University of Arizona

Sense of Place

Geos. 195D

Mt. Lemmon

The Catalinas in late afternoon sun, with
shadows from the Tucsons.
Mt. Lemmon, all the way to the top of the Catalina Mountains, is one of the great single-day natural history tours of Tucson, if not the entire country. Start here with this video about Sky Islands, courtesy of the UA Flandrau Science Center.
Nice patch, available at the
Palisades Visitor Center.

Mt. Lemmon Highway (aka, General Hitchcock Highway)

Mt. Lemmon Highway

This Arizona Daily
Star article explains
who Sara Lemmon
was, one namesake
for the mountain

Sara Lemmon

Frank Hitchcock

Proposed Aerial Tramway Up Mt. Lemmon

An idea to build an aerial tramway up Mt. Lemmon is floated every now and then. In chronological order, many Arizona Daily Star articles:
Sandia Peak, NM

Palm Springs, CA

The Santa Catalina Mountains

Catalina Mountains

This Forest Service pub explains how the Catalinas were named, as well as the other Sky Islands.

Good Book

Islands in the Desert: A History of the Uplands of Southern Arizona, by John P. Wilson.

Catalina Gneiss

Taffy rock. Photo — Paul Sheppard

Gary, action block modelist. Photo — Paul Sheppard

Ta-da! Photo — Paul Sheppard

Gary demonstrating the deck of cards model in video (2:06 minutes)

Gary demonstrating the block model in video (3:32 minutes)
Babad Do'ag (Tohono O'Odham for "Frog Mountain")

Aerial of the Santa Catalinas
(see the frog?)

Babad Do'ag Vista Possibly to be Encroached Upon by Trophy Homes

Babad Do'ag vista, 2023, still unblocked by trophy homes.
Photo — Paul Sheppard (click to see enlarged photo.)

Saguaro Blossoms

On the 2013-2016 trips, a saguaro at Babad Do'ag had already created flower buds, some of which were open as flowers. End of April seems early for saguaro blossoms, but the Arizona-Sonora Desert Museum says this is not unheard of:
2013 saguaro blossoms at Babad Do'ag
Photo — Paul Sheppard

How Trees Grow

Trees grow:
  • Tall from the top (or ends of their branches)
    • Same for roots, but in the opposite direction
  • Wide from the bark
  • Some 95% of a living tree is comprised of dead tissue
    • Quite the opposite life strategy employed by animals

So, how is this situation explainable?

Ecosystem Productivity by the "Thumb Trick"

Ecosystem productivity can be expressed as "basal area," i.e., how much area, say of one acre, is occupied by the main stems of trees. One way to measure this is laboriously measuring each tree in an acre. Another way it to use a point-centered technique that extends triangles into the infinite distance. This is affectionately known as the "thumb trick," an ingenious invention of the 20th Century by an Austrian forester, Walter Bitterlich. The math (below) is easy.

Thumb trick in action, 2016.
Photo — Paul Sheppard

User Fee to Drive the Highway

A user fee is charged to drive the Mt. Lemmon Highway and stop to hike and/or picnic or do whatever to enjoy the mountain. There are various pros and cons to user fees. Some recent voices on this subject:
Paul's Piñon Pine-Nut Muffins

1 cup (~6 oz.) piñon pine nuts, ground
½ cup flour (wheat, corn, or gluten-free)
½ cup water
3 tablespoons honey
2 teaspoons baking powder
½ teaspoon salt
Combine dry ingredients. Add water and honey and mix well. Pour into greased muffin tins. Bake for ½ hour @ 350º F. Makes 24 bite-sized muffins (or ~6 big ones).

Enjoy in the shade of a Madrean mixed woodland of a Sky Island of the American Southwest.

From: Niethammer, Carolyn. 1974. American Indian Cooking: Recipes From the Southwest. University of Nebraska Press.

Live Oaks of the Mixed Madrean Woodland

Quite the kitchen.
Lower-mid elevations of the Sky Islands have the Madrean Mixed Woodland forest type, which includes live oaks that grow throughout the Southwest and down into the Sierra Madre of northern Mexico. Acorns can be a food source for humans, but processing is required. These photos are from the San Jacintos of California, a similar sky island setting as the Catalinas of southern Arizona. Both photos — Paul Sheppard.

