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Posts Tagged ‘fire’

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]

 

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]

 

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)

 

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 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.
 

Odena: 9 meses posincendio

May 1st, 2016 No comments

El 27 de Julio de 2015 un incendio forestal afectó unas 1200 ha en Òdena (Anoia, Catalunya central), una zona dominada principalmente por pino carrasco (Pinus halepensis). Pocos días después ya se empezaba a ver un inicio de la regeneración del ecosistema [1, 2]. En una visita reciente (Abril 2016, 9 meses posincendio), vemos que en gran parte de la zona se han cortado y extraído los árboles quemados (y algunos no quemados). Antiguamente, cuando aun no se daba casi ningún valor a los ecosistemas naturales, y sí a la madera, se sacaban los árboles quemados para obtener algún beneficio económico; y algunas veces por motivos "estéticos". Hoy en día, no parece una acción muy apropiada [3], a no ser que haya una razón de peso, cosa que desconozco en el caso de este incendio.

Los árboles quemados benefician a la regeneración porque retienen un poco el suelo, disminuyen el impacto de las gotas de lluvia en el suelo, mantienen cierta humedad, captan agua de la niebla, sirven de posadero para aves que traen semillas (que contribuyen a la regeneración), y son hábitat para fauna diversa [4]. Cortar los árboles requiere entrar con maquinaría en la zona quemada (con suelos muy sensibles), generar caminos y arrastrar troncos. Esto conlleva la eliminación de todos los beneficios mencionados, ademas de la disminución de parte del suelo y mantillo, la mortalidad de las primeras germinaciones posincendio (por ejemplo del pino), la formación de surcos que pueden ser puntos de inicio de erosión (cárcavas), y disminución de la regeneración natural en general. En general, entrar en una zona recién quemada, y degradar el ecosistema disminuyendo la regeneración y aumentando la erosión, está poco justificado [3]; en algunos casos, estas intervenciones pueden ser más perjudiciales que el propio incendio.

odena
Fotos: a) Pinar con rebrotes de madroño 4 meses después del incendio, antes de cortar los árboles; se aprecia un cierto ambiente forestal. b) surcos del arrastre de troncos durante la extracción de la madera quemada. c) Ambiente 9 meses después del incendio, una vez se han cortado los árboles. d) Germinación de pino 4 meses después del incendio; germinaciones susceptibles a ser eliminadas si se entra con maquinaria o se arrastran troncos. e) pinos vivos (no quemados) cortados y apilados (9 meses posincendio). f) Enebro rojo (Juniperus oxycedrus) que rebrota tras quema y corta (9 meses posincendio). Incendio de Odena, Abril 2016 (fotos: JG Pausas).

Referencias

[1] Odena fire: first visitors, jgpausas.blogs.uv.es 10-08-2015

[2] Odena fire: 55 days postfire, jgpausas.blogs.uv.es 17-10-2015

[3] Lo que no se debe hacer después de un incendio, jgpausas.blogs.uv.es 13-08-2015

[4] Pausas, J.G., Ribeiro, E. & Vallejo, R. 2004. Post-fire regeneration variability of Pinus halepensis in the eastern Iberian Peninsula. Forest Ecology and Management 203: 251-259. [doi | pdf]

Flammable Mexico

April 13th, 2016 No comments

Mexico is a megadiverse North American country with a wide range of climates (e.g., wet tropical, warm temperate, mediterranean, and arid) and a diverse topography (from sea level up to 5700 m asl). These characteristics together with its location in the transition toward Central America make this land a global biodiversity hotspot with species belonging to northern (Neartic) lineages co-occurring with others from southern (Neotropical) lineages. An important factor contributing to this biodiversity are the frequent disturbances in this region where volcanoes, hurricanes, and wildfires are common, together with droughts and floods. Fires occur mainly in April-May (Figure below, [1]); the natural sources of ignition being lightning, especially in mountains, and volcanoes (with clear evidence of fires ignited by volcanoes, e.g. from the Popocatépetl volcano). However, currently most fires are caused by human activities, as in many other countries. Hurricanes add fuel and increase the intensity and probability of fire [2].

