase in fires, together with heavy grazing, has reduced the native matorral and increased the invasive species. In a recent paper, Gómez-Gonzalez et al. [1] show that fire open the window for the establishment of annual plants, and most of them are alien (from the Mediterranean Basin). The successful establishment of alien annuals was due to their ability to maintain rich seedbanks in burned areas and to the greater propagule arrival compared to native species (annuals or perennials). Thus the results demonstrate that fire is a relevant factor for the maintenance of alien-dominated grasslands in the Chilean matorral and highlight the importance of considering the interactive effect of seed rain and seedbank survival to understand plant invasions patterns in fire-prone ecosystems.

[1] Gómez-González S, Torres-Díaz C., Valencia G, Torres-Morales P, Cavieres L.A., and Pausas J.G (in press). Anthropogenic fires increase alien and native annual species in the Chilean coastal matorral. Diversity and Distributions 17: 58-67 [doi | pdf]

Figure: Chilean matorral recently burnt showing the invasion of Fumaria capreolata (flowering), and annual alien species original from Europe (Foto by S. Gómez-González).

Drought and fire are prevalent disturbances in Mediterranean ecosystems. Plant species able to regrow after severe disturbances (i.e. resprouter life history) have higher allocation to roots and higher water potential during the dry season than coexisting non-resprouting species. However, non-resprouters have higher survival rate after summer drought. We expect that, to counteract their shallow-rooting systems and to maximize seedling survival, non-resprouters have traits that confer higher water-use efficiency and higher efficiency in soil resource acquisition than resprouters.

Some time ago we tested this prediction in relation to leaf traits [1] and found that non-resprouters have higher leaf mass per area (LMA; i.e. lower specific leaf area, SLA), leaf dry matter content (LDMC), area-based leaf nitrogen content (LNCa) and integrated water-use efficiency (δ13C) than resprouters, suggesting that they have higher potential for structural resistance to drought and higher water-use efficiency than resprouters.

In a recent paper we have now tested the prediction for root traits in seedlings [2]. We found that non-resprouters have higher specific root length (SRL) and longer, thinner and more branched lateral roots, especially in the upper soil layers. The external links (i.e. the most absorptive root region) are also more abundant, longer, thinner and with higher SVR for non-resprouters. Thus seedling root structure of non-resprouters species allows them to explore more efficiently the upper soil layer, whereas seedling roots of resprouters will permit both carbon storage and deep soil penetration.

Whereas resprouters tend to maximize the surface and the efficiency of the organs for carbon uptake to ensure carbohydrate storage for resprouting (eg, higher SLA), non-resprouters maximize the root surface (eg, higher SRL), since their survival and growth may be limited by soil resources.

[1] Paula S. & Pausas J.G. 2006. Leaf traits and resprouting ability in the Mediterranean basin. Functional Ecology 20: 941-947. [doi | pdf]

[2] Paula S. & Pausas J.G. 2011. Root traits explain different foraging strategies between resprouting life histories. Oecologia 165:321-331 [doi | pdf]

Relationship between average root diameter and specific root length (SRL; log-scale) for resprouting (R+, closed symbols) and non-resprouting (R-, open symbols) species. Intraspecific variability is indicated by segments emerging from each symbol. From Paula & Pausas (Oecologia [2]).

Recently we have highlighted the importance of wildfires in the evolution of plants in many ecosystems worldwide [1 | previous post]. In this line, a recent paper by Bond & Scott suggest that the spread of angiosperms in the Cretaceous (145-65 Ma) was promoted by the development of novel fire regimes linked to the evolution of novel, highly productive (and flammable) plants. They suggest that Creatceous angiosperms were similar to current ruderal (weedy) species, i.e., short, with high maximum photosynthetic rates, rapid reproduction and small seeds. This fast-growing angiosperms would not only compete with regenerating gymnosperms, but would also rapidly accumulate fuel. More fuel would promote more frequent fires, which would help to maintain open habitats in which rapid growth traits of angiosperms would be most favoured, promoting rapid fuel accumulation. The authors emphasize the similitude of this “angiosperm–fire cycle” with  the grass fire-cycle that helped to spread C4 grasses in the Miocene (c. 8 Ma) [3] and with the grass fire-cycle replacing forests by invasive grasses in the modern world [4]. This would also imply that forest was slow to develop until the Eocene, when fire activity dropped to very low levels. This hypothesis could also help to explain the ancient origin of some fire traits like resprouting and the abundance and phylogenetically widespread examples of species with smoke-stimulated germination [1, 5]. In conclusion I think this is a nice and stimulating contribution to the evolution of angiosperms.