Some processing necessary.
•  Guide to the various species of live oaks on the mountain

Fire in the Mixed Madrean Woodland

Fire Effects Tree Overstory Oak Savannas SW Wildland fire plays a role in Madrean mixed woodland oak savannas. Research shows that low-intensity fire in oak savannas of the Southwest are not destructive to either the over- or understory levels, i.e., the oak trees themselves or the chaparral shrubs that grow beneath the trees. These two Forest Service publications document fire effects in oak savannas of the Southwest. Fire Effects Tree Overstory Oak Savannas SW

Gordon Hirabayashi Prison Camp

An abandoned prison camp is located on the highway just above Molino Basin. It's named for Gordon Hirabayashi, who passed away in early January, 2012. See his obituary here.

Sky Islands of the American Southwest

The Sky Islands of the American Southwest are very biodiverse.

Global Change and Stacked Ecosystems of the Sky Islands

Arizona is rightly known as the "Grand Canyon State," but Baja Arizona could be just as reasonably dubbed the "Sky Island State." The Catalina Highway allows a close-up look at Sky Island biogeography, namely, stacked ecosystems. With changing elevation, ecosystems themselves change, from Sonoran Desert down low, to Madrean mixed woodland in the middle, and to Rocky Mountain subalpine forest on top.

Middle Bear Erosion

Middle Bear has evidence of erosion.
  • Did this occur recently, or long ago?
  • Any relationship with fire?
  • How to find out?
  • An excellent opportunity to integrate geology-ecology-culture.

A ponderosa pine tree, now a stump, with roots exposed. Photo — Nina Kolodij, 2015

Mt. Lemmon Hoodoos

hoodoo (n): Column or pinnacle of rock produced by differential weathering and erosion of horizontal strata. Word origin: African.
Hoodoos of Mt. Lemmon: 2017, a brief article on the hoodoos along the Catalina Highway.

Popular for climbing.
Photo — Paul Sheppard

Hoodoos on Cathedral Rock.
Photo — Gary Huckleberry

Fire on the Mountain

A large fire called the Bullock burned parts of Mt. Lemmon in 2002, and other parts were burned in 2003 in the Aspen fire.

Aspen burn area up close, 2007. Photo — Jayme Kelter

Aspen burn area up close, 2010. Photo — Paul Sheppard

Aspen burn area from below, 2014.
Photo — Paul Sheppard

Aspen burn area from above, 2014.
Photo — Paul Sheppard

Aspen burn area from below, 2015.
Photo — Paul Sheppard

Aspen burn area from above, 2015.
Photo — Paul Sheppard

Aspen burn area from below, 2016.
Photo — Paul Sheppard

Aspen burn area from above, 2016.
Photo — Paul Sheppard

Aspen burn area from below, 2017.
Photo — Paul Sheppard

Aspen burn area from above, 2017.
Photo — Paul Sheppard

Aspen burn area from below, 2018.
Photo — Paul Sheppard

Aspen burn area from above, 2018.
Photo — Paul Sheppard

Aspen burn area from below, 2019.
Photo — Paul Sheppard

Aspen burn area from above, 2019.
Photo — Paul Sheppard

Aspen burn area from below, June 2020.
Photo — Paul Sheppard

Aspen burn area from above, June 2020.
Photo — Paul Sheppard

Aspen burn area from below, Sept 2020 (after Bighorn).
Photo — Paul Sheppard

Aspen burn area from below, April 2021.

Aspen burn area from above, April 2021.

Aspen burn area from below, April 2022.

Aspen burn area from above, April 2022.
This is 19 years after the Aspen Fire, two years post-Bighorn Fire. Photo — Paul Sheppard

January 2023: A pano looking up from Inspiration Rock, with snow on the ground.

Aspen burn area from below, April 2023.

Aspen burn area from above, April 2023.

