This reseeding method is especially important at higher altitudes where lodgepoles don't produce serotinous cones.
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Many of the lodgepoles here are serotinous, meaning they grow pine cones sealed with a sappy resin that protects their seeds from flames.
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But when part of the young forest burned again just sixteen years into its regrowth, creating Stumptown, it had not yet produced many serotinous cones.
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When fires are infrequent, the forest has time to mature and build up a stock of serotinous cones that will restart the next generation: hence Densetown.
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This exceptionally high fecundity can be understood as an adaption to regular bushfire. Most Banksia species can be placed in one of two broad groups according to their response to fire: resprouters survive fire, resprouting from a lignotuber or, more rarely, epicormic buds protected by thick bark; reseeders are killed by fire, but populations are rapidly re- established through the recruitment of seedlings. B. sessilis is a reseeder, but it differs from many other reseeders in not being strongly serotinous: the vast majority of seeds are released spontaneously in autumn, even in the absence of fire. The degree of serotiny is a matter of some contradiction in the scientific literature: it has been treated as "serotinous", "weakly serotinous" and "non-serotinous".
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Fires can be beneficial to plant communities by clearing away canopies of litter, inducing serotinous germination, and sanitizing the soils from pathogens.
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The cones are long. The cones have prickles on the scales. Many populations of the Rocky Mountain subspecies, P. contorta subsp. latifolia, have serotinous cones.
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The ageing flower spikes develop woody seed pods known as follicles. B. hookeriana is serotinous — large numbers of seeds are stored in the plant canopy for years until the plants are burnt by bushfire.
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A number of other characteristics of B. prionotes can be understood as secondary responses to weak serotiny. For example, winter flowering ensures that seed is ripe by the beginning of the bushfire season; this is very important for weakly serotinous species, which rely heavily upon the current year's seed crop. Another example is the deciduous florets of B. prionotes. In strongly serotinous species, the old florets are retained on the cones, where they function as fire fuel, helping to ensure that follicles reach temperatures sufficient to trigger seed release.
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The shell-like bracts remain on the plant for a year or longer, well after the seeds have dropped off. The plants are not serotinous. They do not resprout after fires but regenerate from seeds which are shed soon after flowering.
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Section Trifoliae (American hard pines), despite its name (which means "three- leaved"), has two to five needles per fascicle, or rarely eight. The cones of most species open at maturity, but a few are serotinous. All but two American hard pines belong to this section.
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Lodgepole pine cones Plants have evolved many adaptations to cope with fire. Of these adaptations, one of the best-known is likely pyriscence, where maturation and release of seeds is triggered, in whole or in part, by fire or smoke; this behaviour is often erroneously called serotiny, although this term truly denotes the much broader category of seed release activated by any stimulus. All pyriscent plants are serotinous, but not all serotinous plants are pyriscent (some are necriscent, hygriscent, xeriscent, soliscent, or some combination thereof). On the other hand, germination of seed activated by trigger is not to be confused with pyriscence; it is known as physiological dormancy.
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The cones are long, wide, glossy chestnut-brown in colour and frequently remaining closed for several years (serotinous cones). Its closest relatives are the Chir Pine (Pinus roxburghii) from the Himalaya, the Mediterranean pines Pinus pinea, Pinus halepensis, Pinus pinaster and Pinus brutia from the eastern Mediterranean.
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Their serotinous pine cones open only after having been heated by a fire.Dudley, Elizabeth. Forests: A Fact-Filled Coloring Book, 1990, p. 58. The prevalence of forest fire allows the pitch pines to dominate over oaks, which by comparison are usually killed outright by a moderate or intense fire.
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The differences in fire regime between dune crests and swales would have created different evolutionary pressures, with plants on crests adapting to frequent hot fires by becoming strongly serotinous, and plants in swales adapting to patchier, cooler fires with weaker serotiny. Speciation would be made possible by the much reduced genetic exchange between crest plants and swale plants, although evidence suggests that there was some introgression at first. Eventually, however, the need for weakly serotinous plants to produce ripe seed by the bushfire season would have brought forward its flowering season until the flowering seasons no longer overlapped; thus a phenological barrier to exchange was erected, allowing the two populations to drift independently of each other.