References

[1] Pausas J.G. & Keeley J.E. 2009. A Burning Story: The role of fire in the history of life. BioScience 59: 593-601. [doi | pdf | post | slides]

[2] Bond, W. J. and Scott, A. C. 2010. Fire and the spread of flowering plants in the Cretaceous. New Phytol. 188: 1137–1150 [doi]

[3] Keeley, J. E. and Rundel, P. W. 2005. Fire and the Miocene expansion of C4 grasslands. Ecol. Lett. 8: 1-8.

[4] D’Antonio, C. M. and Vitousek, P. M. 1992. Biological invasions by exotic grasses, the grass/fire cycle and global change. Annu. Rev. Ecol. Syst. 23: 63-87.

[5] Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann. Bot. 105: 627-635. [pdf | doi | blog]

In September 2003, a mixed forest of central Portugal (Tapada Nacional de Mafra) burned in a large crown fire. We surveyed the survival of more than 700 trees during 4 years postfire. The results are detailed in a recent paper by Catry et al. (2010, [1]) ; the table below provides a summary on the proportion of the trees that  (a) died, (b) survived but were top-killed (stem and crown mortality) and resprouted from the base, and (c) the stem survived, after 4 years postfire (for tree mortality, the value observed after the first year is given in brackets).

Most pines (P. pinaster and P. pinea) died and few, specially of P. pinea, were little affected by fire; there were a significant positive relationship between crown damage and tree mortality.
Most broadleaved trees survived the fire, and whether the stem survived or died (and resprouted from the base) were related to bark thickness and char height (i.e. fire severity). Castanea sativa showed the highest tree mortality, mostly due to post-resprouting mortality after the first year. Fraxinus angustifolia, Olea europaea and Pistacea lentiscus showed no mortality at all; most Olea and Pistacea individuals resprout from the base, while for Fraxinus the crown of most trees were unaffected. The low effect of fire in Fraxinus angustifolia is probably due to the topographic positions where this species occurs; in addition theses trees are quite tall and with relatively thick bark. Quercus coccifera and Q. faginea showed low mortality and most trees resprouted from the base. Quercus suber showed almost no mortality and almost all trees showed epicormic resprouting, due to their extremely thick and insulating bark [2, 3].

References

[1] Catry F.X., Rego F., Moreira F., Fernandes F.M., Pausas J.G. 2010. Post-fire tree mortality in mixed forests of central Portugal. For. Ecol. Manage. 206: 1184-1192. [doi] [pdf]

[2] Pausas, J.G. 1997. Resprouting of Quercus suber in NE Spain after fire. J. Veg. Sci. 8: 703-706. [pdf]

[3] Aronson J., Pereira J.S., Pausas J.G. (eds). 2009. Cork Oak Woodlands on the Edge: conservation, adaptive management, and restoration. Island Press, Washington DC. 315 pp. [The book] [Ch 1, the tree]

[Update] see: “To resprout ot not to resprout”, Jan 25th, 2012.

En pleno verano, y como cada año, arden unas cuantas hectáreas de nuestros paisajes. En los ecosistemas mediterráneos esto lleva ocurriendo desde hace muchos años, incluso antes de la llegada de los humanos. El fuego y los incendios forestales no es ni mucho menos un invento de los pirómanos, sino que están en la naturaleza desde casi siempre, y por eso hay muchas plantas adaptadas a vivir en zonas con fuegos recurrentes (igual que hay plantas que pueden sobrevivir el pastoreo recurrente). Lo que ha hecho los humanos es modificar el régimen de incendios, aumentado o disminuyendo su frecuencia e intensidad.

