Fire danger, fire hazard, fire risk, …

August 5th, 2017 4 comments

Recently, a colleague ask me about the difference between fire hazard, fire risk and fire danger. I’m not an expert in these concepts, but here is my understanding of these and other related terms. In short, fire hazard is related to fuel (forestry), fire risk is often used for mapping probability of ignitions (geography) and fire danger in typically associated to weather conditions (meteorology); below is a longer answer. Feel free to improve or qualify these definitions by leaving a comments (see top right).

Fire weather: Weather conditions which influence fire ignition, behaviour, and suppression. E.g., extreme (or severe) fire weather refers to very low moisture, high temperatures and strong winds. Fire weather indices (FWI) can provide information for estimating the fire danger (see below).

Fire hazard: the degree of ease to fire ignition and propagation, and the resistance to control (given an ignition source). It depends on the quantity and continuity of the vegetation (fuel) and it is independent of the weather (in contrast to fire danger). It reflects the potential fire behaviour associated to static properties of fuel (fire hazard doesn’t change from one day to the next, in contrast to fire danger). Fire hazard reduction treatments refer to fuel treatments.

Fire risk: typically it refers to the probability of ignition, i.e., the chance that a fire might start. In can be split in lightning fire risk and human fire risk; the later typically decreases with distance to roads and increase with population density. Other authors define fire risk as potential damage (or degradation risk), and thus they include fire hazard and fire vulnerability in the concept of fire risk. Fire risk is relatively static (e.g., a zone with high fire risk), and often used to produce maps (fire risk mapping).

Fire danger: sum of the factors affecting the initiation, spread, and resistance to control in a given area; it is typically expressed as a semi-quantitative index (e.g., from very high to very low). Very often it largely depends on weather (i.e., moisture; sometimes also lightning activity) and reported by meteorological agencies. Because it considers the weather, fire danger is very dynamic (e.g. fire danger today; daily fire danger forecast). Note that if fire danger is based on weather only: (1) the fire danger may be very high in areas where the likelihood of having a fire is very low due to their low fuel (i.e., overestimation in arid ecosystems); (2) weather-based fire danger may fail to capture short-term increases in dead fuel due to strong droughts (underestimation); and consequently, (3) predictions of fire danger for the future under climatic warning may be questionable. A good prediction of fire danger should consider fire risk, fire weather and fire hazard (including fuel dynamics).

Fire damage: detrimental changes in value after a fire (e.g., ecological fire damage, social fire damage); i.e., it refers to negative fire effects. Note that fire may damage some species and favour other; also it depends on the temporal scale, as some short-term effects may be different from mid- or long-term effects.

Fire vulnerability: probability of fire damage; potential effects of fire on values. It is often presented as fire vulnerability maps. Ecological fire vulnerability is typically computed from the type of vegetation, soil and topography, to estimate postfire erosion risk and regeneration capacity.

Map of the Fire Danger Forecast for the Mediterranean region on the 5 Aug 2017 from the Global Wildfire Information System (GWIS, EFFIS-Copernicus). Darker heat colours indicate higher fire danger (green: very low). In fact, this is based on fire weather; note that it is not predicted for arid areas (white, in Africa) where the low biomass may produce extremely unrealistic results (it should probably be green). So it looks more a heat index than a fire danger index. I would also say that the palette of colors seems a bit too contrasted.

 

Postfire germination in Chile

July 22nd, 2017 No comments

In the matorral (chaparral-type vegetation) of Central Chile, natural fires are assumed to have been much less frequent (during the Quaternary) than in the other Mediterranean-type ecosystems (MTEs) of the world [1]. Thus, plant adaptive responses to fire are expected to be uncommon. Resprouting is a relatively widespread trait in Chilean woody species, although this traits is not really an indicator of the fire history as resprouters occur in many environments, not only in fire-prone ones [1,2]. Fire-stimulated germination (i.e., the increased seed germination after a heat shock or after the smoke produced by a fire) is a trait more specifically tied to fire [1,3]. A recent study [4] demonstrates that fire-stimulated germination is not as common in the Chilean woody flora as in other MTEs; i.e., negative seed responses to fire cues were more frequent than positive responses. Some seeds were damaged by fire, but many species were able to resist the heat shock although without an increase on germination. In few species, germination was stimulated (by heat or smoke), but the magnitude of the stimulation was relatively low. The overall effect is that fire-stimulated germination is poorly represented in the Chilean matorral. These results support the idea that this matorral had a history of lower fire activity than other mediterranean-climate regions, despite having a fire-prone climate. This low fire activity has been attributed to the effect of the Andes blocking many summer thunderstorms in central Chile, and thus reducing lightning and natural ignitions [1]. Lightning fires do occur in Chile, but typically further south; most current fires in central (mediterranean) Chile are of anthropogenic origin.

Two views of the Chilean matorral; left: La Campana National Park (photos: S. Gómez-González).

 

References

[1] Keeley JE, Bond WJ, Bradstock RA, Pausas JG, Rundel PW. 2012. Fire in Mediterranean ecosystems: ecology, evolution and management. Cambridge University Press. [the book]

[2] Pausas, J.G., Pratt, R.B., Keeley, J.E., Jacobsen, A.L., Ramirez, A.R., Vilagrosa, A., Paula, S., Kaneakua-Pia, I.N. & Davis, S.D. 2016. Towards understanding resprouting at the global scale. New Phytol. 209: 945-954. [doi | wiley | pdf | Notes S1-S4 | Table S1]

[3] Moreira B. & Pausas J.G. 2012. Tanned or burned: The role of fire in shaping physical seed dormancy. PLoS ONE 7: e51523. [doi | plos | pdf]  

[4] Gómez-González S., Paula S., Cavieres L.A. & Pausas J.G. 2017. Postfire responses of the woody flora of Central Chile: insights from a germination experiment. PloS ONE 12: e0180661. [doi | plos | pdf]   New!

More on: fire and Chile | fire and germination |

Incendios, arte y divulgación

July 18th, 2017 No comments

La Fundación Pau Costa ha puesto el punto 1 del decálogo de incendios forestales (punto que escribí yo), en un marco artístico para facilitar la divulgación:

El decálogo completo en:  enlace (¡firma!) | pdf | post | English

 

¿Hay incendios naturales?

July 14th, 2017 No comments

A menudo me preguntan, ¿pero tu realmente crees que los incendios forestales es un fenómeno natural? Aquí intento responder a esta pregunta. Este texto apareció primero en 20minutos (Ciencia para llevar); aquí incluyo la primera versión que escribí, un poco más larga que la publicada; la principal diferencia está en el último párrafo, que por razones de espacio se recortó en la versión final en 20minutos.

 

Para que se produzca un incendio forestal se requieren tres condiciones: una ignición que inicie el fuego, un combustible continuo e inflamable, y unas condiciones de propagación adecuadas. ¿Se dan estas tres circunstancias en nuestros ecosistemas?

Empecemos por el final, las condiciones de propagación. Una de las principales características del clima mediterráneo es que la estación más seca coincide con la más cálida (el verano), cosa que no se da en la mayoría de los climas del mundo. En verano se genera un periodo relativamente largo con unas condiciones de elevadas temperaturas y baja o nula precipitación, que son ideales para que, si hay un incendio, se propague fácilmente. Además no es raro tener días de viento relativamente fuerte, seco y cálido (por ejemplo, los ponientes en la costa valenciana) que aún facilitan más los grandes incendios.

La siguiente condición es la existencia de un combustible continuo e inflamable. En la mayoría de los ecosistemas ibéricos, la vegetación es suficiente densa y continua que permite, si hay un incendio en verano, que este se pueda extender a grandes superficies. Esto es aplicable tanto a los bosques como a la gran diversidad de matorrales que encontramos en nuestro territorio. De manera que la vegetación mediterránea forma lo que a menudo se llama el combustible de los incendios forestales. No hay que olvidar que este ‘combustible’ está compuesto por una gran diversidad de seres vivos que tienen detrás una larga historia evolutiva; son parte de nuestra biodiversidad. Esta continuidad en la vegetación era especialmente evidente antes de que los humanos realizará esa gran fragmentación que se observa actualmente en nuestros paisajes, principalmente debida a la agricultura, pero también a las abundantes vías y zonas urbanas y periurbanas.

Pero con una vegetación inflamable y unos veranos secos no es suficiente para que haya incendios, se requiere una ignición inicial. Hoy en día, la mayoría de igniciones son generadas por personas, ya sea de manera voluntaria o accidental. Pero, ¿Hay igniciones naturales? La respuesta es . A menudo tenemos tormentas secas en verano, cuando las condiciones de propagación son óptimas, de manera que los rayos generados por estas tormentas pueden actuar como fuente de ignición e iniciar un incendio forestal. Tenemos muchos ejemplos de incendios generados por rayos (la mayoría sofocados rápidamente por los bomberos); y en los meses de verano, la AEMET detecta miles de rayos potencialmente capaces de generar igniciones (Figura 1).

