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A Day in the Life of a Eucalypt

What must it be like to live life as a eucalypt? Before studying plants, I always thought that it must be quite a relaxing life, planted solidly and soaking up the sunshine. Now, after learning more about what is involved in a plant’s life, I know that for many trees, and in particular our eucalypts, daily life can be quite stressful. I recently read the book The Hidden Life of Trees by Peter Wohlleben, which highlighted many of the trials that trees are constantly facing. These included such hardships as being under threat from herbivorous animals, their competition against neighbouring tree species, and the fight against the slow, yet insistent fungi that can cause a tree to rot.

Whilst reading this book, I thought keenly about the hidden behaviours of our own eucalypts in Australia. There is so much that is not fully known about these wonderful trees and little shared about their experiences. This National Eucalypt Day, I would like you to imagine what it must be like to live a day as a eucalypt tree.

It is early morning on a summer’s day and the first gleam of light is about to peak over the horizon. You feel a light breeze ruffle your leaves just as the first beams start to hit your upper branches. You slowly angle your leaves to capture as many of the sun’s shafts as you can and start the day’s conversion of sunlight into sugars, releasing the oxygen created as a by-product.

You pull water up your trunk from your roots and feel it extend through your branches and into your leaves. This is something you do all day and for many eucalypts in summer, it can be quite a struggle when there’s little water around. You make the most of the early sunlight whilst the temperature isn’t too hot and reduce the amount of water you lose from your leaves.

As the day warms up, you start to pull more water up to your crown. It evaporates off your leaves, keeping you cool for a while, but eventually the temperature, particularly in the afternoon, gets too much for you. You close your leaves to the surrounding environment and slowly angle them away from the direct sun. You wait out the hottest time, storing your sugar reserves for later.

As the sun goes down, you open your leaves again to the air around and start letting oxygen and carbon dioxide flow. You use your evening of free breathing to slowly fuel the growth of more leaves, your trunk, branches, roots, flowers – everything. You also use it to produce the oils in your leaves that make you smell so wonderful, and taste so terrible to any interested animals.

You continue the slow movement of materials through the night into the next day where it starts all over again. As a eucalypt tree, you are rarely hungry, nearly always thirsty, and can only breathe when it’s not too hot. You continually store as much energy as possible so that there are always reserves should any unforeseen circumstances come to pass.

The above narration captures a tranquil day in a eucalypt’s life. But what happens when there are strong winds, an insect boom, flooding rain, or a bushfire?

Our trees survive through extraordinary conditions and display incredible behaviours in response to the daily and long-term changes in their environment. Unfortunately, most of these are hidden from everyday view or are on timescales that go unnoticed to the untrained eye. I am endeavouring to appreciate these behaviours in my local eucalypts and am on the look-out for secrets I may have previously been ignorant to. Next time you wander past a eucalypt, or sit under its most welcome shade on a hot day, spare a thought for its efforts and see if you can notice any of its more unobserved habits.


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Sarah Bond

Sarah is a botanist who works at a local indigenous plant nursery in Melbourne. She is interested in engaging the public with the conservation of local flora and fauna.

You can find her on Twitter at @SarahBBond


Hollows as Homes

This is a guest post by Dr Adrian Davis, Hollows as Homes coordinator and Research Associate at the University of Sydney. 

In urban and agricultural areas large, hollow-bearing trees are in decline, but many species of animal rely on them. In Victoria, hollow-using species include at least 31 mammals, 60 birds, 38 reptiles, 15 frogs and many insects (such as bees). Of these, at least 33 species are listed as threatened with extinction. This is why the ‘loss of hollow-bearing trees’ has been listed as a key threatening process nationally.  Hollows as Homes is a citizen science program asking you to report hollows in your local area, and the wildlife using the hollows – but more on that later.

Farms and agricultural areas are often characterised by large, old, isolated trees, or small clusters of trees. These clusters often act as ‘stepping stones’ and can be vital in linking up other small patches of trees on adjacent farms, allowing wildlife to more easily move throughout the landscape. Even a single standing tree with a hollow can provide valuable habitat and provide a nest or roost for an animal that would otherwise not be able to live on that farm. A good example of an animal that depends on clusters of trees on farms is the superb parrot, listed as vulnerable to extinction, which uses paddock trees for nesting, feeding, perching and protection. Retaining existing hollow-bearing paddock trees, ensuring that younger paddock trees are maintained so that they form hollows, and gaining a greater understanding of how wildlife use paddock trees is vital to maintaining wildlife in our agricultural areas.

