Shadows of a Great Forest

The small settlement of Toolangi, located on the ridge of the dividing range approximately 70 kilometres northeast of Melbourne, has long been appreciated for its mountain forest ‘ambience¢. In the context of the much broader environment, it’s located in the ranges surrounding the northern limits of the Yarra Valley. In the viewable distance, the city of Melbourne is located on the banks of the Yarra where it flows into Port Phillip Bay, approximating the southern limits of the Yarra Valley. The Yarra – or Birrarung to the Wurundjeri people (river of mists and shadows) – has been at the centre of their life and culture for thousands of years, and more recently has been regarded as the life blood of Melbourne, being the first place of European settlement and the source of fresh water. Whilst it has its genesis in the tall forests of the mountain ranges further east, tributaries arise around Toolangi that tumble down to their confluence with the Watts and the Yarra and thus represent a physical and, in indigenous terms, a spiritual link between ‘The Bay’, Melbourne and Toolangi. North of the divide lie the traditional lands of the Taungurung people whose waters flow out of the forest on their way to eventually join the Goulburn system.

Visitors and residents of Toolangi appreciate its special qualities, stunning natural vistas and abundant native wildlife, but may be unaware of the spectacular nature of this forested mountainous landscape, when first encountered in the earliest years of European settlement. The underlying geology of a landscape is obviously important in defining a ‘sense of place’ (for instance mountainous), but the vegetation established on that landscape rates high as a signature element of our appreciation and lingering impression of the region.

History can inform us of the natural features that were to be found in pre-European Toolangi. In the late 19th century, Ferdinand von Mueller, Victoria’s State Botanist, was enthusiastically recording the dimensions of the Mountain Ash in the Victorian regions, which he named Eucalyptus regnans (formerly known as E. mygdalina).[i] Paling splitters and sawmill owners were submitting claims that trees upwards of 400 feet tall (122 metres) were being recorded. Mueller was convinced this was true, a measure that significantly exceeded the height of the tallest Coastal Redwoods in California. It was not surprising that Toolangi was said to harbour some of the largest specimens. Mueller was aware of the factors governing the size of the tallest trees in the landscape and stated that it was the perfect combination of elevation, rainfall, temperature, soil depth and fertility that set Victoria apart from other tall forested regions of Australia (even Tasmania – which he said was too cold).[ii] The Toolangi environment exemplified these requirements. For indigenous people and early European settlers, the vista was also very different to the current Toolangi forest.

Today, Mountain Ash Eucalyptus regnans is well known to be the tallest of the Eucalypts, and as such, the tallest flowering plant (angiosperm) in the world. The Toolangi forest is dominated by Mountain Ash and, as may be imagined, the forest was in a mature and untouched state when the early settlers first laid eyes on it. As we now understand, this mature forest was extraordinary in the height of the dominant E regnans trees. It may come as a surprise that most of the forest we see today in Toolangi is relatively young regrowth that has recovered from past bushfires, for example in 1926, 1939, 1967 and 2009. This limiting age factor restricts the height and girth of the regenerating trees in the previously burned landscape. Although some trees survive, if the fire is intense enough, it kills most of the dominant Mountain Ash and marks the beginning of a new forest which proceeds on the long trail of recovery, regrowing as fairly even stands of trees of largely uniform age. Much of this regenerating forest is also recovering from logging operations, where clear felling has been and remains the principal form of harvesting used by the industry since its adoption in the 1970s. This practice leaves a heavy imprint on the forest, as regrowing areas that have been felled are necessarily age-limited by the date of harvest. Hence the extant forest that we witness today is a compilation of age classes over previously burned or logged areas, giving a patchwork of different stages of regeneration and associated height and girth of the living trees.

Another important consideration is the complex structure of a natural forest as an ecosystem, not simply composed of over-storey trees. Such ecosystems contain extremely complex interacting life-forms, including everything from ground-dwelling bacteria and fungi, to a range of understorey plants and the tree species forming the canopy, with associated animal and insect fauna. This is a world of interdependence, where every organism has an important role in a co-operative environment. Some elements are essential to soil formation, others to sharing soil nutrients which assist optimal tree growth. Others assist in water uptake in dry periods. Out of this ecosystem foundation comes a spectacular forest that has a role, particularly in maturity, of regulating climate, water and biodiversity. It is significant to note that as the forest grows older, it progressively stores more carbon, thus assisting mitigation of climate change.