Mexico is a center of diversification of pines (Pinus) and oaks (Quercus), two species groups strongly related to fire [3,4]. Mexico harbors about 50 species of pines and these incorporate all the fire strategies and traits observed in this genus [4]. For instance, there are many fire tolerant pines with thick barks, self-pruning abilities, and in some cases, with basal or juvenile resprouting capabilities; fire embracers (postfire seeders) with thin bark and serotinous cones; and fire avoiders that lack these traits. The country also harbors some 160 Quercus species, ranging from strongly resprouting shrubby species to many tree oaks with relatively thick bark that live in surface fire ecosystems, and including evergreen and drought-deciduous species with a large range of leaf morphologies. I was surprised to see some oaks with very large, and very thick leathery leaves that are deciduous, certainly an outlier in the leaf economics spectrum. More details in [1].

Flamable-Mexico
Figure: Recent fire activity in Mexico (2001-2015) estimated from the monthly number of active fires recorded by the Terra satellite (MODIS hotspots). Top: temporal variability (x-axis ticks indicate the begining of the year). Bottom left: fire seasonality– the flammable season is concentrated into four months (March-June), with a peak in April-May (the end of the dry season). Bottom right: proportion of active fires in each biome (TrDry: tropical dry broadleaf forests; TrConif: tropical coniferous forests: TrMost: tropical moist broadleaf forests; Desert: deserts and xeric shrublands; Others). From [1]

References
[1] Pausas J.G. Flammable Mexico. Int. J. Wildland Fire [doi | pdf]

[2] Fire-wind interactions, jgpausas.blogs.uv.es 30 Oct 2015

[3] 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.]

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

Postfire resprouting of Chamaerops humilis

March 18th, 2016 No comments

"A few, but only a few species of palms, are, like our Coniferae, Quercineae, and Betulineae, social plants : such are the Mauritia flexuosa, and two species of Chamaerops, one of which, the Chamaerops humilis, occupies extensive tracts of the ground near the Mouth of Ebro and in Valencia ..." -- Alexander von Humboldt (1848)

Chamaerops humilis (Mediterranean dwarf palm) is the only native palm in continental Europe, and the northernmost naturally occurring palm in the world. It is native to the western Mediterranean Basin, occurring along the Mediterranean cost of Spain (as mentioned by Humboldt), Portugal, France, Italy, Malta, Morocco, Algeria, and Tunisia. The other palm occurring in the Mediterranean Basin is Phoenix theophrasti, a rare palm growing in the Crete island and in the southern Turkey [MedTrees].

Humboldt probably did not know that Chamaerops humilis resprouts very quick after fire (at that time fire was not considered as part of the natural processes). The resprouting of this species does not necessary come from new dormant buds (as in most typical resprouters) but from the normal apical buds protected from the fire by the leaf bases in the stem. In fact, buds generate leaves that have the upper part affected by the fire, but not the lower part (as in all monocots, the meristem is at the base of the leaves, and thus more protected from the heat of the fire). Consequently the first leaves often show the typical burned-brown-green pattern of the photo below. In addition, it can generate basal suckers from an underground rhizome. C. humilis often flowers very quickly after fire, together with the first leaves (upper photo). Overall it is very resilient to recurrent fires.

Chamaerops-humilis
Chamaerops humilis (one of the few 'social palms' following Humboldt) 2-3 months postfire in the Valencia region (eastern Spain; photos: JG Pausas)

References

Humboldt, A. von (1848). Aspects of nature (original title: Ansichten der Natur, 3rd ed).