A menudo los incendios se ven como una cosa “mala” para la naturaleza; en un artículo de divulgación en la revista “Investigación y Ciencia” (Agosto 2010) damos otra visión del fuego, y hacemos un repaso del papel de este en la evolución de las especies,  la otra cara del fuego. En nuestros ecosistemas, el fuego es una parte integral de los procesos ecológicos, y a lo largo de la historia ha ido moldeando las especies, las comunidades y los paisajes. Sin duda hay ciertos regímenes de incendios que son naturales y característicos de ciertos ecosistemas, y parte de la diversidad de nuestros ecosistemas se explica por la existencia reiterada y predecible de incendios. Sin embargo, también es cierto que hay zonas que están sufriendo regímenes de incendios fuera del rango natural y con graves consecuencias ecológicas. El objetivo de la gestión forestal no debería ser eliminar los incendios, ya que es prácticamente imposible, además de poco natural. Por el contrario, deberían asumirse ciertos regímenes sostenibles de incendios, y aprender a convivir con ellos.

Pausas, J.G. 2010. Fuego y evolución en el Mediterráneo. Investigación y Ciencia, 407 (Agosto): 56-63. [PDF: IyC | jgpausas]

Pausas J.G. & Keeley J.E. 2009. A Burning Story: The role of fire in the history of life. BioScience, 59: 593-601. [caliber] [pdf]

Pausas, J.G., Vallejo R. 2008. Bases ecológicas para convivir con los incendios forestales en la Región Mediterránea – decálogo Ecosistemas, 17(2): 128-129 (5/2008). [link] [pdf]

Pausas J.G., Llovet J., Rodrigo A., Vallejo R 2008. Are wildfires a disaster in the Mediterranean basin? – A review. Intern. Journal of Wildland Fires, 17: 713-723. [pdf] [IJWF CSIRO] [doi]

Mediterranean communities living under high fire recurrence are composed by plant species that are more closely related than what would be expected from the regional species pool (i.e., phylogenetic clustering; Verdú & Pausas 2007). This is because high fire recurrence favors seeder species, and the traits that confer the seeder character (e.g., heat and smoke stimulated germination, Moreira et al. 2010) are evolutionary conserved, that is, closely related species tend to be similar (Pausas & Verdú 2008). In fact, the abundance of seeders species is negatively related to phylogenetic diversity (Coca & Pausas 2009; see Figure 2 below).

The Figure 1 below shows the Net Relatedness Index (NRI, i.e, standardized form of the community mean phylogenetic distance) of woody species coexisting in for communities in contrasted crown-fire regimes (LowFire vs HighFire) at different spatial scales (regional and local). Note that high net relatedness = low mean phylogenetic distance. At regional scale, “LowFire” corresponds to mountain communities living in zones that rarely burnt, and “HighFire” are warm and dry coastal communities subject to a high frequency of crown fires. At local scale (under the same climate), “LowFire” corresponds to communities growing in fertile soils while “HighFire” are communities growing on poor soils where flammability is higher. When comparing from community null models, HighFire communities show higher NRI than expected by chance (phylogenetic clustering), which indicates the importance of habitat filtering in shaping fire-prone communities (Verdú & Pausas 2007, Ojeda et al. 2010).

Fig. 1. Elaborated from Verdú & Pausas (2007) and Ojeda et al. (2010).

Fig. 2. From Coca & Pausas (2009).

