The Ecosystems of Arizona
Content Objectives
• SWBAT name the different major ecosystems
of Arizona and what climatic factors decide
their location within the state.
Colorado/Mojave Desert
0 – 1,000 feet
Colorado Desert
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Nearly all rain falls in winter (less than 5”).
Too far west to get the monsoon moisture.
Least biodiverse ecosystem in Arizona.
Dominated by creosote bush, small shrubs, and
occasional ocotillos.
Chihuahuan Desert
2000-4000 feet
2,000 – 4,000 feet
• Summer Monsoons are primary moisture.
• Little winter rain.
• Dominated by grasses, yuccas, mesquite, and
creosote bush providing main structures.
• Largest desert ecosystem in North America.
Ranges from SE Arizona across New Mexico,
west Texas, and most of northern Mexico.
Sonoran Desert
1,000-3,000 feet
Sonoran Desert
• Receives significant rainfall in both summer
and winter. Thus, two growing seasons.
• Dominated by saguaro cactus, palo verde,
mesquites, ocotillos, and various cacti.
• Is the most biodiverse desert in the world.
Considered the “greenest” desert on Earth
Desert Grasslands
3,000-5,000 feet
Desert Grasslands
• Occur at 3,000-5,000 feet.
• Slightly cooler and wetter than the lower deserts.
• Dominated by grasses, small thorny shrubs, and
various prickly pear cactus species
A grassland with lots of cacti on Table Top Mountain
Chaparral Zone
• Composed of dense woody vegetation 1-3 meters tall.
• More dominant in California, but occurs in the Central
Arizona Highlands, especially near Prescott.
• Dominated by manzanita, scrub oak, and silk tassel,
with agave and yucca common.
4,000-6,000 feet
Chaparral in the Mazatzal Range
Pinyon-Juniper Zone
4,000-7,000 feet
Pinyon-Juniper Zone
• Dominated by pinyon pine, Arizona cypress,
and various juniper species.
• Conifers able to survive extended seasonal
droughts. Trees are very long lived.
• Can survive winter frosts and occasional snow.
Riparian Forests
Occur Anywhere There is Year Round Water
• Dominated by deciduous tree species such as
cottonwoods, Arizona ash, Arizona walnut, Arizona
sycamore, alder, and willows.
Ponderosa Pine Forests
7,000-9,000 feet
Ponderosa Pine Forest
• Occurs at high elevations which receive both winter
snow and summer monsoon rains.
• Typically monotypic with a grassy understory and
occasional small shrubs and agave.
• Gamble oaks are often found in many places.
7,000-9,000 feet
Douglas fir
Ponderosa pine
Western white pine
White fir
Subalpine fir
Aspen
Mixed Conifer
8,000-10,000 feet
Occurs at highest elevations where significant winter snow falls
Spruce-fir Zone
9,000-11,000 feet
Spruce-fir Zone
• Located in highest mountains with extremely low
winter temperatures and significant snow packs.
• Dominated by Englemann spruce, bristlecone
pines, and subalpine firs.
Aspen Stands
8,000-11,000 feet
Aspen Stands
• Actually a subcategory of the mixed-conifer forests.
Grows in regions with significant summer rains.
• They have short lifespans of just over 100 years.
• Completely fire dependent. Without fire to burn out
the conifers, they will be crowded out by shade
tolerant firs and spruces.
Young conifers coming up to crowd out mature aspen stand
The aspens below represent an area of
significant fire about 80 years ago
Inner Basin from Mt. Humphreys
Alpine Meadows
Above 11,000 feet
The only true alpine zone in Arizona is
on top of the San Francisco Peaks
Plus one other on Mount Baldy in the
White Mountains
Great Basin Desert
8,000-11,000 feet
It’s a Cold Desert…Also Known As Sage Brush Country
• Most moisture falls in winter in the form of snow
• Some occasional summer rains
• Coldest desert
• Dominated by sage brush, rabbit brush, and black brush
• Common from N. AZ north to MT and E. WA
All Four Deserts
• Arizona is the only state in U.S. that contains all four North
American deserts.
Content Objectives
• SWBAT name the different major ecosystems
of Arizona and what climatic factors decide
their location within the state.