What is Fagus?
Deciduous beech (Nothofagus gunnii)
- or fagus
as it is best-known - is a humble tree, usually growing to 2 metres or less. You find it in places most would describe as inhospitable. One of its other names - tanglefoot - is ruefully confirmed by bushwalkers caught up in its twisted, ground-hugging branches. Yet this small Tasmanian tree can claim something few other Australian plants can. It is Australia's only winter-deciduous tree, and you will find it nowhere else in the world except Tasmania.
Its autumn display is superb - turning a spectacular range of autumn colours, from rust red through to brilliant gold during late April and May.
Some 100 million years ago, when the forerunners of Nothofagus
first appeared, Tasmania was part of the supercontinent of Gondwana. As Gondwana began to split, Nothofagus
(or Southern Beech) was common in what would later become South America, New Zealand, Antarctica, Australia and their near neighbours.
In fact it was the present distribution of Nothofagus
that first suggested to scientists that these landmasses might once have been joined. The species of Nothofagus
most closely related to fagus are found in South America and New Zealand, strongly supporting the suggestion that Tasmania was formerly linked to those landmasses. Just why fagus is the only deciduous Australian tree derives from that ancestry.
Losing leaves in autumn was a response to long dark winters. The leaves were unable to photosynthesise due to the lack of sunlight, so the trees shut down until spring. But as Gondwana split and Australia drifted northward on its own, the winters became lighter. Other groups of plants, including eucalypts, started to dominate a drier, sunnier Australia.
These more common Australian trees handle winter cold by other methods, such as developing the small, waxy leaves which are common in snow gums and other alpine plants. Only in the remote, wet highland areas of Tasmania - where losing your leaves is still a good defence against winter frosts and snow - has this rare Southern beech survived to thrill visitors each autumn.
Why leaves change colour?
Deciduousness - the seasonal losing of leaves - is brought on by a combination of weather and plant chemistry. During warmer months, chlorophyll in the leaves not only helps convert sunlight into sugar, it also gives the leaves their green colouring. But as the days shorten, chlorophyll starts to break down and another pigment called anthocyanin
takes over. It is this pigment which gives autumn leaves their colour. Eventually, as the leaves cease to take up any further nutrient, they fall to the ground, returning precious minerals to the soil which will feed the next spring growth. Anthocyanin
also effects some more common Australian plants, though in a different way. You may have seen brilliant autumn-like colours in the bark of snow gums (Eucalyptus coccifera)
. The same pigment occurs in their bark as in the leaves of deciduous trees.
Fagus in summer and autumn colours
When and where to see it
Fagus prefers cool, damp places, so it is often best seen in remote highlands. But non-bushwalkers can find some very accessible stands of fagus. Probably the most easily seen is around Lake Fenton in Mt Field National Park
, where there is an observation area. As you drive towards the ski-fields up the Lake Dobson road, you pass through a particularly rocky section, where masses of boulders seem to pour down the steep slopes. Among these boulders are patches of fagus, some easily seen from your vehicle.
For a closer look, park in the Lake Fenton carpark then head off towards the boulder field. Please note that you are in Hobart's drinking water catchment. Don't disturb any soil or leave any waste in the area around Lake Fenton. Also be aware that you are at an altitude of over 1000 m. Temperatures will be much lower than at the bottom of the park near Russell Falls, so warm and waterproof clothing should be carried. Brilliant displays of deciduous beech can also be found higher in the park at Tarn Shelf.
In the north of the State, some of the best fagus is found around Cradle Mountain
. The Loop Track, which circles Dove Lake, is an easy 2 hour walk that passes through some patches of fagus. The even easier Weindorfers Forest Walk also offers easily accessible fagus, including trees that are much taller than the more usual stunted alpine form.
One of the most spectacular displays of fagus is found around Crater Lake. Although this is a couple of hours return walk from the Dove Lake carpark, the sight of the steep slopes of the cup-shaped lake covered in brilliantly coloured fagus, makes it well worth the effort. Again be sure you take suitable clothing and fill in the walker log books. Usually colouring has started by the end of April and continues for a month or so, but the actual time of fagus colouring varies from year to year and place to place. It is best to phone the particular national park before you visit.
Protecting a unique plant
A recent aerial survey found that there was a total of less than 10 000 hectares of fagus growing in the whole of Tasmania - a tiny fraction of our wooded areas. Most of that was in highland areas above 800 m where rainfall was greater than 1800 mm.
A key factor in the survival of fagus is absence of fire. It appears that the deciduous beech is very slow to regenerate after fire. This contrasts with many other Australian plants. Mt Wellington, the spectacular mountain behind Tasmania's capital city, Hobart, provides a good example of how strongly a eucalypt forest can recover from a devastating fire. In 1967 the slopes of the mountain were practically bare; now they are fully covered.
In contrast, research suggests that fagus is very slow to grow back. In some circumstances it may never recover from burning, with other less-susceptible species taking over. This makes the protection of the habitats of fagus crucial.
Much of our fagus is found within the Tasmanian Wilderness World Heritage Area
, and is under the control of the Parks and Wildlife Service. Part of their brief is to study, monitor and protect such species. In the case of fagus, there is much yet to be learned, but one interesting recent find was an individual tree more than 350 years old. Obviously the slow growing tree can survive and thrive in these harsh conditions for a considerable length of time.
Fagus-spotters and other visitors to delicate highland areas can help protect their habitat by following minimal impact bushwalking
guidelines. With such a relatively small distribution, we can never be too careful about protecting this botanical marvel.