4—
Plant Zones

Timothy P. Spira

Desert Scrub Zone (4,000–6,500 ft, 1,219–1,981 m)

A shrub-dominant vegetation covers the valley floors and mountainsides of the White-Inyo Range up to elevations of approximately 6,500 ft (1,980 m) (Fig. 4.1). The vegetation is remarkably uniform in appearance, even though many different species are present. The dominant shrubs are generally less than 3 ft (0.9 m) tall, grayish, small-leaved, and small-flowered.

The most common species is Shadscale (Atriplex confertifolia ), an erect, stiffly branched, spiny shrub with round, crowded deciduous leaves that resemble fish scales. Shadscale commonly occurs on heavy alkaline (pH 8–10) and saline soils locally underlain with a hardpan. At higher elevations, sagebrush (Artemisia spp.) becomes dominant. Other important shrubs include Creosote Bush (Larrea tridentata ), Nevada Ephedra (Ephedra nevadensis ), Rabbitbrush (Chrysothamnus nauseosus ), and Spiny Hopsage (Grayia spinosa ).

At least seven species of sagebrush (Artemisia ) occur in the White-Inyo Range. These aromatic shrubs or herbs with lobed silvery gray-green leaves form a dominant part of the vegetation from the desert floor to the alpine desert. In the Desert Scrub zone, both Bud Sagebrush (Artemisia spinescens ) and Basin Sagebrush (A. tridentata ) are common.

The primary factor preventing tree growth in the Desert Scrub vegetation is the small amount of rainfall (less than 10 in, or 25.4 cm per year). The stress imposed by scanty precipitation is intensified by high summer and low winter temperatures, strong winds, and shallow soils. The wide spacing between shrubs probably reflects intense root competition for soil moisture or a phenomenon known as allelopathy, whereby plants produce chemical substances that inhibit the growth of other plants.

Perennial and annual herbs commonly occur in open areas between shrubs. Among the more conspicuous perennial herbs are penstemons (Penstemon ssp.), the Large White Evening Primrose (Oenothera caespitosa ssp. marginata ), Wishbone Bush (Mirabilis bigelovii ), and various grasses. Showy displays by annuals such as Little Blazing Star (Mentzelia albicaulis ), Wilcox Woolly Star (Eriastrum sparsiflorum var. wilcoxii ), and Chia (Salvia columbariae ) are restricted to favorably moist years.

The vegetation of washes and springs differs dramatically from that of surrounding areas. For example, trees such as Black Cottonwood (Populus trichocarpa ) and Yellow Willow (Salix lutea ) occur in areas where there is a permanent source of water.

Figure 4.1
Desert Scrub. Loosely scattered shrubs in foothills of the White-Inyo Range.

Pinyon-Juniper Woodland Zone (6,500–9,500 ft, 1,981–2,896 m)

The vegetation of the Pinyon-Juniper Woodland zone (Fig. 4.2) derives its name from codominant trees, the Pinyon Pine (Pinus monophylla ) and the Utah Juniper (Juniperus osteosperma ). From a distance, these two tree species look very similar. Up close, however, they are easily distinguished, as Pinyon Pines have gray-green needle-like leaves and woody seed-bearing cones, whereas junipers have yellow-green scale-like leaves and fruitlike berries.

Like many trees in arid environments, Pinyon Pines and Utah Junipers grow slowly. Mature trees are rarely more than 20 ft (6.1 m) tall, and because trees tend to be widely spaced, this community is called a woodland rather than a forest.

Pinyon Pines commonly occur on shallow-soiled, rocky hillsides and mesas, where their deep-spreading roots probe for underground water. Utah Junipers occur on a variety of substrates, including rocky and deep alluvial soils. In moister areas, such as north-facing slopes, trees are taller and more crowded, and the vegetation resembles a dwarfed forest rather than a woodland. In drier areas, trees are commonly absent, and shrubs form the dominant cover.

Important shrubs in the Pinyon-Jumper Woodland include broom and Great Basin Sagebrush (Artemisia nova and A. tridentata ), Bitterbrush (Purshia tridentata and P.

Figure 4.2
Pinyon-Juniper Woodland. Sagebrush (Artemisia  sp.) is the shrubby vegetation in the
foreground, with Pinyon Pine (Pinus monophylla ) and Utah Juniper (Juniperus
osteosperma ) in the background.

glandulosa ), Green Ephedra (Ephedra viridis ), and Curly Rabbitbrush (Chrysothamnus viscidiflorus ssp. viscidiflorus ). In late summer and fall, the golden flowers and silver gray-green foliage of Curly Rabbitbrush is particularly striking along roadsides in both the Pinyon Woodland and Desert Scrub zones.

