Conservation Assessment
for
Scouleria marginata Britton
Photo by Judith Harpel.
September 2005
Judith A. Harpel Ph.D.
USDA Forest Service Region 6 and
USDI Bureau of Land Management, Oregon and Washington
Disclaimer
This Conservation Assessment was prepared to compile the published and unpublished information on Scouleria marginata. It does not represent a management decision by the U.S. Forest Service or Bureau of Land Management. Though the best scientific information available was used and subject experts were consulted in preparation of this document, it is expect that new information will arise. In the spirit of continuous learning and adaptive management, if you have information that will assist in conserving the subject taxon, please contact the interagency Special Status/Sensitive Species Conservation Planning Coordinator in the Portland, Oregon Forest Service/Bureau of Land Management Offices at: http://www.or.blm.gov/isssp/.
Executive Summary
Species and Taxonomic Group
Scouleria marginata Britton, Bryophyte
Management Status
Scouleria marginata is listed as Sensitive on the Region 6 U.S. Forest Service
(R6) Sensitive Species List, and is considered a Tracking species in Oregon by the Oregon-Washington Bureau of Land Management (http://www.or.blm.gov/isssp/).
BLM Tracking species are not considered a Special Status Species for management
purposes. In Washington this species is listed as Threatened by the Washington Natural
Heritage Program (http://www.dnr.wa.gov/nhp/refdesk/lists/plantrnk.html).
Range & Habitat
Scouleria marginata is a western North American endemic species that ranges
from British Columbia, Canada to central California and occurs on bedrock
material or large boulders along perennial rivers. Within the Pacific Northwest,
there are predominantly historical sites in Washington and Oregon.
Threats
There are direct and indirect impacts that may occur to this species. Direct impacts result in the degradation or extirpation of individuals of populations of S. marginata. Because this species is located along perennial river systems, potential direct threats include in-stream activities such as: adding large wood, gold dredging, repositioning of boulders and concentrated recreational activities, such as boat launch sites, that could result in mechanical injury to a site. These direct threats could also lead to permanent changes in stream flow, which could alter the species distribution. Indirect impacts such as siltation or changes in stream flows that result from timber harvest or road construction could also impact this species. Flooding from dam construction and the operational effects of dams on stream flows and water quality, have been known to impact stream bryophytes (Glime 1992). Channel re-alignment projects that divert water flow could also eliminate this species from a stream. According to Bates (2000) and Glime (1992) aquatic bryophytes are very sensitive to organic and inorganic pollutants such as increased nutrients (fertilizer), acidification and heavy metals therefore the addition of fertilizer, or pollutants could also be additional threats. Finally over-collection of S. marginata for scientific purposes could impact this species.
Management Considerations
While this species benefits from riparian reserve management and implementation of the
Aquatic Conservation Strategy, at occupied sites consider the following:
Avoid in stream activities that would damage substratum or populations at sites.
Limit collection of this bryophyte material and substratum (boulders) to minimize
impact to populations.
Avoid developing boat launch sites or other concentrated recreational sites in the vicinity of known locations.
Research, Inventory, and Monitoring Opportunities
Revisit historic sites to determine status of the population and to define the range and distribution of the species.
Conduct purposive surveys to determine the distribution and abundance of S. marginata on federal lands in Oregon and Washington.
Monitor existing populations to establish patterns of change over time.
