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I've been a Canberran since moving here from Adelaide on the first day of 1980. I now live in suburban Duffy with my partner Louise Maher, ABC 666 radio and on-line journalist. Among my early memories is following Sleepy Lizards (Shinglebacks) around the paddocks north of Adelaide, guarded by the faithful bull terrier. I have always been passionate about the natural world, trying to understand how it works, how the nature of Australia came to be, and sharing those understandings. My especial passions are birds, orchids and mammals. For much of my life I have been a full-time naturalist, running bush tours, writing books etc, doing consultancies, presenting a regular radio slot on local ABC, chairing a government environment advisory committee and running adult education classes. Recently I have eased back somewhat, but am still writing, teaching, doing some radio work and running overseas tours - as part of my fascination with our Gondwanan origins I've been running tours to South America for the past decade. I was awarded the Australian Plants Society Award in 2001 and the Australian Natural History Medallion in 2006, both for services to education and conservation.

Thursday, 13 April 2017

Palms; old and successful. Part 1.

Here is another in my irregular series on favourite trees (you can find the most recent one here, and work back from there). I've travelled a bit in some of the warmer parts of the world and I've found that palms can pop up just about anywhere in such places. The family arose by around 80-85 million years ago, apparently in Laurasia (the northern counterpart of Gondwana, comprising what is now Eurasia and North America) from where they spread south.

Kentia Palms Howea forsteriana Old Settlement Beach, Lord Howe Island.
By the sea in coastal forest.
Red Cabbage Palms Livistona mariae, Palm Valley, Central Australia.
In desert ranges.
Palms are flowering plants but despite their woodiness and fact that most of them are trees, they are monocots, like grasses, orchids and lilies. Their trunks differ from those of dicot trees (ie pretty much any other tree you could think of) in not having annual growth rings - unlike dicots, monocots don't produce secondary growth, ie thickening of the trunk with age by laying down new layers of cells annually from the cambial layer. (Quick revision. A 'normal' tree trunk comprises bundles of tubular vessels; the inner ones, the xylem, carry water and some nutrient up from roots to foliage - the innermost xylem tubes are dead and provide the trunk's support. The outer ones, the phloem, carry products of photosynthesis, notably sugars, down from the leaves. The cambial layer lies between them and produces annually new xylem on the inner surface and new phloem outside it.) A palm trunk is basically at full diameter below the ground, and grows only upwards.

In palms the vessels are in bundles encased in fibrous sheaths, scattered through the fibrous woody material. Towards the surface of the trunk the wood is surprisingly hard and dense, becoming softer toward the core. The effect is somewhat like that of a fibre-reinforced fishing rod, very flexible and capable of withstanding storm winds. 
This Coconut Palm on the beach at Cooktown, north Queensland, has survived the full brunt
of more than one tropical cyclone, due to its flexible trunk.
The leaves, generally at the tips of the single unbranched trunk (the exception being in climbing vine palms which may have leaves along the stem), are in one of two distinct forms.
Pinnate leaves on Alexandra Palms Archontophoenix alexandrae, Cattama Wetlands, near Cairns.
Such 'divided' leaves comprise many leaflets growing along the central leaf stem.

Palmate leaves on Queensland Fan Palm Licuala ramsayi, Daintree NP, north Queensland.
These are also compound, but the leaflets all grow from the tip of the leaf stem.
Individual flowers are fairly small and inconspicuous, but they grow in often mighty inflorescences, sprouting from within or just below the foliage.

Inflorescences of Sand Palm Livistona humilis; Litchfield NP above, and Kakadu NP below.
Some palms are wind-pollinated, but the attractiveness of Sand Palm flowers to butterflies is obvious!
Fruit may be berries (comprising a fleshy ovary with seeds embedded in the flesh) or drupes (where the fleshy ovary wall encloses a woody capsule containing seeds).
Alexandra Palms have huge bunches of berries, beloved of birds such as this
Metallic Starling Aplonis metallica, Centennial Lakes, Cairns.

Coconuts Cocos nucifer, Sabah, Malaysia.
These are drupes (the outer fleshy layer soon dries out) and are superbly adapted to long-distance
ocean dispersal, by which they have spread throughout the Pacific.
Coconuts are not the only palm of major economic significance to humans. Date Palms Phoenix dactylifera have been cultivated in the Middle East for at least 7,500 years for their fruit. Sago Palms Metroxylon sagu have long been harvested in south-east Asia for their starchy pith, which is a carbohydrate supply for the production of the palm's massive fruit crop, produced after some 15 years. The harvesters can't afford to let the sago be used for the purpose for which it evolved so the tree is cut down as soon at it flowers, and the trunk cut open to extract up to 300kg of sago! (I grew up with sago pudding, and would be very happy to leave it to the palm, but that's just me...)
Sago Palms, Klias River, Sabah. I think these are wild plants.
Oil Palms Elaeis guineensis, originally from West Africa, have now been spread far and infamously across the tropics, beginning when the Dutch took it to Java in the 1840s. Vast tracts of rainforest are daily being cleared for palm planting in Indonesia, Malaysia, South America and Africa.
Oil Palms west of Sepilok, Sabah.
No wildlife corridors or refuge forest blocks here.
Oil Palms crowding to the Mana River, which marks the boundary of Korup NP in western Cameroon.
 Palms feature widely in botanic gardens.
Darwin Botanic Gardens.

Emerald Botanic Gardens, central Queensland, which makes a special feature of its palm collection.
And of course humans (and Metallic Starlings) are not the only animals to appreciate palms as food or habitat. In Cape York Peninsula and New Guinea the huge Palm Cockatoo Probosciger aterrimus is in part associated with palm swamps, but there may also be a confusion here with unrelated Pandanus spp. too, the seeds of which it certainly also eats.
Palm Tanagers Tanagra palmarum (here in northern Peru) are certainly associated with palms (an observation
reinforced in both its scientific and Spanish names) but not exclusively.
They are found throughout the northern half of lowland South America.
The Palm-nut Vulture Gypohierax angolensis (here in Entebbe Botanic Gardens, Uganda)
is most atypical in eating mostly palm fruit, especially of Oil Palms.
And of course palms are excellent places just to hang around in!
Utilising the palms at Blanquillo clay lick, southern Peru, either while waiting to descend to the clay
(Red and Green Macaws Ara chloropterus, above),
or waiting for unwary prey (Zone-tailed Hawk Buteo albonotatus, below).
 

Brown-throated Sloth Bradypus variegatus in palm (you might need to click on the picture,
it was a long way off!), Yasuní National Park, Ecuador.
I had intended to conclude here with a walk-through of a series of palm species from different parts of the world, but that would make this just too long, so I'll wrap it up next time. I hope you'll be back for it.
Moon through palm fronds, Darwin.
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3 comments:

Susan said...

You missed a trick not posting this 4 days earlier :-) And as you might have seen on my FB, Box Buxus sempervirens can also be considered to be a palm.

I feel sorry for that poor vegetarian vulture -- embarrassing!

Ian Fraser said...

Ah, i was hoping that no-one would think that was what prompted me! I did see your comment on that - curious. Lou tells me that when she was a child on the south coast, churches on that day were filled with real palm fronds, freshly cut from the bush - hmm...
As for the Palm Vulture - I know, poor things! Imagine what their chicks must go through at school!

Flabmeister said...

Its good to see Emerald Botanic Gardens get a plug!

WRT Coconuts are the ones in Africa the same species? If so, were they spread by humans or did they float there too? The found wreckage of MH370 suggests floating things could travel in that direction.