References

• Coca M. & Pausas J.G. 2009. Regeneration traits are structuring phylogenetic diversity in cork oak (Quercus suber) woodlands. J. Veget. Sci. 20: 1009-1015. [doi | pdf | post]
• Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann. Bot. 105:627-635 [doi | pdf | post]
• Ojeda, F., Pausas, J.G., Verdú, M. 2010. Soil shapes community structure through fire. Oecologia 163:729-735. [doi | pdf | post]
• Pausas J.G. & Verdú M. 2008. Fire reduces morphospace occupation in plant communities. Ecology 89: 2181-2186. [doi | pdf]
• Verdú M. & Pausas J.G. 2007. Fire drives phylogenetic clustering in Mediterranean Basin woody plant communities J. Ecol. 95: 1316-323. [doi | pdf]

Until now, the role of fire as a germination cue for Mediterranean Basin plants was unclear. The idea was that heat stimulates germination mainly in Cistaceae and Fabaceae and that smoke had a limited role as a post-fire germination cue, in comparison to other Mediterranean Type Ecosystems (MTE), suggesting that fire-stimulated germination is less relevant in the Mediterranean Basin than in other Mediterranean regions. However, in a recent paper, Moreira et al. (2010) demonstrate that both heat and smoke stimulates the germination (both amount and rate) of a range of woody species from the Mediterranean Basin flora. In addition, some species also showed enhanced seedling growth after the smoke treatment (Figure below). All these results suggest that fire-cued germination in woody plants of Mediterranean Basin may be as important as in other Mediterranean regions, and that fire had a strong role in shaping the Mediterranean species.

Moreira B., Tormo J., Estrelles E., Pausas J.G. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Annals of Botany 105: 627-635. [pdf | doi]

Differences in size between seedlings from untreated (control, left) and treated seeds (smoke, right), for Lavandula latifolia (8 days after seedling emergence). The white squares are of 2.5cm width.

Recurrent wildfires constitute a major selecting force in shaping the structure of plant communities. At the regional scale, fire favours phenotypic and phylogenetic clustering in Mediterranean woody plant communities. Nevertheless, the incidence of fire within a fire-prone region may present strong variations at the local, landscape scale. This study tests the prediction that woody communities on acid, nutrient-poor soils should exhibit more pronounced phenotypic and phylogenetic clustering patterns than woody communities on fertile soils, as a consequence of their higher flammability and, hence, presumably higher propensity to recurrent fire. Results confirm the predictions and show that habitat filtering driven by fire may be detected even in local communities from an already fire-filtered regional flora. They also provide a new perspective from which to consider a preponderant role of fire as a key evolutionary force in acid, infertile Mediterranean heathlands.

Ojeda, F., Pausas, J.G., Verdú, M. 2010. Soil shapes community structure through fire. Oecologia 163:729-735. [doi]  [pdf]

The first author in the flammable, low fertility community.

One key difference between animals and humans is the use of fire; in fact, during the evolution, fire made us humans. For instance, cooking implied higher food energy, as well as an increased the diversity of available food (detoxifying effects of heating, etc…). Furthermore, cooking implied a delay in food consumption, which required the development of social abilities for the distribution of tasks within the group (e.g., collection, accumulation, cooking, defense, even stealing). These factors are thought to have prompted the evolution of large brains and bodies, small teeth, modern limb proportions, and other human traits, including many social aspects of human-associated behavior. However, the moment in which humans started to use fire is still debated. It is often believed that the rise of Homo erectus from its more primitive ancestors was fueled by the ability use fire.

Although the use and control of fire is a human trait, a recent study has demonstrated that chimpanzees have the ability to understand wildfires and predict their behavior (Pruetz & LaDuke 2010). Chimps calmly observed wildfires around them, predict their behaviour and move accordantly without any stress or fear. This suggest that the conceptualization of fire may be a old trait, in the hominids group.

To what extent current humans are losing this trait is another debate, but we may be better off at managing our fire-prone landscapes by learning from chimps!