TABLE OF CONTENTS
Disclaimer………………………………………………………………………………2
Executive Summary……………………………………………………………………3
List of Figures……………………………………………………….…………………6
Introduction:…………………………………………………………………………...7
Goal……………………………………………………………………………..7
Scope……………………………………………………………………………7
Management Status……………………………………………………………7
Classification and Description………………………………………………………..8
Systematics and Synonymy…………………………………………………...8
Species Description……………………………………………………………8
Biology and Ecology…………………………………………………………………...8
Life History and Reproductive Biology…………………………………...... 8
Range, Distribution, and Abundance………………………………………..12
Population Trends…………………………………………………………….12
Habitat…………………………………………………………………………12
Ecological Considerations…………………………………………………….16
Conservation ………………………………………………………………………….16
Threats.………………………………………………………………………...16
Conservation Status…………………………………………………………...17
Known Management Approaches……………………………………………17
Management Considerations…………………………………………………17
Research, Inventory, and Monitoring Opportunities……………………………….18
Definitions of Terms Used……………………………………………………………..18
References Cited………………………………………………………………………..19
List of Figures
Figure 1. Illustration of Scouleria marginata..……………………………………… 9
Figure 2. Microscopic photo of whole leaf………………………………………….. 10
Figure 3. Microscopic photos of leaf cross-sections showing thickend margin…….. 10
Figure 4. Dry material of S. marginata with sporophytes………………………….. 11
Figure 5. Wet material of S. marginata with sporophytes.…………………………..11
Figure 6. Distribution map………………………………………………………….. 13
Figure 7. Close up photo of S. marginata mixed with Scleropodium obtusifolium….14
Figure 8. Habitat photo showing bryophytes along a river..…………………………14
Figure 9. Wet material of S. marginata. …………………………...……………….. 15
Figure 10. Dry material of S. marginata. …………………...………………………..15
Introduction:
Goal
The goal of this Conservation Assessment is to summarize existing knowledge regarding the biology and ecology of Scouleria marginata, threats to the species, and management considerations to provide information to line managers to assist in the formation of options for management activities. This species is of concern due to very limited distribution within the Pacific Northwest. Federal management for this species follows Forest Service Region 6 Sensitive Species (SS) policy.
For Region 6 of the Forest Service, SS policy requires the agency to maintain viable populations of all native and desired non-native wildlife, fish, and plant species in habitats distributed throughout their geographic range on National Forest System lands. Management “must not result in a loss of species viability or create significant trends toward federal listing” (FSM 2670.32) for any identified SS.
Scope
The geographic scope of this assessment includes consideration of the known and suspected range of the species within the Pacific Northwest. An emphasis of species-considerations is provided for federal lands in Oregon and Washington; however, species-knowledge compiled from California and non-federal lands is included as it is relevant to the overall conservation of the species. This assessment summarizes existing knowledge of a bryophyte species that is rare in one portion of its range and more common in another. A summary of known or suspected threats is listed but may change with time. Management considerations can be applied to localities, specifically; however range-wide concerns are discussed. Uncertainties regarding impacts of management actions upon S. marginata are acknowledged where appropriate. Because there are so few sites in the Pacific Northwest and the majority of these sites are scattered and historic, any management activities within the habitat of this species may increase the uncertainty.
Management Status
Scouleria marginata was originally rated under FEMAT (Thomas et al. 1993) and was placed in Category 4 under the original Record of Decision (USDA, USDI 1994). In 2001, it was taken off the Survey and Manage list because it was not closely associated with late-successional and old growth forest, but was being considered for inclusion into the agencies Special Status/Sensitive Species programs (USDA, USDI 2001). According to NatureServe (2004) the global rank for S. marginata is G3. In Oregon it is ranked S1, List 3 by the Oregon Natural Heritage Information Center (2004) and in Washington it is ranked as S2, and Threatened (Washington Natural Heritage Program 2004). In Canada, it is S1 and on the Red List in British Columbia and it is ranked as Endangered on the Canadian Species at Risk list (COSEWIC 2004). Currently, it is on the USFS Region 6 Sensitive Species list and is considered a Bureau Tracking species in Oregon by the Oregon/Washington Bureau of Land Management. Tracking species are not considered as Special Status Species for management purposes. There is no management status for this species in California.
Classification and Description
Systematics and Synonymy
Scouleria marginata Britt. was first described from Spokane Falls, Washington Territory in 1895 by E. G. Britton (1895). It is one of three species within the genus Scouleria in the family Scouleriaceae.
Species Description
Scouleria marginata forms dense, dark green to blackish-green tufts up to 10cm tall. Leaves are 2.5-3.5 by 1-3 mm, with entire or toothed margins, bordered by a multistratose layer of cells that are thick and “rope like”, except at the apex where the margin is only 2 cells thick (Figures 1, 2, and 3). Upper median cells are rectangular to quadrate, 15- 40 by 7-10 μm. The leaf costa ends before the apex. This genus has extremely strong rhizoids that adhere to rock substrates and can withstand periods of turbulent, floodwater events. Illustrations for this species can be found in the following references: Bryophyte Flora North America web site (2004) and Lawton (1971).
