Tasmanian Plants

Since time immemorial, mountains have held special meaning to humans, and coming from a place where the tallest point in the landscape was a measly 169m high, I took the first available opportunity to visit the most accessible mountain when I arrived in Hobart. Thus began my love affair with Mt Wellington. Mt Wellington became my outdoor classroom. I frequented the walking tracks on mountain but I never walked far due to my photographic compulsions. Whatever little distance I managed to cover on foot was sufficient to convince me of the diversity of botanical life on the mountain. Browsing through the scientific literature, I was amazed to discover that the Mt Wellington Range was a stronghold for about a third of Tasmania’s higher plants and up to 60% of Tasmania’s bryophyte flora. I was duly impressed. Appreciation grew.

Those years back when I was doing my undergraduate course, Dr Rob Wiltshire conducted an excursion up the mountain as part of an ecology course to show sophomores the adaptations of eucalypt species to altitude. The class was brought up to the subalpine woodland to look at how eucalypt seedlings cope with frost and excess light. The exercise involved some walking and I took the opportunity to look around for anything flowering. By that stage of my academic life, I must have, I believe, unwittingly gained a reputation for being an incessant questioner, particularly when it came to the identity of plants. Perhaps Rob wanted to silence me before I could ask anything and he pointed to a dark handsome silhouette of a shrub on the rock boulders by the roadside and exclaimed, “Ahhh, do you know what that is?” Of course I did not but I took a stab at it anyway and I was That was when Rob sagaciously replied, with an inflection I can only imagine was meant for dramatic effect, “That’ll be the rare endemic tree daisy, Brachyglottis brunonis.”

I was duly impressed and intrigued. Members of the sunflower family (Asteraceae) such as daisies and groundsels are usually thought of as herbs, particularly in European countries, but then in temperate Australia, tree daisies appear to be a common theme. I learnt later that the tree was named after famed Scottish botanist Robert Brown, hence the specific epithet ‘brunonis‘. Vernacularly, the tree was known variously as the Tree Groundsel, Tasmanian Daisytree or Brown’s Tree Daisy. Interestingly, the only other species of Brachyglottis occur in New Zealand.

My reveries on daisytrees were short-lived in the face of academic pressures. Visits to the mountain trickled.

The final year of my undergraduate studies arrived and one academic unit which piqued my interest was Plant Science Research, in which I would get a chance to try out a mini-project of my own. I toyed with the notion of studying a rare or endemic plants and I felt again the call of the mountain, and remembered the Tasmanian Daisytree, which was both rare and endemic. I sought Rob out and he graciously agreed supervise me on the academic endeavour. We fine-tuned the objectives of the study, which would be to furnish an explanation on why the Tasmanian Daisytree is rare within it’s habitat range. The Tasmanian Daisytree is limited to Mt Wellington and a few other nearby locations. It’s distribution does not exceed 50 square kilometers and it is further restricted only to subalpine woodlands. In it’s habitat, it is also found scattered in a very disjointed manner and there was no obvious reason why this should be so since the subalpine habitat was apparently rather uniform. When we eventually analysed the data we collected and compared the vegetation and environmental factors of areas with and without the Tasmanian Daisytree, little useful information emerged. Areas with and without the Tasmanian Daisytree were not extremely different in terms of their vegetation or environment. Other forces must be responsible for preventing the Tasmanian Daisytree from attaining ubiquity! As far as speculations go, the Tasmanian Daisytree is probably stopped cold in it’s tracks at the seed or seedling stage. We did notice in our preliminary surveys that seedlings of the tree daisy were exceedingly rare.

Limited as the study was, more questions were raised than answered, which is, as I have come to believe, a trend that drives the heartbeat of scientific inquiry. Why the Tasmanian Daisytree chooses to be where it is may remain a mystery for some time and I hope to see one day when I sleuth through the scientific literature, a paper on the lines of: Towards an explanation of the rarity of Brachyglottis brunonis.

In all likelihood, the Tasmanian Daisytree originated on the mountain, and has never managed to move far. It’s rarity only serves to endear one to it’s presence, and presents the all so pleasurable challenge of spotting it among the ocean of other common plants. I can see the Tasmanian Daisytree as no less than the mascot tree of Mt Wellington, the prime botanical feature of Hobart’s Table Mountain. I imagine that the great nature photographer Peter Dombrovskis might thought similarly of the iconic status of the Tasmanian Daisytree when he immortalized in one of his great photographs, a scene of the tree against a backdrop of the weathered face of the Organ Pipes that so characterizes the mountain.

