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Posts Tagged ‘fire’

Fire benefits flower beetles

June 28th, 2018 No comments

For two years we sampled invertebrates after two large wildfires in eastern Spain and demonstrate that two flower beetle species, Protaetia morio and P. oblonga (Cetoniidae; Fig. 1 & 2 below), show a pyrophilous behaviour [1]. These beetles were much more numerous after the fires than in unburnt plots around the fire perimeter; in addition, these species tended to increase in number with the distance from the fire perimeter and with fire recurrence (Fig. 3 below). These results suggest that local populations survived the fire as eggs or larvae protected in the soil, and then they were favoured postfire (i.e., population size increased, compared with unburnt zones). We propose that this could be driven by the reduction of their predator populations, as vertebrates that feed on these beetles are disfavored by fire. That is, the results suggest that these flower beetle species benefit from fire because fire disrupts antagonistic interactions with their predators (predation release hypothesis).


Fig. 1. Protaetia morio: eggs, larva, pupal, and adult (photos: S. Montagud); pitfall trap full of Protaetia beetles (bottom left).


Fig. 2: Protaetia morio (male and famale) and Protaetia oblonga (male and female)

 

Fig. 3: Abundance (number of individuals) of Protaetia morio one and two years after fire (from two fires that occurred in 2012). Green: Unburnt; Yellow: Burnt edge (< 700 m from the fire perimeter); Orange: Burnt center (> 1.3 km from the fire perimeter). P. oblonga showed a similar pattern. For details, see [1].

Reference 

[1] Pausas, J.G., Belliure, J., Mínguez, E. & Montagud, S. (2018) Fire benefits flower beetles in a mediterranean ecosystem. PLoS ONE, 13: e0198951. [doi | plos | pdf]

Protaetia morio by Josep Serra
By J. Serra 7/2021

Incendios: cambios recientes y soluciones

June 19th, 2018 No comments

Recientemente, Greenpeace hizo un par de preguntas a varias personas que trabajan en diferentes ámbitos relacionados con incendios forestales (noticia | documento). Aquí copio mis respuestas.

¿En qué han cambiado los incendios?

En las últimas décadas se ha observado un cambio brusco en el régimen de incendios, aumentando la frecuencia y, especialmente, el tamaño de los incendios. Los incendios requieren de tres factores: combustible (vegetación densa y continua), igniciones, y condiciones propensas a la propagación del fuego (sequedad, viento). Estos tres factores se han visto favorecidos en los últimos años y de manera simultánea:

(1) ha aumentado la cobertura, continuidad y densidad de la vegetación en el paisaje, incrementando la biomasa y el combustible disponible para los incendios;

(2) ha cambiado el clima hacia veranos más cálidos, más secos, y más largos, por lo que se dan mejores condiciones para la propagación del fuego y durante más tiempo; y

(3) ha aumentado la población urbana en las zonas de interfaz urbano-forestal (ver foto), lo que conlleva un mayor número de igniciones, tanto accidentales como provocadas.

En definitiva, actualmente hay más incendios porque tenemos paisajes y climas más propensos a la propagación del fuego, y más igniciones.

De estos tres factores, el que más ha influido en el cambio del régimen de incendios es el aumento de vegetación (biomasa) en nuestros paisajes. Este aumento se debe principalmente al abandono de las actividades rurales (tales como la agricultura, el pastoreo, la extracción de leña, o la gestión de las plantaciones forestales), y a las políticas de exclusión total de los incendios, sin una sustitución por otros sistemas que controlen la vegetación, tales como los herbívoros silvestres, o las quemas y el pastoreo prescritos.

¿Como mitigar el impacto de los incendios?

