Biological Adaptations
Taylah Rich 11MKL
Eucalyptus Regnans (Mountain Ash)
Environment
Eucalyptus Regnans also known as Mountain Ash is a species of eucalyptus native to Tasmania and Victoria.
Mountain Ash grows in pure stands in tall wet forests, often with rainforest understory. It occurs in cool, mostly mountainous areas approximately 1000 metres altitude. In temperate areas Mountain Ash receives over 1200 millimetres of rainfall each year. Mountain Ash is most suited to deep friable clay loam soils, often from volcanic origin.
In Victoria, Eucalyptus Regnans are found in the Otway, Dandenong, Yarra and Strzelecki ranges as well as Mount Disappointment and East Gippsland.
Challenges Faced
Although Mountain Ash has adapted to regenerate after a fire, it remains a fire sensitive species. Unlike most other eucalyptus species, Eucalyptus Regnans are killed completely in severe fires. As this species relies solely on its seeds for regeneration, Mountain Ash can be easily eliminated from a region if fires occur at frequent and regular intervals, as the seeds will not have enough time to regenerate before another fire occurs.
Once a Eucalyptus Regnans tree has germinated its seeds very few of these seeds actually mature. Many seeds are often eaten or destroyed by ants and insects on the forest floor. The germinated seeds also die due to the insuffient light on the densely shaded forest floor.
Figure 10: Eucalyptus Regnans Seeds
Adaptations
Bushfires are quite common in Australia, especially in Victoria and Tasmania where Eucalyptus Regnans are found. Therefore Mountain Ash trees need to adapt to these conditions. These adaptations allow this species of Eucalyptus to regenerate after a fire and facilitate the growth of new plants.
Mountain Ash trees have seeds that germinate only after they have been exposed to a fire. Severe fires kill the mature Mountain Ash trees which prmotes a large release of seeds which can take advantage of the nutrients in the ash bed. This adaptation allows for the ensured survival of Mountain Ash. A fire that could have caused the death of the previous generation triggers the life of a new generation of Eucalyptus Regnans.
Mountain Ash trees also shed bark in long ribbons that hang down low to the ground. This adaptation allows flames to be conducted to the canopy of the tree where the seeds of the species are found in the event of a fire. Fire exposure triggers the germination of the Mountain Ash seeds.
These adaptations allow for the survival of the Eucalyptus Regnans in their natural environment.
Figure 11: Eucalyptus Regnans bark ribbons
Interesting Fact
Eucalyptus Regnans are unusual because unlike other eucalyptus trees, Mountain Ash has adapted to live in high rainfall environments.