I envision that all genuine nature-loving Tasmanians should come to know the iconic tree of the Mountain that oversees Hobart. But the surest way to get acquainted with the tree daisy is still via a guide. You must be asked to look, and given ample opportunity to feel and smell, for it is likely that only then will you recognize. Then, even without it’s brilliant yellow blossoms you will see and recognize the distinctive dark shiny leaves, it’s charismatic branching and the sweet scent of it’s foliage. And forever will it be burned into your memory when your guide then utters in utmost authority: “That’ll be the rare endemic tree daisy, Brachyglottis brunonis.”

(Dedicated to Dr Rob Wiltshire)

Eucalyptus viminalis (White Knight)

It is common knowledge that the Mountain Ash (Eucalyptus regnans) is the worlds tallest flowering tree and that Tasmania has some of Australia’s tallest old growth forests. So magnificent are the Mountain Ashes that significant individuals  have earned appellations such as ‘Centurion’ and ‘Methuselah’. Alas, the legend of the Mountain Ashes have overshadowed the other giants that reside in Tasmania. There are other giants among the eucalypts that are worthy of more general recognition, and it may come as a surprise to some that the White Gum (Eucalyptus viminalis) is one of them.

Practically every plant enthusiast in Tasmania and many tourists who visit the state has seen the grand Mountain Ashes of the Styx or the Tarkine. Few however, even among Tasmanian botanists, have met or are even aware of the giant White Gums of Tasmania’s Northeast. This is because White Gums are often thought of as average sized trees  associated with dry forest. Yet, in the Evercreech Forest Reserve just 10km from Fingal, a forest of giantic white gums, locally called White Knights, preside over the wet forests. For centuries they have watched, like silent sentinels from their statuesque vantage point, the changing landscape of Tasmania’s Northeast. The time is nigh for the White Knights to take their rightful place in the annals of Tasmania’s rich botanical heritage, for nowhere else in the world does one encounter white colossuses such as these.

Another magnificent White Gum in stark contrast to the verdant wet forest understorey

In the 1970s a forester named Des Howe was carrying out a routine survey in the forest about to be fell when he noticed that one of the trees that was to be felled was very tall. A surveyor came in and measured the tree to be an incredible 91m. A more accurate measurement of 89m was later given in the gianttrees website. Girth-wise, the White Knight is just as impressive, being 3.3m in diameter. The White Knight is also believed to be over 300 years old. Due to the presence of the White Knight, 52 hectares in the area was made a forest reserve to preserve the White Knight and other giant White Gums that reside there.

The story goes that botanists initially did not believe that the tall tree reported by the Forestry Commission was a White Gum until leaf and fruit specimens were brought before them. Likewise for me, my experience of the white gum being a average size tree of dry forest was so ingrained that I would have scarcely believed that the White Knights were White Gums until I saw the characteristic seed capsules myself.

It is not difficult to see how the first foresters who came before the presence of the giant white gums likened the trees to Knights, perhaps spotting shiny-clad armour. White has always been the colour of purity and goodness, and there is nothing quite like the sight of Brobdingnagian white boles standing in blazing contrast to a deep green forest understorey. And I am properly awed and impressed, just as the visitors before me that have come to pay their obeisance to the White Knights.

The elephantine girth of the White Knight

A rather recent trend in molecular science has been to use the technique to extort genes to reveal the history of how a plant has extended it’s geographical distribution throughout time.

I have written about how researcher James Worth used molecular techniques to pinpoint the locations (refugia) where Myrtle Beeches (Nothofagus cunninghamii) survived during the last glacial period. Just earlier this year, researchers Paul Nevill, Gerd Bossinger and Peter Ades published a paper in the Journal of Biogeography doing the same for the Mountain Ash (Eucalyptus regnans).

As in James Worth’s Myrtle Beech study, the researchers looked for variations at specific locations in the chloroplast DNA in Mountain Ash individuals distributed throughout the species natural geographical range. Different individuals may exhibit specific sequences which may differ from region to region and these are known as haplotypes.

A large amount of haplotypes found in a population an any given area would suggest that the area is a glacial refugium as we would expect a species to have persisted for longer periods of time in a refugium, thereby accumulating genetic changes. Conversely, places with low diversity of haplotypes could be construed to have been colonized after the glacial period ended, as there wouldn’t have been time enough for a high diversity of haplotypes to develop.

The results of the study showed that Mountain Ashes of the Northeast and Southeast of Tasmania has a high diversity of haplotypes, many of which were unique to the region. This suggests that the Northeast and Southeast of Tasmania harbored refugia that sheltered Mountain Ashes during the glacial period. By contrast, the central parts of Tasmania had a lower diversity of haplotypes. Another way of interpreting this was that there was fixing of haplotypes in that region, suggestive of a more recent colonization of the area following the end of the glacial period.