2020 Bighorn Fire (June 5 – July 13)

First day, north side of Pusch Ridge, photo from USFS

June 6 (Day 2)

June 6 (Evening 2)

June 9 (Day 5)

June 10 (Day 6)

June 11 (Day 7)

June 17 (Day 13), Fire Dept., Summerhaven

July 15, "debris flood," Cañada del Oro

Fire on the Mountain, Episode 1: The Event

Fire on the Mountain, Episode 2: The Aftermath

Fire on the Mountain, Episode 3: The Future Catalinas

Fire and the Future: Tucson's Bighorn Fire One Year Later
Bighorn (Sept 2020) burn area, Loma Linda Vista

Bighorn Fire (2020) Burn Progression Map

Bighorn Fire (2020) Burn Severity Map

Bighorn (Sept 2020) burn area, behind the Iron Door

Bighorn (Sept 2020) burn area, emory oak sprouting already

AZ Illustrated, Nov. 2020: Understanding the Bighorn Fire

Paul on forest fires and CO2 (3:16 min.)

Fire Lookouts

The Santa Catalinas have two fire lookouts, cabins and/or towers where people perch all day looking for fire (smoke) in the forest. The Mt. Lemmon Lookout is just off the very peak, easy to walk to from the last parking lot. It may or may not be open for close visitation, depending on when you visit. Follow the signs.

Wilderness of Rocks, from the Lemmon Lookout, 2021 (post Bighorn Fire)

From to back side

From the front side

Forest Slash Into Compost?

Forest slash (small limbs, branches, needles, cones) is carbon rich but nitrogen poor. Food waste is nitrogen rich but carbon poor. Mix the two and what do you get: high-quality compost.
  • 1/16/15: Local compost business joins forest restoration. An SOP grad, Patrick Pfeifer (Geos. 195D, 2009), solving issues to turn food waste and forest slash into commercial compost. This can be considered applied SOP.
  • Homework assignment for current SOP students: How might you apply Sense of Place in your lives after Geos. 195D? Consider geological-ecological-cultural situations in your home town, or in a favorite vacation spot of yours. Be prepared to speak for between 30 seconds and 1 minute.

  • Historic photo (~1950s) of log milling up on Mt. Lemmon. Might this be a way to reduce fuel loading in forests of the Catalinas while supplying construction boards to Summerhaven?

Coronado National Forest 2010 Forest Plan

National Forests have management plans, official documents on how to manage the forests. The Coronado National Forest Plan is available here. Public comment is open on this. Feel free to exert your new-found sense of place and comment.

2022: Ecosystems on mountain slopes are not migrating uphill fast enough!

Palisades, the final SOP stop, 2017.
Photo — Robin Williams

Too many small trees? Photo — Paul Sheppard

Ladder fuels? Photo — Paul Sheppard

Snow on the Mountain

It snowed in April the day of the 2007 SOP trip, just before the day of the 2010 and 2014 trips, and the next day after the 2015 trip. Unusual, but not unheard of, even for Southern Arizona.

2007: Palisades Ranger Station, ~8,000 ft. elevation.
Photo — Paul Sheppard

2010: The top, ~9,100 ft. elevation.
Photo — Paul Sheppard

2014: Ski Center, ~8,500 ft. elevation.
Photo — Meghan Marriott

2015: Inspiration Rock, ~8,000 ft. elevation, cold and windy. Photo — Paul Sheppard

Extra Shots

2017: American Robin, common at 8,000 ft.
Photo — Robin Williams (click to see full image)

2017: Fish-eye view of the ponderosa canopy.
Photo — Robin Williams (click to see full image)

2019: Mt. Lemmon "horned toad,"
(actual name: Short-Horned Lizard),
at the top 9,100 ft.
Photo — Brandon Groom (click to see full image)

Mt. Lemmon Fall Colors

Mt. Lemmon has many broadleaf tree species, including quaking aspen, cottonwood, alder, bigtooth maple, New Mexican locust, and Arizona walnut, all of which display fall colors. Late October-early November is leaf color season.

fall colors Mt. Lemmon
Photo — Paul Sheppard, November 1, 2015

Mt. Lemmon Sunsets

Mt. Lemmon has a couple vantage points for catching sunsets: The very top, and Windy Point.

sunset Mt. Lemmon
From the top, September 28, 2019 — Paul Sheppard

Team Photo, 2023: Middle Bear

Photo — Paul Sheppard

There's an App for That

The UA College of Science has a free app to help travelers of the Catalina Highway interpret the drive up and down.
Click here to access the download sites.

If you're using this app to do a make-up trip for SOP, take plenty of photos
along the way, including selfies at every stop, and include them in your report.

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Laboratory of Tree-Ring Research, University of Arizona
Tucson, Arizona 85721 USA
Comments to Paul Sheppard: sheppard @