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As a serotinous 're-seeder', a species which has adapted to periodic wildfires which destroy the plants by surviving as fire-proof seeds which can then take advantage of the newly cleared and fertilised area to sprout, P. pruinosa may be sensitive to an increased fire frequency in the Swartberg mountains.
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The leaf sheaths in P. banksiana are less than 2.5 millimeters long. In P. virginiana the needles are twisted and straight. The cones open at maturity, are not serotinous and the scales on the cones have prominent prickles. The sheaths of the P. virginiana are greater than 2.5 millimeters long.
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However, there are an unusually low number of follicles per cone—often only one. Thus the number of follicles per plant ends up roughly average for a Banksia species. Banksia cuneata lacks a lignotuber, so plants are killed by bushfire. However, this species is strongly serotinous: seed is released only following a fire.
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Unusually for a pine, the cones normally point forward along the branch, sometimes curling around it. That is an easy way to tell it apart from the similar lodgepole pine in more western areas of North America. The cones on mature trees are serotinous. They open when exposed to intense heat, greater than or equal to .
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Unusual phenomena in an extreme bushfire in: Proceedings of the 5th Asia Pacific Conference on Combustion Adelaide. 2005Williams, C. 2007. Ignition impossible: When wildfires set the air alight. New Scientist 2615 Eucalypts obtain long-term fire survivability from their ability to regenerate from epicormic buds situated deep within their thick bark, or from lignotubers, or by producing serotinous fruits.
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However, the species is weakly serotinous: fire triggers seed release, yet seed release still occurs in the absence of fire. Seed germination rates are quite high. One study found germination rates better than 77% in most batches tested. Seed is likely to remain viable for a long time, as seed of the closely related B. cuneata remains viable for around ten years.
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Subgenus Pinus includes the yellow and hard pines. Pines in this subgenus have one to five needles per fascicle and two fibrovascular bundles per needle, and the fascicle sheaths are persistent, except in P. leiophylla and P. lumholtzii. Cone scales are thicker and more rigid than those of subgenus Strobus, and cones either open soon after they mature or are serotinous.
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The cones are conic, cylindrical or ovoid (egg-shaped), and small to very large, from 2–60 cm long and 1–20 cm broad. After ripening, the opening of non-serotinous pine cones is associated with their moisture content—cones are open when dry and closed when wet.Dawson, Colin; Vincent, Julian F. V.; Rocca, Anne-Marie. 1997. How pine cones open.
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The serotinous cones of table mountain pine require heat from fire to open and disburse their seeds. The area includes 605 acres of privately owned mineral rights. Abandoned manganese mines near the northern border have cliffs up to 100 feet, earning them the name of the "little grand canyon". Most of the area is designated by the forest service as "Backcountry - Non-motorized".
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The largest lignotubers found have a diameter of 40 cm (16 in). Plants need a lignotuber of diameter to survive low intensity fires. Plants are able to resprout after more intense fires once they reach 15 years of age. I. anemonifolius is also serotinous—the seeds are held on the plant as a canopy- based seedbank and are released after fire.
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This means that the cones are closed and must be exposed to high temperatures, such as from forest fires, in order to open and release their seeds. The variation in their serotiny has been correlated with wildfires and mountain pine beetle attacks. The cones of the coastal Pacific subspecies, P. contorta subsp. contorta, are typically non-serotinous, and those of the inland Pacific subspecies, P. contorta subsp.
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Pinus virginiana is in the family Pinaceae and the order Pinales. A molecular phylogeny indicates that the sister taxa to Pinus virginiana are Pinus clausa, Pinus contorta, and Pinus banksiana. Pinus banksiana has shorter needles than P. viginiana at 2–3.5 centimeters in length, whereas P. virginiana is 2–8 centimeters in length. P. banksiana needles are not twisted, but curved, and has cones that are serotinous and unarmed.