Subalpine Zone (9,500–11,500 ft, 2,896–3,505 m)

The Subalpine Zone (Fig. 4.3) consists of a patchy mosaic of sagebrush and open forest. The discontinuous nature of this vegetation is due largely to differing soil type. On sandstone and granitic soils, sagebrush (Artemisia spp.) is dominant. Where the soil is white, indicating a dolomite substrate, Bristlecone Pine (Pinus longaeva ) predominates.

Limber Pine (Pinus flexilis ) occurs with Bristlecone Pine or forms pure stands. Other conifers, such as Lodgepole Pines (Pinus murrayana ) and Ponderosa Pine (P. ponderosa ), are rare.

Forests of Quaking Aspen (Populus tremuloides ) occur in moist areas, particularly on the east side of the range. On dry slopes at lower elevations, pure stands of Mountain Mahogany (Cercocarpus ledifolius ) are common.

One of the most striking features of the White-Inyo Range is the gnarled, beautifully sculptured Bristlecone Pines. These trees are known to live up to 5,000 years and are commonly considered to be the world's oldest living organisms. Some of the trees that are alive today were young plants when the great pyramids of Egypt were constructed and were mature trees at the time of Christ.

Many of the oldest known Bristlecone Pines grow in the Schulman Grove of the White Mountains at an elevation of about 10,000 ft (3,050 m). Here one can take a self-guided nature trail to Pine Alpha, a 4,300-year-old tree that continues to produce fertile seeds. Pine Alpha derives its name from the first letter of the Greek alphabet because it was the first Bristlecone Pine determined to be more than 4,000 years old. The oldest known living tree, aptly named the Methuselah, is still growing vigorously in the Schulman Grove after more than 4,600 years. One older tree, estimated to be approximately 5,000 years old, grew on Wheeler Peak in Nevada before it was accidentally felled.

Many of the older Bristlecone Pines consist of one or two leafy branches with a narrow strip of living bark running through an otherwise dead trunk. Pine Alpha, for example, has a trunk nearly 4 ft (1.2 m) in diameter with only a 10 in (25 cm)-wide strip of living tissue. Hence, only a small amount of living tissue is necessary to keep a Bristlecone Pine alive.

Figure 4.3
Subalpine. Note sharp transition in vegetation due to edaphic (soil) factors. The sagebrush
(Artemisia  sp.) vegetation in the foreground is on sandstone, and the Bristlecone-Limber
Pine (Pinus longaeva-P. flexilis ) forest in the background is on dolomite.

Bristlecone Pines grow slowly, commonly less than 1 in (2.54 cm) in diameter every 100 years. The wood of these slow-growing trees is very dense and highly resinous and is therefore relatively resistant to the insect, fungal, and bacterial organisms that attack most other trees. The extremely dry air also helps prevent rotting. Because of their unusually slow decomposition rate, Bristlecone Pines can remain standing long after they have died, and fallen trees thousands of years old dot the landscape.

The oldest Bristlecone Pines commonly grow in the harshest areas — low-elevation, south-facing slopes with thin dolomitic soils. On these extremely dry, nutrient-poor sites, Bristlecone Pines grow especially slowly. Trees growing in more favorable areas do not live as long because their more rapid growth results in a less dense, less resinous wood that is more susceptible to disease and decay. Therefore, the harsh environment and slow growth rate of Bristlecone Pines actually contribute to their remarkable longevity.

Alpine Zone (11,500–14,246 ft, 3,505–4,342 m)

The vegetation above treeline is referred to as alpine (Fig. 4.4). In the White-Inyo Range, treeline generally occurs at elevations above 11,500 ft (3,505 m). In many

Figure 4.4
Alpine.
Photo taken on Sheep Mountain at an elevation of 11,600 ft (3,536 m). Note the
lack of trees at this elevation. White Mountain Peak (14,246 ft, 4,342 m) is in background.
Light areas on right represent moonscape-like dolomite barrens.

respects, the Alpine Zone in the White-Inyo Range resembles a high-elevation desert: solar radiation is intense, wind speeds are high, and evaporative water loss is severe. Since precipitation occurs primarily as winter snow, the only water available during the summer growing season is from melting snow and occasional summer storms. Other factors limiting plant growth in the summer are low temperatures, occasional frosts, and a short growing season.

Among the most distinctive areas of the White-Inyo Alpine Zone are the dolomite barrens. Viewed from a distance, the white landscape and apparent lack of vegetation give one the impression of a moonscape. Up close, however, small, loosely scattered plants are visible. Among these are Dwarf Paintbrush (Castilleja nana ), Cushion Phlox (Phlox condensata ), Raspberry Buckwheat (Eriogonum gracilipes ), and Blue Flax (Linum lewisii ).