La política de tolerancia cero a los incendios no ha funcionado en ningún país del mundo. El reto de la gestión no debería ser eliminar los incendios, sino crear paisajes que generen regímenes de incendios sostenibles tanto ecológica como socialmente. Para ello se precisan acciones a distintos niveles, tales como aceptar abiertamente un cierto régimen de incendios (especialmente en zonas poco pobladas y en ecosistemas con adaptaciones al fuego), crear discontinuidades en paisajes forestales homogéneos (por ejemplo, mosaicos agrícola-forestales), o reducir el combustible en zonas estratégicas o próximas a viviendas. También implica decisiones tan conflictivas como limitar la interfaz urbano-forestal, es decir, limitar la expansión de urbanizaciones y polígonos industriales en zonas rurales y naturales. A los efectos ambientales que supone la expansión de estas zonas de interfaz (por ejemplo, en biodiversidad, especies invasoras, contaminación lumínica y visual, etc.), hay que añadir que constituyen una gran fuente de igniciones, y que convierten en catastróficos (socialmente) incluso a regímenes de incendios ecológicamente sostenibles. Los mecanismos para limitar estas zonas pueden ser diversos, incluyendo la recalificación de terrenos (a no urbanizables), o la implementación de tasas (disuasorias) por construir en áreas con alto riesgo de incendios, entre otros. Además, y con carácter más general, incrementar las medidas que frenan el cambio climático contribuiría a reducir los cambios no deseados en el régimen de incendios.


Foto: Ejemplo de interfaz urbano-forestal (Port d’Andratx, Mallorca; foto: @xarxaforestal). Con este modelo de urbanismo, además de aumentar la probabilidad de igniciones, convertimos en catastróficos incluso a regímenes de incendios ecológicamente sostenibles.

 

Más información

Incendios forestales, una visión desde la ecología
Acabar con los incendios es antinatural e insostenible
Cinco cuestiones sobre inflamabilidad e incendios

A fire ecology lesson from the Florida scrub

June 11th, 2018 No comments

Fire is a key ecological factor in many Mediterranean shrublands [1]. But there is another shrubland, the Florida scrub, that share many characteristics with mediterranean ecosystems. Fire is frequent in the Florida scrub, and most plant strategies to deal with fire are the same to those found in mediterranean ecosystems, despite the species are different (a likely case of convergent evolution). The Florida scrub occurs on sandy soils of the Florida Peninsula (USA), under a subtropical climate.

Eric Menges, a fire ecologist at Archbold Biological Station in Florida, explains in this 16-minute video the main adaptive traits of plants to live in the Florida scrub. In his words “the lack of fire is a bigger disturbance than the fire”. All strategies explained in the video also occur in most mediterranean regions, including the Mediterranean Basin (i.e., from Portugal to Syria).

Video “Surviving fire in the Florida scrub”, also available in youtube.

[Versión en español]

El fuego es un factor ecológico clave en muchos matorrales mediterráneos [1,2]. Pero hay otro matorral, el matorral de la Florida, que comparte muchas características con los ecosistemas mediterráneos. El fuego también es frecuente en este matorral, y la mayoría de las estrategias de las plantas para persistir después de incendio son las mismas que las que se encuentran en los ecosistemas mediterráneos, a pesar de que las especies son diferentes (con ejemplos de evolución convergente). El matorral de Florida aparece en suelos arenosos en la península de la Florida (EEUU), en clima subtropical.

Eric Menges, ecólogo en la Estación Biológica Archbold en Florida, explica en este video de 16 minutos los principales estrategias adaptativas de las plantas para vivir en el matorral de Florida. En sus palabras, “la falta de fuego es una perturbación más importante que el fuego”. Todas las estrategias explicadas en el video también ocurren en la mayoría de las regiones mediterráneas, incluida la Cuenca Mediterránea (de Portugal a Siria, pasando por España, claro).

 

References

[1] Keeley J.E., Bond W.J., Bradstock R.A., Pausas J.G. & Rundel P.W. 2012. Fire in Mediterranean Ecosystems: Ecology, Evolution and Management. Cambridge University Press. [the book]

[2] Pausas J.G. 2012. Incendios forestales. Una visión desde la ecología. Catarata-CSIC. [Libro]

 

Marjal del Moro postfire

May 3rd, 2018 No comments

‘Marjal del Moro’ is a small coastal wetland located in the municipalities of Puçol and Sagunt (Valencia, Spain). It is a Special Area of Conservation (SAC; ZEC in Spanish) and a Special Protected Area for the conservation of birds (SPA; ZEPA in Spanish), of the European Union. In January the 4th a wildfire burned 320ha which is ca. 80% of the wetland. Here are some dynamics after the fire.