Cut in hollow for small bird. Photo: John Martin.

Cut in hollow for small bird. Photo: John Martin.

 It’s not just on our farms that hollow-bearing trees play an important role, but within the bush and urban regions as well. Large, old trees - those most likely to contain hollows - are rare in urban areas. If you’re lucky, your local park or street may contain one of these trees; a grandparent of the bush. If you’re even luckier, this tree will contain hollows, although this isn’t guaranteed. In general, our urban areas contain young trees; however, it is likely that many of the species planted will never form hollows, or be allowed to form hollows for reasons of public safety (in case the tree falls). Urban bushland typically contains only half the number of hollows that are present in bushland outside metropolitan areas, and there are fewer hollows in urban parks and streets.

Importantly, not all hollows are the same, and some species prefer particular types of hollows (for example, a deep hollow, a hollow with a small entrance, or a ‘pipe’ style hollow). When we lose the hollow-bearing trees, we also reduce the number of different types of hollows, which can result in competition between wildlife, with some species losing out to more dominant species, such as the rainbow lorikeet taking a hollow from the eastern rosella. It has been shown that there are more aggressive interactions at hollows in urban areas than there are in natural bushland.

Hollows as Homes aims to increase the knowledge and understanding that we have about tree hollows: the distribution of tree hollows, the types of hollows available and how wildlife use tree hollows, including nest boxes and cut-in hollows. In areas lacking natural tree hollows, supplementary hollows, in the form of nest boxes or cut-in hollows, are often provided. However, the effectiveness of these alternatives is still not entirely understood. To help us understand more about how wildlife use tree hollows, nest boxes and cut-in hollows, we are asking people join in the Hollows as Homes program.

Choose a tree in your garden, street, park, bush or paddock that has a hollow or a nest box and report it through the website (this also works as a web-app on your phone). You can provide details about the tree and hollow, such as tree height and the direction the hollow is facing. Ideally, the hollow is in a location that you periodically encounter, such as while walking the dog or sitting in your garden. This provides occasional opportunities for you to observe wildlife using the hollow. If you see that any animals or insects are using the hollow, you can add these observations to your original report of the hollow through the website.

Galah at nest in tree hollow. Photo: J Turbill (OEH)

Galah at nest in tree hollow. Photo: J Turbill (OEH)

In addition, people can participate as a group, designating an area that they regularly visit and collectively assessing the trees for hollows and adding wildlife observations. The group option is ideal for bushcare sites, landcare programs, parks, schools, golf clubs, community gardens, and many more. An unlimited number of people can participate in a group, and, importantly, anyone who is part of the group is able to both view and add wildlife sightings to any of the reported tree hollows or nest boxes within the group boundary.

The information reported through Hollows as Homes will be accessible to the public, especially to land managers. Ideally, this information will inform conservation planning to conserve habitat trees and the provision of supplementary habitat, as well as our understanding of exactly which species are inhabiting our own backyards.

For information on how you can be a part of this program, visit the Hollows as Homes website or Facebook page. Alternatively, you can email Dr Adrian Davis for more information.

Hollows as Homes is a collaborative project between the University of Sydney, the Royal Botanic Garden Sydney and the Australian Museum. It is supported by funding from the Australian Government.

Cover image by Simone Cottrell. 

Six Things You Should Know About Eucalypts

This National Eucalypt Day we are celebrating all the amazing things about our beautiful eucs! So here are some little-known facts about one of Australia's most iconic plant species.

The tallest flowering plant in the world is a Eucalypt.

Given the opportunity, mountain ash (Eucalyptus regnans) will often grow to heights of around 80 metres. However, the tallest mountain ash, know as ‘Centurion’, stands just over 99 metres tall in Tasmania.

