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One-seed Juniper (Juniperus monosperma)

GENERAL BOTANICAL CHARACTERISTICS: Oneseed juniper is a native, long-lived, evergreen tree with often shrubby form, 10 to 40 feet (3-12 m) high with several curved limbs arising near the base [32,42,121,127].

OneseMay 24, 2007 staminate cones, and subglobose ovulate cones [42,127]. Mature cones are dark blue to purple or brownish, and succulent, or at least somewhat fleshy [50,June 1, 2007ref="http://www.fs.fed.us/database/feis/plants/tree/junmon/references.html#132">132]. Seeds are generally 1 per fruit, more rarely 2, reddish-brown and ovoid to globose [50,127]. Juniper seeds are described as having a semipermeable and thick seed coat with a dormant embryo [41]. The cones are often referred to as "berries" in the literature.

Mature oneseed junipers have both tap and lateral root systems. The taproots in 1 study rangMay 24, 2007May 24, 2007May 24, 2007 3 times as long as the tree was tall. Most lateral roots were in the surface 3 feet (1 m) of the soil, most of those concentrated below the surface 6 inches (15 cm) [64]. The deep root system of mature oneseed junipers is adapted for growth on dryJune 1, 2007June 1, 2007June 1, 200764">64,107]. Foxx and Tierney [43] reported rooting depths ranging from 16 to 197 feet (5-60 m).

Oneseed juniper is a slow-growing species. Lymbery and Pieper [80] reported an increase in height of approximately 6.3 inches (16 cm) per decade, with a corresponding increase in stem diameter of 0.5 inch (1.2 cm). Growth rate tends to vary according to site characteristics, however. On a hilly site in southwestern Texas, a oneseed juniper 35 years of age was 14 feet (4.3 m) in height with a diameter of 0.5 inch (1.3 cm) [23].

SITE CHARACTERISTICS: Oneseed juniper occupies xeric sites in semiarid climatic zones [38,51,102]. A typical Arizona site occupied by oneseed juniper receives 10 to 15 inches (250-380 mm) of precipitation annually, and has an average growing season of approximately 120 days [95,134]. Unlike several related species, the distribution of oneseed juniper does not appear to be limited by temperature inversions [59].

Oneseed juniper grows on dry, rocky, open flats, and slopes [32,50,52]. It commonly occurs in canyons or on middle-elevation foothills [50,134]. In many areas this juniper occurs in a zone below ponderosa pine (P. ponderosa) or alligator juniper, but above oak (Quercus spp.)-mountain-mahogany (Cercocarpus spp.) shrublands [96,134].

Because soil moisture is limited on many oneseed juniper sites, competition with others species may significantly influence the occurrence of this tree on a particular site. Grasses can compete effectively with oneseed juniper seedlings for moisture and can limit its distribution in some areas [64,135]. Many oaks also compete for soil moisture, although oneseed juniper appears to be capable of outcompeting them on shallow soils [115]. Where oneseed juniper occurs with Colorado pinyon, junipers show much more adaptation to drought stress than do the pines [107]. These observations were based on tissue water potentials and metabolic activity during the hottest part of the day.

Oneseed juniper grows on a variety of soil textures including gravelly, rocky, or sandy soils [50]. Parent materials include basalt, limestone, and sandstone [38]. Soil characteristics, combined with temperature, moisture and topography influence the upper and lower elevational extent of oneseed juniper [18,134]. Elevational ranges of oneseed juniper reported in the literature are: Arizona 3,000 to 7,000 feet (914-2,130 m) [32,72] Colorado 4,000 to 7,600 feeMay 24, 2007(1,525-2,285 m) [125]

Johnson, Kathleen A. 2002. Juniperus monosperma. In: Fire Effects Information System, [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Available: http://www.fs.fed.us/database/feis/ [2007, May 18].

One-seed Juniper Distribution Maps

Distribution One-seed Juniper (Little, 1971)

Distribution of One-seed Juniper 4 corner states (FIA)

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Seeds & Twigs

Twig (closeup)