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Pinus clausa has larger needles than the P. virginiana. The Pinus clausa has needles that are between 5 and 13 centimeters long, P. virginiana has needles that range between 2 and 8 centimeters long. Pinus clausa is also serotinous. Lastly, Pinus virginiana and Pinus contorta are distributed differently: Pinus virginiana are found on the eastern side of the United States, whereas Pinus contorta are found on the western side.
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Bushfire is especially important in Australia, where much of the vegetation has evolved in the presence of regular fires caused by the Aboriginal practice of firestick farming. As result, components of the vegetation are adapted to and dependent upon a particular fire regime. Disruption of that fire regime can affect their survival. An example of fire regime dependent species is the Banksia species which is both fire-sensitive and serotinous.
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Banksia burdettii is very sensitive to bushfire, and plants are killed by even small fires, the old cones being highly combustible. More cones are burnt and opened in hot fires. This species is strongly serotinous: seed is released only following a fire. Thus plants accumulate a large number of viable seen in an aerial seed bank in fire intervals, which is released all at once after a fire, ensuring population regeneration.
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On the other hand, it is not a typical reseeder either, because of its relatively low fire mortality rates, and because it is only weakly serotinous: although fire promotes seed release, seed release still occurs in the absence of fire. The actual degree of serotiny and fire mortality in B. prionotes varies with latitude, or, more likely, climate. Observations suggest that it is always killed by fire in the north of its range, which is relatively hot and dry, and where individual plants are usually smaller, but may survive fire in the cooler, moister, south. Moreover, it is essentially non-serotinous in the south, since all seed is released by the end of the second year, but seed retention increases steadily to the north, and at the northern end of its range, it typically takes around four years for a plant to release half of its seed in the absence of bushfire, with some seed retained for up to 12 years.
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Further experiments show that seedlings of outcrossing with plants greater than apart are more vigorous and adaptable, suggesting that plants breeding within small fragmented populations are subject to reduced vigour and genetic inbreeding. Banksia ilicifolia regenerates after bushfire by regrowing from epicormic shoots under its bark. Follicles open and release seeds after several years. It is weakly serotinous, like eight other Banksia species, all of which tend to occur in Western Australia's southwestern corner.
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Isopogon anethifolius resprouts from its woody base, known as a lignotuber, after bushfire. It is also serotinous—the seeds are held on the plant as a canopy-based seedbank and are released after fire. These then fall directly to the ground or are blown a short distance by wind. Plants resprouting from the lignotuber can flower in around two and a half years, while seedlings take around three and a half years.
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Section Quinquefoliae (white pines), as its name (which means "five-leaved") suggests, has five needles per fascicle except for P. krempfii, which has two, and P. gerardiana and P. bungeana, which have three. All species have cones with thin or thick scales that open at maturity or do not open at all; none are serotinous. Species in this section are found in Eurasia and North America, and one species, P. chiapensis reaches Guatemala.
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No distinct subspecies have been recognised by Banksia expert Alex George, who nonetheless concedes that further work is needed. Many species of bird, in particular honeyeaters, forage at the flower spikes, as do native and European honeybees. The response to bushfire varies. Some populations are serotinous: they are killed by fire and regenerate from large stores of seed which have been held in cones in the plant canopy and are released after a fire.
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Plants in fire related disturbance-dependent ecosystems can have serotinous pines, or they have a resin over their seeds to delay seed release. When the fire comes through it melts the resin and allows the seed to begin growing. Germination timed to fire is another method for plant survival. Germination timed to fire means that chemicals in a plant will trigger its growth once the ground is heated to a certain temperature by a fire.
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Featured species include bear, deer and grouse. There are stands of pure table mountain pine, mostly on southeast to southwest facing ridges and slopes with dry, well-drained soils; and there are areas of mixed oak and table mountain pine. Table mountain pine requires fire to regenerate because it has serotinous cones that need heat to open and disperse its seeds. Management of these areas require prescribed burns in order to maintain the forest in its present condition.
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Species adaptation to disturbances is species specific but how each organism adapts affects all the species around them. Another species well adapted to a particular disturbance is the Jack pine in boreal forests exposed to crown fires. They, as well as some other pine species, have specialized serotinous cones that only open and disperse seeds with sufficient heat generated by fire. As a result, this species often dominates in areas where competition has been reduced by fire.
