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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

 

Lignotubers

November 17th, 2015 1 comment

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

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

References

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

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

 

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]

 

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