Salicaceae (Willow Family)

Black Cottonwood,Populus trichocarpaT. & G. (Fig. 5.10a ) 40–100 ft (12–30 m) in height; trunk 1–3 ft (0.3–1 m) in diameter; grayish, smooth bark that is furrowed with age; branches spread to form a broad, open crown; leaves ovate, 1.5–3 in (4–8 cm) long (less commonly longer), truncate or cordate at the base, acute at the apex, margins finely serrate, shiny dark green above, paler and glaucous beneath; petioles rounded, 0.6–1.6 in (1.5–4 cm) long; dioecious, male and female catkins rare, 1.5–3 in (4–8 cm) long.

Distribution. Sporadic in the range, occurring mostly near streams, springs, or meadows from 4,900 to 8,850 ft (1,500 to 2,700 m). This species forms part of the riparian community in Wyman Canyon (7,610 ft [2,320 m]), Queen Canyon (7,200–8,300 ft [2,195–2,530 m]), and at Toll House Springs (5,970 ft [1,820 m]).

Black Cottonwood is the largest of the American poplars. It commonly occurs as part of the riparian community in both the desert scrub and pinyon-juniper vegetation zones in the White Mountains. Black Cottonwood is able to capture, use, and store great quantities of water from streams, springs, and the groundwater table. It is commonly intermixed with various willows (Salix spp.). Black Cottonwood is very shade-intolerant, and an individual must occupy a dominant position to thrive.

Figure 5.10
(a) Black Cottonwood. (b) Fremont Cottonwood.
(c) Quaking Aspen. (d) Willow.

Male and female flowers are present on separate trees. Female flowers form hanging clusters that are covered with cottony hairs. When the seeds are released, they are scattered by the wind and form small, white drifts in sheltered places, hence the name cottonwood .

Fremont Cottonwood,Populus fremontii Wats. (Fig. 5.10b ) 40–100 ft (12–30 m) in height; bark whitish gray, roughly cracked; branches spreading, forming a broad, open crown; twigs stout; leaves deltoid, 1–3 in (3–8 cm) long, 1.5–3.5 in (4–9 cm) wide, truncate to cordate at the base, sharply pointed at the apex, margins crenate, yellowish green and glossy above, paler beneath; petioles flattened, 1.5–3 in (4–8 cm) long; dioecious, catkins dense, 2–4 in (5–10 cm) long, female catkins loosely flowered; seeds with long white hairs.

Distribution. Spotty along creeks and streams from 5,580 to 7,875 ft (1,700 to 2,400 m), forming part of the riparian community along Wyman Canyon (6,990 ft [2,130 m]), Silver Canyon (6,800 ft [2,075 m]), and Montgomery Canyon (7,790–8,010 ft [2,375–2,440 m]).

Fremont Cottonwood was named for John C. Fremont. He discovered this large arid-land cottonwood in 1844 on an expedition to Nevada and California. Typically a

southwestern species, it occurs in a few scattered locations in the White Mountains. Fremont Cottonwood occurs in the riparian community at Wyman and Indian canyons, on the east side of the White Mountains, and at Silver, Lone Tree, and Montgomery canyons, on the west side of the range (Peterson and Elliott-Fisk, 1988).

Fremont Cottonwood has been widely planted as an ornamental tree in the West. Whether this species is native or was introduced to the White Mountains is unclear. The distribution of Fremont Cottonwood is very patchy, and the number of individuals at each location is small.

Narrowleaf Cottonwood,Populus angustifoliaJames. 30–60 ft (10–20 m) in height; grayish bark; narrow crown; slender twigs; leaves mostly lanceolate, 1.5–3 in (4–8 cm) long, 0.4–1.2 in (1–3 cm) wide, rounded at the base, somewhat acuminate at the apex, margins coarsely serrate, light green and glabrous; dioecious.

Distribution. Rare; moist habitats; known only from two sites in the range — at Wyman Canyon (7,020–8,200 ft [2,140–2,500 m]) and Queen Canyon (8,300 ft [2,530 m]).

Narrowleaf Cottonwood is common in much of the Rocky Mountain region. Isolated sites in California define the western edge of this species' distribution.

