Tuff crowd: formations of volcanic rock dominate a landscape in southeastern Arizona

Natural History, Feb, 2003 by Robert H. Mohlenbrock

About 27 million years ago, in what is now the southeastern corner of Arizona, a volcano spewed out vast amounts of hot ash and pumice that fused into a 2,000-foot layer of rock known as rhyolitic tuff. Subsequent erosion has transformed the landscape into an incomparable collection of spires, chimneys, and balanced rocks. Located about thirty-five miles southeast of Willcox, Arizona, Chiricahua National Monument was established in 1924 to protect these formations. The botanist and author Janice Emily Bowers has described them imaginatively yet accurately: "chess pieces--pawns and castles, knights and bishops, kings and queens, all crowded together at one end of the chessboard."

When my wife Beverly and I pulled up to the entrance station of the monument, a cheerful and enthusiastic ranger asked if we had ever visited before. "About thirty years ago," I replied. "Well, nothing has changed much," the ranger told us. And she was right. The stone pillars and balanced rocks looked the same, of course, but that wasn't all. A raccoon-like coati scurried across the road and into the adjacent woodland, just as one did thirty years before. A Mexican jay was drinking from a catch basin at a public water fountain, just as Beverly remembered one doing three decades ago. And the thick-billed parrot, the only parrot whose native range once extended north of the Mexican border, was still nowhere to be seen (the species was extirpated from this locale in 1922, and predators have foiled attempts to reintroduce it). But I did notice that the trees lining the road had grown somewhat taller.

We followed the main park road, which winds about eight miles through Bonita Canyon and on up to Massai Point. The canyon is forested mainly with pines and junipers, but other trees grow along the streambed that the road follows for much of the way. (Water flows through the stream most predictably during the months of July and August, when a shift in wind direction brings "monsoon" rains.) At the end of the drive we got a superb view of the rocks and pinnacles below.

On the way back we stopped in Bonita Canyon to hike the Natural Bridge Trail, which heads north for half a mile or so, then turns westward out of the canyon and enters an upland woods. About 120 acres here have been designated Picket Park. The ground cover, particularly on ridges that get the full brunt of the sun, is mostly chaparral, a community of drought-tolerant plants, often with leathery leaves that inhibit evaporation. Oak woodland predominates below the ridges, on rough, south-facing slopes where heavy exposure to the sun combines with steep terrain broken by columns, cliffs, and ledges.

Continuing our hike through Picket Park, we reached a zone where mixed conifer forest, with stands of rare Apache pine and Chihuahua pine, grows amid the rock formations. Finally we came to a pine and oak woodland nestled in a narrow, steep-walled canyon. At the canyon bottom is an impressive stand of Arizona cypress. From there the trail would have taken us south to a rock formation called Natural Bridge, but we decided it was time to turn back.

First-time visitors should be sure to follow the trail to Heart of Rocks for a close-up view of some of Chiricahua National Monument's most popular rock formations, with names such as Duck on a Rock and Punch and Judy [see photograph on this page]. Big Balanced Rock is perhaps the most famous (and most photographed) of all.

HABITATS

Streamside forest Along the streams and washes are Arizona sycamore, Fremont cottonwood, Arizona walnut, velvet ash, and Arizona cypress. Flowering herbs and shrubs include horsetail, seep willow, desert broom, threadleaf ragwort, desert willow, hummingbird trumpet, chokecherry, Apache plume, western white honeysuckle, mutton grass, and skunk-bush.

Chaparral Principal woody plants are alligator juniper, Emory oak, Mexican pinyon pine, Arizona cypress, and the shrubby Tourney oak, deerbrush, and mountain mahogany. Wildflowers, grasses, and flowering shrubs include woolly Indian paintbrush, bristlehead, rabbitbrush, turpentine bush, yellow hawkweed, threenerve goldenrod, dwarf desert peony, American threefold, pinyon ricegrass, century plant, Palmer's agave, and small palmleaf thoroughwort.

Oak woodland The primary woody plants are dwarfed and gnarly and include Toumey oak, silverleaf oak, Arizona white oak, netleaf oak, Emory oak, Mexican pinyon pine, and alligator juniper. Wildflowers and shrubs include longstalk green-thread (whose flowers resemble a dandelion head), Wright's beebrush, antelope sage, evergreen sumac, sotol, century plant, bear grass, ocotillo, cliff fendlerbush, turpentine bush, evergreen rock fern, and beggartick three-awn (a grass).

Mixed conifer forest Ponderosa pine, Douglas fir, and Arizona cypress are the dominant trees above layers of Apache pine, Chihuahua pine, pinyon pine, silverleaf oak, Emory oak, Arizona white oak, alligator juniper, Arizona madrone, and pointleaf manzanita. Among the wildflowers, flowering shrubs, and grasses are Chiricahua Mountain columbine, desert blazingstar, Santa Rita Mountain aster, plains blackfoot, southwestern cosmos, purple locoweed, Alpine false spring parsley, false Solomon's seal, showy goldeneye, cardinal catchfly, Huachuca Mountain geranium, satin bunchgrass, Wright's silktassel, and bear grass.