III. Bensoniella oregana (Abrams & Bacigal.) C. Morton

Area of Application: Throughout the area covered by the Northwest Forest Plan in California.

A. Introduction

Bensoniella oregana is a rhizomatous perennial herb in the Saxifragaceae plant family. It is similar in appearance to other members of this family that occur in similar habitats. Over the years, bensonia, bensoniella and coalscoop have been used as common names

Bensoniella oregana is considered to be closely associated with old-growth habitat, and is classified as a Survey and Manage Strategy 1 and 2 species for California only under the FSEIS/ROD (USDA Forest Service and USDI Bureau of Land Management 1994a, 1994b). B. oregana is listed in the State of California as Rare, listed by the California Native Plant Society Database as Rare in California and elsewhere, and is on the Region 5 and 6 Regional Forester's Sensitive Species Lists. B. oregana is also considered to be endangered and threatened throughout its range (List 1) by the Oregon Natural Heritage Program (1998), and is considered Oregon and Washington Bureau Sensitive under the OR/WA BLM Special Status Plant Policy. These designations for B. oregana reflect concern that a threshold to maintain viable populations may have been passed because of timber harvesting, grazing, road construction, and road maintenance (Copeland 1980).

B. Unique Characteristics, Biology, and Ecology

The following is a technical description of Bensoniella oregana:

Rhizomatous perennial herb, rhizomes scaly; bulbets 0. Leaves basal; petiole 2-15 cm, hairs dense, long, brown; blade 4-20 cm, round-ovate, base cordate, unevenly crenate, more or less glabrous above, veins hairy below. Inflorescence a raceme, 20-40 cm, spike-like, glandular; bracts 0; pedicel <1 mm. Flowers with hypanthium free of ovary; calyx more or less bilateral, lobes 1.5-2.5 mm, obovate; petals more or less equal to the calyx lobes, thread-like, ephemeral; stamens 5, >calyx lobes; pistil 1, ovary superior, chamber 1, placentas 2, parietal. Fruit a capsule, opening before seeds mature (Hickman 1993).

Bensoniella resembles several other species in the Saxifragaceae that grow in similar habitats. Look-a-likes with which B. oregana may be confused include youth-on-age (Tolmiea menziesii), sugarscoop (Tiarella unifoliata), leafy-stemmed mitrewort (Mitella caulescens), and large fringe-cup (Tellima grandiflora). Floral and vegetative characteristics, however, permits the identification of Bensoniella at any time during the year. Key characteristics to look for during field surveys are the salmon-pink anthers when plants are in flower; open, long- styled capsules with many ovules or shiny black seeds when plants are in fruit; and the deeply lobed leaves with light green petioles covered with long shaggy white hairs (possibly brown hairs if older) when plants are vegetative.

Vegetative growth of Bensoniella begins in early June (Copeland 1980). The inflorescence of plants become visible in mid-June and mature by early July. Capsules begin to dehisce by mid July, and mature seeds are shed in mid August. Lang (1988) reports that seeds in many plants are retained until late August and probably later. Pollination mechanisms have not been established (Copeland 1980; Lang 1988). Vegetative reproduction occurs primarily through a well developed system of branching rhizomes just below the soil surface. Rhizomes will branch and then the older portions will die back producing 2 plants from one section of rhizome. Extensive branching produces patches of plants that are genetically identical.

C. Specific Habitat Associations

Known habitat factors associated with Bensoniella oregana populations includes soils of recent colluvial origin with little soil development; soils that remain moist late into the summer but that are never excessively wet or saturated, a condition that may be related to down logs and residual snow; coastal summer fog between 2,000 and 5,000 feet elevation; meadow habitats with gentle (12% average) slopes; indirect sunlight for most of the day, but no direct sunlight or deep shade for extended periods; structural diversity of the vegetation such that understory canopies filter light, overstory canopies that provide peripheral shade, and down logs that provide shade and act as reservoirs for moisture.

