J is for Joshua Trees

One of Arizona’s desert flora is the Joshua Tree, or Yucca brevifolia.  They are perfectly adapted to the environment of only the Mojave Desert, just as the Saguaro epitomizes the Sonoran Desert.  Joshua Trees are not really trees, but members of the Agavaceae Family, like Century Plants. They are not Cacti.  They grow very tall, 15 to 40 feet, and can live 150 years or more.  A great place in Arizona to see them is the Joshua Forest Scenic Road from Wikieup to Wickenburg, where I took these photos.  

Joshua Tree 1

Joshua Tree 3 Joshua Tree 4 Joshua Tree 5

 

 

Eroded

Arizona is a geological laboratory because the natural forces in play are so visible. Erosion is a general term for the weathering of rocks and the transportation of them.  The forces of erosion are gravity, ice, water and wind.

The San Francisco Mountain in Flagstaff is a strato-volcano in the midst of a volcanic field of over 600 smaller volcanos. This largest volcano is now 12, 633 feet in elevation, but it is estimated it reached 16,000 feet before a sideways eruption or glacial erosion, or both, collapsed or carved out the northeastern side of the mountain.

Imagine lines connecting the two outer slopes of the San Francisco Peaks.  That much has eroded away.

Imagine lines connecting the two outer slopes of the San Francisco Peaks. That much has eroded away.

You can see green lichen growing on this large basalt boulder at the base of Mount Elden in Flagstaff.  Weathering and erosion from the lichen, rain, snow, and freezing winter temperatures have  and cracked the boulder in half.

Basalt boulder from the Mt. Elden lava dome.

Basalt boulder from the Mt. Elden lava dome.

In the mesa shown below, you can see how the soft sedimentary layers at the top have been weathered away by wind and water and gravity has piled it around the bottom.

Eroded mesa in northern Arizona.

Eroded mesa in northern Arizona.

Wind is a powerful force in erosion as you can see in the photo of Tsegi Canyon below where it hollows out the sedimentary rock.

To the right in this picture of Tsegi Canyon you can see the wind weathering scooping out the soft rock.

To the right in this picture of Tsegi Canyon you can see the wind weathering scooping out the soft rock.

Water helps to carry away the debris weathered from the higher elevations and the grit and sand in the water help to erode more rocks as it passes.

Downpours of rain quickly run off the land, carrying the weathered particles of rock along.

Downpours of rain quickly run off the land, carrying the weathered particles of rock along. Note the truck crossing the stream.

The classic Arizona erosion example is the Grand Canyon of the Colorado River.

GC erosion best

Dry

Because Arizona is arid by nature, we are tempted to think it has no water.  Since ancient times. residents of this desert land have been ingenious in harnessing the water resources needed for life.  As it was for the ancients, our main renewable resource for water is surface water in streams.

Petroglyph on Shaw Butte in north Phoenix

Petroglyph on Shaw Butte in north Phoenix

 

For almost 1500 years the Hohokam people inhabited central Arizona, farming near the Gila and Salt Rivers.  In about 600,  the Hohokam began to dig canals up to twelve feet deep to bring water to their 110,000 acres of fields.

Petroglyphs of the sun during the seasons of the year, Shaw Butte

Petroglyphs of the sun during the seasons of the year

 

Their amazing irrigation system made it possible to support a population of about 80,000 people.  We do not know what finally disrupted their civilization in about 1450, but they left petroglyphs on hilltops throughout the region.  Their descendants live on as the Tohono O’odham Nation.

In the 1870s, settlers to the central valley followed the lines of the ancient canals and brought water from the same Salt River to their own fields.  Those canals are no longer in use, but newer canals criss-cross the valley bringing water from the river and from new projects. Arizona has developed one of the most sophisticated water management programs in the world. (The Arizona Experience)

Beginning in the early 1900s, Arizona began building a series of dams along the streams and creeks of the state. Lakes behind these dams provide recreational use as well as water supplies for drinking water, irrigation and industry.

Roosevelt Dam on the Salt River was built in 1912.

Roosevelt Dam on the Salt River was built in 1912.

 

As it was for the ancient people, the surface water today is not dependable season to season or year to year.  Additional resources currently are Ground Water, Colorado River Water, and Effluent.  Water from the Colorado River is brought into the middle of the state with the Central Arizona Project, CAP, and used to fill the lakes and recharge the groundwater. Bartlett Lake lengthWith careful management, Arizona is not so dry after all.