Figura 1. Imagen del 31 de Julio de 2015 donde se muestra la localización de 12835 rayos que se registraron durante 6 horas en la Península Ibérica. Los diferentes colores indican diferentes horas, entre las 12 y las 18h. Fuente: Agencia Estatal de Meteorología.

Por lo tanto, las tres condiciones arriba mencionadas se dan de manera natural en nuestros ecosistemas, y por lo tanto podemos afirmar que sí hay incendios naturales. Pero, ¿cuantos?

Las estadísticas de incendios actuales nos dicen que los incendios generados por rayos son una minoría, comparado con la gran cantidad de incendios generados por los humanos. ¿Podría esta minoría de incendios por rayo representar la cantidad de los incendios esperables en condiciones naturales? La respuesta es no. Una gran cantidad de rayos cae en suelo sin vegetación combustible (zonas agrícolas y urbanas) y por lo tanto no producen los incendios que producirían en unas condiciones más naturales. Además, de los rayos que sí generan igniciones en el monte, la mayoría son apagados por los bomberos forestales cuando aun son solo conatos o incendios muy pequeños. Cabe recordar que nuestros bomberos apagan la inmensa mayoría de las igniciones y sólo un porcentaje muy pequeño se escapa y se transforma en los incendios que aparecen en la prensa. Y además, de los incendios que realmente progresan, la mayoría son más pequeños de lo que serían esperable en condiciones más naturales, porque los apagan los bomberos, o porque se detienen en zonas no inflamables (zonas agrícolas, urbanas, cortafuegos, etc.). Como consecuencia, las estadísticas de incendios por rayos, ya sea en número de incendios como en área afectada, no reflejan la importancia que tendrían los incendios en condiciones naturales, sino que los subestima. Algunos de los incendios que actualmente se dan por actividad humana, en realidad están sustituyendo a incendios naturales.

Es decir, en unos paisajes más naturales (con menos presión humana) que los actuales, sería de esperar que hubiese menos incendios que en la actualidad porque habría muchas menos igniciones (la actual elevada población genera muchas igniciones), pero en muchos casos, esos incendios podrías ser más grande. En cualquier caso, el balance probablemente sería de menos área afectada por incendios que actualmente; pero sí habría incendios frecuentes. A todo esto hay que añadirle que actualmente estamos cambiando el clima, de manera que la estación con incendios tienden a ser más larga, y las olas de calor más frecuentes, y todo ello incrementa la actividad de los incendios; pero ahora no entraremos en detalle en ello.

Además, hablar de condiciones o paisajes ‘más naturales’ es complicado por varias razones. ¿Cuanto hacia atrás en el tiempo son esas condiciones ‘más naturales’? Los humanos han poblado la Península ibérica desde hace muchos años, modificando las igniciones, cambiando la estructura de la vegetación, así como la cantidad y tipo de herbívoros. Esto ha llevado a continuos cambios en la cantidad y continuidad del combustible y en el régimen (frecuencia, intensidad, y estacionalidad) de incendios. Y si nos vamos a periodos antes de los humanos, tanto el clima como la cantidad y tamaño de los herbívoros (también consumidores de biomasa, como el fuego) era bastante diferente. Por lo tanto, lo importante no es si el régimen de incendios actual es ‘natural’ o no. Lo importante es si el régimen de incendios actual y futuro es ecológica y socialmente sostenible, considerando el cambio climático. Eliminar los incendios es imposible, antinatural y ecológicamente insostenible. Nuestra sociedad ha de aceptar la existencia de incendios, aprender a convivir con ellos, adaptar las estructuras y los comportamientos, y gestionar las zonas semi-urbanas y los paisajes rurales para que el régimen de incendios sea ecológica y socialmente sostenible. Esto incluye gestionar y planear la zonas semi-urbanas, la plantaciones forestales, y los parques naturales, pensando que lo normal es que un día les llegue un incendio.

Todo esto y más en: ‘Incendios forestales’ Ed. CSIC-Catarata.

[Actualización 30/7/2017] Un ejemplo: La sierra de los rayos. El País, 30 Julio 2017

Homage to Louis Trabaud

June 6th, 2017 No comments

Louis Trabaud (born in Montpellier, 2nd Feb. 1937) has recently passed away (Collioure, 16th April 2017). He was a research on plant ecology at Centre d’Ecologie Fonctionnelle et Evolutive (CEFE) of the CNRS, France. He was a pioneer of fire ecology in the Mediterranean Basin and set the basis of this topic for the region; he was especially influential to the fire ecologist of Spain (including me), and was awarded Professor Honoris Causa by the Univeristy of León (Spain) [1]. He was also award in France as Chevalier du Mérite Agricole (Order of Agricultural Merit). As a person, Louis Trabaud was very kind and always happy to help any student.

His research was especially focused on mediterranean shrublands around Montpellier (garrigue), i.e., shublands dominated by Quercus coccifera, Cistus species, Rosmarinus officinalis, Fumana species, etc… sometimes with an overstory of Pinus halepensis. He performed the first fire experiments in the Mediterranean region to study the regeneration of these shrublands, where he recurrently burned them in different seasons to demonstrate their high resilience. He also performed the first studies in the Mediterranean Basin on heat-stimulated germination and on flammability traits. He produced many papers, some in French (the most earlier ones) and others in English, and also wrote or edited some books. The full Trabaud’s publications list (books and scientific papers) is available here.

Louis Trabaud, together with his friend Roger Prodon, organized the International Workshop on Fire Ecology in Banyuls-sur-Mer (south of France) in the years 1992, 1997, 2001; these workshops were key in building the knowledge on fire ecology for the region; they were the meeting point for all mediterranean fire ecologist; we all met there for the first time and we all have very good memories from those meetings.

Participants of the 2001 Banyuls meeting organized by Louis Trabaud (in the middle, with glasses and a pale sweater) and Roger Prodon (second from the right).

 

References
[1] Texto en memoria de Louis Trabaud, por la Universidad de León (in Spanish)

 

Incendios y biodiversidad

May 31st, 2017 No comments

El 12 de Mayo de 2017 impartí una charla titulada Incendios forestales y biodiversidad en el IVIA (Valencia), en la que expliqué las principales adaptaciones de las plantas mediterráneas a los incendios, y cómo estudiamos esas adaptaciones en el marco de la ecología del fuego. La conclusión es que el fuego explica una parte de la biodiversidad de nuestros ecosistemas. La charla tuvo cierto impacto en los medios (enlace). Aquí podéis ver la charla integra así como la discusión posterior:

Más información: www.uv.es/jgpausas | @jgpausas | Incendios forestalesFire and diversity at the global scale | Fire adaptations in Mediterranean basin plants | Evolutionary fire ecology in pines | Ulex born to burn (II) | Serotiny |

Fire and diversity

May 26th, 2017 1 comment

In a recent paper [1], we studied the relationship between plant diversity (Fig. 1a) and fire activity (Fig. 1b) for the different ecoregions of the world, and found a strong positive relationship (Fig. 2), even after taking into account productivity and other major environmental variables [1]. This is the first global assessment of the importance of fire as major determinant of species diversity. There are at least two (not mutually exclusive) mechanisms by which fire may drive plant diversity at the scale and grain considered. 1) A selective process; there is both micro and macro evolutionary evidence suggesting that fire regime can drive population divergence and diversification [2-5]. And 2) Fires generate landscape mosaics and thus more habitat types and more niches likely to be filled by different species. In fact, the two processes are linked as landscape mosaics are also appropriate frameworks for population divergences and selective processes in fire-prone ecosystems [6]. That is, our results suggest that fire generates the appropriate conditions for a large variety of plants in many regions worldwide. Or, in other words, a world without fires (if possible at all) would be less diverse.

 


Fig. 1. Maps of plant diversity (logarithm of the number of species divided by the ecoregion area) and fire activity (estimated by 15 years of remote sensing data for each ecoregions, standardized from 0 to 1) for each terrestrial ecoregion of the world. From [1].


Fig. 2. Plant diversity in each terrestrial ecoregion (number of species divided by area, log scale; Fig. 1a) plotted against an indicator of fire activity (Fig. 1b); the two lines refer to fitted lines for low and high radiative power (an indicator of fire intensity). Form [1].

References

[1] Pausas J.G. & Ribeiro E. 2017. Fire and plant diversity at the global scale. Global Ecol. & Biogeogr. [doi | pdf | data & maps (figshare)]

[2] He T, Pausas JG, Belcher CM, Schwilk DW, Lamont BB. 2012. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytol. 194: 751-759. [doi | wiley | pdf | suppl.]

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

[4] Hernández-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. Am. J. Bot. 100: 2349-2356. [doi | amjbot | pdf | supp.]

[5] Pausas, J.G. 2015. Evolutionary fire ecology: lessons learned from pines. Trends Plant Sci. 20: 318-324. [doi | sciencedirect | cell | pdf]

[6] Castellanos, M.C., González-Martínez, S. & Pausas, J.G. 2015. Field heritability of a plant adaptation to fire in heterogeneous landscapes. Mol. Ecol. 24, 5633-5642. [doi | pdf | suppl.]  

