Posts Tagged ‘Desert’

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A thorny issue

June 23, 2010

Related to the last post, it is amazing how many kinds of thorns, bristles, hooks, spikes, prickers, sharp edges, pointed leaves, pointed branches, as well as claws, scales, fangs, spines, and hooves you find in the Sonoran desert, and generally in the arid western USA.

In a contrary kind of way, almost all of these indicate that there’s probably a nice, juicy, succulent hunk of flesh nearby.

But you’ll get hurt if you try to get at it!

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Why does the cactus look like that?

June 16, 2010

The first thing you notice about a cactus is generally the spines. Some have short, nasty little almost invisible fishhooks, some inches-long needles. Then there’s the form of the plant. Most cacti are plump, rounded, often stubby. They tend to be grayish-green in color. And they usually do not have obvious leaves.

Why?

Whenever you come across questions like this, think about the ecosystem where the organism lives. Cacti live in dry climates with a lot of sun, and few other plants, especially leafy ones.

So keeping cool is an issue. A light neutral color does not absorb a huge amount of the sun’s heat. There are very few plants with dark bark, or skins, or leaves in the desert.

Retaining moisture is perhaps the most important issue for a desert plant. The blunt, compact shape of cacti, their thick skins, and lack of leaves are all moisture-conserving features.

And lastly, toothsome, moist leaves would attract all kinds of herbivores. So the lack of leaves discourages plant-eaters, and the big spines and tough hide protect any soft, moist tissue a cactus does have.

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Signs of the Elders

August 12, 2008

Striking petroglyphs are found carved into the dense basalt rocks of Hedgepeth Hills in Glendale, Arizona.  

Rock art, Hedgepeth hills

Rock art, Hedgepeth hills

Over thousands of years, people traveled from nearby and far away to gather the dense basaltic rock they could use for food-grinding stones and other tools. And while they were there, they carved pictures in the weathered surface of the rocks.

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Strangeness in the desert soil: Caliche

May 4, 2008

Here’s one way to encounter caliche. Some friends pulled over one night in the New Mexico desert and camped in their truck. Happily for the desert, there was rain in the night. Unhappily for the humans, the next morning they found themselves surrounded by a huge pond of extremely slippery ankle-deep goo. Only after a long dirty struggle were they able to push their truck back onto the road. Caliche is what allowed a mudbath to form in the middle of the desert.

Another way to discover caliche is to dig a hole almost anywhere in the desert. Soon, inches or feet deep, you’ll hit a layer of what seems to be cement, even in places where you know there’s never been any construction.

What you’ve found is caliche, a white layer of soil, rich in calcium carbonate, clay, and other minerals that have been driven down into the ground by the hard infrequent desert rains, until the minerals form an often impervious layer of soil, also known as hardpan.

Wikipedia can tell you more.

When rain falls on an area with dense caliche, rather than sinking into the soil, the water runs off, if it can find a channel, sometimes causing the surprising desert flash floods, because so little water is absorbed into the ground. Or it puddles up, creating a sea of mud.

Digging a simple hole can require a pickaxe. Since the calcium carbonate can be alkaline enough to harm plant roots, planting in an area with caliche means that you may have to add conditioners as well as nutrients to the soil– and make sure there is drainage, even if that means digging a drainage hole through the caliche.

The Arizona Master Gardener, a great source of information, gives details of how to deal with it.

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Dry rain

April 3, 2008

Even the simplest things about the desert can be strange.

Rain, for instance.

When you need rain the most, where you need it most, seems to be the place you find it least.

And sometimes it comes unusually close, but never arrives.

An eerie and frustrating example is the dry rain that can occur in the desert west, called “virga.”

virga

In the distance, you will see the clouds form, then curtains of rain finally begin to fall. But the rain disappears in the middle of the sky, between cloud and land.

Leaving you high and dry. Or low and dry.

Virga actually does happen in other regions, and can involve snow as well as rain.

It’s a sight to see, watching the rain come down, but never land on land.

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Spring begins in the Sonoran Desert

March 20, 2008

Desert Wildflowers

Tour images of the desert in spring.
Early spring in Sonoran Desert mountains.

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Hello arid world!

February 18, 2008

Welcome to the DesertMysteries blog