Alpine vegetation of Tasmania
[5] Often in Tasmania, the dominant species of a mountain's vegetation will gradually decrease in height with altitude to become a component of the alpine shrubbery.
[6] This approach is justifiable as of the 300(+) species found in the alpine and treeless subalpine zones, only 10 are restricted to the area above the climatic tree-line.
In the eastern and central parts of the state, Jurassic dolerite caps the summits having intruded into the Permian and Tertiary sediments.
[8] These dolerite caps have a characteristic topography having an elevated rocky rim and a short, steep face above rock scree.
[5] Chemically, dolerite is potentially a very rich source of nutrients however the slow rate of its weathering only allows for soils of moderate fertility.
Frequent hot northerly airflows also occur during January–March which have a strong desiccating effect on the alpine soils, placing the plants under transpirational stress.
[13] Tasmania's mountains are relatively low in altitude (generally below 1500m) in comparison to that of other regions of the world thus UV radiation is not as big a factor compared to that of other alpine habitats.
Additionally alpine shrubby vegetation contains aromatic oils and contain large accumulations of dead foliage which burns rapidly.
After 20 years of succession a network of small cushions emerges through grass and herbs and displaces these species in wetter areas.
[14] After 50 years of succession, heaths and shrubberies form progressive invasion of woody species most of which become established in old bolster moor cushions which have dried.
Estimations based on areas that have been burnt in the past suggest that 150–200 years of succession is required to develop 10-20% cover of conifers as a low mat under 10 cm in height.
The direct effects of grazing such as eating and trampling the vegetation causes a reduction in structural complexity and an increase in bare ground cover.
The indirect effects of grazing can be equally destructive such as the introduction of exotic weeds and fertilizer application by aerial spreading.
[16] Wildfires poses an additional threat to alpine plants and animals, with many species apparently vulnerable to an increase in fire frequency.
[16] Increased levels of UV radiation may penetrate to the earth's surface as a consequence of damage to the ozone layer in recent times.
[5] Tasmania's alpine plants have developed a variety of physiological, morphological and behavioral adaptations to deal with the challenges they face in their environment.
[5] Additionally Tasmania's alpine plants have life cycles which are very precisely linked to their short growing season.
[5] The densely crowded shoots with a high degree of branching, restrict air movement and maintain a moist internal atmosphere within the cushion.
Small needle-shaped leaves with a relatively large surface-area to volume ratio are efficient in rapid energy transfer and heat dispersion while retaining structural strength.
Scleromorphy is a common feature amongst alpine species and has provided an evolutionary advantage as Australia's recent climate has become more arid.
[18] Plants in alpine environments are subjected to water stress from a combination of inadequate precipitation, thin soils, periodic high winds and insolation.
[5] Adaptations include thick cuticles, rolled leaf margins, sunken stomata or lacking leaves altogether.
Experiments include climate manipulation, such as using a rain exclusion shelter to study the effects of drought on alpine flora and invertebrates.
The high mountain cushion community is typically composed of Dracophyllum minimum, Pterygopappus lawrencei, and Phyllachne colensoi.
[5] The coniferous vegetation is represented by two gymnosperm families, Cupressaceae (Diselma archeri, Athrotaxis cupressoides, A. selaginoides) and Podocarpaceae (Michrocachrys tetragona, Microstrobos niphophilus, Podocarpus lawrencei).
[5] Tall heaths with plants up to 2m (Orites acicularis, Leptospermum rupestre, Coprosma nitida) are usually found in areas of better drainage usually with a rock strewn surface.
In drier areas, Poa labillardieri is dominant in tall, dense tussocks with shrubs of Pimelea pygmaea, Leucopogon stuartii, and Epacris petrophila, which may merge into Eucalyptus coccifera woodlands.
