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saguaro national monument ARIZONA
saguaro national monument ARIZONA
Napier Shelton based on an earlier work by Natt Dodge NATURAL HISTORY SERIES 1972 National Park Service U.S. DEPARTMENT of the INTERIOR For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402—Price $1.25 Stock Number 2405-0292...
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preface
preface
This book is a simple account of the natural history of Saguaro National Monument. It is intended to help you understand the relationships between land, climate, plants, wild animals, and man in the environment of a hot desert. While it includes brief profiles of many representative species, it is not intended to serve as a guide to the monument. It does indicate where the several distinctive natural communities exist, and when and where to look for certain plants and animals. For identification
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the desert scene
the desert scene
Scattered through the wide, lonely Sonoran Desert, isolated mountain ranges raise jagged blue silhouettes against the sky. The high ones wear a crown of dark pines and a speckled mantle of oaks. Lapping against their feet is the desert sea, studded with the green masts of giant saguaro cactuses rising above a motley crew of tough, strange, often handsome subordinates. On either side of the Santa Cruz Valley in southeastern Arizona, Saguaro National Monument embraces two of these ranges, with the
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Geological Time Table
Geological Time Table
Summer thunderstorm in the Rincon Mountain Section. The Catalina Mountains rise in the background....
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climate: the vital factor
climate: the vital factor
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. Why, we might ask, is this part of the globe so dry? Essentially, the dryness of the Son
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rocks: foundation and soilmakers
rocks: foundation and soilmakers
Soils are derived from the fragmentation and decomposition of rocks. Combinations of soils and climate, varying from place to place, create an almost infinite number of environments with differences so subtle and small as to make it appropriate to refer to them as microenvironments. Though these differences be minor, they are often sufficient to create niches each of which becomes a habitat for a particular group of plants and animals. Thus it is that the saguaros and other desert vegetation in
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Major Vegetation Types in Saguaro National Monument
Major Vegetation Types in Saguaro National Monument
Biologists have developed several systems for classifying assemblages of plants and animals over broad regions, and one of the most widely known is that of C. Hart Merriam. Around the turn of the century, he conceived a system of “life zones,” named for the parts of the continent where they are best developed: Tropical, Lower Sonoran, Upper Sonoran, Transition, Canadian, Hudsonian, and Arctic. In Saguaro National Monument, the Lower Sonoran Zone corresponds to the desert scrub type; the Upper So
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Succulents
Succulents
A large group of desert plants conserve water for use in periods of drought by storing it in specialized tissues during the wet season. Some of these “succulents,” principally the yuccas, eschevarias, and agaves, have developed water-storage tissues in their leaves. A few, notably the NIGHTBLOOMING CEREUS (see appendix for scientific names of plants), have slender stems but an enormous, carrot-shaped root in which the moisture-storage tissue is located. The GOURDS also have large, thick, moistur
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The Saguaro—Monarch of the Monument
The Saguaro—Monarch of the Monument
Of all the species of cactus recorded in Saguaro National Monument, the giant SAGUARO (pronounced sah- WAH -roe) holds the center of interest. From the visitor’s standpoint, all other plants, no matter how bizarre in appearance or peculiar in living habits, are merely stage scenery for setting off the star of the desert drama. For size, this vegetable mammoth tops all other succulents of this country; heights of more than 50 feet and weights of more than 5 tons have been reported. There have bee
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Other Common Cactuses
Other Common Cactuses
Many other cactuses share the saguaro’s environment. The BARREL CACTUS is sometimes mistaken for a young saguaro, but can easily be distinguished by its curved red spines. Stocky and unbranching, this cactus rarely attains a height of more than 5 or 6 feet. It bears clusters of sharp spines, called “areoles,” with the stout central spine flattened and curved like a fishhook. In bloom, in late summer or early autumn, this succulent plant produces clusters of yellow or orange flowers on its crown.
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Non-Succulents
Non-Succulents
For the diversity of devices for adaptation to an inhospitable environment, the many species making up the non-succulent desert vegetation provide an absorbing field for study. As we have seen, there are two ways to survive the harsh desert climate; one is to avoid the periods of excessive heat and drought (“escapers”); the other is to adopt various protective devices (“evaders” and “resisters”). Short-lived plants follow the first method; perennials, the second....
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Perennials
Perennials
Chief among the requirements for year-round survival in the desert is a plant’s ability to control transpiration and thus maintain a balance between water loss and water supply. In this struggle, the hours of darkness are a great aid because in the cool of the night the air is unable to take up as much moisture as it does under the influence of the sun’s evaporating heat. Therefore, less exhaling and evaporating of water occurs from plants, and both the rate and the amount of water loss are redu
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Ephemerals
Ephemerals
Every spring, after a winter of normal rainfall, parts of the southwestern deserts are carpeted with a lush blanket of fast-growing annual herbs and wildflowers—the early spring ephemerals. The monument does not get massive displays, however, since it is lacking in the species that make the best show. But it does have many annuals that are beautiful individually or in small groups. Many of these “quickies” do not have the characteristics of desert plants; some of them, in fact, are part of the c
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major plant communities of saguaro
major plant communities of saguaro
SAGUARO NATIONAL MONUMENT Tucson Mountain Section Biotic Communities In any region where a great range of altitude exists, the vegetation grows in a continuum of overlapping but recognizable zones. Climate being the major controlling factor of this zonal distribution, the plants of each band grow higher on south-facing slopes than on cooler, moister north slopes. In Saguaro the major plant communities roughly correspond to altitudinal bands—with the desert at the lower, drier levels, and the tra
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Oak-Pine Woodland
Oak-Pine Woodland
The thinning and final disappearance of saguaros along the trailside, although mesquite and ocotillos seem almost as numerous as on the floor of the desert, indicate that you are entering a slightly cooler, wetter environment. An occasional MEXICAN BLUE OAK or ARIZONA ROSEWOOD appears among the mesquites along the washes. The grasses that increasingly cover the ground as you climb include HAIRY , SIDEOATS , and SPRUCETOP GRAMA ; CURLY MESQUITEGRASS ; TANGLEHEAD ; TEXAS BLUESTEM ; and WOLFTAIL .
