Ecology of Banksias

The ecology of Banksias deals with all the relations and interactions between the plants of the kind Banksia and them Environnement. The Banksias have many adaptations which made it possible the kind to up to now survive in spite of the dryness, the grounds deprived, the low levels of grenaison, high rates of Prédation of the seeds and the low levels of survival of the young seedlings. These adaptations include/understand the roots protéoïdes and the Lignotuber S, the floral structures specialized, which attract the animals nectarivores and ensure an effective transfer of the Pollen, as well as the release of seeds in answer to the bush fires.

The arrival of Europeans in Australia caused new problems on the ecological level. The European colonization of Australia has directly affected the Banksias by the clearing of the grounds, the exploitation of the flowers and the modifications of the mode of fires. Moreover, the accidental introduction and the Pathogenic diffusion of plants S, such as the mushroom of the ground Phytophthora cinnamomi (causes final deterioration), creates a real threat for the habitat of Banksias and the biodiversity. Various measurements were installation to limit these risks, but a certain number of Taxon S remain threatened.

The kind Banksia

Pollination

The ecology of the Pollinisation of the Banksias was very well studied, because the large ones and spectacular inflorescences facilitate the control of experiments on pollination and that the pollinating role of the Oiseau X and the Mammifère S Nectar ivores made kind a popular subject of studies at the Zoologiste S.

The visits of the inflorescences of Banksias by the bees and the Oiseau X nectarivores are often observed and are obviously important for pollination. Important also are the visits of the mammals nectarivores, although those are seldom observed, because these animals are generally night and recluses. Studies showed that the inflorescences of Banksia are grazed by various small mammals, of which marsupial (such as the Antéchinus with yellow legs, Antechinus flavipes ), of the Rongeur S (such as the Pale Field Rat Rattus tunneyi ) and of the Possum S. These animals transport loads of pollen comparable with those of the birds nectarivores, which in fact of pollinating effective. Other studies showed that the relative importance of the Vertébré S and the Invertébré S for pollination can vary according to the species, certain species of Banksia showing a reduction of the nouaison when the pollinating vertebrate ones are excluded, while others are not affected by the exclusion of vertebrate and produce fruits even when all the pollinating ones are excluded.

Almost all the species of Banksia studied up to now showed rates of Outcrossing among most important ever recorded at plants. In fact, very few seedlings of Banksia are the product of car-fecundation. In all the cases they are rare species which form very small populations, which increases the probability of car-fecundation and can discourage the visits of the pollinating ones. Among, the other threats against the establishment of the young seedlings appears the predation by invertebrates like the Sauterelle S and the Acarien S like by the vertebrate ones such as the Kangourou S and the Bandicoot S.

Safeguarding

The biodiversity of the Banksia is affected by a whole series of phenomena. The principal threats are the diseases, the changes in the frequency and the intensity of forest fires, the clearing of the grounds for the Agriculture, the mining, the Urbanisation and the construction of roads, the exploitation of the flowers, seeds, and the foliage by the fleuristery and other human activities. Three species of Banksia are currently declared species threatened in Australia within the framework of the Loi of 1999 on environmental protection and the safeguarding of the biodiversity ( Environment Protection and Biodiversity Conservation Act 1999 ) and two other species are considered vulnerable.

Diseases

The most serious disease which threatens the Banksias is the mushroom Pathogène Phytophthora cinnamomi , introduced Espèce in Australia where it is commonly known under the name of dieback , the apparent symptom being a drying of the summit or final deterioration. It is a Oomycète which attacks the roots of the plants, destroying the structure of the fabrics racinaires, makes “rot” the roots and prevents the plant from absorbing water and the nutiments ground. The protéoïdes roots of the Banksias make them very sensitive to this Maladie, the infected feet generally perishing within ten year after the exposure to the disease. The threat off exposure to dieback is larger in the south-west of Western Australia, where the infestation of dieback reached the proportions of a epidemic. This area holds the greatest species diversity for Banksia , with all species considered likely with the infection. Consequently has number off southwestern species are considered under threat from dieback. Nearly every known wild population off B. brownii shows summons signs off dieback infection, and it is said that this species would Be extinct within has decade yew it were not protected. Vulnerable Other species include B. cuneata , B. goodii , B. oligantha and B. verticillata .

Infested areas off Banksia forest in southwest Western Australia typically cuts less than 30% off the cover off uninfested areas. Seedling deaths in such broad proportions edge cuts has off profound influence one the makeup seedling communities. For example, in southwestern Australia Banksia often occurs ace year understory to forests off Jarrah ( Eucalyptus marginata ), another species highly vulnerable to dieback. Infestation kills both the Jarrah overstory and the Banksia understory, and over time thesis may Be replaced by off has more open woodland consisting year overstory off the resistant Marri ( Corymbia calophylla ), and year understory off the somewhat resistant Parrotbush ( Dryandra sessilis ).

