Kosciuszko National Park #2; to tree or not to tree?

In my last posting I talked a bit about this significant alpine and montane park, but I couldn't do it justice in one entry, so here's a bit more, specifically on trees - where and why they aren't, and a few that are! The alpine zone, ecologically, is that area above the tree line, where the vegetation comprises only shrubs and herbs. 

Granite-strewn alpine zone, Kosciuszko National Park.

It is a phenomenon of mountain landscapes everywhere.

El Cajas National Park, Ecuador; here in the tropics the tree-line is close to 4000masl.
The habitat is known here as paramo.

Andes north of Cusco, Peru. Again the altitude is 4000masl, but here we can see the trees pushing higher up the mountains in the shelter of gullies. Locally this is called puna.

Torres del Paine National Park, Chilean Patagonia.
At 51 degrees south, the foreground is less than 300 metres above sea level.

It can look a bit bleak at first glance, but the beauty is both in the huge spaciousness of it, and in the detail of life at smaller scale. The alpine zone is defined throughout the world, as we approach the poles and increase in altitude, by the point at which the mean temperature of the warmest month is less than 10 degrees C. Here there is simply not enough available solar energy to build and maintain the massive trunks and supporting root systems that define a tree. In Kosciuszko this occurs at about the 1800 metres above sea level (masl) mark, but it changes with local conditions; in sheltered situations it can be as high as 2000masl. As we'd expect it gets higher at lower latitudes, and falls towards sea-level closer to the poles, as illustrated above.

In Australia the true alpine zone comprises around 0.01% of the land surface, and most of that is in Tasmania. It is a relic of the glacial times, most recently between approximately 25,000 and 10,000 years ago, when cold windy treeless steppes covered much of south-eastern Australia. Now the habitat and its plants and animals survive only on a few high isolated mountain islands.

The actual tree-line can be quite dramatic.

Tree line at around 1850masl, Kosciuszko NP.

Tree line at 1000masl, near Puerto Natales, southern Chile.

Lower down of course there are trees, with the wonderful Snow Gums Eucalyptus pauciflora being the only ones capable of surviving up to the tree line. Here are a few trees that demanded to be admired and recorded on our weekend visit.

Old Snow Gums, above and below, Charlottes Pass. Here at 1850masl trees are at their limits of growth and
they survive because the massive granite boulders provide a heat sink. Nonetheless they probably
only grow for a few weeks a year, and these are hundreds of years old.

 

Black Sallee E. stellulata in the rain.
The name comes from an old English word for willow, and was applied because they often grow in
boggy and frosty situations. Normally the trunk is a beautiful smooth olive-copper colour, but the bark
turns red just before dropping off.

Candlebark Gum E. rubra.
The common name is based on the observation that in a fire, burning bark from this gum can be
hurled hundreds of metres ahead of the fire front. For most of the year the trunk is white, but the old bark before being
shed turns dramatically red, orange or pink.

I still want to show some of the relatively few flowers and fewer animals that we saw - next time.

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