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Posts Tagged ‘epicormic resprouting’

Marmaris postfire regeneration

December 5th, 2021 No comments

During last summer, over 170,000 ha burnt in Turkey. One of these fires was the Marmaris fire, a fire of about 12,500 ha in SW of the country. The area includes part of the Marmaris National Park and an Special Environmental Protection Area. Most of the area were covered by Pinus brutia forests, a Mediterranean pine that has some serotinous cones.

Four months after the Marmaris fire, I visited the area together with Çagatay Tavsanoglu. Some plants were resprouting and some geophytes flowering (Cyclamen, Arisarum). Pine seedlings had started to germinate; there were also many other seedlings but still too small to identify them (e.g., Cistus species). Below are a few examples of plants that were regenerating after the fire (click on the photos to enlarge them).

 

Postfire in a Mexican arid ecosystem

April 24th, 2019 No comments

Arid ecosystems have a climate appropriate for fires, but their low biomass often limits the frequency and intensity of fires; yet they still occur. A recent study evaluated the survival and resprouting of four species 6 months after a fire [1] in Tehuacán-Cuicatlán Biosphere Reserve (Puebla, Mexico), and show that most individuals of the four species survived:

  • Dasylirion lucidum (Asparagaceae): the apical bud of most (97%) plants survived and quickly produced new leaves; few individuals shows basal resprouts.
  • Juniperus deppeana (Cupressaceae): 75% of the trees survived, some resprout from the base, others from epicormic buds (see also here)
  • Echinocactus platyacantus (Cactaceae): 95% survived
  • Agave potatorum (Asparagaceae): 90% survived and continued to growth new leaves from the central of the plants

All species are endemic of Mexico except Juniperus deppeana that also occurs in the southwestern USA (Arizona, Texas, New Mexico).

 

Landscape dominated by Dasylirion lucidum 6 months after a fire in Tehuacán, Mexico [1].

 

Dasylirion lucidum (a), Juniperus deppeana with epicormic resprouts (b), Echinocactus platyacantus (c), and Agave potatorum (d) six months postfire in Tehuacán, Mexico [1].

 

References

[1] Rodríguez-Trejo, D. A., Pausas, J. G. & Miranda-Moreno, A. G. 2019. Plant responses to fire in a Mexican arid shrubland. Fire Ecology 15:11 [doi | pdf]  

[2] Pausas J.G. Flammable Mexico. Int. J. Wildland Fire 25: 711-713 [doi | pdf]

More on: México fires | Juniperus deppeana postfire |

 

 

El surar de Pinet – a small isolated population of cork oak

October 15th, 2018 2 comments

In early August, a lightning-ignited fire burned about 3200 ha of the municipalities of Llutxent, Gandia and Pinet (in Valencia, Spain): the Llutxent fire [1]. The area includes a small and isolated patch cork oak (Quercus suber; Fig. 1), the Pinet cork oak forest (locally known as el surar de Pinet) [2]. The Pinet forest (ca. 80 ha) was a mosaic of shrublands, oaks and pines (Pinus pinaster); and the fire burned most of the forest. The area is not the most optima for cork oak because of the climate (relatively dry for the species) and the soils (not too acidic). However, peripheral populations are typically genetically, morphologically and functionally different from the core populations, and can hold an important proportion of the species’ genetic diversity, thus their conservation is required.

Cork oak is a very good postfire resprouter from epicormic (stem) buds [3,4,5]. However, given that this population is in the edge of their environmental conditions, and the rainfall of the last year was below the long-term average, there were concerns about their postfire regeneration.

Happily 1 month after the fire there were some oak resprouting epicormically [1], and two month after the fire, basically all individuals were resprouting (Fig. 2). Because some plants may die after their initial vigorous resprouting [6], we should keep monitoring the resprouting of this population, but it seems that the population is saved. The fire temporally reduced the shrublands and killed most pines of the forest, and thus it could be an opportunity for managers to increase the cork population size using local acorns.

 

Fig. 1. Cork oak (Quercus suber) in the Iberian peninsula. Light grey is the species distribution; dark grey is the data from forest inventories; crosses are small isolated populations. In red is the population of Pinet (Valencia) that burned in August 2018. Map from [4]

 

Fig. 2. Pinet population of cork oak two months after fire with their characteristic epicormic resprouting.