1 month after the fire (18th February 2018):

At this time, Tamarix trees (salt ceder) were not resprouting, but some other plants already started to resprout (click to enlarge):

 

4 months after fire (1st May 2018):

Note that the two trees (salt ceders, Tamarix) are the same ones from the picture above (taken in February). At this time, Tamarix species were already resprouting (click to enlarge):

 

Thanks to E. Laguna for his help on the species identification.

 

Fire-dependent and fire-adapted animals

January 17th, 2018 No comments

Plants show a plethora of adaptive traits for persisting under recurrent fires [1]. However, fire-prone ecosystems also harbor a rich fauna, and little is know about their adaptive traits for fire survival. In a recent paper [2] we review this issue and suggest that many animals are adapted to the open habitats generated by fire; yet although they require fires for survival (fire-dependent animals), they do not necessarily show any specific morphological adaptation to fire. However, these species would become very rare or even extinct in the absence of fires generating their habitat. In addition, in some cases, animals from these fire-prone ecosystems show specific fire adaptation (fire-adapted animals). Currently, there are few examples of morphological adaptations to fire in the animal kingdom (reviewed in [2]). In part this may simply reflect the low number of studies that have attempted to look for fire adaptations. We propose that there remains significant scope for research on fire adaptations in animals, and especially in relation to the rich behavioral traits that allow persistence in fire-prone ecosystems. This is because, in contrast to plants, most animals are unitary organisms with reduced survival when directly burnt by fire, but are mobile and can move away from the fire. That is, behavioral traits are poorly explored under the framework of the evolutionary fire ecology and may provide a rich source for fire adaptations. Developing this understanding is critical to better understand the role of fire in determining the biodiversity of our landscapes.

Photo 1: An owl hunting in the fire front (fire-foraging) at Aransas National Wildlife Refuge in Texas (Photo: Jeffrey Adams/USFWS; from www.fws.gov).

 

Photo 2: The rhea (Rhea americana) is a flightless bird living in Brazilian savannas; it has a cryptic colors in postfire environments, when it sits in the ground in cannot be differentiated from burn stems (Photo: JG Pausas, 2009).

 

References

[1] Keeley J.E., Bond W.J., Bradstock R.A., Pausas J.G. & Rundel P.W. 2012. Fire in Mediterranean Ecosystems: Ecology, Evolution and Management. Cambridge University Press. [the book]

[2] Pausas J.G., Parr C.L. 2018. Towards an understanding of the evolutionary role of fire in animals. Evolutionary Ecology. [doi | pdf]  

More on fire and evolution

 

A diversity of Belowground Bud Banks (BBB) for resprouting

January 15th, 2018 No comments

Many plants are able to survive recurrent disturbance by resprouting from a bud bank. In fire prone ecosystems, plants must protect their buds from fire heat or perish. One way to protect them is by growing a thick insulating bark or sink the buds in the stem [1,2]. Another way is to locate the buds below ground, as soil is an excellent heat insulator (belowground bud bank or BBB). In fire-prone ecosystems, there is a diversity of ways by which plants successfully conceal their buds below ground that enable them to survive and resprout vigorously after fire [3]. There are at least six locations where belowground buds are stored [3]: roots, root crown, rhizomes, woody burls, fleshy swellings and belowground caudexes. These support many morphologically distinct organs (figure below). Considering their history and function, these organs may be divided into three groups:

(a) Those that originated in the early history of plants and that currently are widespread; they act as a resprouting source after a range of disturbances, not just fire. These include bud-bearing roots and root crowns.

(b) Those that also originated early and have spread mainly among ferns and monocots; they are often tied to seasonal stresses and have been highly successful under recurrent fire regimes. Theses include non-woody rhizomes and a wide range of fleshy underground swellings. They are characteristic of the geophyte growth forms occurring in many ecosystems, often tied to seasonal stresses; they have been highly successful under recurrent fire regimes.

