Archive

Archive for September, 2017

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

Incendios Chile 2017: restauración y regeneración

September 17th, 2017 No comments

Los incendios del verano 2016/2017 en Chile central afectaron alrededor de unas 600,000 ha [1]. Ahora, y como es natural, la sociedad demanda la restauración urgente de los ecosistemas nativos afectados (>60% de la zona afectada fueron plantaciones forestales [1,2]). La restauración ecológica debe estar basada en el conocimiento, y no se debe realizar de manera generalizada y arbitraria. Una restauración inapropiada es un gasto económico innecesario y a veces incluso perjudicial para el ecosistema; por ejemplo, realizar plantaciones con maquinaria pesada en un ecosistema donde muchas plantas rebrotan después del incendio puede ser contraproducente, ya que puede limitar la regeneración natural. Por lo tanto, las acciones de restauración ecológica requieren de un diagnóstico del terreno previo [3] en el que se evalúe el potencial de erosión del suelo, el potencial de regeneración natural, y la potencial pérdida de especies (incluyendo los efectos de posibles especies invasoras posincendio). Las acciones de restauración deben ser específicas para cada una de las zonas donde se detecten estos problemas dentro del perímetro incendiado. Probablemente no se requerirá restauración alguna, aunque si un control del pastoreo, en aquellos sectores en los que no haya peligro de pérdida de suelo y la regeneración de la vegetación y de la mayoría de especies no esté comprometida. Se requieren actuaciones urgentes en zonas con pérdida potencial de suelo. Y en zonas sin riesgo de erosión, pero con pérdida de especies, se requieren acciones restaurativas a medio-largo plazo (por ejemplo, plantaciones con especies nativas).

A inicios de septiembre de 2017 (6–7 meses después de los incendios) muchas de las especies del matorral esclerófilo afectado por los incendios estaban rebrotando (fotos abajo); algunas otras estaban germinando (p.e., el tevo), aunque la mayoría de germinaciones observadas eran plantas herbáceas. También se observaron pies de especies arbustivas que no habían rebrotado (y que no se pudo determinar la especie), aunque no se puede asegurar que no lo hagan en los próximos meses. Sería interesante saber si en los sectores quemados hay especies que no rebrotan ni germinan después del incendio, pues las poblaciones de estas especies si habrían sido gravemente perjudicas por el fuego, y serían las especies a considerar en una restauración ecológica de la zona.


Fotos: Ejemplos de especies que estaban rebrotando a inicios de septiembre (7 meses después de los incendios): A: Tevo (Trevoa trinervis); B: Litre (Lithraea caustica); C: Quillaia (Quillaja saponaria); D: Bollén (Kageneckia oblonga); E: Mitique (Podanthus mitiqui); F: Patagua (Crinodendron patagua); G: Berberis sp.; H: Boldo (Peumus boldus).

Referencias
[1] Incendios en Chile 2017, jgpausas.blogs.uv.es/2017/02/10/
[2] Chile 2017 fires: fire-prone forest plantations, jgpausas.blogs.uv.es/2017/09/16/
[3] Investigador aborda desafíos de la restauración ecológica tras los incendios en Chile; www.lignum.cl/2017/09/06/

Más información sobre: incendios en Chile | rebrote |

 

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

 

FireStats icon Powered by FireStats