 

 

Pinus canariensis

May 7th, 2017 No comments

The last post was about Pinus brutia [1] from the Eastern Mediterranean basin. Another pine of the mediterranean group (Pinaster group) is Pinus canariensis, endemic of Canary Islands, in the north west of Africa (in the Atlantic). P. canariensis have a thick bark and resprouts vigorously from stem buds (epicormic resprouting) after crown fires. In addition, it produce serotinous cones, a clear adaptation to recruit after fire [2,3]. Very few other trees have strong adaptations to both survival and regeneration postfire; P. canariensis is among the best fire-adapted trees in the world, likely to survive very different fire regimes.

Pictures of Pinus canariensis (by JG Pausas except mid-right from NASA).
· Top-left: 5 years after a crown-fire (La Palma, Canary Is.).
· Mid-left: plantation 2 years after fire (Vall d’Ebo, Alicante, eastern Spain; planted in the 50s).
· Bottom-left: Contrasted response of Pinus halepensis (left; fire-killed serotinous pine) and P. canariensis (right, resprouting) two years after fire (Alicante, eastern Spain).
· Top-, bottom-right: epicormic resprouts 3 months after fire (Tenerife, Canary Is.).
· Mid-right: a fire plume from a wildfire in La Palma (Canary Is.).

References
[1] Pinus brutia, jgpausas.blogs.uv.es, 19 Apr 2017

[2] 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 Plant Sci. 16: 406-411. [doi | sciencedirect | trends | pdf | For managers]

[3] Pausas, J.G. 2015. Evolutionary fire ecology: lessons learned from pines. Trends Plant Sci. 20: 318-324. [doi | sciencedirect | cell | pdf]

 

Pinus brutia

April 19th, 2017 No comments

Pinus halepensis is a strongly serotinous pine [1,2] occurring mainly in the western part of the Mediterranean Basin (especially in Spain; see map below). The most phylogenetically closely related species to P. halepensis is Pinus brutia that occurs in the eastern Mediterranean Basin (mainly in Turkey). P. brutia is called ‘red pine’ in Turkish (Kızıl çam) because sometimes the upper part of the trunk is reddish (as in P. sylvestris); the leaves are pale green as in P. halepensis. In relation to their fire response strategy [3], the main differences between the two species are that P. brutia is taller, the bark is thicker and the serotiny level is lower. Our observations suggest that P. brutia have relatively few serotinous cones, and most of then are less than 4 years old; P. halepensis have a higher proportion of serotinous cones, with many of them over 5 year old (and some more than 20 year old) [1].

Distribution maps of P. halepensis and P. brutia (from Wikipedia)

 
Pinus brutia forest, serotinous cones (2 serotinous and one non-serotinous (open)), and an example of a bark of more than 5 cm thick (the gaude was too short!). Photos from SW Turkey (by JG Pausas). For an example of serotinous cones in P. halepensis, see here.

 

References
[1] Hernandez-Serrano A., Verdú M., González-Martínez S.C., Pausas J.G. 2013. Fire structures pine serotiny at different scales. Am. J. Bot. 100: 2349-2356. [doi | pdf | supp.]

[2] Castellanos, M.C., González-Martínez, S. & Pausas, J.G. 2015. Field heritability of a plant adaptation to fire in heterogeneous landscapes. Mol. Ecol. 24, 5633-5642. [doi | pdf | suppl. | blog]

[3] Pausas, J.G. 2015. Evolutionary fire ecology: lessons learned from pines. Trends Pl. Sci. 20: 318-324. [doi | pdf | blog]

Eastern Mediterranean tour, 2017

April 18th, 2017 No comments

It is a pleasure to visit the different ecosystems of Lebanon and Turkey, and to meet old students and colleagues.

Cedar (Cedrus libani) forest, Al Shouf Biosphere Reserve, Lebanon

Anatolian steppe (bushes are Astragalus), central Turkey

Pinus brutia forest, SW Turkey

Postfire flowering: Gladiolus illyricus

April 4th, 2017 2 comments

On the 4th of Sep 2016, a wildfire burnt 800 ha in Xàbia, north of Alacant (Marina Alta, eastern Spain). About 7 months later (March 2017), Gladiolus illyricus shows a spectacular blooming:

 

21-03-2017 005_sm
IMG_1363_Gladiolus-illyricus_sm
Gladiolus illyricus. Photos by: Toni Bolufer (top), Juli G Pausas (bottom)

For more examples of postfire flowering, see: jgpausas.blogs.uv.es/tag/postfire-flowering/

De incendios y cipreses (y 6)

March 13th, 2017 No comments

Después de casi 5 años de despropósitos [1-5], ya se ha puesto fin a esa idea absurda de querer plantar cipreses para frenar los incendios forestales en Valencia. Los miles de plantones de ciprés que estaban preparados para tal finalidad se han regalado a diferentes ayuntamientos con la condición de no plantarlos en el medio natural (Levante, 21 Feb 2017). Quizá decir que este cambio ha sido posible gracias al nuevo marco político de la Diputación de Valencia.

ellevante_cipreses
Para compensar estos despropósitos, aquí un pequeño homenaje a estos árboles (clicar para ampliar): Cipreses en el Coliseo de Roma, en la Torre de Pisa, en la Mezquita de Córdoba (campanario), y en el teatro de Mérida (fotos: JG Pausas).

Referencias

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

 

Flammability and coexistence

March 3rd, 2017 No comments

In the cover of the March issue of the Journal of Ecology (105:2) there is a picture of Palicourea rigida (Rubiaceae), a plant growing in the Brazilian savannas (cerrado). It is an example of a plant that survives in a very flammable environment (grassy savanna) thanks to a set of traits conferring very low flammability, including a very low specific leave area and a thick corky bark. Grasses generates fast fires of low intensity (fast-flammable strategy), and in this environment, having low flammability is adaptive as it increases survival (non-flammable strategy). That is, different (contrasted) flammability strategies allows coexistence. For the definition of the different flammability strategies see [1].

Pausas-2017-JEcol_cover2(photo by J.G. Pausas)

 

[1] Pausas J.G., Keeley J.E., Schwilk D.W. 2017. Flammability as an ecological and evolutionary driver. Journal of Ecology 105: 289-297. [doi | wiley | pdf | blog | brief]

 

Chile wildfires: MEDECOS declaration

March 1st, 2017 No comments

Some of the scientists attending the recent MEDECOS (International Conference on Mediterranean Ecosystems, Sevilla, February 2017 [1]) wrote a declaration on the recent wildfires that affected very large areas of Chile [2]. The declaration is composed of 10 statements (a decalogue) and is available here:

English version  |   Spanish version

Chile.2017.01.25Central Chile, MODIS image of January 25, 2017 (by NASA).

References:
[1] MEDECOS XIV
[2] Incendios en Chile 2017

Homage to Coutinho: fire adaptations in cerrado plants

February 28th, 2017 No comments

Professor Leopoldo (Léo) M. Coutinho (1934–2016; Fig. 1) from the University of Sao Paulo, Brazil, studied fire adaptations in Brazilian savannas (cerrado) during the 1970s, when very few researchers recognized fire as an evolutionary force. One of his important contribution on the cerrado ecology was on fire-stimulated flowering (Fig. 2), but he also studied serotiny, nutrient cycling, fire germination, water balance, among other topics [1,2]. However, his research is little known, partly because he was not part of the dominant Anglo-Saxon culture but also because he was ahead of his time, when fire and evolution were still distant concepts [1].

Coutinho2Figure. 1. Professor L. M. Coutinho in a Brazilian cerrado (photos by A. C. Coutinho)

Fig1_CoutinhoFigure 2: Frequency distribution of the flowering intensity index (from 0 to 4) after fire (shaded; 90 days post-fire) and in control conditions (white) in 47 species (belonging to 20 families) of a cerrado ecosystem (prepared from data in Coutinho 1976). The 31 species with the highest post-fire flowering belong to 17 different families. From [1]

References

[1] Pausas J.G. 2017. Homage to L. M. Coutinho: fire adaptations in cerrado plants. Intern. J. Wildland Fire,  [doi | pdf]

[2] Pivello, V.R. 2016. Professor Leopoldo Magno Coutinho: a visão de uma discípula. Biodiversidade Brasileira, 6(2): 4-5.

 

Incendios en Chile 2017

February 10th, 2017 No comments

Esta entrada se ha realizado en colaboración con Susana Paula (ICAEV, Universidad Austral de Chile)

En las últimas semanas una gran cantidad de incendios han afectado cerca de 600 mil hectáreas en la zona central de Chile, con unas 1600 casas destruidas, 11 fallecidos y varios miles de afectados [1]. Esto ha generado una alarma social, y se han publicado numerosas opiniones, muchas de ellas sin datos o con poco rigor. Aquí intentamos analizar lo ocurrido, de manera muy breve, partiendo de una base científica y de los datos oficiales proporcionados por el Sistema de Información Digital para el Control de Operaciones (SIDCO) de la CONAF (Gobierno de Chile).