References

• Pausas J.G. & Keeley J.E. 2009. A burning story: The role of fire in the history of life. BioScience 59: 593-601 [doi] [pdf]
• Pruetz JD & TC LaDuke 2010. Reaction to fire by savanna chimpanzees (Pan troglodytes verus) at Fongoli, Senegal: Conceptualization of  fire behavior and the case for a chimpanzee model. Am J Phy Anthropol (in press) [doi]
• Wrangham RW, Jones JH, Laden G, Pilbeam D, Conklin-Brittain NL. 1999. The raw and the stolen: Cooking and the ecology of human origins. Current Anthropol 40: 567–590.
• Control of fire by early humans [Wikipedia]

2010

• 2nd Human Dimensions of Wildland Fire Conference, San Antonio, Texas, USA, April 26-29, 2010 [web]
• Spatial and temporal patterns of wildfires: models, theory, and reality, European Geosciences Union, General Assembly 2010, Vienna, Austria, 02 – 07 May 2010, [web]
• 2nd International Conference on Modelling, Monitoring and Management of Forest Fires, Kos, Greece, 23 – 25 June 2010, organised by Wessex Institute of Technology, UK [web]
• 3rd Fire Behavior and Fuels Conference: Beyond Fire Behavior and Fules: Learning from the Past to Help Guide Us in the Future. Hosted by: International Association of Wildland Fire; 25-29 October, 2010, Spokane, Washington, USA [web]
• 6th International Conference on Forest Fire Research, Coimbra, Portugal, 15-18 November 2010 [web]

2011

• 3rd International Meeting of Fire Effects on Soil Properties, University of Minho, Guimarães, Portugal, March 15-19, 2011 [web].
• Catching Fire: New Methods and Research for Identifying Anthropogenic Fire and Landscape Modification, Sesion in the 76th Annual Meeting of the Society for American Archaeology, March 30 – April 3, 2011, Sacramento, California [web]
• 5th Intarnational Wildland Fire Conference, Sun City, South Africa, 9-13 May 2011 [web], organised by the IAWF

During a week (30/Nov – 4/Dec, 2009), about 600 ecologist meet in Savannah (Georgia, USA) for the 4th International Congress on Fire Ecology and Management [web], organised by the Assotiation for Fire Ecology (AFE). The congress included 10 plenary talks and 9 concurrent sessions of 20-minute talks distributed in different topics, plus about 150 posters. The topics discussed include all kind of topics related fire ecology and management; there was however a clear bias towards topics on management, and few talks dealt with pure ecology or the evolutionary consequences of living in fire prone-ecosystems. Four one-day field trips and five workshops completed the program of the Congress.

One of the focus of the conference was the importance of fire management by indigenous, and how modern fire management can learn form that. W. Trollope give a very nice example of the interaction and knowledge transfer between indigenous and modern societies. Current fire managers have a lot to learn from indigenous on this topic. The contrast between the eco-cultural fire management paradigm (many small frequent fires) versus the bio-physical (modern) fire management paradigm was stresses by many of the speakers, from many countries (Brasil, Venezuela, EEUU, Canada, Australia).

The other topic that emerged quite important during the conferences was the role of fire in the global carbon cycling. Prescribed burning is a common and a needed practice for land management in many ecosystems, to maintain low fuel loads (i.e., to prevent catastrophic fires) and to enhance biodiversity (“More prescribed fires mean less wildfires”). This message need to get through the society as there is the possibility of social and political rejection of prescribed fires in order to reduce emissions of greenhouse gases. The reduction of prescribed fires would have catastrophic consequences in long-term. The AFE produced a position paper on this topic (pdf).

Other topics I found very interesting were Flammability and Fire history. Understanding flammability is still in its infancy. The large databases on fire history, from both charcoal in sediments and tree scars, is allowing us to better understand the fire history in many ecosystems although still much effort is needed.

The organisers made an effort for the congress to be international, and thus they invited plenary speakers representative of different parts of the world (Australia, Africa, North America, South America, Central America, South Europe, and Central Asia). However, most participant (>90%) were from USA, and the second country represented was Canada. Thus the conference was biased towards fire ecology in North America. I would say that the other continents (Europe, Australia, Africa, South America, Asia) were represented by less than about 5 scientists each. I suppose that for this congress to become international, next edition should be held outside of North America.

Pinewoods (Pinus elliottii, I think) with palmetto (Serenoa repens, I think) dominant in the undertory, mantained by prescribed fires (ca. 2-3 years) in Okefenokee National Wildlife Refuge (one of the field trips of the congress).