On granite substrates above 12,000 ft (3,658 m), Alpine Fell-fields are common. The plant cover on these rock-strewn fields and slopes is fairly dense, sometimes covering all of the available soil surface. Important species include Mono Clover (Trifolium andersonii ssp. monoense ), Fell-field Buckwheat (Erigonum ovalifolium var. nivale ), Whorlflower (Penstemon heterodoxus ), and numerous grasses and sedges. Two of the more common grasses, Junegrass (Koeleria macrantha ) and Squirreltail Grass (Sitanion hystrix ), extend down into the Pinyon Woodland zone.

Dwarf Sagebrush (Artemisia arbuscula ) is widely distributed on dry, sandy soils. On talus slopes, the rocky substrate is unstable, and the soil is poorly developed; hence, the vegetation is quite sparse. Interestingly, three of the more conspicuous species present on talus slopes are restricted to elevations higher than 13,000 ft (3,962 m). These high alpine species are White Mountain Sky Pilot (Polemonium chartaceum ), Alpine Daisy (Erigeron vagus ), and Broad-podded Parrya (Anelsonia eurycarpa ).

The lower precipitation in the White-Inyo Range relative to the nearby Sierra Nevada results in a more open, less luxuriant vegetation. However, in areas of the White-Inyo Range where streams and ponds provide a source of water throughout the summer season, the vegetation can be relatively lush. In moist alpine areas, grasses and sedges predominate, particularly Tufted Hairgrass (Deschampsia caespitosa ) and Alpine Sedge (Carex subnigricans ). Meadow species with showy flowers that form colorful displays include Little Elephant's Head (Pedicularis attolens ), Meadow Mimulus (Mimulus primuloides var. primuloides ), and Alpine Gentian (Gentiana newberryi ).

A conspicuous feature of alpine plants is their prostrate growth form. By growing close to the ground, these plants gain shelter from potentially damaging winds. Plants with tightly interwoven clumps of leaves and a hemispherical shape are called cushion plants. Examples include Fell-field Buckwheat (Eriogonum ovalifolium var. nivale ) and Cushion Phlox (Phlox condensata ). Similar to cushion plants, but with greater lateral growth, are mat-forming species such as Mono Clover (Trifolium andersonii ssp. monoense ) and Whorlflower (Penstemon heterodoxus ). The close-knit foliage of these species counters cold nighttime temperatures by trapping daytime heat. For example, the interior of a cushion plant may be as much as 20°F (6.7°C) warmer than the surrounding air. Rosette plants, such as Alpine Gentian (Gentiana newberryi ) and Dwarf Lewisia (Lewisia pygmaea ssp. pygmaea ), represent a third prostrate growth form. These

plants have leaves that lie flat on the ground and receive direct sunlight as well as the added heat from the ground below.

Alpine plants tend to have well-developed root and/or rhizome systems. In fact, most alpine species have more of their biomass underground than aboveground. Along with absorbing water and nutrients from the soil, a primary function of the underground portion is food storage, particularly during the long winter season, when plants are dormant. Following snowmelt in late spring or summer, stored food reserves are used to initiate rapid vegetative growth. Because flower buds are generally produced one or more years prior to flowering, open flowers are commonly present shortly after vegetative growth is initiated each year.

For a number of reasons, sexual reproduction in alpine plants occurs infrequently. Flowers may fail to produce fruits and seeds due to limited resources, lack of pollination, or insufficient time prior to the onset of winter conditions. Low germination rates and high seedling mortality may further limit reproductive success. However, the ability of many alpine species to reproduce vegetatively and to persist for many years, once successfully established, may partially compensate for infrequent reproduction by seed.

Representative Species of Major Plant Zones

Desert Scrub Zone (4,000–6,500 ft, 1,219–1,981 m)

Pinyon-Juniper Woodland Zone (6,500–9,500 ft, 1,981–2,896 m)

Subalpine Zone (9,500–11,5OO ft, 2,896–3,505 m)

Alpine Zone (11,500–14,246 ft, 3,505–4,342 m)

References

Barbour, M. G., and J. Major (eds). 1988. Terrestrial vegetation of California, 2d ed. John Wiley & Sons, New York.

Lloyd, R. M., and R. S. Mitchell. 1973. A flora of the White Mountains, California, and Nevada . University of California Press, Los Angeles.

Munz, P. A. 1968. A California flora . University of California Press, Los Angeles.

Ornduff, R. 1974. An introduction to California plant life . University of California Press, Los Angeles.

Zwinger, A. H., and B. E. Willard. 1972. Land above the trees: A guide to American alpine tundra . Harper & Row, San Francisco.