Natt N. Dodge

“ Then, under the influence of winter rains and the soil-warming effects of early spring sunshine, they burst into rapid growth. One of a host of species, this early spring ephemeral is enabled by these favorable conditions to flower and mature its seed before the pall of summer heat and drought descends upon the desert. With their task complete, the parents wither and die. Their ripened seeds are scattered over the desert until winter rains enable them to cover the desert with another multicolored but short-lived carpet of foliage and bloom. ”

“ In reality they are compromises—beautiful, wild, but still bearing the marks of human occupation. In Saguaro, as we have seen, fire control has produced a forest different from that known to the Indians who once lived here; grazing has depleted the ground cover; and hunting has removed the desert bighorn from its rocky haunts. In these days of burgeoning population, when human influence is affecting every natural landscape, environmental management becomes necessary to approach the ideal of naturalness. ”

“ As the city of Tucson sprawls in all directions, the monument’s two divisions, islands in an encroaching sea of civilization, must withstand ever-accelerating hazards. Vandalism takes an increasing toll of the saguaros; housing developments creep toward the monument borders. Smog drifts over the fragile plant communities, threatening to choke them—as the polluted air from Los Angeles is already strangling forests in the distant San Bernardino Mountains. ”

“ But what happens when man, with his machines and his passion for progress, institutes changes of a speed and kind and on a scale drastically different from those brought about by earthquakes, storms, shifting climates, and other natural phenomena? What happens to the living things that have adapted to the harsh desert environment when that environment is drastically altered? ”

“ The fauna of each community is made up of animals adapted to the climatic conditions and the available food, cover, and water. In Saguaro, some animals, such as the desert kangaroo rat and the cactus wren, are restricted by their life requirements to a narrow belt; others, such as the gray fox and great horned owl, are more adaptable and live in all the major plant communities. ”

“ Climate is the chief arbiter of life on earth. Each plant and animal, including man, has tolerance limits for heat and water below or above which it dies. The Sonoran desert, with its low and uncertain rainfall and high summer temperatures, thus presents one of earth’s most taxing environments. For most desert plants and animals, the main problem presented by this climatic combination is a scarcity of water. ”

“ Snakes begin to come out of hibernation. April and May see the apex of spring activity, as insects swarm around the flowering plants, and birds take advantage of this proliferation of food to raise their young. The desert now is 80 yellow with the blossoms of paloverde, mesquite, acacia, and brittlebush.
But April also marks the beginning of a drought that intensifies through May and June, making these last 2 months the year’s parching crucible in which reproductive ability is tested. If winter rains have been meager, the heat and drought of May and June can kill all the young of many birds. ”

“ How do the seeds of ephemerals “know” when it is time to germinate? Experiments have revealed that the seeds of annuals will germinate only when enough water percolates through the soil to dissolve away a “growth inhibitor” in their coats. A single light rain will not do the job. In this way premature sprouting into a too-dry environment is prevented. The winter annuals, furthermore, will only germinate when soils are cool, and the summer annuals when soils are warm. These finely tuned adaptations thus allow plantlife to take full advantage of favorable seasons in the desert. ”

“ Evidence of such evolution we have seen in the plants of the Sonoran Desert, notably the giant saguaro cactus, whose prickly ancestor lived in the West Indies only 20,000 years ago.
Thus nature is ever-changing; and the inexorable rule for all living things is, “adapt or perish.” Before technological man enters the scene, the slow evolutionary process can keep pace with the changing environments, though here and there a species is dropped by the wayside. Generally, communities of living things reach new equilibria without serious disruption. ”

“ The short-lived leafy plants of summer and winter are able to compress their entire active life into 6 to 12 weeks when conditions are most suitable. Thus, they can escape all the rigorous periods of the desert climate by living for 8 or 9 months in the dormant seed stage. Some of the spectacular and colorful flowers of the monument are among these ephemerals that survive desert 44 conditions by escaping them. It must be remembered, however, that when drought conditions or abnormally cold spring weather upset the norm—a not unusual occurrence—response of ephemeral plants is greatly restricted. ”

“ A spectacular inhabitant of the grassland transition and open oak woodlands you are now entering is the AMOLE, or SHINDAGGER, whose rapidly growing blossom stalks attract attention from May to as late as August. The plants themselves, which grow crowded together in patches, consist of rosettes of succulent leaves superficially resembling bunches of flattened, green bananas. The stiff, needle-sharp leaf tips can inflict painful jabs on man and beast. ”