References

[1] Llutxent 1 month postfire, jgpausas.blogs.uv.es/2018/09/18/

[2] Pausas J.G., Ribeiro E., Dias S.G., Pons J. & Beseler C. 2006. Regeneration of a marginal Cork oak (Quercus suber) forest in the eastern Iberian Peninsula. J. Veget. Sci. 17: 729-738. [pdf | doi | wiley ]

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

[4] 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]  

[5] Pausas J.G. & Keeley J.E. 2017. Epicormic resprouting in fire-prone ecosystems. Trends in Plant Science 22(12): 1008-1015. [doi | sciencedirect | pdf]

[6] Moreira B., Tormo J, Pausas J.G. 2012. To resprout or not to resprout: factors driving intraspecific variability in resprouting. Oikos 121: 1577-1584 [doi | pdf]

More on cork oak: posts | book | papers

 

 

Llutxent 1 month postfire

September 18th, 2018 No comments

In early August a wildfire ignited by a lightning burned about 3200 ha, affecting mainly the municipalities of Lutxent, Gandia and Pinet (in Valencia, Spain). One month later I visited the area, and below are the main plant species that were already resprouting. There were also two species already flowering, both geophytes: Urginea (Drimia) maritima and Scilla autumnalis; they showed flowers but not the leaves (they are protanthous: flowering before the foliage appears [1]). There were also many seedling germination from the seedbank, but they were too small to identify. 

The area affected by the fire include a small marginal population of Quercus suber (cork oak; el surar de Pinet) that we had studied few years ago [2]. This oak was also resprouting (epicormically).

(click to the photo to enlarge)

 

Notes and references

[1] The terminology of the flower/leaf phenology is a bit confusing; here is my understanding following Simpson (Plant Systematics, 2011) and Lamont & Downes (2011, Pl. Ecol. 212):

· Synanthous (syn= same time): flowers and leaves develop at the same time
· Hysteranthous: flowering occurring out of phase with leafing
· Protanthous (pro= early): flowers develop before the leaves
· Seranthous (ser= delayed): flowers develop after the leaves

[2] Pausas J.G., Ribeiro E., Dias S.G., Pons J. & Beseler C. 2006. Regeneration of a marginal Cork oak (Quercus suber) forest in the eastern Iberian Peninsula. Journal of Vegetation Science 17: 729-738. [pdf | doi | wiley]

More on postfire flowering | Quercus suber (cork oak)

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

 

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]

 

Pinus canariensis

May 7th, 2017 No comments

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

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

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

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

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

 

Fire adaptations in Mediterranean Basin plants

September 7th, 2015 No comments

Few days ago a botanist colleague ask me whether there were some fire adaptations in the plants of the Mediterranean Basin, similar to those reported in other mediterraenan-climate regions. So I realised that researchers working on other topics may not be aware of the recent advances in this area. Here is my brief answer, i.e., some examples of species growing in Spain that show fire adaptations; this is by no means an exhaustive list, but a few examples of common species for illustrative purpose. You can find a description of these adaptations and further examples elsewhere [1, 2, 3, 4]. It is also important to note that plants are not adapted to fire per se, but to specific fire regimes, and thus some adaptations my provide persistence to some fire regimes but not to all [1]. That is, species that exhibit traits that are adaptive under a particular fire regime can be threatened when that regime changes.

  • Serotiny (canopy seed storage): Pinus halepensis, Pinus pinaster, with variability in serotiny driven by different fire regimes [5, 6]
  • Fire-stimulated germination: There are examples of heat-stimulated germination, like many Cistaceae (e.g., Cistus, Fumana [7, 8]) and many Fabaceae (e.g., Ulex parviflorus, Anthyllis cytisoides [7, 8]), as well as examples of smoke-stimulated germination like many Lamiaceae (e.g., Rosmarinus officinalis, Lavandula latifolia [7]) or Coris monspeliensis (Primulaceae [7]). There are also examples of species with smoke-stimulated seedling growth (Lavandula latifolia [7])
  • Resprouting from lignotubers: Arbutus unedo, Phillyrea angustifolia, Juniperus oxycedrus, many Erica species (e.g., E. multiflora, E. arborea, E. scoparia, E. australis) [4, 17]
  • Epicormic resprouting: Quercus suber [9, 10], Pinus canariensis [4]
  • Fire-stimulated flowering: Some monocots like species of Asphodelus, Iris, Narcissus [11, 12]
  • Enhanced flammability: Ulex parviflorus shows variability of flammability driven by different fire regimes [13] and under genetic control [14]. Many Lamiaceae species have volatile organic compounds that enhance flammability (e.g., Rosmarinus officinalis [16]).
  • Thick bark and self-pruning (in understory fires): Pinus nigra [3,15]