We recently proposed (Aug/2009) that “The spread of humans, perhaps concomitant with climatic changes, contributed to the mass disappearance of megafauna such as mammoths and other large herbivores (i.e., the Pleistocene-Holocene extinction); this extinction would also have resulted in fuel buildup and the consequent change in fire activity, as suggested by the contemporary effects of megaherbivores.” (Pausas & Keeley 2009; see also Flannery 1994).

Today (20/Nov/2009), in a paper in Science, Gill et al. demonstrate this link between megafauna extinction and fire activity by studying the fossils spores of a coprophilous fungi (Sporormiella) from a lake sediments in Indiana, North America, together with charcoal and pollen from the same sediments (ca. 14,000 years of history). Sporormiella produced spores in the dung of large herbivores, and the amount of spores can be considered an index of the abundance (or biomass) of herbivores vertebrates. The authors demonstrate that the decline in megafauna is associated to an increased fire activity. This also make us to think about the idea of Pleistocene rewilding (Donland et al. 2005) for fuel control and fire reduction.

These papers and other recent ones are putting fire ecology in the front-line of ecology as they demonstrate the strong influence of fire in shaping nature; they emphasize the importance of fire for understanding present, past and future ecosystems as well as global processes. For instance, Nevle & Bird (2008) recently demonstrated that the massive reduction of American natives by the European invasion of America, drastically reduced fire activity and the consequent increase in forest (carbon sequestration) contributed to the ca 2% global reduction in atmospheric CO2. Despite the importance of fire in the global context, they are still poorly represented in global models (Bowman et al. 2009).

References

Bowman D.M.J.S. et al. (2009). Fire in the Earth System. Science, 324, 481-484.

Donlan C.J. et al. (2006). Pleistocene Rewilding: an optimistic agenda for 21st century conservation. The American Naturalist 168: 660-681

Flannery T. (1994). The Future Eaters: An Ecological History of the Australasian Lands and People. Reed Press, Port Melbourne, Australia.

Gill JL et al. (2009). Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America. Science 326: 1100-1103.

Nevle R.J. & Bird D.K. (2008). Effects of syn-pandemic fire reduction and reforestation in the tropical Americas on atmospheric CO2 during European conquest. Palaeogeography, Palaeoclimatology, Palaeoecology 264: 25-38.

Pausas J.G. & Keeley J.E. (2009). A burning story: The role of fire in the history of life. BioScience 59: 593-601. [caliber] [BioOne] [doi] [pdf]

Journals:

Papers of fire ecology can be found in any ecology journal; in addition there some specific journal on fire science:

• International Jounrnal of Wildland Fire: a multidisciplinary journal dedicated to reseach on all aspects of wildfires. A SCI-journal with peer-reviewed articles.
• Fire Ecology (AFE)
• Fire Management Today (mainly US management issues)
• Wilfire Magazine
• Journal of Fire Science and Fire Technology are not related to wildfires, but to the fire science in general; they  include very few ecological papers (e.g., on plant flammability, etc..)
• Lists of fire-related papers on other major journals: here & here

Reference databases:

• Tall Timbers Reference database [search]
• EUFireLab e-Library [search] (mostly European references)
• Reference lists: [citeUlike | ScholarGoogle ]

Prominent books:

• Bond & van Wilgen (1996) Fire and Plants [preview]
• Whelan (1995) The ecology of fire [preview]

[Update] new book: Keeley et al. (2012) [link]

Images from two different tree species (A and B), from different Families (and different Orders), taken in different continents…

A1 A2 A3

B1 B2

The thick bark offers protection to fire and thus these species are both adapted to live in fire-prone ecosystems [1].