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Flora of North America: Cupressus macnabiana The seed cones are oblong- ovoid to cuboid, 15–25 mm long and 13–20 mm broad, with six (rarely four or eight) scales, each scale bearing a prominent umbo; they are strongly serotinous, not opening to release the seeds until the parent tree is killed by wildfire. This enables heavy seed release to colonize the bare, fire- cleared ground. The pollen cones are 3–4 mm long, and release their pollen in the fall.
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In result, the lodgepole pine are creating cones with thick- scaled cones, whilst the crossbills have evolved deeper bills to counter this. The seeds of younger serotinous cones (1–10 years) are harder for the crossbill to pry open due to them being strongly bonded together. It is the older and weathered cones that are more readily accessible as the scales begin to separate. The Cassia crossbill will mainly eat seeds from cones on the pine tree itself, but fallen cones are also foraged on as well.
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In the Gibraltar Range and Sydney regions, plants are killed by fire and regenerate from seed. They are serotinous, storing their seed in old cones, forming a seedbank in their canopy which is released after bushfire. A field study found that seeds were dispersed short distances (generally or less), with those closest to the parent plant faring the best. In Little Desert National Park in northwestern Victoria and also eastern , it grows as a low shrub which suckers (grows shoots from lateral roots) after fire.
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The short-billed black cockatoo breaks off old cones with follicles to eat the seed, often doing so before the seed is ripe. B. speciosa is serotinous, that is, it has an aerial seed bank in its canopy in the form of the follicles of the old flower spikes. These are opened by fire and release seed in large numbers, which germinate and grow after rain. Seed can last for many years; old spikes 11 to 12 years old have been found to have 50% viable seed.
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A 1980 field study at Cheyne Beach showed it to be pollinated by the New Holland honeyeater and white-cheeked honeyeater. Banksia baxteri is serotinous, that is, it has an aerial seed bank in its canopy in the form of the follicles of the old flower spikes. These are opened with fire and release seed in large numbers, which germinate and grow after rain. Seed can last for many years; old spikes 9 to 12 years old have been found to have seed that remains 100% viable.
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The adult specimens of this protea are killed when they are caught in the wildfires which periodically pass through the native habitat, but the seeds can survive such events. Protea species which have adapted to frequent fire regimes in their habitat in such a manner are called 'reseeders', or, more technically, serotinous. The fruit are stored in the old, dried inflorescences, which are persistently retained on the plant after senescence, although they eventually fall off. According to Rourke, drought-stricken plants in their natural habitat shed their seeds much faster than those growing in cultivation.
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In B. prionotes, however, seed release is triggered at relatively low temperatures: in one study, 50% of follicles opened at , and 90% opened at ; in contrast, the closely related but strongly serotinous B. hookeriana required respectively. Floret retention would therefore be to no advantage, and might even prevent seed from escaping spontaneously opened follicles. Seed release in B. prionotes is promoted by repeated wetting of the cones. The seed separator that holds the seeds in place is hygroscopic; its two wings pull together then wet, then spread and curl inwards as it dries out again.
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These shoots are able to grow, flower and set seed two to three years after a fire. The woody infructescences also release seeds as their follicles are opened with heat, although a proportion do open spontaneously at other times. One field study in Ku-ring-gai Chase National Park found 10% opened in the absence of bushfire, and that seeds germinated, and young plants do grow. Older plants are serotinous, that is, they store large numbers of seed in an aerial seed bank in their canopy that are released after fire.
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Different levels of cone serotiny have been linked to variations in the local fire regime: areas that experience more frequent crown-fire tend to have high rates of serotiny, while areas with infrequent crown-fire have low levels of serotiny. Additionally, herbivory of lodgepole pines can make fire-mediated serotiny less advantageous in a population. Red squirrels (Sciurus vulgaris) and red crossbills (Loxia curvirostra) will eat seeds, and so serotinous cones, which last in the canopy longer, are more likely to be chosen. Serotiny occurs less frequently in areas where this seed predation is common.