(c) And those that originated later in history and are strongly tied to fire-prone ecosystems. These are woody rhizomes, lignotubers and xylopodia. They are characteristic of the geoxyle growth form.

Recognizing the diversity of BBBs is the starting point for understanding the many evolutionary pathways available for responding to severe recurrent disturbances.

Figure: Stylized diagrams of 16 belowground bud bank structures that enable plants to resprout postfire (highlighted in red). Broken horizontal line indicates position of soil surface. Structures characterized by woody tissues, in pink; fleshy tissues, in blue; and neither woody nor fleshy, in orange (usually highly sclerified primary tissues, fibrous or ‘wiry’). Shoots highlighted in apple green: stems with leaves, branched; leaves only, unbranched. Roots highlighted in olive green: triangular-shaped roots indicate a primary system, those arising directly from the bud-storing structures are adventitious. Drawings from [3]. From top left to bottom right:

· Xylopodium (in red) joined to tuberous root (in blue); Lignotuber; Root Crown; Woody Rhizome, here arising from a burl
· Bud-bearing lateral Root arising (here) from a burl (the root is not necessarily woody); Taproot Tuber; Bulb; Corm, with previous year’s corm still present
· Stem Tuber; Non-woody Fleshy Rhizome; Rhizophore (note buds are only supported by the oldest rhizophores); Adventitious Root Tuber
· Non-woody fibrous Rhizome with a monopodial arrangement leading to expansive clone; Non-woody fibrous Rhizome with sympodial arrangement leading to a caespitose habit; Stolons that produce new ramets postfire (note that it is not a BBB); Belowground Caudex

For details and a full description of each structure, see reference [3].

References
[1] Pausas J.G. 2017. Bark thickness and fire regime: another twist. New Phytologist 213: 13-15. [doi | wiley | pdf | post1, post2]

[2] Pausas J.G. & Keeley J.E. 2017. Epicormic resprouting in fire-prone ecosystems. Trends in Plant Science 22: 1008-1015. [doi | pdf | post ]

[3] Pausas J.G., Lamont B.B., Paula S., Appezzato-da-Glória B., Fidelis A. 2018. Unearthing belowground bud banks in fire-prone ecosystems. New Phytologist  [doi | pdf | suppl | BBB database]

More posts on resprouting

 

Wind-driven fires

December 26th, 2017 1 comment

We often tend to think that the main driver of fires is drought, but in many cases wind is extremely important; and the perfect combination is a strong wind after a long drought period. Foehn-type (adiabatic) winds are especially important for fires as they are fast-moving hot and dry winds that quickly dry out the vegetation, and thus they spread the fire very easily. In the recent months, we have witnessed several very destructive wind-driven fires, affecting many infrastructures and lives. Wind-driven fires are common in Southern California where the Santa Ana winds blow after the summer. They typically occur in October, although this year they came later, in December. For instance, the Thomas fire started at the early December, and has now become the largest wildfire in California history (> 110,000 ha, Fig. 1) with more than 1000 houses destroyed, more than 100,000 residents evacuated, and several fatalities. This fire has been largely driven by Santa Ana winds.

Although less frequently, there are also wind-driven fires in Northern California, the wind is called Diablo wind. This year Diablo driven fires has been particularly important and destructive; during October more than a dozen wildfires north of San Francisco had killed more than 40 people, burned approximately 65,000 ha and destroyed more than 7,000 structures (see also, washingtonpost.com, treehugger.com).

Both Santa Ana and Diablo winds are Foehn winds going down from the mountains (inland) to the coast (Santa Ana and Diablo winds at a glance). Wind-driven fires are natural in California and have been generating large fires since long ago, but the increasing population living in the wildland-urban interface is making these fire more destructive than ever. In addition, climate change is extending the fire season into the late fall and winter, increasing the probability of large fires.

