San Bernardino Bluegrass

Poa atropurpurea

Description

San Bernardino bluegrass, Poa atropurpurea, a member of the grass family (Poaceae), is a dioecious (separate male and female plants), tufted perennial with creeping rhizomes. The inflorescence is an erect, dense spike-like panicle (compound floral axis) 8-18 in (20-45 cm) high. The lemmas (lower of the two bracts enclosing the flower in the spikelet of grasses) are smooth, faintly nerved and less than 0.14 in (3.5 mm) long. The glumes (scaly bracts of the spikelets) are 0.06-0.08 in (1.5-2 mm) long. This species flowers from early May to June or July. San Bernardino bluegrass may be distinguished from P. pratensis (Kentucky bluegrass), with which it is often associated, by its shorter inflorescences, contracted panicles, and glabrous lemmas and calluses (extension of the inner scale of the spikelet).

Habitat

San Bernardino bluegrass occurs in montane meadows in the Big Bear region of the San Bernardino Mountains, as well as in meadows in the Laguna Mountains and Palomar Mountains of San Diego County at elevations of 6,000-7,500 ft (1,800-2,225 m), near the drier margins of meadows that are vernally wet marshlands. Eleven population centers of San Bernardino bluegrass currently are known to exist in the San Bernardino Mountains and are often found at meadow sites with California taraxacum. Clones, consisting of numerous erect culms (stems), are about 3 ft (90 cm) in diameter and may intermingle. Two of the 11 known populations in the San Bernardino Mountains are about 23 acres (9,2 hectares) in size and are located on Forest Service land at Holcomb Valley and Wildhorse Meadows, one 5-acre (2-hectare) site at North Baldwin Lake is administered by California Department of Fish and Game, one 20-acre (8-hectare) site is cooperatively owned by the Forest Service and a private youth camp, Hitchcock Ranch, and seven sites, about 50 acres (20 hectares) total, are privately owned. Fewer than 100 acres (40 hectares) of habitat for this species are known to remain in the San Bernardino Mountains.

Distribution

In 1979, four known populations of San Bernardino bluegrass were reported in the Laguna Mountains of San Diego County. In 1981, a collection of San Bernardino bluegrass was reported from Mendenhall Meadow in the Palomar Mountains of San Diego County. By 1993, San Bernardino blue-grass was thought to be extirpated from the Laguna Mountains and the Palomar Mountains, when two populations, each consisting of about 50 individuals, were located within the Cleveland National Forest in the Laguna Mountains. More than 1,000 plants were reported at seven sites near Laguna Meadow. Five of these sites appear to encompass the four sites reported in 1979; the other two are apparently newly reported sites. In total, this species is known from less than 20 populations throughout its range.

Threats

This species is imperiled by a variety of activities that result in habitat modification, destruction, degradation, and fragmentation. These activities include urbanization, off-road vehicle activity, alteration of hydrological conditions, and vandalism.

Co-occurrence of male and female plants of this species is necessary for seed production. Collections made in 1994 from Big Laguna and Mendenhall meadows of San Diego County were all female culms; in the Cleveland National Forest only four male plants, two at each of two different sites, were found. Although it is possible that the San Diego County populations have turned apomictic (not needing fertilization), the severe imbalance between male and female plants could limit reproduction.

Conservation and Recovery

The San Bernardino bluegrass survives as 11 known populations, occurring on less than 100 acres (40 hectares) of land. Two critical habitats are on federal land managed by the Forest Service in Cleveland National Forest, one is owned by the California Department of Fish and Game, and one is co-owned by the Forest Service and a private youth camp. These publicly owned habitats should be protected against any threatening activities. Their protection should be written into the management plans for the areas. The other seven critical habitats are on private land, and are threatened by destruction or degradation. These should be protected. This could be done by acquiring the habitats and designating them as ecological reserves, or by negotiating conservation easements with the landowners. The populations of the San Bernardino bluegrass should be monitored, and research undertaken into its basic biology and ecological requirements.

Contact

U.S. Fish and Wildlife Service
Carlsbad Field Office
2730 Loker Avenue West
Carlsbad, California 92008-6603
Telephone (760) 431-9440
Fax: (760) 431-9624

Reference

U.S. Fish and Wildlife Service. 14 September 1998. "Endangered and Threatened Wildlife and Plants; Final Rule To Determine Endangered or Threatened Status for Six Plants From the Mountains of Southern California." Federal Register 63 (177): 49006-49022.