Lake County Stonecrop

Parvisedum leiocarpum

Description

Parvisedum leiocarpum (Lake County stonecrop), is a low, erect to spreading annual in the stonecrop family (Crassulaceae) with reddish stems 1-2 in (2-5 cm) tall. The fleshy, oblong leaves are 0.16-0.20 in (0.4-0.5 cm) long and fall off the stem by flowering time. The inflorescence is a cyme of campanulate (bell-shaped) yellow flowers that are crowded on curving stems in two rows. The five petals are 0.12-0.14 in. (0.3-0.4 cm) long with large, club-shaped, red nectaries. The five carpels have smooth surfaces. Lake County stonecrop flowers in April and May.

Parvisedum leiocarpum was described as Sedella leiocarpa in 1940 from an area 6.5 mi (10.5 km) north of Lower Lake, Lake County, California. The plant was then placed in the genus Parvisedum six years later and gave it the specific rank of Parvisedum leiocarpum. Two similar species occur within the range of Parvisedum leiocarpum. Parvisedum pentandrum differs in having shorter petals, top-shaped flowers, and carpels with glandular bumps on the surfaces. Crassula connata differs in having only one to a few, four-petaled flowers above each leaf base not arranged in definite cymes.

Habitat

Lake County stonecrop is found on volcanic substrates in areas of impeded drainage, such as in and along the margins of vernal pools and depressions in bedrock.

Distribution

The historical range of the species encompasses six collection localities within a 10 mi (16 km) radius from Siegler Springs near Lower Lake, Lake County, California. The elevations of occurrences range from 1,300-2,600 ft (400-800 m). Lake County stonecrop has apparently disappeared at three sites within this area. The extant populations of P. leiocarpum collectively cover a total area of less than three acres. All populations occur on private lands.

Threats

Lake County stonecrop is endangered because of the vulnerability of its restricted habitat to threats posed by urbanization, agricultural land conversion, drainage, vernal pool and pond construction, ditch construction, off-highway vehicle use, road maintenance, and random natural events.

Attempted drainage has altered the hydrology of two of the three remaining vernal pools containing populations of Lake County stonecrop. Drainage attempts at one of the sites resulted in severe erosion and a reduction of habitat and plant numbers. Maintenance of Highway 29 by CALTRANS also threatens to harm individuals of this population, which is found within the highway right-of-way. Discing has occurred at the third population site. All populations occur on privately owned land next to major roads. Off-highway vehicle use has occurred at two of the three Lake County stonecrop population sites. Within the range of Lake County stonecrop, habitat continues to be converted into vineyards and orchards.

Because they are small and delicate, Lake County stonecrop plants would likely be severely damaged if trampled by livestock. Because cattle grazing occurs in the area surrounding at least one population of Lake County stonecrop, trampling may pose a threat to this population.

Conservation and Recovery

The surviving population of the Lake County stonecrop occurs at only three critical habitats, with a total area of about 3 acres (1.2 hectares). This habitat is on private land, and is a risk from development activities, agricultural land-use (including livestock grazing), and other threatening activities. The critical habitats of the Lake County stonecrop should be protected. This could be done by acquiring the private land and establishing ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Lake County stonecrop should be monitored, and research undertaken into its biology and habitat needs, including methods of beneficial management.

Contacts

U. S. Fish and Wildlife Service
Sacramento Fish and Wildlife Office
2800 Cottage Way, Room W-2605
Telephone: (916) 414-6600

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Complex
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

Reference

U.S. Fish and Wildlife Service. 18 June 1997. "Endangered and Threatened Wildlife and Plants; Endangered Status for Four Plants From Vernal Pools and Mesic Areas in Northern California." Federal Register 62 (117): 33029-33038