Al contrario que otros ecosistemas mediterráneos, los ecosistemas de Chile central no han tenido una historia reciente (durante el Cuaternario) de incendios naturales. Esto es debido a que la elevación los Andes durante el Mioeno bloqueó las tormentas estivales y los rayos asociados, y por lo tanto limitó los incendios forestales naturales [2]. Los incendios no volvieron a ser importantes en la zona central de Chile hasta la llegada de los humanos. Por lo tanto, muchas especies nativas de los ecosistemas de Chile no están especialmente adaptadas a un régimen con incendios relativamente frecuentes e intensos, ni han adquirido características que les confiere una especial inflamabilidad. Esto contrasta con las especies que viven en otros ecosistemas mediterránenos del mundo donde se encuentras plantas que se ven favorecidas por los incendios, incluyendo plantas muy inflamables en las cuales su reproducción incrementa con el fuego. En cualquier caso, existen en Chile muchas plantas que rebrotan bien después de incendio. De manera que los incendios actuales en Chile podrían generar efectos negativos en la biodiversidad de los bosques nativos (p.e, mortalidad de no rebrotadoras, invasión de exóticas), aunque habrá que evaluar la regeneración con detalle. Sin embargo, cabe destacar, que gran parte del paisaje ardido no corresponden a sistemas naturales, sino a plantaciones forestales de especies exóticas (Figura 1).

Fig1_supreficie-region
Figura 1. Superficie afectada por incendios durante este verano (hasta la fecha), en las diferentes regiones de Chile (de izquierda a derecha: de norte a sur), separando la superficie de bosque nativo (en verde) y de plantaciones de eucaliptos y pino (en azul). La linea y puntos, representa el promedio afectado por incendios en cada región, durante el periodo 1977-2016. Elaboración propia a partir de datos oficiales de SIDCO-CONAF (Chile).

 

Para que se den grandes incendios, se requiere igniciones, baja humedad y elevado combustible. En general, en las zonas altamente pobladas, las igniciones antrópicas son muy frecuentes, y se generan frecuentes conatos o incendios pequeños que son fácilmente extinguidos. Sólo se generan grandes incendios de difícil extinción, si el clima y el combustible son apropiados para ello. La gran actividad de incendios de estos días en Chile responde, en gran manera, a esos dos factores. Las condiciones climatológicas de este periodo, han sido muy propicias para los incendios. Según la Dirección Meteorológica de Chile, este enero es el mes con la temperatura máxima, la mínima y la media más altas desde que se tienen datos [3,4]. Por lo tanto, las condiciones meteorológicas para los incendios eran óptimas, más que nunca.

A ello cabe añadir que Chile central tiene un paisaje forestal muy inflamable, formado por grandes plantaciones de pinos y eucaliptos utilizados para la producción de papel y madera (Figura 1, [5-7]). Ninguna de estas especies son nativas de Chile, sino de zonas donde el fuego es una perturbación natural, y donde ser una planta inflamable no es necesariamente un problema, incluso es beneficioso para la reproducción. En Chile, estas plantaciones proporcionan gran cantidad de combustible (elevada biomasa, formaciones densas), de elevada inflamabilidad (los pinos y los eucaliptos tienen resinas y compuestos volátiles que les hacen muy inflamables), y con unas estructura muy homogénea (plantaciones densas, monoespecíficas y coetáneas); todo ello facilita la propagación de los incendios. Además, estas plantaciones, en muchos casos llegan hasta el límite con poblaciones, poniendo en riego a la gente en caso de incendio.

Un análisis de las regiones con mayor superficie quemada (superior al valor promedio histórico, Fig. 1; es decir, las regiones de Valparaiso (V), Metropolitana (RM), O’Higgins (VI) y Maule (VII)), sugiere que, en general, los incendios seleccionan las plantaciones de manera positiva, y los bosques nativos y zonas agrícolas de manera negativa (Figura 2). Es decir, que las plantaciones se quemas más (desproporcionadamente), que el resto del paisaje, cosa que enfatiza la elevada inflamabilidad y combustibilidad de las plantaciones actuales de Chile (Figura 3). Un reciente estudio, realizado de manera independiente y utilizando datos de satélite, llega a similares conclusiones [8].

Fig2_residuos_V-VIIFigura 2. Análisis de las áreas afectadas por incendios según tipos de uso (Plantaciones, Bosque nativo, matorral+pastos, y zonas agrícolas), en relación a lo disponible en cada una de las 4 regiones que más han ardido (V, RM, VI, VII; ver Figura 1). Los datos positivos, significan que el fuego ha seleccionado de manera positiva ese tipo de uso (se ha quemado más de lo esperado por la superficie que ocupa); los datos negativos indican que el fuego tiende a evitar ese tipo de uso. Por ejemplo, en la Región Metropolitana (RM, en verde) se ha quemado más o menos lo que se espera según las proporciones en paisaje de plantaciones y nativo (valores cercanos a 0). En cambio, el las demás regiones, hay una fuerte tendencia a que las plantaciones se quemen más de lo esperado según su abundancia en el paisaje (valores positivos), mientras que los bosques nativos, el matorral, o las zonas agrícolas se queman de manera similar o menos de lo esperado según su abundancia (valores negativos). La región VII (Maule) es la más extrema en selección positiva de plantaciones y negativa del resto de usos, y es la región donde más superficie ha sido afectada (Fig. 1). Elaboración propia a partir de datos oficiales de SIDCO-CONAF (Chile).

 

Las grandes plantaciones forestales de Chile pueden haber sido económicamente rentables, y haber contribuido a la economía del país, pero todo indica que son social y ecológicamente poco apropiadas (véase vídeo ilustrativo, abajo). Da la impresión que la política forestal de Chile está pensada en una época con una escala de valores y un clima del pasado. Dada la importancia de la industria forestal en Chile, la política forestal requiere actualizarse urgentemente, considerando el cambio climático, los incendios, y la calidad de vida de la población local.

 

Peumo-Eucaliptos
Figura 3. Impacto de un incendio cerca de Penco (Región del Bío-Bío). Se observa la poca inflammabilidad del peumo (Cryptocarya alba, del bosque nativo, derecha). Foto: Fernando Saenger.

 

Referencias

[1] Wildfires in Chile and Argentina, Global Fire Monitoring Center

[2] Keeley JE, Bond WJ, Bradstock RA, Pausas JG, Rundel PW 2012. Fire in Mediterranean ecosystems: ecology, evolution and management. Cambridge University Press

[3] Todos los días de enero las temperaturas superaron los 30 ºC

[4] Escenario favorable para incendios

[5] Peña-Fernánde F. & Valenzuela-Palma, L. 2008. Incremento de los incendios forestales en bosques naturales y plantaciones forestales en Chile. En: González-Cabán, Armando, Coord. 2008. Proceedings of the second international symposium on fire economics, planning, and policy: a global view. Gen. Tech. Rep. PSW-GTR-208, Albany, CA [PDF en: español | inglés]

[6] Invasión de especies pirófitas en Chile con financiamento estatal, el mostrador 24/1/2017

[7] Plantaciones forestales e incendios, 27/1/2017

[8] Primer estudio satelital muestra que más de la mitad de lo quemado corresponde a plantaciones forestales

UPDATE: Declaración de MEDECOS sobre los incendios de ChileEspañol | English

 

 

MEDECOS XIV

February 6th, 2017 1 comment

The XIV International Conference on Mediterranean Ecosystems (MEDECOS), has been successfully held on Sevilla, Spain, 31st Jan – 4th Feb, 2017, together with the conference of the Spanish Society of Terrestrial Ecology (AEET). For details, see the web page of the meeting and the post conference comments in the J. Ecol. blog. My contributions to this MEDECOS include two talks on fire and biotic interactions, two on resprouting, and one on fire hazard:

  • Pausas J.G – Fire and biotic interactions: the benefits of the disruption
  • García Y., Castellanos M.C., Pausas J.G. – Fires do not jeopardize reproduction of Chamaerops humilis despite disrupting its pollination
  • Tavsanoglu C. & Pausas J.G. – Resprouting ability encapsulates the most functional variability in the Mediterranean Basin flora
  • Paula, S. & Pausas J.G – Worldwide geographic and phylogenetic distribution of lignotubers
  • Cáceres M. de, Casals P., Álvarez D., Pausas J.G., Vayreda J., Beltrán M. – The role of understory fuel characteristics in the fire hazard of Mediterranean forests

The last day I attended to the field trip to Los Alcornocales Natural Park (a mosaic of cork oak forests and heathlands), where I enjoyed a long conversation on alternative vegetation states in non-tropical ecosystems (e.g., PDF) with William Bond (photo below).

Thank you very much to the organizers of MEDECOS, especially to Juan Arroyo (Universidad de Sevilla) and Montse Vilà (Doñana-CSIC) for this nice and smooth conference.