 

Incendios forestales (de vegetación) en México

March 1st, 2016 1 comment

Recientemente se ha publicado un nuevo libro sobre incendios forestales. El libro describe la importancia y los regímenes de incendios en los diferentes ecosistemas de México, así como aspectos sobre historia y manejo del fuego [1]. Es un libro extenso, enciclopédico, con unas 1700 páginas publicadas en 2 volúmenes. El primer volumen (18 capítulos) representa un paseo por la gran variedad de paisajes de México (pinares, bosques de encinos, de oyamel, de galería, pastizales, matorrales, selvas, bosques mesófilos de montaña, sabanas, manglares, palmares, etc.), y en cada uno de ellos se explica el régimen de fuego y las respuesta de las especies y ecosistemas. El segundo volumen (11 capítulos) aborda cuestiones de comportamiento, prevención, y combate del fuego, así como una historia del fuego desde sus inicios (con los primeros ecosistemas terrestres [2]) hasta el uso del fuego en las culturas mesoamericanas y en el México actual. Si hay algo que se encuentra a faltar sería una visión evolutiva; quizá los lectores pueden encontrar esas visión en mi propio libro [3]. Más comentarios sobre el libro y sobre México en [6].

Dante-Rodriguez-Trejo_libroPortadas del volumen 1 (izquierda) y 2 (derecha)

A veces se ha considerado que el concepto de incendios forestales se refiere sólo a los incendios que ocurren en bosques, o incluso a incendios que ocurren en plantaciones forestales. Para evitar ese mal entendido, el autor titula el libro 'incendios de vegetación', ese decir, para enfatizar que el libro se refiere a incendios en cualquier tipo de vegetación. En España, actualmente el término 'forestal' se refiere a cualquier tipo de vegetación natural (también llamado monte), y en ese contexto es cómo a menudo usamos el concepto de incendios forestales [3]. Así es como lo explicaba yo en el prólogo del libro 'Incendios forestales':

"Los incendios son fuegos que se propagan sin control humano; cuando ocurren en la naturaleza se llaman incendios forestales. El término forestal está relacionado con una clasificación tradicional de los usos del suelo, donde el uso forestal incluye cualquier zona terrestre que no sea de uso urbano ni agrícola. De este modo, el término incendios forestales se refiere a los fuegos no controlados (sean de origen natural o antrópico) que ocurren en los ecosistemas terrestres, y que se propagan por la vegetación, sea ésta del tipo que sea (bosque, sabana, matorral, pastizal, humedal, turbera, etc.). Por lo tanto, incendios forestales, y por extensión este libro, no sólo hace referencia a bosques, como a veces se ha interpretado, sino a cualquier tipo de ecosistema terrestre" [3]

En inglés también hay una amplia nomenclatura para referirse a los incendios forestales, como por ejemplo, wildfires (principalmente utilizado en Norte América), forest fires (Europa), bush fires (Australia), vegetation fires, landscape fires, etc., todos ellos describen los incendios en cualquier tipo de vegetación.

Referencias:

[1] Rodríguez Trejo, D. A. 2015. Incendios de vegetación. Su ecología, manejo e historia. 2 vol. Ed. Colegio de Postgraduados, Biblioteca Básica de Agricultura, México.

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

[3] Pausas J.G. 2012. Incendios forestales. Una visión desde la ecología. Ed Catarata-CSIC. Madrid. [libro]

[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 Phytol. 194: 751-759. [doi | wiley | pdf | suppl.]

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

[6] Pausas J.G. 2016. Flammable Mexico. Int. J. Wildland Fire [doi | pdf]

 

Olive trees resprouting

February 22nd, 2016 No comments

The typical image on a cultivated olive tree (Olea europaea) is a short squat tree with a thick gnarled trunk. Below are some olive trees with a slightly different shape, after being burned twice in different wildfires (1994 and 7/2015) in Montán (Castelló, eastern Spain). Before 1994 these trees were single-stemmed with the typical thick trunk; they were planted long ago for olive production. The 1994 fire killed the main stem and the tree produced many resprout from the base, around the trunk (it became multi-stemmed). In 2015 in burned again killing those 21 year-old resprouts and producing many new ones (the green ones in the pictures, 7 month-old resprouts). The 2015 fire also consumed the main stem that had died in the 1994 fire, including the base of the stem, and thus it produced a hole in the middle of the tree (second picture). This is quite common.

