9/09/2008

A word about ecotones in the Klein Karoo

OK I have never pretended to be a biologist in spite of a growing fixation on succulents, but there are a few concepts from biology that just seem REALLY IMPORTANT and stuck with me somehow.

The first is the "ecotone" - basically the line marking the edge of the area where a species is successfully living (actual definition is more systemic) - so maybe i don't know the right term but I'm trying to say, the edge of the world for a particular species.

For example, anybody ever driven the Extraterrestrial Highway? Otherwise known as NV state route 375? It was laid out to skirt the Joshua tree ecotone - literally - on one side (south) of the highway there is a semi-geometric grid of Joshua Trees as far as the eye can see. On the other side.... none.

Why do I like this idea so much? It's pleasantly mathematical - as in calculus plus binary - somehow asymptotic to one, then zero. It has a pleasing physics sensation like quantum mechanics - can't see the line when you're looking at it? And in a geological sense - to which it is often correlated, any way - it reminds me of the brittle-ductile transition. A hard and distinct theoretical boundary - but more often than not, shifted or curved by strain rate, temperature, moisture, other mysterious factors.... easy to describe in the abstract, hard to pinpoint in the field. LOVE IT LOVE IT LOVE IT***.

This absolutely beautiful, Georgia-OKeefeish, [absolutely cuter than any foram] pink Aloe plant reminded me of the ECOTONE concept. Succulent people - please name it ??? This beauty and her blushing sisters were found on one hill, in one mapping area, facing one way, on one formation. Literally about 50m3 of real estate, bounded by changes in slope, strike or lithology. Beyond that - another subspecies of different colour, size or shape. To a girl from the California Chaparal this explodes my little mind. Even the plants here are on geologic time.... and the geology? on astronomic time I think. Billions instead of millions. I know I left nothing for scale but that aloe is about a meter across.


Two formations down section - we found this little beast. He is in the lower Prince Albert siltstones, which are pink. OK this section is often madly folded and thickened but the stratigraphic thickness is about 10m. Maybe 15m. Above that: Dark brown siltstones and shales. Below: green glaciomarine diamictites. Literally this guy crosses geologic boundaries and his whole life plan for camoflage is over.
I'm desperately sorry I don't have a photo, but THERE IS A DARK BROWN ONE EXACTLY LIKE HIM IN THE NEXT UNIT UPSECTION. again, a perfect match to the chippy opally silty rocks.


*** You know what i got a lot of crap for recently? "ILOVEITILOVEITSOMUCH".
Turns out this is just more evidence that Americans are flakey. but you know what? IDO FRICKIN LOVE IT SO MUCH. It's that great to be here and see these things. No time for post-colonial understatement.

3 comments:

Garry Hayes said...

I dunno, instead of following the edge of the Joshua Tree range have you considered that the aliens only own one side of the road, and harvest only the trees growing on their side? It's a neat highway for the fact that Rachel is the only settlement on the entire route. I drove it all late one night and Rachel looked like a metropolis in the darkness. No UFO's though, I was kinda disappointed.

Erik said...

Have you read "The Beak of the Finch" by Jonathan Weiner? It's a non-technical (I understood everything in it and I'm an engineer) but very interesting look at how living things can evolve in response to surprisingly small or fast changes in their environment. And it's not just handwaving either; it's all backed up by actual measurements and observations.

Julie said...

Your succulent looks like Aloe striata, or Coral Aloe to me. It sure is beautiful.