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Effects of Fire on Alpine communities in Tasmania
Fire is known to play a role in effecting the species composition and community structure of global terrestrial vegetation. The immediate effects of fire on vegetation is usually dependent on the intensity of the fire while the long term responses of vegetation and how they recover after a fire has moved through is related to both intensity as well as frequency, known as a fire regime. In Australia fire is an important natural environmental variable. Fire has the opportunity to affect most of the land surface areas and there are many opportunities for fire to promote or adversely affect biodiversity within plant communities. Overall, vegetative communities in Australia are believed to be well adapted to particular fire regimes. More specifically, Australian alpine plant communities are often referred to as being resilient to fire to the extent that interactions between fire and adaptive traits may in fact facilitate reproduction and survival of particular species. However, evidence would suggest that this classification should not be extended to include Tasmanian alpine plant communities. In Tasmanian alpine communities fire has been seen to have potentially devastating effects. Decades after fire in Tasmanian alpine regions there are obvious structural differences when comparing them to those that haven’t been burnt.

Western Tasmania versus Eastern Tasmania

Some evidence suggests that geographical factors may also play a role in how alpine plant communities in Tasmania recover after a fire. It has been suggested that when fire burns through mosaics of vegetation reflecting fundamental edaphic and topographic factors it merely reinforces naturally determined patterns. Regeneration time after a fire has been seen to be more rapid for alpine communities towards the east of the state when compared to that of the more oligotrophic western mountains. Much or the reasoning for this has been related back to soil health and soil recovery associated with fertility. There is a strong floristic gradient from the mountains on the eastern and central part of the state where the soil is fertile to that of the western mountains where soil is considered to be less nutritious and essentially infertile.

Tasmania Versus Mainland Australia

There are key differences in the structure and network of alpine vegetation between Tasmania and mainland Australia. Tasmanian alpine plant communities are more typically characterized by coniferous and deciduous heathlands while in mainland Australia such communities are best described as tall herb fields. Adaptations to fire are prevalent in the most widespread and abundant of Australia’s endemic plant communities and it is therefore suggested that they must have evolved with frequent fires. However, this cannot necessarily be said for Tasmanian alpine vegetation. In Tasmanian alpine areas, lighting provoked fires are rare and it has therefore been suggested that burning of these areas has not been extensive or frequent. Furthermore, in most western Tasmanian alpine communities glaciation has affected topography and brought about the presences of large water bodies that hinder the movement of fires that has again prevented a regular fire regime. Overall, there is strong evidence indicating that perhaps fires have not been a regular event in the alpine areas of Tasmania. There are a number of Australian alpine plant species that do not possess mechanisms for regeneration or recovery from fire and it is therefore suggested that natural fire barriers and climate have been important for their existence and survival. Fire sensitive species such as Athrotaxis selaginoides, Athrotaxis cupressoides, Lagarostrobus franklinii, Diselma archeri, Microstrobus, niphophilus and Notophagus gunii. These plants have gravitational seed dispersal with no adaption for wind and all are killed as individuals by fire and have no soil seed store. These many of these are found in Tasmanian alpine communities such as Mount Field in the southwest. Mount field is a heavily glaciated moderate sized alpine habitat with high rainfall and therefore it is reasonable to believe that this has contributed to the survival of such fire sensitive species through the prevention of regular high intensity bush fires. Thus it is also reasonable to suggest that the occurrence of a bush fire in these areas would cause a devastating blow to the structure and composition to this alpine vegetation. Climatic differences between Tasmania and the mainland are also believed to play some role in the differences in long-term responses to fire between Tasmanian alpine communities and mainland Australian. Mainland Australian post fire alpine vegetation typically restores it pre fire appearance in less than a decade however, in Tasmanian alpine communities even after half a century bare ground remains at high levels. These differences have been put down to climatic differences between the maritime mountains of Tasmania and the continental mainland mountains.