 

fireadaptations2

References

[1] Keeley et al. 2011. Fire as an evolutionary pressure shaping plant traits. Trends Plant Sci 16:406-411. [doi | pdf]

[2] Keeley et al. 2012. Fire in Mediterranean Ecosystems. Cambridge University Press. [book]

[3] Pausas JG. 2012. Incendios forestales. Catarata-CSIC. [book]

[4] Paula et al. 2009. Fire-related traits for plant species of the Mediterranean Basin. Ecology 90:1420-1420. [doi | pdf | BROT database]

[5] Hernández-Serrano et al. 2013. Fire structures pine serotiny at different scales. Am J Bot 100:2349-2356. [doi | pdf]

[6] Hernández-Serrano et al. 2014. Heritability and quantitative genetic divergence of serotiny, a fire persistence plant trait. Ann Bot 114:571-577. [doi | pdf]

[7] Moreira et al. 2010. Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora. Ann Bot 105:627-635. [doi | pdf]

[8] 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]

[9] Pausas JG. 1997. Resprouting of Quercus suber in NE Spain after fire. J Veget Sci 8:703-706. [doi | pdf]

[10] Catry et al. 2012. Cork oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors. PLoS ONE 7:e39810. [doi | pdf ]

[11] Postfire flowering: Narcissusjgpausas.blogs.uv.es 2 May 2015

[12] Postfire blooming of Asphodelous, jgpausas.blogs.uv.es 5 Apr 2014

[13] Pausas et al. 2012. Fires enhance flammability in Ulex parviflorus. New Phytol 193:18-23. [doi | pdf]

[14] Moreira et al. 2014. Genetic component of flammability variation in a Mediterranean shrub. Mol Ecol 23:1213-1223. [doi | pdf]

[15] He et al. 2012. Fire-adapted traits of Pinus arose in the fiery Cretaceous. New Phytol 194:751-759. [doi | pdf | picture]

[16] Flammable organic compounds: Rosmarinus officinalis, jgpausas.blogs.uv.es 2-Oct-2015

[17] Paula et al. 2016. Lignotubers in Mediterranean basin plants. Plant Ecology [doi | pdf | suppl. | blog]

 

Afrotropical and neotropical savannas are different

July 29th, 2013 No comments

Savannas are typically ecosystems dominated by grasses with a variable tree density (e.g., [1]). However, the savanna biome is very large, it occurs in different continents, and includes a large variability in the vegetation structure and composition. Fire and herbivory are the main disturbance factors shaping savannas worldwide and because the different climatic conditions and the different evolutionary histories among different savannas, fire and herbivory regimes also varies among savannas. Because plants are not adapted to fire and herbivory “per se” but to specific regimes of herbivory and fire [2], we expect different strategies to cope with these disturbances in different savannas. In this framework, we have recently compared savannas from Africa and from South America (afrotropical and neotropical savannas respectively) [3]: Afrotropical savannas have a dryer climate and are more intensely grazed than neotropical savannas, and thus the amount of available fuel is typically lower in afrotropical than in the neotropical savannas. Consequently fires tend to be more intense in neotropical savannas. In afrotropical conditions, young woody plants tend to grow quickly in height to soon locate the canopy above the flame zone before the next fire, and above the browsing height. Thus these plants tend to have a pole-like or lanky architecture (the lanky strategy). In contrast, in neotropical savannas where herbivory pressure is lower they require a thick corky bark for protection against relatively intense fires (the corky strategy) [3]. Despite the two fire escape strategies appear in both Africa and South America, we suggest that the lanky strategy is more adaptive in afrotropical savannas, while the corky strategy is more adaptive in neotropical savannas [3].


Figure: Diospyros hispida A.DC. (Ebenaceae), a South American example of a plant with the corky strategy. Although the trunk was fully burned one year earlier (dark branches and trunk), the bark protected the lateral buds which enabled epicormic resprouting and the formation of lateral resprouts (light grey branches). This photo was taken in Emas National Park (cerrado ecosystem, Brazil) at the beginning of the rainy season (2011) when this deciduous plant starts to produce new leaves (Photo: V.L. Dantas). For an example of the lanky strategy see [4].

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

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

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

[4] Archibald, S. & Bond, W.J. 2003. Growing tall vs growing wide: tree architecture and allometry of Acacia karoo in forest, savanna, and arid environments. Oikos, 102: 3-14.

 

Bark harvesting and Cork oak vulnerability to fire

July 11th, 2012 No comments

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


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

References

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

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

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

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

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

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

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