“ Flowers of the mesquite, paloverde, catclaw, saguaro, and other desert plants are “alive” all through the day, as many species of insects seek nectar and pollen or prey on other insects attracted to the blossoms. Insects are fed upon by various species of birds; flycatchers flock to parts of the desert where nectar-yielding flowers are numerous. Because of the absence of extreme cold, the desert climate enables insects to be active throughout much of the year and to support a considerable bird population. ”

“ Many other desert creatures, including certain 63 snakes and lizards and some spiders, depend upon insects for food. The body juices of the insects provide the all-important moisture—which these creatures can get from no other source. Bats, too, are insect eaters, spending the hours of darkness in seemingly aimless and erratic flight while foraging for moths and other night-flying insects that visit the light-colored blossoms of night-blooming plants.
Some species of insects may become so numerous that they threaten the very life of the plants on which they live. ”

“ For the desert is hotter and drier in some places than in others. The gradual downslope changes in vegetation reflect the decrease in the amount of soil moisture available to plants—a condition caused by the decreasing size of soil particles and consequent shrinkage of water-holding space between particles. Desert washes encourage plant growth because they channel water and cold air. Strangely enough, night temperatures are often lower in a desert valley than farther up the slopes. ”

“ West of Spud Rock are abundant small groves of MEXICAN WHITE PINE.
A cone-bearing tree growing with Douglas-fir—exclusively on higher northern and northeastern slopes of Mica Mountain—is the WHITE FIR. Flattened, gray-green needles curving upward from the branches, and large, green cones growing upright on limbs near the tops of the trees identify this beautiful evergreen. On open stands, limbs of even the large trees grow from the trunk almost down to the ground. ”

“ Although billions of saguaro seeds are produced yearly in the extensive stands of the monument, only a very few find favorable locations for germination and growth. Trees, rocks, dead limbs, pebbles—anything that reduces evaporation in the immediate vicinity of the seed—improve the chance of germination. These kinds of shelter not only provide the necessary moisture conditions, but also hide the seed from armies of ants, rodents, and other animals searching for food. ”

“ Just as grassland merges with oak woodland and chaparral, and these with oak-pine woodland, so you will notice, as you climb steadily higher, that these woodlands gradually mingle with the open pine forests that cover much of the Rincon Mountains above 6,000 feet. PONDEROSA PINE is the “big tree” of the Rincons, usually growing in clear, open stands. Through its high canopy of spreading branches, sunlight mottles the shaded forest floor. Its presence indicates still cooler and wetter conditions than those below. Here you will need blankets at night, though summer days are warm. ”

“ Just as plants depend for their existence on soil, water, and sunlight, so animals, including man, depend on plants. For green plants are the basic food producers in nature, manufacturing carbohydrates, proteins, and other essential compounds from minerals, air, and water, with the help of chlorophyll and the sun’s energy. Animals get their food either by eating green plants or by eating animals that have eaten plants. Microscopic decomposers complete this food chain, breaking down dead plants and animals into substances that once again can be used by plants. ”

“ Animals and plants share some of the same basic problems—particularly, how to stay within tolerable temperature limits, and how to maintain an adequate supply of water. Plants solve these problems mostly by structural adaptations, animals mostly by behavioral. In the desert, for instance, cold-blooded animals such as snakes and lizards (which have no internal control over body temperature) crawl underground or into shade during the midday heat of summer, and come out to hunt food during the cooler hours. Birds and mammals cool themselves through evaporation of water from their bodies. ”

“ Among the smaller perennials are many that add to spring flower displays when conditions of moisture and temperature are 41 favorable. Perennials do not need to mature their seeds before the coming of summer as do the ephemerals; a majority start blossoming somewhat later in the spring, and gaily flaunt their flowers long after the annuals have faded and died. When the heat and drought of early summer begin to bear down, they gradually die back, surviving the “long dry” by their persistent roots and larger stems. ”

“ The white-winged dove’s interest in the saguaro is in the nectar and fruit.
Predators are an integral part of the bird population, one of the smallest and most active being the LOGGERHEAD SHRIKE. This black-and-gray bird gorges itself on beetles and grasshoppers when insects are abundant, turning to lizards, rodents, and small birds at other times. It has the unusual habit of impaling its prey on thorns for future use. The RED-TAILED HAWK is the commonest of the large soaring hawks, which live mainly on rodents and reptiles. ”