One consideration that remains to be addressed is the ease with which Eucalypts hybridize. E. regnans for example may hybridize with E. oliqua (Stringybark) and E. delegatensis (Gum-topped Stringybark). Hybridization may result in chloroplast sharing between species and a more comprehensive study will probably be needed to ensure that all these factors are taken into consideration.

For now it seems we are getting closer toward reading the the silent tale of survival that the ancestors of the Mountain Ashes in the Northeast and Southeast have etched in the genes of their descendants.

A single field trip up toward the Central Highlands offers plenty for a plant lover to see and do. One thing that must be done however, is to pay homage to the cider gums (Eucalyptus gunnii) of the highland areas.

This cider gum is a tree of immense significance to Tasmania’s natural history. It is aptly named the cider gum for it’s sap, which has been reported to be used by the aborigines to make a much relished fermented drink (see article). I  was way too late to experience the spring sap that allegedly drips from the tree inviting all to partake of it’s sweetness. What would I give to try that out! It would be one of the most direct means of communion with the cider gum. On this occasion however, my objective was merely to make an acquaintance with the Cider Gum in it’s natural abode.

I drove along the Highland Lakes road north of Miena hoping to catch sight of some cider gums. There are two known subspecies, both of which are endemic to Tasmania. The more common one, E. gunnii subsp. gunnii (simply referred to as the cider gum) is well distributed throughout the highland regions of the southeast, central, and western Tasmania. The other subspecies, E. gunnii subsp. divaricata is known as the Miena Cider Gum, and has a much more restricted distribution to a small area around Miena around the Central Highland lakes. It’s status as a subspecies of the commoner cider gum was only recently elucidated in a publication by Prof. Brad Potts, Dr Wendy Potts and Dr Gintaras Kantvilas in 2001. Previously, the Miena Cider Gum was known as Eucalyptus divaricata.

I practically screeched to a halt when I sighted just by the side of the road, two large and stately trees which I suspected might be the Miena Cider Gum.

I got out and scanned the surrounds. There were quite a number of dead trees in the vicinity but these two trees were different. They exuded a vibe of vitality. I studied them intently, looking out for characters that might give me an opportunity for identification.

A low hanging branch gave me access to photograph a cluster of their leaves and their capsules. The adult leaves also had a slightly pale whitish (glaucous) appearance and there was the persistence of very glaucous, rounded and oppositely arranged juvenile leaves.

Prof Pott’s paper had mentioned that the capsules of the Miena Cider Gum also tend to be more glaucous. The capsules are supposedly a slightly more sub-urned shaped compared to the more consistently bell shaped capsules of the commoner subspecies.

The combination of characters of the Miena Cider Gum seemed to match the specimen I was looking and I am happy to conclude that that was what my specimen was.

More important than the dry an technical act of nailing an subspecific identity to the tree however, was the feeling of communion. Few experiences compare to an acquaintance with trees of such haunting magnificence and presence. There is no words for it, only feelings that linger. Silence would probably make the best conveyance of this.

Tasdendro goes live!

The study of tree rings or dendrochronology is the scientific method of dating the age of trees based on the patterns of tree rings.

The topic of tree rings is close to my heart, particularly given that it is a major part of my current job scope (I work for the Forest Ecology lab in the School of Plant Science and I study the tree rings of an Australian cypress pine Callitris columellaris).

I am hence very pleased to announce the launching of tasdendro.org, a website with the intention of collating all the known information of Tasmanian dendrochronology. The web site was set up under the auspices of the Forest Ecology lab. In particular, Clay Trauernicht, a postgraduate student of the lab, has played a key role in the setup of the website.

The website is coupled with a newly set up storage facility with the purpose of being a repository for tree core material collected from Tasmania.

Given the current interest in climate change and the topic of carbon storage (see my earlier post on Sam Wood’s study), the setting up of such a facility and the Tasdendro website couldn’t have come at a more opportune time!

When it comes to plant identification guides, there are still some of the opinion that a good illustration is one of the best aids for identification. Sometimes a good illustration is even better than a photograph because photographs can have many distracting elements like shadows or noisy backgrounds etc. It is no surprise that most taxonomic publications and many old guidebooks use line drawing. The Native Trees of Tasmania authored by Jamie Kirkpatrick and illustrated by Sue Backhouse is now in it’s seventh edition, a testimonial to the endearing qualities of illustrated guides.