Bond-Pausas_sm

William Bond (left) and myself (right) in a Cork oak forest (photo: F. Ojeda)

A new pyroendemic annual plant

January 21st, 2017 No comments

Recently, the annual plant Chaenorhinum rubrifolium (Plantaginaceae) has been recorded for the first time in Turkey, and it was found in a recently burned area only (8 months after a fire); no individuals were found outside the burn perimeter [1, 2]. To understand the mechanisms of germination, the authors performed a range of germination tests in which seeds were submitted to different fire-related treatments like heat shocks, smoke treatments, and the application of some chemical compounds present in the smoke (NO3, karrikinolide) or analogue to those in the smoke (mandelonitrile, a cyanohydrin type compound). The results are pretty clear (Figure below): the chemical compound of smoke break their seed dormancy and stimulates the germination [1].

Overall C. rubrifolium is a clear example of a postfire seeder species, but given their strong dependency of fire, at least in Turkey, we can call it a pyroendemic plant, that is, a plant in which seedling germination and successful recruitment is restricted to immediate postfire environments [3]. Pyroendemic annuals are common in mediterranean-climate regions [4], but they have been little studied in the Mediterranean basin [5,6].

It would be interesting to study the germination of this species from other localities (e.g., it is not rare in Spain); previous research comparing plant regeneration traits from shared species between the East and the West of the Mediterranean basin show that intraspecific variability is higher at the local scale than between distant regions [7]. At least in the West, there are some varieties of C. rubrifolium that are unlikely to be pyroendemics as the ones occurring in dune systems.
çagatay-pyroendemic-smoke
Figure: Summary of the germination response of Chaenorhinum rubrifolium to fire-related treatments: Control (untreated seeds), Heat (a range of heat shocks were tested), Smoke (mean value from a range of smoke concentrations), and different chemical compounds related to smoke: NO3 (nitrate), MAN (mandelonitrile), and KAR1 (karrikinolide). Seeds were 4 month-old; the germination for Smoke and KAR1 treatments were nearly 100% when using 2 year-old seeds (after-ripening). For details see [1].

References

[1] Tavşanoğlu Ç, Ergan G, Çatav ŞS, Zare G, Küçükakyüz K, Özüdoğru B. 2017. Multiple fire-related cues stimulate germination in Chaenorhinum rubrifolium (Plantaginaceae), a rare annual in the Mediterranean Basin. Seed Sci. Res. [doi]

[2] Zare G., Özüdoğru B., Ergan G., Tavşanoğlu Ç. (submitted) Taxonomic notes on the genus Chaenorhinum (Plantaginaceae) in Turkey.

[3] Keeley JE, Pausas JG. 2017. Evolution of ‘smoke’ induced seed germination in pyroendemic plants. South African J. Bot. [doi | pdf]

[4] Keeley JE, Bond WJ, Bradstock RA, Pausas JG, Rundel PW. 2012. Fire in Mediterranean ecosystems: ecology, evolution and management. Cambridge University Press. [the book]

[5] Moreira B, Pausas JG. 2017. Shedding light through the smoke on the germination of Mediterranean Basin flora. South African J. Bot. [doi | pdf] | post]

[6] Tormo J, Moreira B, Pausas JG. 2014. Field evidence of smoke-stimulated seedling emergence and establishment in Mediterranean Basin flora. J. Veget. Sci. 25: 771-777. [doi | wiley | pdf | post]

[7] Moreira B, Tavşanoglu Ç, Pausas JG. 2012. Local versus regional intraspecific variability in regeneration traits. Oecologia 168: 671-677. [doi | pdf | post]

 

Manual para la medición de caracteres funcionales de plantas

January 4th, 2017 No comments

En 2003 se publicó el  primer manual para la medición estandarizada de caracteres funcionales de plantas [1], y en 2013 se realizó una segunda versión más completa y actualizada [2]. Estas dos versiones se publicaron en inglés en la revista Australian Journal of Botany. Ahora, la misma revista, publica la traducción de la segunda versión (2013) en español y la pone disponible a todo el mundo.

Versión en inglés: Handbook  y  supplementay material  [2]

Versión en español: Manual  y  material suplementario  [3]

Original en:  Australian Journal of Botany

 

Emas2009Fotografía: Midiendo caracteres funcionales en plantas de la sabana brasileña (cerrdao) [4]

 

Referencias

[1] Cornelissen, J.H.C., Lavorel, S., Garnier, E., Díaz, S., Buchmann, N., Gurvich, D.E., Reich, P.B., Ter Steege, H., Morgan, H.D., van der Heijden, M.G.A., Pausas, J.G. & Poorter, H. 2003. Handbook of protocols for standardised and easy measurement of plant functional traits worldwide. Aust. J. Bot. 51: 335-380. [doipdf | CSIRO pub]

[2] Pérez-Harguindeguy N, Díaz S, Garnier E, Lavorel S, Poorter H, Jaureguiberry P, Bret-Harte MS, Cornwell WK, Craine JM, Gurvich DE, Urcelay C, Veneklaas EJ, Reich PB, Poorter L, Wright IJ, Ray P, Enrico L, Pausas JG, de Vos AC, Buchmann N, Funes G, Quetier F, Hodgson JG, Thompson K, Morgan HD, ter Steege H, van der Heijden MGA, Sack L, Blonder B, Poschlod P, Vaieretti V, Conti G, Staver AC, Aquino S, Cornelissen JHC. 2013. New handbook for standardised measurement of plant functional traits worldwide. Australian Journal of Botany 61(3): 167-234. [doi | pdf | Suppl. Mat.]

[3] Pérez-Harguindeguy N, Díaz S, Garnier E, Lavorel S, Poorter H, Jaureguiberry P, Bret-Harte MS, Cornwell WK, Craine JM, Gurvich DE, Urcelay C, Veneklaas EJ, Reich PB, Poorter L, Wright IJ, Ray P, Enrico L, Pausas JG, de Vos AC, Buchmann N, Funes G, Quetier F, Hodgson JG, Thompson K, Morgan HD, ter Steege H, van der Heijden MGA, Sack L, Blonder B, Poschlod P, Vaieretti V, Conti G, Staver AC, Aquino S, Cornelissen JHC. 2013. Nuevo manual para la medición estandarizada de caracteres funcionales de plantas. Australian Journal of Botany 61(3): 167-234. [doi | pdf | Mat. Supl.]

[4] Dantas V., Batalha MA & Pausas JG. 2013. Fire drives functional thresholds on the savanna-forest transition. Ecology 94:2454-2463. [doi | pdf | appendix]

Scale mismatch in ecology

January 2nd, 2017 No comments

A recent paper suggested that fire-vegetation feedback processes may be unnecessary to explain tree cover patterns in tropical ecosystems and that climate-fire determinism is an alternative possibility [1]. This conclusion was based on the fact that it is possible to reproduce observed broad scale patterns in tropical regions (e.g., a trimodal frequency distribution of tree cover) using a simple model that does not explicitly incorporate fire-vegetation feedback processes. We argue that this reasoning is misleading because these two mechanisms (feedbacks vs fire-climate control) operate at different spatial and temporal scales [2]. It is not possible to evaluate the role of a process acting at fine scales (e.g., fire-vegetation feedbacks) using a model designed for reproducing regional-scale pattern; i.e., there is a mismatch between the scale of the question and the scale of the approach for addressing the question. While the distribution of forest and savannas are partially determined by climate, the most parsimonious explanation for their environmental overlaps (as alternative states) is the existence of feedback processes [3,4], as has been shown in many ecosystems, not only tropical ones [4]. Climate is unlikely to be an alternative to feedback processes; rather, climate and fire-vegetation feedbacks are complementary processes acting at different spatial and temporal scales [2].
Fig2b
Figure: Fire activity (based on remotely sensed data) for savannas and forests located in the range of environmental conditions where both occurs, for Africa and South America (Afrotropics and Neotropics, respectively). From [2,3].

References
[1] Good, P., Harper, A., Meesters, A., Robertson, E. & Betts, R. (2016) Are strong fire–vegetation feedbacks needed to explain the spatial distribution of tropical tree cover? Global Ecol. and Biogeogr. 25, 16-25.

[2] Pausas J.G. & Dantas V.L. 2017. Scale matters: Fire-vegetation feedbacks are needed to explain tropical tree cover at the local sacle. Global Ecol. and Biogeogr. [doiwiley | pdf]

[3] Dantas V.L., Hirota M., Oliveira R.S., Pausas J.G. 2016. Disturbance maintains alternative biome states. Ecology Letters 19: 12-19. [doi | wiley | pdf | suppl | blog]

[4] Pausas, J.G. 2015. Alternative fire-driven vegetation states. J. Veget. Sci. 26:4-6. [doi | pdf | suppl.] | blog]

 

Summary 2016

December 22nd, 2016 No comments

The ecology of bark thickness (2): another twist

December 3rd, 2016 No comments

Sometime ago we proposed that “at the global scale, a significant proportion of the variability in bark thickness is explained by the variability in fire regimes”, and specifically predicted that frequent low intensity fires select for thick bark [1]. In addition, we suggested that differentiating between inner and outer bark thickness would help to better understand the functional role of bark, especially in non-fire prone ecosystems. The paucity of available data at a global scale limited an empirical demonstration of the proposed framework.