Quaking Aspen,Populus tremuloides Michx. (Fig. 5.10c ) 10–50 ft (3–20 m) in height; straight trunk; smooth, greenish-white bark (darkening at base with age); slender twigs that commonly droop; leaves round-ovate, 1–2 in (2.5–5 cm) long and about as wide, broadly rounded to cordate at the base, sharply pointed at the apex, margins crenate or serrulate to almost entire, glabrous and green above, paler beneath; petioles flattened, 1–2.5 in (2.5–6 cm) in length; flowers rare, dioecious, male catkins 1.5–2.5 in (4–6 cm) long, female catkins 2–4 in (5–10 cm) long; tiny seeds (2 million/pound), brown with white hairs.

Distribution. Occurs predominantly in the Subalpine Zone from 9,025 to 10,825 ft (2,750 to 3,300 m) in rocky areas and moist locations along streams or at the edges of meadows. Major stands occur on the east side of the range on the South Fork McAfee Creek (10,825 ft [3,300 m] and below), Crooked Creek (9,850 ft [3,000 m]), and Indian Creek (8,850 ft [2,700 m]).

Quaking Aspen forests are one of the most productive communities in the White Mountains. Major stands are located on the eastern slopes of the range. This species does not inhabit a distinct zone, as in some parts of the Great Basin region; instead it has a patchy distribution. It is possible that Quaking Aspen was previously more extensive in the range and that these are relict stands (Peterson and Elliott-Fisk, 1988).

Even though an aspen stand can produce millions of seeds annually, reproduction — or, more properly, stand growth and maintenance — is predominantly vegetative. New trees arise from a common root system; groves of these trees are referred to as clones. All of the trees that make up an individual clone are genetically identical.

Quaking Aspen is intolerant of both shade and competition from conifers. Therefore, this taxon does not occur intermixed with coniferous woodlands in the White-Inyo Range, but only in disjunct stands. Quaking Aspen is best developed on moist soils derived from colluvium or glacial till.

Dwarf Quaking Aspen trees occur in two localized exposed sites at the head of Silver Canyon (10,400 ft [3,170 m]) and on the slopes surrounding the South Fork McAfee Creek (10,800 ft [3,292 m]). These trees are considered to be genetic dwarfs. According to Strain (1964), Dwarf Aspen exist in a more severe environment than nondwarfs. Dwarf Aspen take on a recognizably different growth form and typically have short trunks with many low branches, giving the tree a shrublike appearance. The leaves of Dwarf Aspen are somewhat larger than those of nondwarfs.

Willows,SalixL. spp. (Fig. 5. 10d ) May attain height of 10–20 ft (3–6 m); bark light in color, on older trees fissured and darker; commonly multistemmed above base; twigs slender, yellow to reddish; leaves long, simple, mostly narrow, pinnately veined, and alternately arranged; petioles short; dioecious, catkins distinct, yellow to green; seeds tiny (2–3 million/pound) with small tufts of hair.

Distribution. Common in riparian areas throughout the range, 4,500–10,000 ft (1,375–3,050 m). Salix exigua rarely occurs in nonriparian sites.

Willows line creeks and streams throughout the White Mountains. Eight species are known to exist in the range. The most common include Salix exigua, S. lasiolepis, and S. lutea , which occur from 4,500–10,000 ft (1,370–3,050 m). The other species have a more sporadic distribution and include S. geyeriana, S. laevigata, S. lasiandra, S. pseudocordata , and S. orestera (Peterson, 1986; Peterson and Elliott-Fisk, 1988).

Willows commonly have multiple, branching trunks and take on either a tree or a shrub form. Of the 175 species native to North America, only 30 attain tree size. Willows are commonly associated with Quaking Aspen, Water Birch, and cottonwoods in the White-Inyo Range and locally form an impenetrable wall of vegetation.

Although willows are an easily recognizable element of the riparian community, the identification of individual species can be a difficult task. Male and female flowers occur on separate plants, and both are needed to make a correct identification.

Willows are intolerant of shade and dry soils. Germination rates are low, but many seeds are produced by each plant. The seeds have fine, cottonlike hairs, which aid in their dispersal by wind. Because this species is riparian, seeds are also transported by water.