Pyrophyte

Pyrophytes are plants which have adapted to tolerate fire.

Fire acts favourably for some species. "Passive pyrophytes" resist the effects of fire, particularly when it passes over quickly, and hence can out-compete less resistant plants, which are damaged. "Active pyrophytes" have a similar competing advantage to passive pyrophytes, but they also contain volatile oils and hence encourage the incidence of fires which are beneficial to them. "Pyrophile" plants are plants which require fire in order to complete their cycle of reproduction.

Passive pyrophytes

Sequoia sempervirens with remainings of a fire older than 100 years

These resist fire with adaptations including thick bark, tissue with high moisture content, or underground storage structures. Examples include:

• Longleaf pine (Pinus palustris)^[1]
• Giant sequoia (Sequoiadendron giganteum)
• Coast redwood (Sequoia sempervirens)
• Cork oak (Quercus suber)
• Niaouli (Melaleuca quinquenervia) which is extending in areas where bush fires are a mode of clearing (e.g. New Caledonia).
• Venus fly trap (Dionaea muscipula) – this grows low to the ground in acid marshes in North Carolina, and resists fires passing over due to being close to the moist soil;^[2] fire suppression threatens the species in its natural environment.^[3]
• White asphodel (Asphodelus albus)

For some species of pine, such as Aleppo pine (Pinus halepensis), European black pine (Pinus nigra) and lodgepole pine (Pinus contorta), the effects of fire can be antagonistic: if moderate, it helps pine cone bursting, seed dispersion and the cleaning of the underwoods; if intense, it destroys these resinous trees. ^{[citation needed]}

Active pyrophytes

Some trees and shrubs such as the Eucalyptus of Australia actually encourage the spread of fires by producing inflammable oils, and are dependent on their resistance to the fire which keeps other species of tree from invading their habitat.

Pyrophile plants

Other plants which need fire for their reproduction are called pyrophilic. Longleaf pine (Pinus palustris) is a pyrophile, depending on fire to clear the ground for seed germination.^[4]

The passage of fire, by increasing temperature and releasing smoke, is necessary to raise seeds dormancy of pyrophile plants such as Cistus and Byblis an Australian passive carnivorous plant.

Imperata cylindrica is a plant of Papua New Guinea. Even green, it ignites easily and causes fires on the hills.

Evolution

99 million-year-old amber-preserved fossils of Phylica piloburmensis, belonging to the modern pyrophytic genus Phylica, show clear adaptations to fire including pubescent, needle-like leaves, further affirmed by the presence of burned plant remains from other Burmese amber specimens. These indicate that frequent fires have exerted an evolutionary pressure on flowering plants ever since their origins in the Cretaceous, and that adaptation to fire has been present in the family Rhamnaceae for over 99 million years.^[5]

See also

• Fire ecology
• Serotiny

References

1. Boyer, W. D. (1990). "Pinus palustris". In Burns, Russell M.; Honkala, Barbara H. (eds.). Conifers. Silvics of North America. Vol. 1. Washington, D.C.: United States Forest Service (USFS), United States Department of Agriculture (USDA) – via Southern Research Station.
2. W. Schulze; E.D. Schulze; I. Schulze & R. Oren (2001). "Quantification of insect nitrogen utilization by the venus fly trap Dionaea muscipula catching prey with highly variable isotope signatures". Journal of Experimental Botany. 52 (358): 1041–1049. doi:10.1093/jexbot/52.358.1041. PMID 11432920.
3. Leege, Lissa (19 August 2002). "How does the Venus flytrap digest flies?". Scientific American. Retrieved 2008-08-20.
4. Jose, Shibu; Jokela, Eric J.; Miller, Deborah L. (2006), Jose, Shibu; Jokela, Eric J.; Miller, Deborah L. (eds.), "The Longleaf Pine Ecosystem", The Longleaf Pine Ecosystem: Ecology, Silviculture, and Restoration, Springer Series on Environmental Management, New York, NY: Springer, pp. 3–8, doi:10.1007/978-0-387-30687-2_1, ISBN 978-0-387-30687-2, retrieved 2022-10-24
5. Shi, Chao; Wang, Shuo; Cai, Hao-hong; Zhang, Hong-rui; Long, Xiao-xuan; Tihelka, Erik; Song, Wei-cai; Feng, Qi; Jiang, Ri-xin; Cai, Chen-yang; Lombard, Natasha; Li, Xiong; Yuan, Ji; Zhu, Jian-ping; Yang, Hui-yu (February 2022). "Fire-prone Rhamnaceae with South African affinities in Cretaceous Myanmar amber" (PDF). Nature Plants. 8 (2): 125–135. doi:10.1038/s41477-021-01091-w. ISSN 2055-0278. PMID 35102275. S2CID 246443363.