Wind-driven fires have also occurred this year in north-western Iberia (Spain and Portugal), caused by the hurricane Ophelia. Typically, tropical hurricanes do not get to Europe, but this year the Ophelia touched western Europe (probably due to the warming of the ocean) and spread massive fires in Portugal and Spain that were fuelled with large poor-managed forest plantations; the ashes from these fires reached England and Ireland (Fig. 2 below).

In conclusion, global change is likely modifying wind patterns, and thus to understand new fire regimes we need to predict wind regime; however, predicting future wind regimes is more difficult than predicting temperature changes.
 

Figure 1. The beginning of the Thomas fire (started in Ventura, Southern California) was clearly driven by Santa Ana winds (Image: NASA / MODIS, December 5, 2017). This fire has grown and become the largest wildfire in California history (> 110,000 ha).

 

Figure 2. Massive October wildfires in NW Iberia were fueled by the hurricane Ophelia; smoke and ashes from these fires reached England and Ireland  (Image: NASA Terra / MODIS, October 16, 2017); see also Severe Weather Europe. You can see an animation from NASA Earth here.

 

More on fire and wind

 

Pinus canariensis epicormic resprouting

November 23rd, 2017 No comments

The cover of the December issue of Trends in Plant Science (22:12) is a picture of Pinus canariensis resprouting epicormically (from stem buds) 3 months after a fire in Tenerife (Canary Islands, Nov 2012). It features our review paper on this type of resprouting [1]. Many plants resprout from basal buds after disturbance, however epicormic resprouting is globally far less common, and the Canary Island pine is a very good example; it resprouts in this way even after intense crown fires.

 

[1] Pausas J.G. & Keeley J.E. 2017. Epicormic resprouting in fire-prone ecosystems. Trends in Plant Science 22: 1008-1015. [doi | sciencedirect | pdf | post ]

More on: epicormic resprouting | pines | resprouting

 

Juniperus deppeana postfire

November 18th, 2017 No comments

Some trees species, like many Eucalyptus, resprout from a lignotuber (a basal burl [1]) when young, and from epicormic (stem) buds [2] at the adult stage. This seems also the case for Juniperus deppeana (alligator juniper), at least the ones from the Trans-Pecos region, Far West Texas, USA. Big trees can survive surface fires (Fig. 1a below) thanks to their relatively thick bark (Fig. 1b). In the upper part of the Guadalupe mountains, a fire in May 2016 spread throughout the surface, crowning in some specific spots. In these areas, smaller trees were resprouting from lignotubers (Fig. 1c) while large trees were resprouting from epicormic buds (Fig. 1d). In this dry forest in Guadalupe, Juniperus deppeana is abundant; in addition, two other conifers relatively rare in Texas are also common: Pinus ponderosa and Pseudotsuga menziesii (Douglas fir); many of the large individuals of the latter species were dead from a recent drought previous to the fire. The forest also included some oaks, both tree and shrub oak species, and an understory with grasses, Agave and Dasylirion species.

 

Figure 1. Photos of Juniperus deppeana (alligator juniper). a) A very large juniper with fire scars from surface fires (and Dylan Schwilk, Texas Tech University, in front of it). b) Detail of the bark. c) Basal stem excavated to show that postfire resprouts originates from a below-ground bud bank, a lignotuber. d) Postfire epicormic resprouting. Photos a) and b) from Davis Mountains, c) and d) from Guadalupe Mountains (1.5 years after a fire), Trans-Pecos region, Texas, November 2017.

 

References

[1] Paula S., Naulin P.I., Arce C., Galaz C. & Pausas J.G. 2016. Lignotubers in Mediterranean basin plants. Plant Ecology 217: 661-676. [doi | pdf | suppl.]