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Flowering apparently occurs only after rain, and hence may be separated by periods of many years. Pollinators have not been recorded for the species, but extensive data from other Banksia species suggests that insects, birds and nectariferous mammals would all play a role. There is clearly no shortage of pollinators, as most "cones" contain plenty of follicles. Although most follicles observed are closed, a few open ones have been found, suggesting that the species is weakly serotinous: that is, a few follicles open spontaneously or in response to rain, but most remain closed until burnt.
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The seed separator thus acts as a lever against the seeds, gradually prying them out of the follicle over the course of one or more wet-dry cycles. The effect of this adaptation is to ensure that seed release occurs not in response to fire, but in response to the onset of rains following fire. The relative importance of serotiny can vary among populations of the same plant species. For example, North American populations of lodgepole pine (Pinus contorta) can vary from being highly serotinous to having no serotiny at all, opening annually to release seed.
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Unusual flora and fauna found in the area include a globally rare shrub, the pirate bush; vascular plants, the small spreading pogonia and sword-leaved phlox; and an invertebrate the orangefin madtom. There are stands of pure table mountain pine, mostly on southeast to southwest facing ridges and slopes with dry, well-drained soils; and there are areas of mixed oak and table mountain pine. Table mountain pine requires fire to regenerate because it has serotinous cones that need heat to open and disperse its seeds. Management of these areas require prescribed burns in order to maintain the forest in its present condition.
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The Cassia crossbill will exclusively forage for lodgepole pine cones that are found in the South Hills and Albion Mountains region. A primary reason why this species of crossbill can exist in such a small area and on a singular food source is due to the lack of squirrels, the usual primary seed dispersal of the lodgepole pine. As a result, serotinous cones are especially abundant in this region, which allows cones with seeds to accumulate in high quantities that will last for decades. This has led to a coevolutionary arms race between the crossbill and lodgepole pine, as the Cassia crossbill is the primary selective agent.
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Hazard reduction or controlled burning is conducted during the cooler months to reduce fuel buildup and decrease the likelihood of serious hotter fires.Guidelines for Low Intensity Bushfire Hazard Reduction Burning Retrieved on 11-3-2009 Controlled burning stimulates the germination of some desirable forest trees, and reveals soil mineral layers which increases seedling vitality, thus renewing the forest. Some cones, such as those of lodgepole pine and sequoia, are serotinous, as well as many chaparral shrubs, meaning they require heat from fire to open cones to disperse seeds. In industrialized countries, controlled burning is usually overseen by fire control authorities for regulations and permits.
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This behaviour, known as serotiny, makes B. telmatiaea dependent upon a suitable fire regime for successful regeneration; indeed, excessive fire frequency may be one reason why B. telmatiaea does not occur further south, despite suitable habitat throughout southwest Australia. Unlike most serotinous Banksia species, the seeds of B. telmatiaea are not released immediately after the passage of a bushfire. The follicles open straight away, but at first the seeds are blocked from falling out by the winged seed separator. If moistened, these wings close up, and as they dry they open out again, levering the seeds out of position, making it possible for them to fall.
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Like many plants in Australia's southwest, Banksia hookeriana is adapted to an environment in which bushfire events are relatively frequent. Most Banksia species can be placed in one of two broad groups according to their response to fire: reseeders are killed by fire, but fire also triggers the release of their canopy seed bank, thus promoting recruitment of the next generation; resprouters survive fire, resprouting from a lignotuber or, more rarely, epicormic buds protected by thick bark. Banksia hookeriana is a reseeder—killed by bushfire and regenerating by seed. It is also serotinous, in that it holds its seeds in seed pods of old spikes in the plant canopy.
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In the southern hemisphere, fire-mediated serotiny is found in angiosperms in fire-prone parts of Australia and South Africa. It is extremely common in the Proteaceae of these areas, and also occurs in other taxa, such as Eucalyptus (Myrtaceae) and even exceptionally in Erica sessiliflora (Ericaceae). In the northern hemisphere, it is found in a range of conifer taxa, including species of Pinus, Cupressus, Sequoiadendron, and more rarely Picea. Since even non-serotinous cones and woody fruits can provide protection from the heat of fire, the key adaptation of fire-induced serotiny is seed storage in a canopy seed bank, which can be released by fire.