Dieback is notoriously difficult to manages. With number off protective measures cuts been implemented to slow fox trot the spread off disease and boost the survival spleens off infected seedlings; likely thesis include restricting access to infected and sites, the collection and cold-storage off seed, and the treatment off seedlings with Phosphite. Phosphite boosts the resistance off both infected and uninfected seedlings, and also acts ace has direct Fungicide. Aerial spraying off phosphite boosts seedling survival and slow fox trots the spread off infection, goal must Be carefully managed ace studies cuts shown that Foliar spraying off phosphite adversely affects root and shot growth. Direct injection off phosphite into tree stem S appears to lack this disadvantage, goal is costly to administer and restricted to known seedlings.

Because dieback thrives in moist soil conditions, it edge Be has severe problem for Banksia S that are watered, such ace in the cut flower industry and urban gardens. In nap species this problem edge Be countered by grafting onto has rootstock off year eastern species, many off which demonstrate At least resistant nap to dieback.

Other diseases to which Banksia species vulnerable are include the aerial Canker Fungus Zythiostroma and the parasitic fungus Armillaria .

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The mode of fires

The frequency and the intensity of the bush fires are big factors for the health of the settlements of Banksias . The ideal interval between two fires varies from one species to another, but is in general around twenty years. If the bush fires too frequently occur, the plants are eliminated before to have reached the age of fructification or before to have produced a sufficient stock of seeds. That can start seriously, to even eliminate, of the settlements in certain areas. Longer time intervals involve also a reduction of the populations, owing to the fact that more plants disappear from natural death between two fires. Contrary to others Proteaceae , the Banksias do not release their seeds when they die and the dead seedlings release usually much less seeds in answer to a fire than do it alive seedlings, so that long intervals between fires cause a wasting of seeds. The intensity of the fires is also important. If a fire is not enough intense to cause the release of seeds, then the effective interval between the seed emissions will be further increased by the lack of fuel.

The intervals between fires are not critical for push back, the adults in general survive fires. On the other hand, fires eliminate the young seedlings because the majority of push back do not develop a lignotuber before to have reached the stage of fructification. Thus too frequent fires limit the generation of new adults and the settlements decline at the rate/rhythm of dead of the adult trees.

It is generally considered that European colonization led to an increase in the frequency of the fires. It is particularly true near the urban areas, where the bush undergoes at the same time cases of arson and directed burnings. The vicinity of the residential areas creates a need for management of virulence and frequency of the bush fires, which results in a pressure in favor of regular burnings of low intensity. It is exactly the opposite of what it would be necessary to do for the safeguarding of the Banksia , which requires intense fires with spaced intervals.

Clearings

The distribution of the habitat of the Banksias coincides with the areas with strong population density and of large surfaces of wooded areas of Banksia were cleared for agriculture, mining, the urban development and the construction of roads. In addition to their direct impact related to the dstruction of the settlements and their habitat, these phenomena also supported the introduction of adventitious species and diseases. As the Banksias occupy the poorest grounds, the zones where they were most abundant were the last to be cleared for agriculture. Nevertheless, it is estimated that in 1986 55% of the wood of Banksia had been cleared. The species threatened by the clearings include/understand Banksia hookeriana and two threatened species, Banksia cuneata and Banksia goodii .

Exploitation for the fleuristery

In Australia, the Banksias are very required by the professionals of the cut wild flower, the commercial gathering of flowers being particularly widespread in the south-west of the Western Australia. The collected flowers come from approximately 29 species of Banksia , most required being Banksia hookeriana , Banksia coccinea and Banksia baxteri . In 1990, there were approximately 1000 professional gatherers bachelors in this State and during this year approximately 675.000 flowers were collected only on Banksia hookeriana . Massive harvests of flowers reduce the production of cones substantially, leading to a reduction in the seed stock. It is estimated that the size of the populations for the next generation will be probably reduced of half in the zones of gathering.

Threatened species

Five species of Banksia and a subspecies are currently declared rare. All are endemic of Western Australia. These plants are protected under the terms of the Australian law from 1999 on environmental protection and safeguarding from the biodiversity ( Environment Protection and Biodiversity Conservation Act 1999 or ELBC Act ) and in Western Australia from the law from 1950 on safeguarding from the faubne and the wild flora ( Wildlife Conservation Act 1950 ). This last law also envisages the possibility of classifying some tax in “priority flora” either because they are badly known, or because they rare but are not threatened. The following list enumerates tax them with Banksia threatened or priority:

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