California populations of Bensoniella typically occur along the periphery of meadows adjacent to seeps and small streams in the true fir zone. Oregon populations occur in similar habitats in the mixed conifer and mixed evergreen zones. Elevation ranges between 600-1500 meters (2000-5000 ft.) in Oregon and 900-1400 meters (3000-4600 ft.) in California (Lang 1988). Prolonged moisture, edge habitat along streams and meadows providing partial canopy cover, and soils derived from ancient sedimentary rock are key habitat components (Copeland 1980; Lang 1988). Populations are most often found on north aspects. Bensoniella is most commonly associated with Senecio triangularis, Mitella ovalis, Viola glabella, and Asarum caudatum (Lang 1988). It appears to tolerate some disturbance if subsurface drainage and other critical factors are not altered (USDA Forest Service and USDI Bureau of Land Management 1994b, Lang 1988).

D. Range of Bensoniella oregana

1. Known Range

Bensoniella is limited to the Klamath Mountain Province and Coast Range of southwest Oregon and northwest California. There are approximately 86 occurrences in Oregon and 6 occurrences in California. The California occurrences are geographically isolated from the Oregon sites by approximately 176 kilometers (110 miles). All 6 California sites occur within a 10 kilometer (6 mile) radius of Snow Camp Mountain in central Humboldt County. There are 4 occurrences on private land and 2 in the Six Rivers National Forest with less than 1000 plants occurring on federal land (Imper 1989; Seevers and Lang 1987). One of the Six Rivers National Forest sites is an experimental population established in 1980.

2. Suspected Range

A potential still exists to discover additional sites in the northern most extent of the California Coast Range, the southern Oregon Coast Range and the Klamath Mountain Province of Oregon and California. Surveys under the ROD for the NFP pertain only in the California portion of the species range. Agency special status species or Threatened, Endangered and Sensitive species policies may go beyond the Survey and Manage requirements and require surveys on agency lands throughout the species range.

E. Timing of Surveys

The peak of the blooming period for Bensoniella oregana is from mid-June through early July. Plants fruit between mid-July and mid-August. Although vegetative characteristics permits the identification of Bensoniella at any time during the growing season, the density of associated vegetation may make it difficult to detect populations during this phenological stage. Surveys should be conducted during the flowering or fruiting periods (mid June through mid August) when plants are most easily seen and identifiable.

F. Threats

Management Recommendations (Hoover and Holmes 1998) identified the major threats to B. oregana as follows:

• Erosion and alteration of hydrology
• Reduction of cover from logging, wind-throw, and firewood cutting
• Grazing
• Recreation

REFERENCES

Copeland, W. 1980. Bensoniella oregana: Field study and status report, final summary. Six Rivers National Forest, Eureka, California.

Hickman, J. (Ed.). 1993. The Jepson manual: Higher plants of California. University of California Press, Berkeley, California.

Hoover, L. and R. Holmes. 1998. Management Recommendations for Bensoniella (Bensoniella oregana (Abrams & Bacigal.) C. Morton). Unpublished manuscript.

Imper, D. 1989. Update on population size of Bensoniella oregana at Rooster Rock. Unpublished Report. Six Rivers National Forest, Eureka, California.

Lang, F. 1988. Species management guide for Bensoniella oregana (Abrams & Bacigal.) Morton. Siskiyou National Forest, Grants Pass, Oregon.

Oregon Natural Heritage Program. 1998. Rare, Threatened and Endangered Species of Oregon. Oregon Natural Heritage Program, Portland, Oregon. 92 pp.

Seevers, J. and F. Lang. 1987. Species management guide for Bensoniella oregana (Abrams & Bacigal.) Morton. Bureau of Land Management, Medford, Oregon.

USDA Forest Service and USDI Bureau of Land Management. 1994a. Final supplemental environmental impact statement on managing of habitat for late successional and old-growth species within the range of the northern spotted owl. Portland, Oregon.

USDA Forest Service and USDI Bureau of Land Management. 1994b. Final supplemental environmental impact statement on managing of habitat for late successional and old-growth species within the range of the northern spotted owl. Appendix J2, Results of Additional Species Analysis. Portland, Oregon.