There’s a new book on Tasmanian wattles titled Wattles of Tasmania now out in bookshops which follows in the tradition of the illustrated field guide. The author and illustrator Marion Simmons is a well known figure among wattle enthusiasts for her illustrations and written work on Australian wattles (see Marion Simmons profile).

Wattles of Tasmania is unique in that it contains everything one needs to become a self-made expert on the wattles of Tasmania. The book is packed with detailed descriptions and illustrations of all the species of Tasmanian Acacias, including the introduced ones. The taxonomy and nomenclature is also up to date. I found out for example, that what I have known as Acacia verniciflua (Varnished Wattle) for some time now is now Acacia leprosa var. graveolens.

Definitely a valuable addition to the library any wattle connoisseur.

Classical texts tell us that the Mountain Ash (Eucalyptus regnans), one of the world’s largest flowering plants can attain an age of perhaps 350-450 years. Using dendrochronological methods and radiocarbon dating, Sam Wood from the Forest Ecology Lab has found evidence that these giants attain an age of 500 years.

Prof. David Bowman also appears in the news clip discussing the role of fire in the regeneration of the giants.

And the trees that Sam examined were probably not the oldest!

Most bushwalkers probably know of the Common Native Cherry (Exocarpos cupressiformis) as a bush food but it is still worth blogging about.

Whenever I see ripe fruit on the Common Native Cherry, I always pluck some for refreshment. While we certainly don’t NEED native tidbits to supplement our well stocked lunch boxes of sandwiches, fruits and nuts, it is a most sublime feeling to appreciate what the bush has to offer. The act of harvesting wild edible fruit, little as there may be, feels like a sort of communion. I give thanks for such opportunities.

The Common Native Cherry grows common in open eucalypt woodland. In it’s ideal state, the Common Native Cherry is a dense small dull green conical tree attaining a height of no more than 8 m. Most of the time though, a good proportion of the fruit-bearing branches are well within reach. Talk about low hanging fruit.

The branches are green, groovy and leafless, giving it the same general appearance of some native Cypress Pines (Callitris spp.). In addition, the Common Native Cherry sometimes has wooden galls as well, giving the impression that it bears cones. However, small spikes of minute yellow flowers present on the branches at most if not all times of the year will distinguish it immediately.

Also, the fruits of this tree are unmistakable. Usually only one flower out of the spike is fertilized and the fruit is really only the hard ovoid structure held on the end of a fleshy receptacle which gets more succulent and redder as the fruit ripens. In many ways these fruits resemble minute versions of the curious fruits of cashew nuts (Anacardium occidentale). The edible part is not actually the fruit but the red ripened and swollen receptacle, which has a sweet taste (See my DISCLAIMER). I don’t often see ripe ‘fruits’ on all trees in any one given locality so there must be some staggering of fruit production.

While it is not very apparent, the Common Native Cherry is actually a semi-parasitic plant which parasitises on the roots of eucalypt trees around it.

It might be surprising for some to learn that the Common Native Cherry is from the Santalaceae, the same botanical family that bears the well known sandalwood (Santalum album). Macabre is the thought that the ‘blood’ of the Common Native Cherry’s victims goes into the making of the succulent fruits we enjoy.

Sap-sucker or not, I imagine that the Common Native Cherry must have been to Tasmanian aborigines what wild blackberries are to Europeans. Wild sweet juicy fruit is good anywhere!

The weather on Monday (26 Oct 2009) was so nice and balmy today that despite having a splitting headache I chose to go for a short walk.

Having, in my absent mindedness forgotten how to get to the Knocklofty Park entrance, I settled for a short walk at the Leonard Wall – Valley Street Reserve.

The small reserve is relatively new and was erected in 2003 in memory of the well known ornithologist Leonard Ernst Wall (1921-2004).

The first impression of the place was that it is overun with weeds. Particularly prominet was the Meadow Foxtail (Alopecurus pratensis). This was the first time I’ve ever seen so much of this grass growing in one place. However, it is obvious that there have been some efforts to plant native species on the slopes of the reserve.

In all, I counted at least 32 species of weeds and 30 native species there (See checklist).

The highlight of my short walk must have been an old and imposing Blue Gum (Eucalyptus globulus) tree at the top of the reserve. It had ramified trunk right near the base and each trunk had a girth of say, over 2 meters. In the aerial photograph in the checklist page, the crown of this tree can be seen to cover a significant portion of the small reserve.

By the size alone I doubt this Blue Gum was planted. If it was it must have been planted about a century ago. I imagine the tree must be a remnant of old Hobart, and has borne silent witness to all the changes that have taken place for the past century.

What would such trees say if we could hear?