A recent paper has now provided evidence for the fire hypothesis of bark thickness at a global scale [2, 3]. Specifically, Rosell [2] regressed bark thickness against fire frequency and climate parameters and showed that the most sensitive part of the bark in relation to fire was the outer bark, while the inner bark was quite variable and slightly related to both fire and climate [2]. In the early paper [1] we also mentioned that little was known about the role of bark thickness in arid ecosystems. Recent research support the role of bark as a fire protection mechanisms in some arid ecosystems [4, 5].

To advance in the relationship between bark thickness and fire, it is necessarily to consider not only fire frequency, but also fire intensity, and to scale these fire characteristics with plant life-histories ([3], see figure below). This is because the relationship between fire regime and bark thickness is not expected to be simple and linear, but a bit more complex, including some threshold-type relationships (figure below).

Little by little we are improving our understanding on the role of bark as a fire-protection mechanism, and how fire regimes has shaped bark thickness in many ecosystems.

Fig2_FlameHeight-FRI_art

Figure: Bark thickness as a function of fire regime: flame height (an indicator of fire intensity) and mean fire return interval (fire frequency). Fire regime is scaled by the characteristics of the plant (height to the base of the crown and longevity, respectively). The shaded area represents the areas where thick bark is adaptive for fire protection, i.e., when return intervals are shorter than the lifespan of the plant and fires are of low intensity (flame height is shorter than the distance to the base of the crown, e.g., surface fires); the shade area is limited thresholds (values of 1 in the axes). The unshaded area represents the conditions where thick barks are not adaptive (thin bark is more likely), i.e., when fires are crown-fires or when the return interval is long (in relation to the longevity of the plant). From [3].

References

[1] Pausas, J.G. 2015. Bark thickness and fire regime. Functional Ecology 29:317-327. [doi | pdf | suppl. | blog]

[2] Rosell J.A. 2016. Bark thickness across the angiosperms: more than just fire. New Phytologist 211: 90–102

[3 ] Pausas J.G. 2017. Bark thickness and fire regime: another twist. New Phytologist 213: 13-15. [doi| pdf] <- New!

[4] Schubert, A. T., Nano, C. E. M., Clarke, P. J. & Lawes, M. J. 2016. Evidence for bark thickness as a fire-resistance trait from desert to savanna in fire-prone inland Australia. Plant Ecol. 217: 683-696.

[5] Cousins, S. R., Witkowski, E. T. F. & Pfab, M. F. 2016. Beating the blaze: Fire survival in the fan aloe (Kumara plicatilis), a succulent monocotyledonous tree endemic to the Cape fynbos, South Africa. Austral Ecol. 41:466-479.

La huella del fuego

November 30th, 2016 1 comment

La huella del fuego es un documental sobre incendios forestales en España realizado por el equipo del programa Crónica, de La 2 de TVE, y que se emitió el 28 Noviembre 2016. En él participaron algunas de las personas que recientemente realizaron el decálogo sobre incendios forestales (decálogo | blog). Podéis ver un  resumen del documental, o el programa entero aquí:

También en www.rtve.es/alacarta

Nota: el documental no está relacionado con el libro que tiene el mismo título (de L. Otero 2006), que describe la historia de los bosques de Tierra del Fuego.

Flammability strategies

November 24th, 2016 No comments

We live on a flammable planet [1,2] yet there is little consensus on the origin and evolution of flammability in our flora [3]. Part of the problem lies in the concept of flammability. In a recent paper [4] we suggest that flammability should not be viewed as a single quantitative trait or metric, rather we propose that flammability has three major dimensions that are not necessarily correlated: ignitability, heat release, and fire spread rate. These dimensions define three flammability strategies observed in fire-prone ecosystems: the non-flammable, the fast-flammable and the hot-flammable strategy (with low ignitability, high flame spread rate and high heat release, respectively). The non-flammable strategy refers to plants that do not burn (or rarely) in natural conditions despite living in fire-prone ecosystems: this is because they have biomass with very low ignitability (low flammability at the organ scale) or because their plant structure does not allow the ignition of the biomass (low flammability at the individual scale). The hot- and the fast-flammable strategies refer to flammable plants with contrasted heat release and spread rate. Flammability strategies increase the survival or reproduction under recurrent fires, and thus, plants in fire-prone ecosystems benefit from acquiring one of them; they represent different (alternative) ways to live under recurrent fires. This novel framework on different flammability strategies helps us to understand variability in flammability across scales [4].

 

flammability-strategies
Figure: Conceptual model describing the three plant flammability strategies in fire-prone ecosystems. While many plants fall at intermediate levels of these axes (i.e., the null model for flammability), plants in fire-prone ecosystems benefit from being at the extremes, forming the three flammability strategies considered here. From [4]

References
[1] The-fire-overview-effect, jgpausas.blogs.uv.es/2016/09/18/

[2]  A new global fire map, jgpausas.blogs.uv.es/2013/03/06/   [doi | pdf]

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

[4] Pausas J.G., Keeley J.E., Schwilk D.W. 2017. Flammability as an ecological and evolutionary driver. J. Ecol. 105: 289-297 [doi | wiley | pdf | brief for managers]
UPDATE: featured on the cover J Ecol 105(2): cover | blog

 

Future fires

November 11th, 2016 No comments

There is a tendency to think that fires will increase in the near future due to global warming. This is because many fire risk prediction are based on climate only. However fire regime changes not only depend on climate [1]; there are other factors, like land-use changes, CO2, plant invasion, fragmentation, etc. that are also important drivers of change in fire activity [1]. Even plant drought stress (and flammability) not only depends on climate [2,3].

A recent simulation study [4] suggests that global burned area is certainly predicted to increase in the following decades when simulations are based on climate only (blue line in the figure below). However, adding the effect increased CO2 reduces the predicted burned area to no increase (green line below). Furthermore, when adding increased population density and urbanization (black and red lines), the model predicts much more area burnt in the last century (black lines 1900-2000) and a reduction of future burned area (red lines). The predicted reduction of fire during 1900-2000 is consistent with global charcoal records [5] and can be explained by increasing agriculture, land use and fragmentation. Overall, this study suggests that global area burned is unlikely to increase in the following decades.

Note that 1) this is a model, so take it with caution! 2) This model is at the global scale, but changes in different directions are expected in different regions, and this can have biodiversity consequences (even if the global balance is steady); for instance, in the Mediterranean Basin, fire are likely to keep increasing as land abandonment and fuels are increasing [6]. And 3) there is a high uncertainty in some fire drivers. For instance, temperature is likely to keep increasing, however, rainfall and wind changes are very uncertain, and landuse and emissions are subject to uncertain changes in environmental policies in different countries. In any case, this study gives us an idea of the possible sensitivity of different parameters.

Knorr-2016-NatClimChange
Figure: Simulation of global area burned for 1900 to 2100 under different scenarios: a) climate only (blue line); b) climate + CO2 (green); c) climate + CO2 + population & urbanization (black lines; red area for the future predictions). From [4].

References
[1] Pausas J.G. & Keeley J.E., 2014. Abrupt climate-independent fire regime changes. Ecosystems 17: 1109-1120. [doi | pdf | blog]

[2] De Cáceres M, et al. 2015. Coupling a water balance model with forest inventory data to predict drought stress: the role of forest structural changes vs. climate changes. Agr. For. Meteorol. 213: 77–90. [doi | pdf | suppl. | blog]

[3] Luo, Y. & H. Y. H. Chen. 2015. Climate change-associated tree mortality increases without decreasing water availability. Ecol, Let. 18:1207-1215.

[4] Knorr W, Arneth A, & Jiang L, 2016. Demographic controls of future global fire risk. Nature Clim. Change 6:781-785.

[5] Marlon JR, et al. (2008). Climate and human influences on global biomass burning over the past two millennia. Nature Geosci, 1, 697-702.

[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 | pdf | blog]

 

Smoke-stimulated germination (2): Shedding light through the smoke

November 1st, 2016 No comments

There are some plants with seeds that have a dormancy period and that fire can stimulate their germination. In some species, it is the heat of the fire that breaks seed dormancy and triggers germination (heat-stimulated germination, [1, 2]). In others, germination is stimulated by chemicals produced during the combustion of the organic matter (e.g., chemicals found in the smoke and charred wood) [1, 3]; we call this process, smoke-stimulated germination [5]. That is, in fire-prone ecosystems many plants have evolved seeds with sensitivity to heat and/or to chemicals produced by fire [1, 2, 3].

There are many species from a wide phylogenetic range with smoke-stimulated germination [5]; they appear in different regions worldwide and are stimulated by different combustion-related products, both organic and inorganic [4, 5]. All this suggest that smoke-stimulated germination is a trait that has appeared multiple times during the evolution, and thus is another example of convergent evolution [5].

In the Mediterranean Basin we currently know about 67 species (from 19 families) showing a significant increase in germination in response to smoke [6]. Families with many smoke-stimulated species in this region are Lamiaceae, Ericaceae and Asteraceae. However, there is still a lot of research to be done on smoke-stimulated germination in Mediterranean Basin flora, as many species have not yet been tested; in fact, very few annuals has been tested [6] despite there is evidence from field studies (3) and from other Mediterranean regions suggesting that smoke-stimulated germination is important in annuals.

