Tuesday, January 17, 2012

Arizona Trivia Tuesday - Mountains and Deserts and Trees, Oh My! (Part II - Deserts)

According to the Arizona Fish and Game Department, there are 21 deserts in the world, and parts of 4 of them can be found in Arizona -- all four of the major deserts found in the continental United States.

Here is a map that shows the approximate boundaries of the four deserts with portions in Arizona:

Each of these deserts is slightly different in character.

The Sonoran Desert is probably the one most people think of when (if?) they think of an Arizona desert. It is the green one on the map above, and is in southwestern and central Arizona, as well as Southeastern California and its namesake, the State of Sonora in Mexico.

The Sonoran desert is one of the wettest deserts in North America and averages from 5 to 17 inches of rain per year, depending on where you are and varying from year to year. For example, the Phoenix area averages about 8 inches per year. Most of the rain falls during the summer monsoon season (about a month of intermittent intense but short storms) and the winter "rainy" season (gentler, longer lasting but still intermittent rainy spells).

It is also the largest of the desert areas in Arizona, surrounding cities you've probably heard of like Phoenix, Tucson, and Yuma, and ones you may not have heard of, like Gila Bend, Casa Grande, and Ajo.

The key Sonoran Desert plant is the iconic saguaro cactus, like the one Snoopy's brother, Spike, lived in near Needles, California. When there are lots of them together, I sometimes think they look a little like people standing around at a cocktail party, waving to their friends across the room with one hand and holding their drink in the other:

Other times I think they look a little like Spongebob's pal Patrick - kind of goofy. Of course there are other cactuses, too, such as the prickly pear and the ocotillo. And let's not forget tumbleweeds. Yes, they really do exist, and they are quite prickly.

Critters in the Sonoran desert include coyotes, roadrunners, mountain lions, bobcats, gila monsters, and the Sonoran desert tortoise (not to be confused with the Giant tortoises found in places like the Galapagos Islands). The Desert tortoise is generally 10 to 15 inches long, and can live for up to 100 years.

The Mojave Desert is found primarily in California, but stretches into parts of northern and western Arizona, Nevada, and (according to some but not all maps) possibly Utah, as well. It is the blue one on the map above.

Death Valley, California, is in the Mojave Desert. The Mojave Desert is slightly higher in elevation than the Sonoran, and averages only about 5" of rain per year. The key plant is the Joshua tree, also known as the Yucca palm, a very strange looking plant indeed:

You'll also find Mohave desert tortoises here, which are similar to the Sonoran desert tortoises but are considered a different species.

The Great Basin Desert is often called the largest U.S. desert, covering approximately 190,000 square miles (most of those are not, of course, in Arizona). It is the brown one on the map above, and it stretches from the Sierra Nevada Mountains to the Rocky Mountains, and from the Columbia Plateau in the North to the Mojave and Sonoran Deserts in the South. In Arizona, it is found primarily along the north rim of the Grand Canyon, with some scattered portions south of the Canyon; some experts disagree that this area is part of the Great Basin Desert would call it the Colorado Plateau instead, and consider it a separate region.

Regardless where you think the borders lie, the Great Basin Desert is considered a "cold desert," with its generally higher elevations (at least 3000 feet, generally 4000 to 6500 feet) and northern latitude. It also receives more regularly spaced rainfall, approximately 7 to 12 inches per year.

With its higher elevation, cooler climate, and more regular rainfall, the plants and animals differ substantially from the Saguaros and Joshua trees and heat-adapted critters found at lower elevations. Typical plants in the Arizona portion of this desert include sagebrush, blackbrush, saltbush, and greasewood, with occasional yuccas and very few cactuses. A single blackbrush plant can live to be 400 years old!

Here is a photo of a sagebrush plant:

Animals in the Great Basin Desert include mule deer, with their huge ears, bighorn sheep, and pronghorn antelope (along with the usual desert species such as lizards and snakes). Ranches in the Arizona portion of the Great Basin desert also host two introduced buffalo herds.

A baby Mule Deer:

The Chihuahuan Desert is the one in orange on the map above. Many consider it to be the largest North American desert (as opposed to U.S. desert); others (including the Wikipedia writers and the drawers of the map above, apparently) consider it to be the second largest North American desert, after the Great Basin Desert. It is found in portions of southeastern Arizona, New Mexico, and Texas, as well as large portions of Northern Mexico, including the Northern half of the Mexican State of Chihuahua, its namesake (and also the namesake of a certain small dog).

The elevation is typically higher than the Sonoran Desert, ranging from 1000 to 10,000 feet. Additionally, although total rainfall is similar to the Sonoran desert (ranging from 6 to 16 inches, and averaging around 9 inches per year), most of its rain falls in the summer rainy season; it lacks a winter rainy season.

Thus, the plants and animals are a bit different from the Sonoran desert. Instead of desert tortoises, you'll find hawks and prairie dogs. Javelina, coyotes, and jackrabbits are also common. Jaguars have been reported, too, but extremely rarely, as they are endangered and there aren't many of them.

Agave plants are common in this region. Agave plants are not cactuses - they are actually members of the lily family! - and are also commonly known as "century plants." They grow and accumulate nutrients for many years, usually about 30 years, then they grow a tall flower stalk, flower once, and then die. Flower stalks on some varieties can reach up to 30 feet tall! Some varieties of agave plants are used to make tequila and mezcal.

The agave lecheguilla, a very small agave species, is found only in this desert and is considered an "indicator plant" for the desert. Here are two photos, one flowering, one not:

Although the plant is small, the flower stalks range from 6 to 15 feet.

The Chihuahuan desert is one of the most biologically diverse desert regions; I haven't even scratched the surface of the cool plants and animals that can be found there.

Join me next week for part III - Trees!


Silliyak said...

Thank you. Very interesting. We have a number of agave's at our coast house and we've seen about a half dozen bloom over the last 15 years or so. Just the "bundle" that the sprout comes out of dies, the larger group remains alive.

Janie Junebug said...

I always wondered what a Joshua Tree looked like, and now I know. I also wondered about Spanish moss, and now sometimes I get sick of it. Would you please email me? I want to ask you a question and I know you don't check your blog email regularly. Thank you for the information.


SkylersDad said...

very cool!

Johnny Yen said...

As Skyler's Dad says, very cool! Most people don't realize that deserts are chockful of life. Nature is remarkably ingenious at creating life even at the places where the environment makes it very difficult. I was actually a biology major for my first two years of college (before I switched to Political Science) and loved learning about deserts.