“ In bloom, in late summer or early autumn, this succulent plant produces clusters of yellow or orange flowers on its crown. The widely circulated story that water can be obtained by tapping the barrel cactus has little basis in fact, although it is possible that the thick, bitter juice squeezed from the plant’s moist tissues might, under extreme conditions, prevent death from thirst. Desert rats, 34 mice, and rabbits, carefully avoiding the spines, sometimes gnaw into the plant’s tissues to obtain moisture. ”

“ Another member of the weasel family, the BADGER, is occasionally seen in the desert although it is by no means limited to that habitat. The badger feeds mainly on rodents, which it digs from burrows with its strong forelegs and heavy claws.
The RACCOON, longer-legged than the badger, is readily recognized by its gray fur, black mask, and ambling gait. It inhabits brushy canyons having permanent water, and sometimes wanders up into the pine belt in summer. Amphibians, scarce as they are, and other water creatures are among the preferred foods of raccoons ”

“ The PRAYING MANTIS is another large insect, usually green and inconspicuous among the foliage of desert plants, which it frequents in search of small insects. Ants of many species are active almost everywhere in the desert, harvesting seeds of various plants. Some species construct mazes of underground nest tunnels and deposit the excavated materials on the surface, forming conical, sometimes, craterlike, anthills.
The small desert hairy scorpion is the only scorpion in the monument that is dangerous to humans. ”

“ Perhaps those most frequently seen are the GOPHER SNAKE and the COACHWHIP. Many desert snakes hunt only at night; others that are normally active during days of moderate temperatures become night hunters during hot weather. Although they are not abundant, there are several kinds of rattlesnakes in the monument, the commonest desert species being the WESTERN DIAMONDBACK 66 and MOHAVE RATTLESNAKES. Except for the small, very rare, and secretive ARIZONA CORAL SNAKE, rattlesnakes are the only poisonous snakes in the monument. ”

“ Quick to attract attention because of their apparent lack of foliage, the JOINTFIRS, of which there are several desert species, grow in clumps of harsh, stringy, yellow-green, erect stems. The skin or outer bark of the stems performs the usual functions of leaves, which on these plants have been reduced to scales. Small, fragrant, yellow blossom clusters, appearing at the stem joints in spring, are visited by insects attracted to their nectar. ”

“ Life in the desert begins a new cycle. This rainy period usually lasts into March.
On the mountain slopes, of course, the same seasonal patterns of heat and precipitation occur, but they are tempered or enhanced by elevation. With increasing elevation, temperatures decline and precipitation increases. When July temperatures at headquarters are averaging in the nineties, they will be in the sixties on top of the Rincons. In the cactus forest at the foot of Tanque Verde Ridge only about 10 to 12 inches of rain fall in a year, while Manning Camp, at 8,000 feet, gets about 18 to 25 inches. ”

“ Desert animals get much of their water from the plants and animals they eat, but some species, such as mule deer and Gambel’s quail, require large amounts of drinking water as well.
Cold weather poses another problem. Most reptiles and some mammals solve this one by hibernating underground or in rock dens, where temperatures remain moderate throughout the year. Many birds and some mammals migrate to areas where temperatures are warmer and food is more abundant, which may mean going farther south or simply moving down the mountainsides. ”

“ Immediately to the south, in southern Nevada and southeastern California, is the Mohave Desert, with cool winters during which most of the year’s precipitation comes, and with plant cover consisting mostly of shrubs such as creosotebush. At higher elevations grows the Joshua-tree, a giant yucca. The Chihuahuan Desert, with cool winters and summer rainfall, covers the broad plateau of north-central Mexico, extending into southern New Mexico and west Texas. ”

“ In lower elevations of the Tucson Mountain Section, the gray-blue foliage of IRONWOOD is a common sight, but the species does not range farther eastward. Its wisterialike lavender-and-white flowers blossom in May and June. The nutritious seeds are harvested by rodents and formerly were parched and eaten by Indians. The wood is so dense that it sinks in water; Indians used it for making arrowheads and tool handles.
Ferns—commonly, plants of dank woods and other moist habitats—seem entirely out of place in the desert ”