Yesterday morning, we drove eastward across the flat landscape of Tucson, which was ablaze with the brilliant gold flowers of paloverde trees. Picking up the Catalina Highway, we continued toward the massive ridge of the Santa Catalina Mountains and soon climbed into the Coronado National Forest on the Sky Island Scenic Byway. This toll road, currently $5 per vehicle, winds upward and northward for almost 28 miles, to the summit of Mt. Lemmon.
Leaving the desert plain, we soon entered a zone of saguaro cacti, which continued to dominate the spectacular scenery to an elevation of 4000 feet. This habitat gave way to mountain shrublands between 4000 and 6000 feet, highlighted by massive towers (hoodoos) of granite. A rich, pine forest appeared above 6500 feet and continued to the summit of Mt. Lemmon (over 9100 feet), where it was scarred by wildfires earlier this decade.
One of numerous "sky islands" across the Great Basin and Desert Southwest, the Mt. Lemmon massif supports ecosystems that require a cooler, wetter climate than is found at lower elevations. For every 1000 feet of elevation gain, the air temperature drops 3 degrees F, producing a Canadian climate in the midst of the Sonoran desert; indeed, the temperature atop Mt. Lemmon is, on average, about 20 degrees cooler than that in Tucson. In addition, these isolated ranges cause air to rise as it sweeps across the region, producing upslope precipitation; these intermittent rain and snow showers support a coniferous forest habitat, home to a variety of species that could not survive in the hot, arid climate of the surrounding desert.