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"The Effect of Season of Fire on Serotinous Proteaceae in the Western Cape" - BW van Wilgen and M Viviers This is a highly gregarious species and is found in dense stands of hundreds of thousands of individuals, usually on mountainsides on stony sandstone soils, and particularly numerous in the vicinity of Villiersdorp. Its distribution covers Kogelberg, Kleinmond, Klein River, the Groenland Mountains north of Grabouw, Hottentots-Holland, Du Toit's Kloof Mountains, Riviersonderend Mountains and the Swartberg above Caledon."Proteas of Southern Africa" - Rebelo, Page & Paterson-Jones (Fernwood Press, 1995) Leucadendron microcephalum was first described by Michel Gandoger & Hans Schinz in Bull. Soc. Bot. France 60: 52. 1913.
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It is generally only weakly serotinous in the southern part of its range, that is, it lacks a canopy seed bank as follicles on old flower spikes in the canopy release their seed after two years, but populations retain more seed as populations move north. Lower canopies and drier climates predispose to hotter fires that are more likely to kill plants and effect seed release, and thus facilitate seedling recruitment. All banksias have developed proteoid or cluster roots in response to the nutrient poor conditions of Australian soils (particularly lacking in phosphorus). The plant develop masses of fine lateral roots that form a mat-like structure underneath the soil surface, and enable it to extract nutrients as efficiently possible out of the soil.
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Resprouting from the woody base several months after a bushfire, Lane Cove National Park Lambertia formosa regenerates after bushfire by resprouting from its woody lignotuber, but is also serotinous in that it has a seed bank held in its canopy to be released after fire. The number of flowers produced by plants growing back from fire peaks two or three years afterwards. A field study in Brisbane Water National Park north of Sydney found that plants that had experienced two short (less than seven-year) intervals between bushfires had reduced reproductive output as measured by lower numbers of follicles, compared with plants in areas which had had no or one short inter-fire interval. Plants can live for over 60 years.
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Seed separator of Banksia marginata, with winged seeds still cohering A seed separator is a structure found in the follicles of some Proteaceae. These follicles typically contain two seeds, with a seed separator between them. The seed separator is nothing but a little chip of wood, but in some cases it serves an important function: in serotinous species, the follicles open only in response to fire, but the seed separator remains in position, thus preventing the seeds from falling out immediately, onto burnt or burning ground. Some separators loosen and fall out once they have cooled, thus ensuring that the seeds are released only after the fire has passed; others loosen and fall only after they have been moistened, thus ensuring that the seeds are released at the first rain after fire.
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Like many plants in Australia's southwest, Banksia aculeata is adapted to an environment in which bushfire events are relatively frequent. Most Banksia species can be placed in one of two broad groups according to their response to fire: reseeders are killed by fire, but fire also triggers the release of their canopy seed bank, thus promoting recruitment of the next generation; resprouters survive fire, resprouting from a lignotuber or, more rarely, epicormic buds protected by thick bark. B. aculeata is killed by fire because it possesses neither thick protective bark nor a lignotuber to reshoot from. It is serotinous—it accumulates a canopy seed bank that is released only in response to fire—so populations typically recover rapidly after a fire, but this strategy makes it dependent on a suitable fire regime.
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In Oregon, field burning has been widely used by grass seed farmers as a method for clearing fields for the next round of planting, as well as revitalizing serotinous grasses that require fire in order to grow seed again. The Oregon Department of Environmental Quality began requiring a permit for farmers to burn their fields in 1981, but the requirements became stricter in 1988 following a multi-car collision in which smoke from field burning near Albany, Oregon, obscured the vision of drivers on Interstate 5, leading to a 23-car collision in which 7 people died and 37 were injured. This resulted in more scrutiny of field burning and proposals to ban field burning in the state altogether.2008 In the European Union burning crop stubble after harvest is used by farmers for plant health reasons under several restrictions in the cross compliance regulations.
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