This photo is in many ways familiar to anyone who has spent time in the desert surrounding Tucson. Saguaros preside over black volcanic rock distinctive to the Tucson Mountains and other persistent Sonoran Desert plants: prickly pear cactus, Christmas cholla, palo verde, and ocotillo. The rest is an indeterminable tangle of dormant shrubs. Amidst the desert, canvas tents and canopies glare bright and cast deep black shadows in the intense midday sun. There isn’t a cloud in the sky. Just outside of the camp kitchen is a woman, pregnant and in a dark and substantial dress, shading her eyes from the unrelenting sun as she gazes towards something outside of the frame. The woman is Mary Lloyd. It’s 1906 and she is at Tumamocville, the camp at the Desert Laboratory at Tumamoc Hill that a few scientists and their families once called home.

The Desert Laboratory was established in 1903 by Frederick Coville, chief botanist for the USDA and arid plants enthusiast, and was backed by the Carnegie Institute with the goal of learning how plants function in extreme desert conditions. After scouting for a site across the southwestern United States and Sonora, Mexico, Coville settled on Tumamoc Hill at the western edge of Tucson, then a small town with a population around 10,000. The high plant diversity of the Sonoran desert and the convenience of relatively undisturbed nature near civilization made this site ideal. Colville was not the first person to be drawn to the Tumamoc; Native Americans intermittently inhabited it for 2,500 years. Within a couple of years, a stone-walled laboratory with a greenhouse that still stands today was constructed and plant scientists flocked there, drawn by the opportunity to research the adaptations of unique and little-studied desert flora. The permanent researchers eventually built homes at the base of the hill, but the Tumamocville tents remained for visitors.

Many key findings in the fields of natural history, plant physiology, and ecology were made in the early years at the Desert Laboratory. Effie Spalding repeatedly measured the girth of saguaros and discovered that their pleats allow them to expand and store water after rain. Burton E. Livingston studied how water moves through plants and into the atmosphere. William A. Cannon showed how plants with different root depths do not compete for moisture. Volney Spalding understood that it would take many years to fully observe the relationships among plants and their environment. He set up several large plots across Tumamoc to track plants’ locations over time, with the hope that successors would continue the work and be able to determine long-term patterns. Forrest Shreve continued studying the plots and they are still studied today, making them the oldest continuously censused ecology plots. In addition to carrying Spalding’s torch, Shreve forged the field of desert ecology. He determined that environmental constraints on plant distribution are variable. For instance, his research on Mt. Lemmon showed that plants in high altitudes, such as ponderosa pines, are limited by soil moisture and plants at lower elevations, such as saguaros, are limited by temperature.

Francis E. Lloyd, Mary’s husband, visited Tumamoc in the summer of 1904. That summer, he experimented with ocotillo and the environmental cues that make it leaf out. He returned to the Desert Laboratory for a short, six-month stint in 1906 to investigate the mechanisms that allow desert plants to take in carbon dioxide without losing water in the desert heat. The resulting book made a lasting impact in the field of plant physiology. This time, Mary and their first son, still in the womb, accompanied him. Francis and Mary met years before at Columbia University, where he taught and she studied education.

I don’t know much about Mary’s experience in Tumamocville. I hope she appreciated the raw beauty as much as her husband did. According to a piece about the Desert Laboratory that Francis wrote in 1905, he took a strong liking to the desert. He did not mind the summer heat and describes the view from the hill in familiar detail.

“The view commanded from the laboratory site is a panorama of rare beauty. To the north lies the range of the Santa Catalina Mountains, extending through 40° of the horizon. Its rugged topography scarcely noticeable in the glare of the high sun is thrown into bold relief when the shadows begin to lengthen. Then the dazzling purples and yellows of midday give way to the deep blues and purples of the valleys contrasted with the reddening tones of the higher slopes and ridges.

To the east stands the rounded mass of the Rincon Mountains, the illumination of which by the afternoon sun is most remarkable. The vividness of details, the shimmer of heat, the blaze of reflected light modified by the merest veil of purple—these are faint expressions of what one quite fails to describe. To the west the desolate defiles of the Tucson Mountain, seen at short range, gives us, with the sun in the same position, a contrast picture of hard and rugged profile, dark browns and black shadows. To complete the panorama, one needs but to climb to the top of the hill, from which may be seen in the far distance the deserts of Sonora and the malpais—the rendezvous of the few 'bad men,' now so hard to find.”

Francis Lloyd had recently purchased a struggling journal called Plant World and brought it to the Desert Laboratory. Here, it was revitalized and it became a valuable platform to share desert plant discoveries with the outside world. The Ecological Society of America, which had several Desert Laboratory researchers among its founders, later took over Plant World and renamed it Ecology. The journal remains a premier outlet for ecological research.

The Desert Laboratory was handed over from the Carnegie Institute to the Forest service in 1940, then purchased by the University of Arizona two decades later. Today, it is still an active research site. Even with all the changes, the Desert Laboratory has been a protected ecological research preserve since the fence went up to keep the cattle out in 1906 and it has been a National Historic Landmark since 1976.

My own work as a plant ecologist brings me to Tumamoc Hill regularly, where I track the germination, survival, and reproduction of individual tiny winter annual plants. We just completed the 34th season of that study. I am grateful to be part of a legacy of research, both in my particular project and at the Desert Laboratory.

Tumamoc was a fairly remote site in 1906, but now the city engulfs it. My days there are soundtracked by the persistent hum of cars and the sporadic roar of aircraft. I take lunch breaks in the shade of my lab’s lifted Dodge Ram 2500, my own miniature and portable Tumamocville, population: 1, where I scarf burritos from one of several Mexican drive-thrus down the street while reading the news on my iPhone. Unlike Mary Lloyd in her heavy dress and smart hat, I dress in today’s casual field gear made of engineered fabrics with registered trademarked names. When the Catalinas go red at the end of the day I drive back to my climate-controlled home, free of desert critters. Even with these new and improved comforts, it’s still hot and thorny out in the field. This photo reminds me that while some things change rapidly, others do not. The desert changes slowly and our awe of it is unwavering.

Thanks to the Lloyd family for preserving this photo and generously sharing it with Tumamoc Hill’s director Dr. Michael Rosenzweig, and to Dr. Rosenzweig for sharing it with Territory.

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