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  • Posted by Lee

Only the Tropics are Missing


In 1889, based on his observations from the Grand Canyon to the top of Humphreys Peak near Flagstaff, Arizona, C. Hart Merriam developed the concept of life zones that contain different plants and animals with changes in altitude and latitude. Of the seven life zones he described, six are found in New Mexico; only the tropical life zone is missing. Altitudes in New Mexico vary from 2,842’/866 m in the southern part of the state at Red Bluff Reservoir to 13,161’/4011 m in the north on the summit of Wheeler Peak. Simultaneously, the amount of annual precipitation varies from less than 10 inches/25 cm per year in the southern deserts, Rio Grande Valley, and San Juan River Valley to 20-30 inches/51-76 cm at elevations above 7,000’/ 2134 m. Life zones have distinctive plants and animals whose habitat is dependent upon available water supply, soil, exposure, environmental factors, human encroachment, and humidity within specific altitudes.

Any trip through New Mexico and the mountains may begin in one climate zone and end in a totally different climate zone, making it possible for travelers to see vegetation in a desert and above timber line all in one day. Below are the life zones found in New Mexico and a brief description:

Lower Sonoran

3,000’/914 m through 5,000’/1524 m

The Lower Sonoran life zone is found along the southern Rio Grande Valley (Rio Abajo), the Deming Plain, and the Tularosa Basin. Predominant plants (zone indicators) are grama grass, mesquite, creosote bush, and several cacti such as ocotillo and yucca species.

Upper Sonoran

5,000’/1524 m through 7,000’/2134 m

Juniper, piñon pine, and buffalo grass are found along the upper Rio Grande (Rio Arriba) in the Upper Sonoran life zone. The plants of this life zone provide valuable cool grazing and ranching land as well as thousands of acres of sagebrush that prevent erosion.

Transition

7,000’/ 2134 m through 8,000’/2438 m

Large forests of ponderosa pine (yellow pine), which comprise much of the timber reserves in the state, grow in the Transition life zone. There are also varieties of oak, willow, maple, birch, locust, wild plum, and cherry in this zone. Bushes such as currant, gooseberry, buckthorn, wild rose, and snowberry furnish the undergrowth. Kinnikinnic spreads a green carpet on the rocky forest floor with brilliant red berries in fall.

Canadian

8,000’/2438 m through 10,000’/3048 m

In the Canadian life zone, mixed conifer such as Douglas fir and quaking aspen trees create sweet smelling forests. During the fall season each year, forests of aspen turn vibrant gold, making this zone easily recognizable.

Hudsonian (Subalpine) 10,000’/3048 m through 12,000’/3658 m

Engleman spruce, bristlecone (foxtail) pine, cork-barked fir, and limber pine mark the onset of the Hudsonian zone below timberline. This region receives the heaviest snowfall and is sometimes called the “snow zone”. Abundant moisture gives it luxuriant vegetation. Sub-alpine meadows contain elephantella, bistort, roes crown, paint brush and pearly everlasting flowers. The spruce forest in this zone contains twin flower, lady slipper, and fairy slipper plants. Along the streams are chiming bell, monkshood, Parry primrose, arnica, and larkspur flowers. This zone is also the life zone for sheep grazing in the mountains.

Arctic Alpine (Alpine)12,000’/3658 m through 13,000’/3962 m

The mountain region above timberline is known as the Arctic Alpine life zone and consists of grasslands, meadows, rock fields, and cliffs. On high meadows alpine sunflowers (Rydbergia), marsh marigolds, large cushions of moss campion, and innumerable dwarf flowers bloom in brilliant colors. Among these are forget-me-nots, dwarf primroses, and gentians. Rocks beyond the last tundra are often covered with colorful lichens.

The vegetation of New Mexico is as varied as the landscape as shown in this gallery of photographs: red chili drying in Chimayo, sotol cactus in the Sacramento Mountains, grasslands and pronghorns in the San Augustin Plains, aspen in full fall color in the Sangre de Cristos, tall ponderosa pine in the Jemez, alpine columbine, cottonwood in the Gila, tall yucca (the New Mexico State flower) near the Hatchet Mountains, and cholla cactus at the base of Ortiz Mountain.


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