About Me

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Canberra-based naturalist, conservationist, educator since 1980. I’m passionate about the natural world (especially the southern hemisphere), and trying to understand it and to share such understandings. To that aim I’ve written several books (most recently 'Birds in Their Habitats' and 'Australian Bird Names; origins and meanings'), run tours all over Australia, and for the last decade to South America, done a lot of ABC radio work, chaired a government environmental advisory committee and taught many adult education classes – and of course presented this blog, since 2012. I am the recipient of the Australian Natural History Medallion, the Australian Plants Award and most recently a Medal of the Order of Australia for ‘services to conservation and the environment’. I live happily in suburban Duffy with my partner Louise surrounded by a dense native garden and lots of birds.

Tuesday, 28 May 2013

Desert Oaks; beautiful desert giants

If I were to ask you to nominate Australia's most photographed tree, I wonder what you'd suggest? Perhaps the Cazneaux Tree (a River Red Gum in the southern Flinders Ranges, made famous by Harold Cazneaux's 1937 photograph The Spirit of Endurance, and rephotographed numerous times since)? Or maybe the Curtain Fig at Yungaburra on the Atherton Tablelands of north Queensland, a massive Strangler Fig visited by every tourist bus in the area, and there are many of them!
A segment of the Curtain Fig Ficus virens, Yungaburra, a massive tree.
You'll probably have other suggestions, but my bet is on a tree that most people don't even realise they're photographing. 

Every day hundreds of people gather in central Australia at set areas to watch the sun going down on mighty Uluru, previously known for a while to English speakers as Ayer's Rock. The viewing areas are extensive, so there's no real sense of crowding, and the tour buses use a different area from private cars. A couple of weeks ago we joined them. Here is a selection of photos, taken over a 40 minute period from before to after sunset - just five of 18 that I ended up keeping.

So, if every one of the people there on just that one evening took that many pictures - and many would have taken far more - that's thousands of pictures a day, and it's not peak visiting season yet.

And, you see the tree? I suspect that most photographers don't even really notice it. Here it is again closer up, the shots taken just 10 minutes apart - the light changes are truly stunning.

This tree - my nomination for the title of Most Photographed Tree in Australia - is a Desert Oak, Allocasuarina decaisneana. It is my favourite tree species of the Australian central-western deserts, limited to an area of eastern Western Australia, south-western Northern Territory and a tiny bit of north-western South Australia. They are the only casuarinas in central Australia, most of the family being near-coastal in distribution. (Some time ago the genus Casuarina was controversially split into two, creating the genus Allocasuarina based on minor differences.)

It has adapted to life in the sandy dune country, where spiny spinifexes (hummock grasses of the genus Triodia) dominate the understorey.
Desert Oaks, Chambers Pillar, Northern Territory.
Unlike many other casuarinas, adult Desert Oaks are largely fireproof, recovering from epicormic shoots in the crown; at the same time seedlings sprout in the wake of the fire.

Stand of Desert Oaks south of Alice Springs.
In the photo above the beautiful adult trees appear to be growing above another bottle-brush-shaped species, but this is an illusion. The seedlings don't resemble the adult trees at all.
Desert Oak seedlings, Uluru - Kata Tjuta National Park.
Close to the ground the young trees are a spiky tangle, resisting grazing. The crown doesn't form for years; during this time the emphasis is on sending a tap root deep into the soil. When it strikes ground water many metres down, the crown finally develops and the side branches wither. 

The timber is hard and heavy and was used by the desert peoples for tools and weapons but, perhaps fortunately, it doesn't hold its shape after cutting and drying, so wasn't harvested by European settlers.

The species name honours a Belgian botanist, Joseph Decaisne, who spent his working life - much of the 19th century - working in Paris, especially at the Muséum d'Histoire Naturelle, where he began as an apprentice gardener. He never visited Australia, though he described some species from French expeditions returning from there. He rose to become regarded as the leading French botanist of his time, though it is often said that it was his studies into fruit varieties which were his main achievement. It was the great German-Australian botanist Ferdinand von Mueller who honoured Decaisne with the name.

There are separate male and female flowers but, unlike in many casuarinas, they occur on the same tree. The seed cones are magnificent, and can be up to 10cm long.
Desert Oak seed cones.
One day I'll do a posting on casuarinas in general, but for today I wanted to focus on this one beautiful species. 

Meantime, do you have another nomination for most-photographed tree? I'd love to hear.

There will be more postings inspired by the wonderful arid lands we've just visited; thanks for waiting for me!



Susan said...

I've got photos of this Desert Oak (with some big rock in the background, just like yours...) and several of the young ones, which amused me as they look just like feather dusters.

I also noted the sign near the rock requesting that people do not pick themselves fly whisks from the Allocasurinas, as if everyone did it they'd be denuded in no time.

Ian Fraser said...

Hi there - that was quick! The sign's still there (and elsewhere in the park) but sadly not everyone seems able to read it...

Flabmeister said...

Welcome back. I was thinking it was about time!


awaywithwords said...
This comment has been removed by the author.
awaywithwords said...

I like the idea that the Desert Oak is the most photographed tree in Australia, and enjoyed the reasoning that led you to that conclusion.
Some years ago, I saw trees near the Rock that seemed more green than grey, and someone told me they were Desert Oaks. I was trying to figure how they could be so green, when everything else is dry, and read (where?) that their roots grow down to the water table.
I wonder if you can confirm these observations.

Ian Fraser said...

Hello Stephen and thanks for visiting. Yes, the straggly immature trees look that way because they're putting all their energy in putting roots down to the water table; when they get there they spread out and look more like 'real' trees.

bongopete said...

I love the Allocasurinas and have grew a few thousand of them at Two Wells school nursery .
Locally here we have stricta and glauca species .Im amazed by the small cones on some and almost large marble size cones on trees at lower York peninsula .
Ive harvested lots of seed and am trying direct seeding around the district .I wanted the cones for jewellery making and felt I really need to plant the seeds so ive past lots on to trees for life and direct seeded lots.Though im yet to see much results from my seeding .
I would love to find someone who maybe harvesting Desert Oak seeds for planting so I could acquire some large cones .
When cut into slices they have a nice starr pattern in them wnich is beaut for pendants
Any ideas Ian where or who I might get some cones from .Thanks Peter

Nellie Fitzferal said...

I'm trying to find out how long a desert oak could live for...a park ranger pointed out a tree he believed was around 900 years old...up along the Tanami track..could this be possible?

Ian Fraser said...

Hello Nellie. I think it's possible, but I'd certainly need some proof before I accepted such an extraordinary proposition. For instance there would need to have been no major fires in all that time, which would be pretty unlikely. Did the ranger indicate any basis for his belief beyond an opinion? Intriguing stuff, thanks for raising it.

Nellie Fitzferal said...

Dear Ian
thanks for your reply...the Ranger was using the girth of the tree as his estimate. I wish I'd phtographed it for your perusual.

dum pa said...

there is a desert oak on curtain springs station that has been carbon dated at nearly 500 years old

Nellie Fitzferal said...

well ... not quite 900 but well on the way ! Gives me hope that his belief was not so far fetched.

Scott Davidson said...

These are some great shots. I wonder how old the oldest tree in Australia is. It is not something that I have given much thought.