Mountain ash is the tallest flowering plant in the world.  Image:  https://adayintheleaf.com

Mountain ash is the tallest flowering plant in the world. Image: https://adayintheleaf.com

Eucalyptus trees can sequester gold.

In 2003, geoscientists discovered a stand of eucalyptus trees that had tiny portions of gold (about one-fifth of the diameter of a human hair) present in their leaves. The eucalypts were able to absorb the gold from the soil around their roots because they were growing directly above a gold deposit.

Eucalypts give the Blue Mountains their name.

The vegetation in the Blue Mountains is dominated by eucalypts, which release volatile oils called terpenoids into the air. These tiny droplets of oil scatter light in a way that causes the mountains to appear blue. You can see the oil glands in a eucalyptus leaf by holding it up to the sun and looking for white and yellowish spots.

The Blue Mountains owe their name - and colour! - to the eucalypts that dominate the landscape.  Image: Adam J.W.C. via Wikimedia Commons.

The Blue Mountains owe their name - and colour! - to the eucalypts that dominate the landscape. Image: Adam J.W.C. via Wikimedia Commons.

Eucalypt, eucalyptus and gum tree are not interchangeable labels.

The word ‘eucalyptus’ refers to a single genus of trees. The word ‘eucalypt’ refers to a group of species that belong to multiple genera, including Eucalyptus, Corymbia and Angophora. The term ‘gum tree’ refers to some species of eucalypts that exude a sticky, tannin-like substance called kino, more commonly known as gum. This means that a gum tree is not always a Eucalyptus tree, that a Eucalyptus tree is not always a gum tree, and that a eucalypt can be a gum tree, a Eucalyptus tree, or both. Confused yet?

Eucalypt leaves don’t make koalas drunk.

The notion that koalas are constantly in a state of drunkenness due to the toxicity of eucalypt leaves is a common misconception. In reality, eucalypt leaves contain so little energy that koalas must eat an enormous amount of them (up to one kilogram a day). Furthermore, koalas must sleep for up to 22 hours a day in order to conserve the little energy that they do obtain from their diet.

Despite popular opinion, eucalyptus leaves do not make koalas 'drunk'.  Image: Rennett Stowe via Wikimedia Commons

Despite popular opinion, eucalyptus leaves do not make koalas 'drunk'. Image: Rennett Stowe via Wikimedia Commons

 

For all the fun facts there are to learn about eucalypts, one of the best things about them is their iconic symbolism throughout Australian culture – let’s celebrate how lucky we are to have such unique and beautiful trees growing amongst us. Happy National Eucalypt Day!


Emma Walsh is a science graduate who enjoys sharing her love of nature with others. In the past, she has worked as a wildlife presenter, and enjoys teaching children about our native wildlife and its conservation. Her other interests include gardening and bushwalking.

 


Banner image courtesy of Peter Woodard via Wikipedia.

Species of the Month: November

Garden Skink (Lampropholis guichenoti)

Amongst the leaf litter lies an impressive creature; sleek and scaled, agile and alert, a formidable predator — although the latter is only of concern to small invertebrates! Measuring a mere nine centimetres, in length the Garden Skink (Lampropholis guichenoti) is possibly one of the most common skink species found within Victoria and most certainly within suburbia.

They are an attractive slender skink often with a copper to brown-grey upper body, a dark brown and a pale stripe running from head to tail along the sides of their body, and a cream coloured underbelly. The species may be found throughout most of the state, with the exception of the semi-arid regions to the north and west. The species occupies a range of tree-filled habitats; however, they have also become accustomed to modified human environments and may be found happily living within backyards amongst the suburbs of Melbourne.

Given its diminutive size and secretive behaviour, it is perhaps not surprising that this species is often overlooked. It is quite conceivable that many Melburnians may be cohabitating with Garden Skinks without realising. Nevertheless, the little guys play an important role in maintaining the ecological balance of natural systems, ensuring that populations of small invertebrates — which make up the bulk of their diet — are kept in check. This is particularly helpful if you happen to grow your own veggies, as the small skinks can aid in mitigating the negative effects of many terrestrial insect pests.