[2] Pausas J.G. & Keeley J.E. 2017. Epicormic resprouting in fire-prone ecosystems. Trends in Plant Science 22(12): xx-xx. [doi | pdf]

More on: epicormic resprouting | lignotubers

 

Postfire epicormic resprouting

September 22nd, 2017 No comments

Many plants resprout from basal buds after disturbance, and this is common in shrublands subjected to high-intensity fires [1]. However, resprouting after fire from epicormic (stem) buds is globally far less common. In a recent paper we review the ecology and evolution of this mechanism [2]. Many plants can generate epicormic shoots after light disturbances (e.g., browsing, drought, low intensity fires, insect defoliation, strong winds), but this does not mean they generally resprout epicormically after fire, as the heat of a fire may kill epicormic buds if they are not well protected (e.g., by a thick bark). The most well-known examples of epicormic resprouting are many species of eucalypts (Fig. 1A below), the cork oak (Quercus suber [3], Fig. 1B below), and Pinus canariensis ([4], Fig. 1C, D below). There are other pines and oaks that also resprout epicormically, and many species from savannas, especially those from the Brazilian savannas (cerrado) where many trees have a thick corky bark [5].

Epicormic resprouting has appeared in different lineages and on different continents and thus it is an example of convergent evolution in fire-prone ecosystems. It is an adaptation to a regime of frequent fires that affect tree crowns. It has probably been favoured where productivity is sufficient to maintain an arborescent growth form, fire intensity is sufficient to defoliate the tree canopy crown, and fire frequency is high (in conifers, too high for serotiny to be reliable) [2]. Given the high resilience of forest and woodlands dominated by epicormic resprouters, these species are good candidates for reforestation projects in fire-prone ecosystems [3].

Figure: Examples of postfire epicormic resprouting after a crown fire from very different lineages: (A) Eucalyptus diversicolor 18 months after fire in Western Australia. (B) Quercus suber woodland 1.5 years postfire in southern Portugal. (C) Pinus canariensis woodland a few years after fire; (D) epicormic resprouts of P. canariensis 3 months postfire. Photos by G. Wardell-Johnson (A); F.X. Catry (B) and J.G. Pausas (C, D), from [2].

References
[1] 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 Phytologist 209: 945-954. [doi | wiley | pdf | Notes S1-S4]

[2] Pausas J.G. & Keeley J.E. 2017. Epicormic resprouting in fire-prone ecosystems. Trends in Plant Science 22: xx-xx. [doi | pdf]

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

[4] Pinus canariensis, jgpausas.blogs.uv.es/2017/05/07

[5] Dantas V. & Pausas J.G. 2013. The lanky and the corky: fire-escape strategies in savanna woody species. Journal of Ecology 101 (5): 1265-1272. [doi | pdf | suppl.]

More information on: epicormic resprouting | cork oak | pines

Chile 2017 fires: fire-prone forest plantations

September 16th, 2017 No comments

During the 2016/17 fire season in central Chile, wildfires burned about 600,000 ha, a record for the region (most of the area burned between 18-Jan and 5-Feb, 2017). Two factors are considered the main responsible of such a large area burned: (1) an intense drought with strong head waves (January was the hottest month in record), and (2) the fact that the region is covered by large and dense tree plantations that create a continuous fuel bed. The tree planted are two alien species: Pinus radiata and Eucalyptus sp., from California and Australia, respectively. Most burned area (+60%) were plantations, and if we standardize the area burned in relation to the area with each landuse in the region (plantations, native forest, grasslands, agriculture) we see that the plantations were more affected by fire than expected by their area in each region; and this contrast with the other landuses (Figure 1, [1]). That is, tree plantations were an important driver for the large area burned (highly flammable).

Interesting is that the two species planted not only are highly flammable, they also have very good (although very different) postfire regeneration mechanisms, because both are originally from fire-prone ecosystems and have adapted to coupe with crown fires. Pinus radiata have serotinous cones (closed cones that open with fire) and showed an extraordinary “natural” seedling regeneration postfire (Figure 2 top), while those eucalytps planted show epicormic (stem) resprouting that allows a quick canopy recovery (even young trees, Figure 2 bottom). All suggest that these plantations were born to burn!

Figure 1: Analysis of the areas affected by fires according to types of use (forest plantations, native forest, Scrubland + pastures, and agricultural areas), in relation to what is available in each of the 4 regions that have burned the most (V, RM, VI, VII are: Valparaiso, Metropolitana, O’Higgins, and Maule). Positive data means that fire has positively selected this type of use (it has burned more than expected by the area it occupies); the negative data indicate that fire tends to avoid such landuse. There is a strong tendency for plantations to burn more than expected according to their abundance in the landscape (positive values), while native forests, scrub, or agricultural areas are burned similar or less than expected according to their abundance (negative values). The region VII (Maule) is the most extreme in positive selection of plantations and negative of other uses. Elaborated on the basis of official SIDCO-CONAF data (Chile) [1].