But remember, plants are not the only organisms that have evolved in response to chemicals present in the smoke, humans too! [7].

smoke-germinationFigure: Germination (proportion of seeds) in control conditions (light yellow) and after a smoke treatment (blue) for four Mediterranean species in which germination is strongly dependent on smoke: Coris monspeliensis (Primulaceae), Erica umbellata (Ericaceae), Onopordum caricum (Asteraceae) and Stachys cretica (Lamiaceae) See [6].

 

References
[1] 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]

[2] Moreira B and Pausas JG. 2012. Tanned or Burned: the role of fire in shaping physical seed dormancy. PLoS ONE 7:e51523. [doi | plos | pdf]

[3] Tormo, J., B. Moreira, and J. G. Pausas. 2014. Field evidence of smoke-stimulated seedling emergence and establishment in Mediterranean Basin flora. J. Veget. Sci. 25: 771-777. [doi | wiley | pdf | blog ]

[4] Smoke-stimulated germination, jgpausas.blogs.uv.es/2011/12/02/

[5] Keeley J.E. & Pausas J.G. (in press). Evolution of ‘smoke’ induced seed germination in pyroendemic plants. South African J. Bot. [doi | pdf] <- New

[6] Moreira B. & Pausas J.G. (in press). Shedding light through the smoke on the germination of Mediterranean Basin flora. South African J. Bot. [doi | pdf] <- New

[7] Smoke and human evolution, jgpausas.blogs.uv.es/2016/08/31/

De incendios y cipreses (5)

October 11th, 2016 2 comments

Después de una serie de despropósitos sobre el posible uso de cipreses ignífugos [1-4], por fin parece que se encaucen las cosas: Los cipreses que estaban destinados para hacer de barrera cortafuegos en el monte, parece que finalmente se utilizarán en jardinería [5], y esperemos que para jardines urbanos, lejos del monte. En paisajes con incendios recurrentes, plantar cipreses en zonas semi-urbanas (en la interfaz urbano-forestal), no es recomendable, ya que si llega el fuego, o simplemente pavesas, pueden prender de manera intensa y actuar como antorchas. Por ello, los bomberos temen las casas rodeadas de cipreses, y de hecho, está prohibido plantarlos en jardines de diversas zonas de EEUU. Hay evidencias de que los cipreses pueden ejercer de captadores de pavesas (foto). La idea de utilizarlos como cortafuegos estaba fuera de toda lógica [4].

Cipreses-quemadosFoto: Valla de cipreses que prendió durante el incendio de La Granadella (4/Sep/2016, La Marina, Alicante). Nótese que el incendio no llegó directamente a la valla (los pinos y campos de cultivo  de los alrededores no se vieron afectados); es probable que el fuego llegase con una pavesa, como pasó con los distintos focos de este mismo incendio [6].

Referencias

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

[5] La investigación española sobre cipreses cortafuegos acabará en plantas de jardín,  eldiario.es

[6] El SEPRONA concluye que todos los focos del incendio de la Granadella fueron provocados por las pavesas (xabiaaldia.com);  Una colilla mal apagada provocó el incendio de Xàbia (eldiario.es); El Seprona cree que una colilla originó el incendio y el viento causó los tres focos (levante-emv.com).

¿Será este el último post sobre el tema? ¿Se habrá ganado una pequeña batalla?
(podéis dejar vuestra opinión en los comentarios)

 

Postfire flowering: Lapiedra martinezii

October 8th, 2016 No comments

Lapiadra martinezzi
Lapiadra martinezzi (Amaryllidaceae) flowering after fire in eastern Spain. This is also an example of an hysteranthous geophyte (flowering before appearing the leaves).

Upper left: From La Granadella (Benitatxell, La Marina Alta, Alicante), one month after a high intensity wildfire that occurred the 5 Sept 2016.
All others: in a Pinus halepensis open woodland that was burned (at low intensity) in April 2016 (for firefighting training) near Valencia; photo taken the 29th Sept 2016. There were many individuals (hundreds to thousands) flowering and some with fruits. We did not find any flower in the surrounding unburned area.

For other species with fire-stimulated flowering, see: jgpausas.blogs.uv.es/tag/postfire-flowering/

 

Fire benefits plants by disrupting antagonistic interactions

October 2nd, 2016 2 comments

There are many plants that benefit from fire. Typical examples are those that despite they may be killed by fire, the germination of their seeds is stimulated by the fire (either by the heat or by the smoke; [1,2]), and thus they recruit very well (high offspring abundance) and often increase there population size postfire. Species with fire-stimulated flowering [3,4] also benefit from fire. In a recent paper [5] we propose that there may be another mechanisms by which fire may benefit plants: fire may remove seed predators, and thus create a window of opportunity for reproduction under a lower predation pressure (predator release hypothesis). This is specially applicable to specialist plant-insect interactions. We documented two cases: in Ulex parviflorus, a plant species with fire-stimulated germination [1,2], fire eliminated there specialist seed predator weevil (Exapion fasciolatum, Apioninae, Brentidae) and thus increased the available seed number for germination. Similarly, in Asphodelus ramosus, a fire-stimulated flowering species [3], fire reduced the specialist herbivore and seed predator (Horistus orientalis, Miridae, Hemiptera) and increased their fruit production. Thus, fire, by disrupting the antagonistic interactions, benefit plants; the temporal window of this predator release is likely to depend on fire size. For more information see reference [5].

Ulex-Exapion

Figure: Proportion of predated fruits of Ulex parviflorus in unburned sites (grey boxes) and at the edge and center of a recently burned area (white boxes), 2 and 3 years postfire. Data from two large wildfires in Valencia (2012) [5]; Edge and Center of the burned area refer to <1 km and >1.5 km from the fire perimeter, respectively. Photo of the seed predator (Exapion) from BioLib.cz.

References

[1] 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]

[2] Moreira B and Pausas JG. 2012. Tanned or Burned: the role of fire in shaping physical seed dormancy. PLoS ONE 7:e51523. [doi | plos | pdf]

[3] Postfire blooming of Asphodelous, jgpausas.blogs.uv.es/2014/04/05

[4] Postfire flowering: Narcissus, jgpausas.blogs.uv.es/2015/05/02

[5] García Y., Castellanos M.C. & Pausas J.G. 2016. Fires can benefit plants by disrupting antagonistic interactions. Oecologia 182: 1165–1173. [doi | pdf] <- New!!

 

The fire overview effect

September 18th, 2016 No comments

The overview effect is the feeling and awareness reported by some astronauts when viewing the entire Earth during space-flight. Fire ecologists have our own overview effect! When remote sensed fire information was available for the first time at the global scale, it provided a magnificent and unprecedented view of the importance of fires on the Earth, and fires become a global issue. This remotely sensed information was a very valuable data because, for the first time, it was possible study some fire ecology processes at the global scale (for example [1]). Here is an animation for a 10 years period (2000-2010). It shows that on our planet, fires are widespread and something is always burning; we live in a flammable planet.

 


MODIS Rapid Response System Global Fire Maps, NASA. Each colored dot indicates a location where MODIS detected at least one fire during a 10-day period.

More global fire animations: youtube | Earth Observatory |

Reference

[1] Pausas J.G. & Ribeiro E. 2013. The global fire-productivity relationship. Global Ecol. & Biogeogr. 22: 728-736. [doi | pdf | appendix | erratum | blog]

 

Smoke and human evolution

August 31st, 2016 1 comment

In this blog we have discussed that some plants have evolved seeds with sensitivity to chemicals produced by fire in such a way that these chemicals stimulate the germination of the plants after a fire; we call this process smoke-stimulated germination [1-3]. Well, plants are not the only organisms that have evolved in response to chemicals present in the smoke, humans too! A recent paper show that modern humans are the only primates (including early hominids as Nearthentals and Denisovans) that carry a mutation increasing tolerance to smoke chemicals produced by fires [4]. This mutation could have given an evolutionary advantage to modern humans in relation to other hominids as allowed them to use fire for many important activities (e.g., cooking, hunting, defense, heating, agriculture). This high exposure to smoke would have also increased the susceptibility to pulmonary infections, and even the evolution of some of them (tuberculosis [5]). The tolerance to smoke also allowed modern humans to have some tolerance to pollution and to smoke cigarettes! That is, the ability to smoke could be a side effect (an exaptation, if you’d like) of been adapted to use fire, and in fact, it currently acts as a secondary sexual character!

woody-allen-smoking
Smoking as a secondary sexual character (Woody Allen in Manhattan, 1979).

References
[1] 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. [doi | pdf | post]

[2] Tormo, J., B. Moreira, and J. G. Pausas. 2014. Field evidence of smoke-stimulated seedling emergence and establishment in Mediterranean Basin flora. Journal of Vegetation Science 25: 771-777. [doi | wiley | pdf | post]

[3] Smoke-stimulated germination, jgpausas.blogs.uv.es/2011/12/02/

[4] Hubbard, T.D., Murray, I.A., Bisson, W.H., Sullivan, A.P., Sebastian, A., Perry, G.H., Jablonski, N.G. & Perdew, G.H. (2016) Divergent Ah receptor ligand selectivity during hominin evolution. Mol. Biol. Evol., 33:2648-2658.