A maturing forest also gains resistance to burning because of subtle changes in structure such as reduced ‘leafiness’ in the canopy, mid-storey and under-storey strata. Also, the ever-increasing canopy height makes a crown fire less likely to occur, as Mountain Ash have tall clean trunks with a distance of more than 30 metres before flames could begin to touch the canopy. At ground level, the progressive impact of the Superb Lyrebird is evident. Its endless search for food turns over tons of soil, resulting in higher moisture content with reduced combustible material exposed to flames. Bandicoots and native rodents also have a role in turning over and aerating the soil, making it more permeable and absorbent of rain fall and leaf drip from the forest over-storey. Another vital influence is the hard work of ‘detritivores’ such as the larvae of the many species of moths (Lepidoptera) that feed on and break down leaf and branch litter, and thus convert combustible fuel into moisture-laden soil, which progressively deepens over eons of time. These complex natural processes play a key role in enabling the ecosystem to fulfil the evolutionary potential of this ancient forest.

One huge example of a mature Mountain Ash was located (in the 1890s) within the Maroondah catchment (see image) and was named the Mueller Tree in honour of the great botanist.[iii] Locally and in later times, the same tree was also known as Furmston’s Tree.[iv] As evident in the image, it was a true giant. This magnificent tree was later measured accurately at 64 feet (19.7 metres) circumference at 6 feet (1.8 metres) above ground level, and height of 307 feet (94 metres) with a broken top. These huge dimensions signified a long life-span (perhaps 500 years or more), which sadly came to an end in 2001, when it finally toppled in a storm and the hollow trunk was shattered. It was one of a population of trees of similar great age that had survived many fire events, as indicated by the young regenerating forest surrounding them, and growing back after fires.

With a deeper understanding and appreciation of the nature of the tall forests and ecosystems that support and characterise them, has come the realisation that the oldest forest systems are also the champions at yielding pure water to the mountain streams, including those that flow down to Melbourne via the Yarra Valley. The forests of Toolangi on the northern side of the watershed also supply valuable flows to the Goulburn/Murray system via streams such as the Yea and Murrindindi rivers. The term ‘headwater forest’ applies, and exists in the mountain ridges and sheltered valleys that, ideally, are characterised by old growth forest areas. They shade and shelter the ground and their hydrological efficiency helps to recharge aquifers, provide runoff to streams and not surprisingly, attract the rains that maintain the flows of all these significant arterial waterways.

It is encouraging that magnificent old growth forest remnants, as shown in the images here, can still be found in the much-modified forest of today. In the past they were the dominant canopy-forming vegetation and would have been present in relatively small numbers widely separated, lending a park-like atmosphere to the environment. Consequently, today we celebrate the Kalatha Giant (see image), Blackbeard (both approximately 400 years old) and other massive Toolangi forest remnants and imagine a landscape previously graced with numerous examples of such wonders of a mature forest. All we have to do is leave nature alone and give her a chance, allowing ecosystems to flourish in their full capacity and trees to grow to their full potential. She will do her best to restore and rebuild forest cathedrals and protect us into the future.

References

Ashton, D. ‘The Environment and Plant Ecology of the Hume Range, Central Victoria’. Proceedings of the Royal Society of Victoria, Vol. 112, No. 2, December 2000

Beardsell, D. & C. The Yarra: A Natural Treasure, Royal Society of Victoria, 1999

Caire N. J. ‘Notes on the Giant Trees of Victoria’. The Victorian Naturalist, 21.9.1905, pp. 122-128

Hardy, A. D. ‘Giant Eucalypts of Victoria’. The Gum Tree: official organ of the Australian Forest League, June 1921, pp. 15-16

Hardy, A. D. ‘Australia’s Giant Trees’. The Victorian Naturalist, March 1935. pp. 231-241

Mace, B. R. ‘Mueller: Champion of Victoria’s Giant Trees’. The Victorian Naturalist, Vol. 116, August 1996

Mueller, F. V. 2nd Census of Australian Plants. 1870

Mueller, F. V. Australian Vegetation. Part 5 of the official record, Intercolonial Exhibition, Melbourne 1866-67

Mueller, F. V. Letter to ‘The Argus’, 25 May 1889

[i] Mace, B.R. ‘Mueller: Champion of Victoria’s Giant Trees’. The Victorian Naturalist, Vol. 116, August 1996.

[ii] Mueller, F. V. 2nd Census of Australian Plants, 1870.

[iii] Hardy, A. D. ‘Giant Eucalypts of Victoria’. The Gum Tree: official organ of the Australian Forest League, June 1921, pp. 15-16.

[iv] Healesville & District Historical Society.