 


Figure. 2. Postfire regeneration of tree plantations. Top: Extraordinary postfire seedlings regeneration of Pinus radiata (adult trees are dead). Bottom: epicormic resprouting of eucalypts (mixed with dead pines). Photos from early September (ca. 7 months after fire), in the Nilahue Barahona fire (O’Higgins region, Chile).

References

[1] Incendios en Chile 2017, jgpausas.blogs.uv.es/2017/02/10

More information on:  Chile and fires | Serotiny | Epicormic resprouting

UPDATE (Jan 2019): this post and this other have inspired the following article:

Leverkus AB, Murillo PG, Doña VJ, Pausas JG. 2019. Wildfires: opportunity for restoration? Science 363 (6423): 134-135. [doi | science | pdf]

 

Fire danger, fire hazard, fire risk, …

August 5th, 2017 4 comments

Recently, a colleague asked 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 the probability of ignitions (geography), and fire danger is typically associated with weather conditions (meteorology); below is a longer answer (see Fig. 1). Feel free to improve or qualify these definitions by leaving a comment (see top right).

Fire weather: Weather conditions that influence fire ignition, behaviour, and suppression. E.g., extreme (or severe) fire weather refers to very low moisture, high temperatures (heat waves) 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 with 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 (risk of ignition). It can be split into lightning fire risk and human fire risk; the latter typically decreases with distance to roads and increases with population density in rural or semi-rural areas. 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 (in contrast to fire danger; 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 is reported by meteorological agencies (weather-based fire danger). 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; Fig. 2 below); (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 others; 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. Societal vulnerability is typically associated with exposure, sensitivity, and adaptive capacity; these characteristics depend on socio-economic level and cultural experience.

Fig. 1. Schema of the different concepts related to fire danger and fire vulnerability. Sometimes, fire danger + fire vulnerability is called (overall) fire risk.
Fig. 2. Map of the Fire Danger Forecast for the Mediterranean region on 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 like 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 |

¿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:

También disponible en la web del IVIA, GV

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|

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).

Los ecosistemas de Chile central parece que hayan tenido una actividad historia de incendios naturales (durante el Cuaternario) menor que los otros ecosistemas mediterráneos. 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 devienen importantes en la zona central de Chile con 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), donde alternan plantaciones y bosque nativo. En primer plano, un peumo (Cryptocarya alba, especie del bosque nativo) parcialmente afectado. 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

Más información sobre: incendios en Chile |

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

UPDATE: Chile 2017 fires: fire-prone forest plantations

 

 

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 2 comments

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 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]

The first version of this paper was my talk at the University of Campinas, Unicamp: link

UPDATE: paper featured on the cover of 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 plants in which fire can breaks seed dormancy and stimulate 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. 2018. Evolution of ‘smoke’ induced seed germination in pyroendemic plants. South African J. Bot. 115: 251-255 [doi | pdf] <- New

[6] Moreira B. & Pausas J.G. 2018. Shedding light through the smoke on the germination of Mediterranean Basin flora. South African J. Bot. 115: 244-250 [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. 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.The first resprouting leaves often show the typical burned-brown-green pattern of the photo below. This is because in palms (and in all monocots), the meristem is at the base of the leaves (more protected), and thus even burned leaves can still grow from the base and showing the upper part burned. In addition, C. humilis 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

[UPDATE 1/2018]

[Español] Decálogo de incendios forestales: pdf | web (adhiérete)

[English] Forest fire decalogue: pdf  |  web (with option for supporting it)

[Català] Decàleg d’incendis forestals: pdf  |  web (adhereix-t’hi!) 

[Português] Decálogo do fogo: pdf

[Italiano] Decalogo di fuoco: pdf

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]