Can you guess the species name of A and B?    [ Answer: A | B ]

Notes

[1] See also: The ecology of bark thickness | The ecology of bark thickness (2): another twist

Fire management is facing two extreme views (see a discussion and references in PDF):

• Large fires are controlled by fuel, and are the consequence of the fire suppression policy (build-up of fuels). Thus to reduce fire danger, fuel control is needed (the patch mosaic model)
• Large fires are controlled by climate (mainly severe droughts) and thus fuel management is of little relevance

A recent paper is conclusive in that in California, large chaparral fires are controlled by climate and they burn through a vegetation mosaic of differetn ages since fire, and thus in landscapes under severe weather conditions there is little hope fuel treatments will provide barriers to fire spread. Strong dry winds, Santa Ana winds, are driving many of the large chaparral fires (Figure below).

Keeley, J.E. and P.H. Zedler. 2009. Large, high intensity fire events in southern California shrublands: debunking the fine-grained age-patch model. Ecological Applications 19:69-94. [journal] [pdf] [brief for managers]

Santa Ana wind-driven fires (MODIS, 26 Oct 2003)

Fires in the Mediterranean basin: The question is weather these results also apply to other Mediterranean regions. The role of droughts in recent fires (e.g., see the 2007 European heat wave and the consequences on large fires in Greece and Croatia; Figures below) and the importance of dry winds in many fires (e.g., ponientes in eastern Spain) suggest that a similar process may be occurring in the Mediterranean basin, although due to the long and intense land use in this area, fuel structure may also need to be considered for understanding some past fire regime changes [pdf].

Temperature anomalies in Europe, summer 2007

Fires in Greece, summer 2007

Ground (peat) fires are rare in the Mediterranean basin, but here is an example, in a wetland that burns because drained for agricultural purposes. Overexploitation of water resources (illegal wells and canalisation of the rivers) has caused the water-table to drop, and made prone to burn. This is happening in a National Park classified as a UNESCO biosphere site and an EU protected area because of its birdlife …

• Spanish wetlands shrouded in smoke as overfarming dries out peat, Guardian.co.uk, 19 Oct 2009
• EU Investigates Dried Up Spanish Wetland, Fox News (Ass. Press), 22 Oct 2009
• Spanish wetland facing destruction as farming starves it of water, Guardian.co.uk, 22 Oct 2009
• More news

News in Spanish | Noticias:

• Un insólito incendio subterráneo azota las Tablas de Daimiel, El País, 12 Oct 2009
• Medio Ambiente admite que el daño en las Tablas ‘es irreversible’, El País, 13 Oct 2009
• Trasvase de emergencia contra el incendio subterráneo de Daimiel, El País, 14 Oct 2009
• El parque nacional de Las Tablas de Daimiel agoniza, LaVanguardia.es, 18 Oct 2009
• Hallado otro foco del fuego subterráneo de Daimiel, El Pais, 20 Oct 2009
• Cuatro fuegos bajo Daimiel, El Pais, 31 Oct 2009
• Greenpeace augura un “futuro agónico” a Las Tablas de Daimiel, Europa press, 7 Nov 2009
• Salvemos las Tablas de Daimiel, CLM en Vivo [video]
• Ecologistas rechazan el tasvase a Daimiel [video]
• Más noticias.
• Información previa sobre el estado del Parque, en El País, 1 Jun 2008

Tablas de Daimiel National Park: [wikipedia-EN | wikipedia-ES |  video ].

When talking about peat fires we remember the 1997 Indonesia fire which burned 8 million hectares and countless millions of people suffered from air pollution (see figure below). In that area there was abundant and thick peat (which is a very important carbon store) that was drained for land development and agriculture (e.g., palm oil production), making them prone to fire. As a consequence of burning this dry peat, the 1997 Indonesia fire emitted a vast amount of carbon dioxide to the atmosphere. Indeed, the growth rate of carbon dioxide in the atmosphere doubled and reached the highest levels on record; it was equivalent to 13-40% of the mean annual global carbon emissions from fossil fuels yet it came from a small area of the globe (Page et al. 2002).

Air pollution over Indonesia and the Indian Ocean on October 22, 1997 (TOMS satellite instrument)

Certainly we need to preserve wetlands and peatlands, not only for their biodiversity value, but also for their role in the global carbon budget.