Alpine vegetation of Tasmania

Alpine vegetation refers to the zone of vegetation between the altitudinal limit for tree growth and the nival zone. Alpine zones in Tasmania can be difficult to classify owing to Tasmania’s maritime climate limiting snow lie to short periods and the presence of a tree line that is not clearly defined.

Approximately 111 700 ha of Tasmania is alpine and subalpine habitat (2%). Australia wide, there is only 198 400 ha meaning 56% of Australia’s alpine & subalpine habitat is restricted to Tasmania. The altitude at which alpine vegetation occurs ranges from 750m in the southwest to 1400m in the northeast.

From the Latin word Alpinus, from Alpes ‘Alps’. Globally, alpine vegetation is defined zone of vegetation between the altitudinal limit for tree growth and the nival zone. In areas where mountains can be considered typically alpine, the vegetation zones are often divided into distinct altitudinal bands. The alpine band usually consists of low growing herbaceous species given the cessation of most woody vegetation at the upper limit of the subalpine band. The upper limit of the alpine band often gives way to bare rock and permanent snow which continues on to the summit.

In Tasmania, such distinctive altitudinal bands do not occur. Typically the tree line is not well defined and usually located close to the mountain summits, often no more than a few hundred meters below. There is no permanent snow lie and vegetation continues to the summits. 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. This environmental gradient allows for the subtle sorting of species into communities without the existence of an abrupt break from forest to shrubland. Consequently, Tasmanian alpine and treeless subalpine vegetation is often considered as a single vegetation unit given the term alpine. 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.

Tasmania’s alpine landscape is dominated by two bedrock systems originating from different geological periods. In the eastern and central parts of the state, Jurassic dolerite caps the summits having intruded into the Permian and Tertiary sediments. These dolerite caps have a characteristic topography having an elevated rocky rim and a short, steep face above rock scree. Chemically, dolerite is potentially a very rich source of nutrients however the slow rate of its weathering only allows for soils of moderate fertility.

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