It doesn’t take much effort to employ the services of the Garden Skink either; simply by providing mulch for them to forage in or some rocks or logs for basking, you might be able to encourage this humble garden inhabitant to visit your backyard (although it is also important to ensure that cats and dogs that may harm Garden Skinks are kept at bay, as well as refraining from pesticide use). They are also a very interesting species to observe, particularly at this time of year. If one sits still and quiet in Garden Skink habitat, they are likely to be rewarded with an insight into the small reptile’s world. Up to a dozen or more may emerge from the leaf litter within a few metres of the observer where at first there appeared to be none. This is because Garden Skinks tend not to be territorial, instead favouring to spend energy foraging rather than expending energy on patrolling and chasing away intruders. Having said this, it is not uncommon to see fights erupt during breeding season — which is occurring at present — in which one individual will latch onto another’s torso and tumble about until its grip loosens. The reasoning for these disputes is not particularly well understood, but it is thought that it probably relates to hierarchical dominance and associated mating rights. If you sit still enough they may even come right up to you, but just remember to refrain from handling them, as they have a tendency to ‘drop’ their tail in high stress situations, which is not ideal as it requires a lot of energy for another to grow back.

So on warm days, keep an eye out for this remarkable little Aussie who may be calling your backyard home. Alternatively, if they do not appear to be present, perhaps consider making some of the small changes discussed to entice them into your garden.

                                                                                                                         Author: Nathan Gregory

 

Mountain Ash (Eucalyptus regnans)

 

The tallest flowering plant on the planet, Mountain Ash is a species that towers over its neighbours. With the botanical name of Eucalyptus regnans, this species is a member of the genus that dominates the tree flora of Australia. There are over 700 Eucalyptus species, with less than ten species occurring exclusively outside Australia.

Trees of this species can reach up to 100m tall, with anecdotal evidence suggesting that some trees can grow even taller. Mature trees can measure as much as 15m around the base. Mountain Ash grow tall and straight, often with branches present only beyond 30m above the ground. They have fibrous, brown-grey bark for the first 15m above the ground, beyond which the bark peels away in ribbons to reveal the pale, smooth bark underneath. If undisturbed, Mountain Ash can live for up to 500 years.

Mountain Ash usually grow in deep soils and are found in mountainous areas with high levels of precipitation. This means that Mountain Ash are usually found in cool temperate rainforests and wet sclerophyll forests. Mountain Ash forests can be found in the Dandenong Ranges, Strzelecki State Forest, Walhalla, and in the Otways.

Mountain Ash is unusual compared to many other eucalypts because it has evolved to survive in wetter environments. They produce up to three times the amount of leaf litter than other species. In addition, Mountain Ash possess no insulating bark and no lignotuber, which are both adaptations to minimise damage caused by fire. The excess leaf litter, the stringy nature of the bark and the oily leaves, in addition to the lack of insulating bark and lignotuber make Mountain Ash fire sensitive. Mountain Ash don’t shoot from epicormic buds after a fire, instead the release huge quantities of seeds, which fall to the ground and germinate in the ash-ridden soil below. This species flowers profusely between December and May.

Mountain Ash forests are environmentally significant for a number of reasons. They provide habitat for many species of our native fauna, most notably the Wedge-tailed Eagle (Aquila audax) and the Leadbeater’s Possum (Gymnobelideus leadbeateri). Old-growth mountain ash forests are most significant in this respect because mature trees develop tree hollows, which are essential to many species of mammals and birds that require hollows for nesting.

Mountain Ash is also economically important. It is a hardwood timber and is used extensively as a source of timber for flooring, furniture, and other construction purposes. In the twentieth century it was used in the production of newsprint. Mountain Ash is favoured in the logging industry in part due to its fast growth rate: individuals of this species can grow up to one meter a year.

As you would expect, the main threat to Mountain Ash forests is logging. Although Mountain Ash are not threatened as a species, old growth Mountain Ash forests only exist in small pockets due to extensive logging. As mentioned earlier, the complete loss of these old growth forests would have significant implications for many of our native faunal species. These ancient forest giants are an iconic and essential component of our cool temperate rainforests and wet sclerophyll forests. And given their lengthy lifespan, the history that our remaining giants have experienced is awe-inspiring!

Author: Emma Walsh