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Ponderosa Pine Forest
Ponderosa Pine Forest
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
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Invertebrates
Invertebrates
Insects are generally not bothered by excessive heat, and many species are active during the hottest hours. This is especially true when the plant blossoming season is at its height. 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-
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Amphibians
Amphibians
As might be expected, amphibians are scarce in the monument because of lack of permanent water. The few springs and seeps, however, furnish excellent breeding places for several species of amphibians. Best known among these are the RED-SPOTTED TOAD , LEOPARD FROG , and CANYON TREEFROG , the latter common near Manning Camp. A spectacular desert amphibian and the second largest toad in the United States, is the huge COLORADO RIVER TOAD , sometimes found near residences in the evening when outdoor
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Reptiles
Reptiles
Except for small lizards, reptiles are not much in evidence in the monument. Nevertheless, they are present and are important in the various plant-and-animal communities in which they live. Almost all lizards are insectivorous, and along with birds and other insect-eaters help to keep the number of insects within bounds. A notable exception is the GILA ( HEE -lah) MONSTER , (See appendix for scientific names of reptiles) largest of the lizards found in the United States. (It is one of the world’
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Birds
Birds
Because of its great variety of habitats, ranging from luxurious desert vegetation to deep mountain forests, Saguaro National Monument provides food and shelter for many species of birds. Some of these reside all year within a single zone, while others move upward in summer, returning to the desert when the mountaintops are covered with snow. Other species pass through the monument in spring and autumn in their annual migrations between Latin America and summer nesting grounds in northern United
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Mammals
Mammals
The most frequently seen mammals in the monument are rodents and members of the hare clan. Among the latter group are two rabbits. The DESERT COTTONTAIL is common in the lower levels of the desert, and the EASTERN COTTONTAIL inhabits the mountains to 8,600 feet. Adaptable to a wide range of environmental conditions, these animals augment the water they obtain from springs with moisture derived from sap. There are two species of JACKRABBITS (actually hares) in the monument. They remain at the low
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the rhythms of nature
the rhythms of nature
Natural landscapes may appear unchanging, but this is illusion. Within the apparent constancy, daily and seasonal cycles, fluctuations in numbers, and long-term change are the rule. Daily cycles are obvious to those who are about at the edges of the day. Take 24 summer hours in the cactus forest of Saguaro National Monument. When the first light comes over the mountains, curve-billed thrashers and cactus wrens sing noisily among the chollas. Other birds soon join in. The early morning walker is
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the impact of man
the impact of man
Man has been a part of the scene in this region for several thousand years, but until recent times his influence on it was minimal. Only with the rapid technological development of the last century has man been able to make a major impact on this landscape. Thus the story of man, here as elsewhere, is a story of gradually accelerating power to change environments, a power that now threatens to destroy environments, and with them, man himself. From carbon-14 dating in Ventana Cave, we know that m
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Suggested Reading
Suggested Reading
Arnberger, Leslie P. Flowers of the Southwest Mountains. Southwestern Monuments Association, Popular Series No. 7. Globe, Ariz. 1962. Benson, Lyman D. The Cacti of Arizona. University of Arizona Press, Tucson. 1969. Burns, William A. (ed.). The Natural History of the Southwest. Franklin Watts, Inc., New York. 1960. Dodge, Natt N. Flowers of the Southwest Deserts. Southwestern Monuments Association. Popular Series No. 4. Globe, Ariz. 1961. ——. Poisonous Dwellers of the Desert. Southwestern Monume
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Reptiles and Amphibians of the monument.
Reptiles and Amphibians of the monument.
This checklist names reptiles and amphibians that have been seen, or that should occur, according to range maps and distribution records in important reference works, in the monument. Four of these species are found only in the Tucson Mountain Section; they are: desert iguana, desert horned lizard, western shovel-nosed snake, and sidewinder. An asterisk marks those species most commonly seen in the daytime. The desert (D) habitat is the rather flat or gently rolling terrain below 3,200 feet in e
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Birds of the monument
Birds of the monument
This checklist is based entirely on written records of observations of birds seen in the monument. Names are in accordance with A.O.U. Checklist of North American Birds, 5th edition, 1957. (See checklist of reptiles and amphibians for description of habitats.)...
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Mammals of the monument
Mammals of the monument
This checklist names mammals that have been observed, and those that, mainly according to collection records and distribution maps in The Recent Mammals of Arizona , by E. Lendell Cockrum, 1960, may occur in the monument. One species, the desert kangaroo rat, probably occurs only in the Tucson Mountain Section. (See checklist of reptiles and amphibians for description of habitats.)...
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Photograph Credits
Photograph Credits
“As the Nation’s principal conservation agency, the Department of the Interior has basic responsibilities for water, fish, wildlife, mineral, land, park, and recreational resources. Indian and Territorial affairs are other major concerns of America’s Department of Natural Resources.” The Department works to assure the wisest choice in managing all our resources so each will make its full contribution to a better United States—now and in the future. National Park Service U.S. DEPARTMENT of the IN
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