[5] Chisholm, R.H., Trauer, J.M., Curnoe, D. & Tanaka, M.M. (2016). Controlled fire use in early humans might have triggered the evolutionary emergence of tuberculosis. Proc. Natl. Acad. Sci. USA, 113, 9051-9056.

Fire ecology in Plant Ecology: homage to Peter Clarke

July 8th, 2016 No comments

The journal Plant Ecology has now published an special issue on Fire Ecology to homage Peter Clarke, who died in December 2014 after a long battle with cancer. Peter (University of New England, Australia) made a significant contribution to the fire ecology of Australia; many of his colleagues and collaborators have contributed to this issue (including myself). Link to the special issue.

Fire-Ecologists
Photo: Peter Clarke (center; arms crossed) and colleagues visiting the Otay Mountains (San Diego, southern California) in November 2006 after attending the 3rd International Fire Ecology and Management Congress in San Diego. From Left to right: Malcom Gill, Dylan Schwilk, Ross Bradstock, Peter Clarke, William Bond, and Juli Pausas. Photo by Jon Keeley.

Diversidad política (3)

July 2nd, 2016 No comments

Tras las Elecciones Generales del 20 de Diciembre de 2015, la diversidad política del Congreso de los Diputados de España incrementó considerablemente, y fue la más elevada de la historia de nuestra democracia; y ya explicamos las ventajas de tener un congreso con elevada diversidad (elecciones 2008,  elecciones 2015). La desventaja es que la elevada diversidad es más difícil de gestionar, especialmente en sociedades poco maduras dramáticamente (lo más simple de gestionar son las dictaduras, que tienen una diversidad muy baja). La composición del Congreso que salió de esas elecciones no supo gestionar esa diversidad, seguramente por la falta de experiencia democrática, es decir, falta de capacidad de diálogo, de capacidad para aceptar las diferencias, y de excesivo deseo de poder de los lideres. Ello nos llevó a repetir las elecciones 6 meses más tarde.

Las Elecciones Generales del 26 de Junio 2016 dieron un resultado en parte parecido a las anteriores, pero con un poco menos de diversidad (Figura). ¿Se ha reducido suficiente la diversidad para que los políticos sean capaces de ponerse de acuerdo y formar un gobierno?
DivPolitica1977-2016

Figura: Valores de diversidad (expresada por el índice de diversidad de Shannon-Weaver) según el número de votos (rojo) o de escaños (azul) en los diferentes partidos políticos, en las diferentes Elecciones Generales al Congreso de los Diputados de España realizadas durante la democracia (elaborado a partir de la base histórica de resultados electorales del Ministerio del Interior).

Dado que sólo han transcurrido 6 meses entre las dos elecciones, es tentador analizar las causas de las diferencias, al menos por lo que hace a los grandes partidos y los grandes números (Tabla):

  • Se redujo un poco el número de partidos. La ley electoral española perjudica a los partidos pequeños de ámbito estatal, y eso forzó ha hacer algunas uniones antes de las elecciones, en lugar de hacerlas después (cosa que permitiría que el programa conjunto se realizase según los votos de cada uno de los partidos y así reflejaría mejor el deseo de los votantes).
  • El PP aumentó en votos, probablemente a expensas de C’s y de otros partidos menores, que disminuyeron en votos (Tabla, números en azul; este cambio aumenta la dominancia y disminuye la diversidad). Quizá los votantes de derechas castigaron el pacto Cs-PSOE y asumieron la corrupción como una mal menor (cosa bastante sorprendente en un país que desea ser moderno y democrático)
  • La abstención aumentó en más de 1 millón, y probablemente se concentró en las confluencias de izquierda, que perdieron aprox. 1 millón de votos, y en menor medida en el PSOE (Tabla, números en rojo). Parece que los que decidieron no votar en el 26J después de haber votado en 20D eran gente de izquierdas (desencantados, o votantes de IU que no aceptaron la coalición con Podemos). Si eso es cierto, no deja de ser curioso que haya gente de izquierdas que le de igual el partido que gobierne.

Tabla: Comparación (en número de votos y abstenciones) entre las elecciones generales al Congreso de los Diputados del 20D del 2015 y las del 26J del 2016.  Datos según el Ministerio del Interior (29 Junio 2016). [1] Incluye a Podemos, IU y las confluencias afines (Compromís, Mareas, Equo, Podem, …). [2] Opciones que no cuentan para la formación del Congreso.

Taula2015-2016(3)

Conclusiones 26J 2016:

1) A muchísimos españoles (unos 8 millones) les parece bien y reprueban la corrupción, los grandes recortes en sanidad y educación, la reforma laboral y la ley mordaza, entre otras. Consideran que es lo mejor para el país, o quizá, que más vale malo conocido, que bueno por conocer.

2) Una coalición muy reciente, dominada por un partido muy nuevo (Podemos) se mantiene con mas de 5 millones de votos, indicando las ansias de cambios importantes de una buena parte del electorado.

3) Muchísimos españoles (unos 11 millones) no opinaron acerca de cómo les gustaría que se organizase el país, y parce que les da igual cómo se repartan los impuestos que pagan.

4) El hecho de que los resultados sean bastante diferentes a lo previsto por las encuestas sugiere una cierta respuesta a estas encuestas, y por lo tanto, una cierta inmadurez política.

5) Aun no se sabe si se conseguirá formar gobierno, pero el Congreso salido de estas elecciones parece que representará peor a la población (menos votos) que el que se formó en el 2015, y especialmente a la población con ideas de izquierda (una parte no votó). En cualquier caso, será un Congreso mucho más diverso que el de las anteriores legislaturas (ver linea azul en la figura de arriba); cosa que es positiva para todos.

Todo ello asumiendo que no hay fraude en el recuento de votos; la falta de transparencia ha despertado algunas alarmas (p.e., lagranjahumana).

Enlaces:
Diversidad política (2). jgpausas.blogs.uv.es/2015/12/30/
Diversidad política (1): pérdida de diversidad política en España. jgpausas.blogs.uv.es/2008/03/11/

Brazil 2016

June 27th, 2016 No comments

Summary of my June 2016 tour:

  • Brasilia: meeting point with S. Paula;  visit to the Jadim Botánico and the Chapada Imperial [photos A, E]
  • Pirenópolos: IAVS 2016; talk: “Plant strategies in fire-prone ecosystems: hidden buds” [photo B]; Pireneus
  • Rio Claro: Univesidade Estadual Paulista (UNESP); meeting with A. Fidelis & students (Luis, Talita, etc.). Visiting the Itirapina experimental fires [photo C]. Talk: “Fire, traits, and biodiversity: a global perspective”.
  • Piracicaba: Universidade de Sao Paulo (USP), meeting with B. Appezzato-da-Glória and collaborators to study underground resprouting structures [photo D]
  • Campinas: Universidade Estadual de Campinas (UNICAMP); meeting with V. Dantas and students (Paulo, André, etc.) [photo F]
  • Sao Paulo: meeting W. Delitti (USP)

brasil2016c
Photos: A (top left):  Susana Paula, Ericaulaceae and myself; B (top right) : my talk in Pirenópolis; C (bottom left): A. Fidelis and her students in front of an ‘underground tree’. D (center): Xylopodium with tuberous roots in Aldama (Appezzato-da-Glória lab); E (middle right): tree with a corky bark in the cerrado of the Jardim Botánico (Brasilia); E (bottom right): Having a drink with Vinicius Dantas in Campinas.

Related posts:

– Brazil 2015, jgpausas.blogs.uv.es 16 Mar 2015

– Fire shapes savanna-forest mosaics in the Brazilian cerrado, jgpausas.blogs.uv.es 14 May 2014

– Afrotropical and neotropical savannas are different, jgpausas.blogs.uv.es 29 Jul 2013

– Fire generates intraspecific trait variability in neotropical savannas, jgpausas.blogs.uv.es 28 Aug 2012

– Disturbance maintains alternative biome states, jgpausas.blogs.uv.es 9 Nov 2015

 

Fire behaviour by Vareschi

May 13th, 2016 No comments

Recently I came across this figure published in 1962 by Volkmar Vareschi [1] which nicely synthesize variations in temperatures in the flame and in the soil, as well as flame height and flame spread (time and distance) in a simple hand-drawing. It is not easy to see a figure on fire behaviour as simple and illustrative as this one; I only miss a bit of colour. It refers to a burn of a Trachypogon savanna in Los Llanos, Venezuela. Vareschi (1906-1991) was born in Austria and moved to Venezuela in 1950; he is considered a pioneer in tropical plant ecology; one of his papers was about savanna fires [1].

 

Vareschi-1962-burnFigure 2 from [1]

 

References

[1] Vareschi, V. (1962) La quema como factor ecológico en los Llanos. Boletin de la Sociedad Venezolana de Ciencias Naturales 23, 9-31.
 

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