Olea resprouting 1
Olea resprouting 2
Photos: Olive trees (Olea europaea) resprouting after two fires (1994, 7/2015; JG Pausas 2/2016).

More on resprouting: Lignotubers | Resprouting at the global scaleEvolutionary ecology of resprouting and seedingPhysiological differences between resprouters and seedersTo resprout or not to resprout | Differences between resprouters and non-resprouters | Fire, drought, resprouting: leaf and root traits |

 

Convivir con el fuego: Decálogo de incendios forestales

February 3rd, 2016 No comments

Hace ya unos años escribimos un decálogo donde proponíamos unas bases ecológicas para convivir con los incendios forestales [1]. Ahora, la Fundación Pau Costa, en el marco de su 5º aniversario, ha compilado otro decálogo [2], este más amplio en temática y con muchos más autores, pero con un objetivo similar, aprender a convivir con el fuego. Los interesados en apoyar el decálogo tienen la posibilidad de hacerlo firmando el formulario que hay al final del mismo.

IMG_2313_sm
Foto: Quema experimental en Ayora (Valencia, 4/2009) realizada con la finalidad de entender el efecto de los incendios en los ecosistemas mediterráneos.

Referencias

[1] 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. [enlace | pdf]

[2] Decálogo de incendios forestales, Pau Costa Fondation, [enlace | pdf]

[3] Pausas, J.G. 2012. Incendios forestales. Catarata-CSIC. [Libro]

[4] 'Conviure amb el foc', entrevista en El Temps, 24 Julio 2012 [pdf]

[5] Otros textos de divulgación sobre incendios y ecología [divulgación]

[6] Towards prescribed fires, jgpausas.blogs.uv.es, 7 Oct 2013

 

Fire in the root of humans (2)

January 16th, 2016 No comments

Many people have the idea that fires scare animals and fled them in panic. However this is not always true, some species react still and calm and move away to safe sites. Some time ago I mentioned a study demonstrating that chimps in wild, when they see a wildfire, they react calmly, predict their behaviour and move accordantly without any stress or fear, suggesting that they have some understanding of fire behaviour [1]. Few days ago I came across other studies [2,3] suggesting that different species of primates not only react calmly to fire but after a fire, they increase their home range to include the area burned and used it for searching food, including 'cooked' fruits! So wildfires were very important in the history of humans [4], they could have contribute to the first step towards humanity from our ancestors ...


Figure: In captivity, some apes are able to light a fire a roast vegetables (see youtube1, youtube2). Photo from www.dailymail.co.uk

References
[1] Fire in the root of humans, jgpausas.blogs.uv.es 19-1-2010.

[2] Jaffe KE, Isbell LA 2009. After the fire: benefits of reduced ground cover for vervet monkeys (Cercopithecus aethiops). Am. J. Primatol. 71:252-260.

[3] Herzog NM, Parker CH, Keefe ER, Coxworth J, Barrett A, Hawkes K 2014. Fire and home range expansion: A behavioral response to burning among savanna dwelling vervet monkeys (Chlorocebus aethiops). Am. J. Phys. Anthropol. 154:554-560.