Covered with Cacti

Saguaro, Carnegiea Gigantica

Saguaro, Carnegiea Gigantica

 

Arizona has more cacti than any other state!  Of course, there is more to Arizona flora than cacti.  However, what a wonderful distinction to have.  The iconic Saguaro is native to the Sonoran Desert in Arizona, the Mexican state of Sonora, and a small area of California. The Saguaro blossom is the State Wildflower of Arizona.

Our arid climate has led to wonderful adaptive plants that flourish here. Cacti quickly store the scant rainfall in their thick stems for the drought i
YFperiods.  Most cacti have fleshy stems that expand and shrink according to the water stored inside.  The stems are green, so cacti photosynthesize even though their leaves have adapted to become spines.  The spines protect the waxy flesh from predators such as birds, ground squirrels and rabbits. Desert birds nevertheless build their nests in cacti such as the Cholla and the Saguaro.

Here is a selection of  additional cacti that you may encounter on an Arizona trip.

Teddy Bear Cholla, Cylindropuntia bigelovii.

Teddy Bear Cholla, Cylindropuntia bigelovii.

Barrel Cactus, Ferocactus

Barrel Cactus, Ferocactus

Prickly Pear,  Opuntia engelmannii

Prickly Pear, Opuntia engelmannii

Mammillaria Grahamii

Mammillaria Grahamii

 

 

 

 

 

 

Hedgehog Cactus, Echinocereus engelmannii

Hedgehog Cactus, Echinocereus engelmannii

Barrel Cactus, Ferocactus

Barrel Cactus, Ferocactus

Buckhorn Cholla, Cylindropuntia acanthocarpa

Buckhorn Cholla, Cylindropuntia acanthocarpa

Prickly Pear, Opuntia Engelmanii

Prickly Pear, Opuntia Engelmanii

 

 

 

 

 

 

 

Botanical gardens are worth a visit if you want to see Arizona’s many cacti species.  Here are some of my personal favorites: In the Phoenix area: Desert Botanical Garden, Boyce Thompson Arboretum In the Tucson area: Arizona-Sonora Desert Museum,

Brown

I have heard it asked, “Why is Arizona so brown?” There is brown here. However, if you look, you will find a full palette of color.

There is also the blue of lakes, like Lake Pleasant near Phoenix.

There is also the blue of lakes, like Lake Pleasant near Phoenix.

Even in the driest parts of the desert, the cacti conspire to add amazing color.

Even in the driest parts of the desert, the cacti conspire to add amazing color.

Purple Phacelia in North Mountain Preserve, Phoenix.

Purple Phacelia in North Mountain Preserve, Phoenix.

Desert Globe Mallow in bloom.

Desert Globe Mallow in bloom.

 

 

 

 

 

 

Oak Creek Canyon

Oak Creek Canyon

Oak Creek Canyon Redrock near Sedona.

Oak Creek Canyon Redrock near Sedona.

Lush forest on Mt. Lemmon near Tucson.

Lush forest on Mt. Lemmon near Tucson.

Young poppy in the desert

Young poppy in the desert

Ponderosa forest on the Colorado Plateau of northern Arizona

Ponderosa forest on the Colorado Plateau of northern Arizona

Arid

The most common adjective people seem to associate with Arizona is “dry.” Many factors combine to create an ecosystem that many label as desert.  The amount of  annual precipitation alone, 10 inches or less, is not the whole story.  Arizona is also sunny, sometimes windy and experiences temperature extremes.  During a twenty-four hour period, a range of 40 degrees is not unusual. These extremes increase
the amount of water that escapes back into the air. The composition of the soil also affects how much water is available.  Yet, Arizona is not devoid of plant and animal life.  Our deserts and high mountain ranges support abundant flora and fauna that is well-adapted to this arid home. Plants and animals here are expert conservationists to make the most of what moisture is available.

Much of the Sonoran Desert depends on seasonal rainfall and responds quickly to a brief storm.

Much of the Sonoran Desert depends on seasonal rainfall and responds quickly to a brief storm.

Reflections in Wet Beaver Creek, northern Arizona

Wet Beaver Creek is an oasis in the Sonoran desert in northern Arizona. It is a perennial stream that is a crucial source of water for elk, bear, deer, mountain lion, small animals and birds.

Willcox Playa

The Willcox Playa is an ancient lake bed in southern Arizona that receives only occasional rain but is an important stopover for migratory birds.