When can I see the desert in bloom?

Checklist of Plants of the White Sands

A Discussion of Dunes Ecology With Revised Checklist

INTRODUCTION

White Sands National Monument preserves a sea of graceful white gypsum sand dunes--a landscape of stark natural beauty. Life is difficult in the dune field, even for plants adapted to desert conditions. The dune field environment is unusually harsh: plants must endure burial by moving dunes, nutrient-poor gypsum soil, and extreme fluctuations of temperature. Only about 60 species of plants, one quarter of those growing in the adjacent Tularosa Basin, have found a way to survive in the dunes.

This guide combines previously compiled, revised checklists of plants of the White Sands. The following discussion of the ecological aspects of the dunes should help the observer to locate and identify individual species of plants. By placing the checklists in ecological context, it is hoped that the observer will come to think of each plant as a member of a life community interrelating with the dune movement.

ECOLOGICAL ASPECTS

Ecology is the study of the interrelationships between plants and animals and their physical surroundings. It is literally a study of the home or household of living things. In understanding the ecology of the White Sands, several rather distinct homes, or habitats, must be considered. Most of these habitats are named in terms of the physical surroundings because, as in most arid lands, the inorganic part of the environment is the most prominent and has the greatest influence on the organic parts.

Interdune flats: As the gypsum sand dunes move northwestward across the Tularosa Basin, pieces of the underlying desert floor are exposed between the individual dunes. Most of the plant species inside the dune field grow only in these interdune flats, where conditions are less hostile. Better soil and protection from wind and blowing sand allows plants to survive for a while-- until the next dune buries them.

The most showy wildflowers in the interdune flats include Centaury, a gentian with bright pink flowers; Sand Verbena, with its fragrant lilac-like smell; Stick-leaf, with yellow, star-like flowers; Woody Paperflower, which stands out against the white dunes in bright yellow clumps in the fall; and Yellow Evening Primrose.

Marginal Dunes: These extend into the dune field two or three miles from its southern and eastern boundary. Most of the dunes in this habitat are slow-moving, scattered and separated by large grassy, interdune areas. Although the dunes are still the prominent feature here, the effects of vegetation in slowing the rate of dune movement is very evident.

The marginal dunes themselves have become relatively heavily populated with flora able to withstand such physical conditions. There are eight species of plants that routinely grow on the marginal dunes. The Soaptree Yucca is found scattered throughout this part of the dune field. Yuccas that can be seen on the tops of dunes actually germinate in interdune areas. As a dune begins to bury them, the yuccas elongate their stems, growing upward as much as a foot per year, to keep their leaves above the sand.

Two large shrubs, Skunkbush Sumac and Hoary Rosemarymint, can also extend their stems and outgrow slow-moving marginal dunes. Their stems and roots can then anchor the dunes, further slowing dune movement and allowing other plants to take root on the relatively stable soil.

This developing plant community attracted animal life from the adjacent desert, which became fit to live on the dunes through evolutionary adaptation. Thus, the marginal dunes are now an ecological complex of unexpected variety and diversity.

Transverse and Barchan Dunes: In the center of the dune field, the physical forces of nature reign supreme. The paucity of plant life in the interior of the dune field is indicative of the harsh environmental conditions that prevail. Large transverse and barchan dunes creep forward many feet per year, overwhelming all plant life in their paths. Even the fast-growing yucca and rosemarymint cannot outgrow these dunes. No plants grow on the tops of the dunes, and only a few hardy species are able to live in the interdune flats until they are covered by sand. This interdune environment, known as the Abronia (Sand Verbena) association, is characterized by openings invaded first by Evening Primrose. These pioneers occupy the lee slope of the migrating dunes, the most recently created portion of the interdune flat. Moving out toward the center (older portion) of the flat, the Primrose is replaced by Indian Ricegrass and, later, Groundsel. The last plants to invade are Sand Verbena, Ephedra, Greenthread, and, finally, Alkali Sacaton.

Alkali Flat and Lake Lucero: The transverse-barchan dunes grade to the west into a narrow zone of embryonic dunes. The latter mark the eastern boundary of an ancient lake bed called the Alkali Flat. Here alkaline conditions prevent the growth of plant life except for a few scattered grasses and a scaly pseudo- evergreen known as Pickleweed. Lake Lucero, at the southern end of the Alkali Flat, occasionally contains standing water. There is little plant growth in the bed of Lake Lucero due to extreme alkaline conditions and infrequent flooding. However, alkaline- tolerant grasses sparsely fringe the shore of the lake.

Alluvial Fans: The alluvial fans at the base of the San Andres Mountains have coalesced to form a broad slope known as a bajada. The lowermost slopes of this extend into the monument and border the Alkali Flat on the west. The bajada is cut at frequent intervals by deep washes or arroyos that empty onto the Alkali Flat and Lake Lucero. Large Honey Mesquite hummocks are the dominant vegetative feature. The mesquite community soon gives way to Creosote Bush higher up on the slopes, near the monument boundary.

Saltbush Flats: The center of this high desert basin, the Tularosa, is vegetated mainly by Four Wing Saltbush and salt- tolerant bunch grasses. As grazing land, it is now very poor but, in the 1800's before the introduction of range cattle, it supposedly was predominately grassland having more of the appearance of plains than desert. A combination of drought and overgrazing may have allowed the hardy saltbush to take over. The eastern and southern edges of the marginal dunes are bordered by these saltbush flats. This grey-green monotony is broken by an occasional splash of bright red blossoms of the Claret Cup Hedgehog Cactus in the spring and stands of Golden Crownbeard in the fall.

Exotic plants: Tamarisk, or salt cedar, is a Mediterranean shrub introduced into North America. The aggressive tamarisk has spread throughout the southwest, growing thickly along streams, ponds and other seasonally-wet areas. At White Sands, tamarisk has invaded many interdune areas, where water is close to the surface. To protect native plants, the National Park Service is actively trying to control the spread of tamarisk within the monument. Other exotic plants now found in the park include Russian Thistle, or tumbleweed, and African Rue.

CLIMATIC FACTORS

This high desert basin, averaging 4,000 feet in elevation, is subject to harsh and sometimes rapidly changing climatic conditions. Summers are hot, averaging 95°F highs in July and August, with occasional readings over 100°F. Winter days are relatively mild, but nighttime temperatures routinely drop below freezing. Cold spells can send the mercury to below zero. The lowest temperature on record is a -25°F. Snowfall is infrequent, but heavy snows have occurred on occasion. Precipitation averages about eight inches per year, with most of this occurring during summer thunderstorms, often accompanied by hail.

Wind is the dominant climatic factor here, especially from February through May. The prevailing southwesterly winds blow unimpeded across the desert and at times reach gale proportions. Storms sometimes last for several days in the spring. This is the time of greatest dune movement, when living conditions for dune plant and animal communities become extremely harsh.

PLANT CHECKLIST

The following checklist has been compiled by various qualified individuals over the years since White Sands was established as a National Monument in 1933. Much of the work has been done by National Park Service personnel and volunteers. The latest revision was prepared by park volunteers Paul Shaw and Jeanine Derby. A Flora of New Mexico by W.C. Martin and C.R. Hutchins is the source for scientific names used in this checklist.

Separate checklists of birds and other animals of the white sands are available at the monument bookstore.

Last Updated: Wednesday, 22-Dec-2004 10:08:24 Eastern Standard Time
http://www.nps.gov/archive/whsa/plantlst.htm