[4] Pausas J.G. & Keeley J.E. 2009. A burning story: The role of fire in the history of life. BioScience 59: 593-601 [doijstor | BioOne | pdfpost]

 

Heritability of serotiny (2): a molecular approach

December 2nd, 2015 No comments

Not long ago we demonstrated that serotiny (i.e., the capacity to accumulate a seed bank in the canopy until the seeds are released by fire) is an heritable trait in pines [1]. This analysis was based on a classical provenance – progeny common garden experiment. However, trait variability under controlled environmental conditions may not fully reflect the variability observed in the field, and thus this estimate of heritability may not reflect how traits respond to natural selection. This is because there is higher environmental variability in the field and also because garden experiments typically include individuals that would not survive in the field (i.e., artificially increases progeny survival) [2]. With the aim of obtaining a more realistic estimate of heritability of serotiny, we have recently estimate it directly in the field for two pine species (P. halepensis, P. pinaster) [3]. Because in the field it is not possible to construct a pedigree, we used the relatedness among individuals estimated from molecular markers (SNPs) for the same individuals from which we had estimated serotiny previously [4]. The variance in serotiny was modelled incorporating the environmental variability (climate and fire regime) using a Bayesian 'animal model'. As expected, field heritability was smaller (around 0.10 for both species) than previous estimates under common garden conditions (0.20). The difference is not surprising because wild P. halepensis and P. pinaster populations extend over heterogeneous landscapes with large environmental variations. Our results highlight the importance of measuring quantitative genetic parameters in natural populations, where environmental heterogeneity is a critical aspect. The heritability of serotiny, although not high, combined with high phenotypic variance within populations, confirms the potential of this fire-related trait for evolutionary change in the wild [2].

Pinus patula
Fig: Serotinous cones of P, halepensis and P. pinaster can be observed in previous posts (P, halepensis, P. pinaster). The photo here shows serotinous cones of Pinus patula from central Mexico (in a foggy rainy day).

References

[1] Hernández-Serrano, A., Verdú, M., Santos-Del-Blanco, L., Climent, J., González-Martínez, S.C. & Pausas, J.G. 2014. Heritability and quantitative genetic divergence of serotiny, a fire-persistence plant trait. Annals of Botany 114: 571-577.  [doi | pdf | suppl. | blog]

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

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

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

 

Lignotubers

November 17th, 2015 1 comment

Lignotubers are swollen woody structures located at the root-shoot transition zone of some plants; they contain numerous dormant buds and starch reserves [1]. They are ontogenetically programmed, that is, they are not the product of repeated disturbances; and thus they can be observed at very early stages of the plant development (other types of basal burls may be a response to multiple disturbances). Lignotubers enables the plant to resprout prolifically after severe disturbances that remove the aboveground biomass, thus they are considered adaptive in fire-prone ecosystems [2]. Lignotubers are not well-known in many floras because they are often below-ground (i.e., detected only after excavation) and because they are often confused by other non-ontogenetically determined basal burls; thus some reports of lignotubers in the literature are mistakes. In a recent review [1] we provide examples of species with a clear evidence of lignotubers in the Mediterranean basin, together with detailed morphological and anatomical description of lignotubers in saplings. The species with lignotuebers in the Mediterranean basin include many Erica species (e.g. E. arborea, E. scoparia, E. australis, E. lusitanica, E. multiflora), the two Arbutus species (A. unedo, A. andrachne), Rhododendron ponticum, Viburnum tinus, Phillyera angustifolia, Quercus suber (not obvious macroscopically!), Tetraclinis articulata and Juniperus oxycedrus (but not in all populations!). Please let me know (email address here) if you know of other Mediterranean basin species with lignotubers! Thanks

lignotubers
Figures: Examples of lignotubers for Mediterranean basin species. A Juniperus oxycedrus (resprouting after fire). B Viburnum tinus. C Arbutus unedo. D Quercus suber (not a clear basal swelling). E Olea europaea. F Phillyrea angustifolia (adult), G Phillyrea angustifolia (saplings). In many species (e.g., V. tinus, A. unedo and P. angustifolia) the lignotuber is only evident after excavating the root-shoot transition zone.

References

[1] Paula S., Naulin P.I., Arce C., Galaz C. & Pausas J.G. 2016. Lignotubers in Mediterranean basin plants. Plant Ecology  [doi | pdf | suppl.]

[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 | pdf | For managers]

 

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