Currently there is only one other species, Scouleria aquatica that could be confused with S. marginata. Both species often grow mixed together or in separate patches within the habitat. The primary characteristic that is used to separate these two species is the thick-walled marginal cells that form a distinct band around the edge of the leaf in S. marginata. Scouleria aquatica often has bistratose marginal cells but they never have a bank of thick “rope-like” cells along the margin. When conditions are right this character can often be seen with a hand lens in the field. A second characteristic used to distinguish the two species is the peristome teeth. Scouleria marginata does not have peristome teeth while S. aquatica does have teeth. This character is often difficult to determine in the field because the peristome teeth are fragile and usually broken off in S. aquatica, thus making it difficult to see in the field with a hand lens.
Biology and Ecology
Life History and Reproductive Biology
Scouleria marginata is dioicous. The capsules are immersed to emergent, spherical to obovoid, dark brown to rusty red, compressed or flattened, and often black when dry. The columella is persistent, exserted above the urn. The operculum is low, conic and remains attached to the columella. (Figures 4 and 5). The persitome is lacking. Spores are large, 40-55µm and densely papillose. Spore dispersal may be by water although wind dispersal is more common in bryophytes. No specialized asexual reproductive structures have been reported for this species but fragmentation may play a role in dispersing this species.
Figure 1. Scouleria marginata E. Britton.
Figure 2. S. marginata whole leaf, note the thickened margins.
Photo by Judith Harpel.
Figure 3. S. marginata leaf cross sections showing thick marginal border. Photos by Judith Harpel.
Figure 4. Dry material of S. marginata with sporophytes. Photo by Judith Harpel.
Figure 5. Wet material of S. marginata with sporophytes. Photo by Judith Harpel.
Range, Distribution, and Abundance
According to Churchill (1985), S. marginata has the most restricted range of the three species within the genus. Scouleria marginata is a Western North America endemic species that is known from British Columbia, Washington, Oregon, Idaho, and California (Figure 6). In Washington it is known from Chelan (Wenatchee National Forest), Klickitat, Kittatas, and Spokane Counties. In Oregon, it occurs in Clackamas, Douglas (Umpqua National Forest), and Jackson Counties (Roseburg Bureau of Land Management and Rogue River National Forest). In California, it is reported from Alpine, Calaveras, Del Norte (Six Rivers National Forest), El Dorado (El Dorado National Forest), Sequoia National Forest), Mariposa, (Yosemite National Park), Placer, Plumas, (Plumas National Forest), Shasta, Siskyou, (Klamath National Forest), and Toulumne and Tulare, (Sequoia National Forest), Counties. Idaho sites include, Bonner, Idaho (Clearwater National Forest), Boise, Kootenai, Lewis, Owyhee and Valley Counties.
In the northern portions of its range S. marginata is never abundant when found and usually grows mixed in with or next to the more common species Scouleria aquatica. In California, in the lower elevation zones of the western Sierra Nevada and Coast Range, S. marginata is often abundant on the rocks along the major rivers but becomes less frequent and often mixed in with S. aquatica at higher elevations. It is also absent from the rivers on the east side of the Sierra Nevada Mountains (Shevock pers. comm. 2005).
Population Trends
Although there are no specific population details for S. marginata, the population trends appear to vary within its range. In the northern portions of its range, it becomes infrequent and is usually mixed with S. aquatica. In Washington, only one of the eight sites has been re-located and several of the other Washington historic sites are likely to have been extirpated. The only known Canadian site may have been extirpated within the last 20 years (McIntosh 2002). The loss of these historic sites indicates a decline in the northern portion of its range. In 1996, a historic 1963 Washington site was relocated. A recent, March 2005 visit to that site found the population still extant and a new site was found about 1.5 miles downstream. Although there have been several new sites identified within southern Oregon over the last few years, these sites are also all mixed with the more common S. aquatica. The limited occurrence of this species in the northern portions of its range may be the result of competition with the more common, widespread species S. aquatica or it could reflect a lack of survey effort. At the present time, we do not have sufficient information on the range and distribution, ecological factors, or threats to clearly determine the population trends for this species.
Habitat
Scouleria marginata occurs on bedrock material or very large boulders along the margins of perennial river systems (Figures 7, 8, 9, and 10). It is frequently submerged but is usually exposed during periods of low water flow. The rock material may be granitic or volcanic in origin but must be large enough so it will not be moved during turbulent floodwater events. According to Churchill (1985), S. marginata occurs from sea level up to 1200 m. Because there are so few known sites it is not possible to determine if stream velocity plays an important role in determining where this species will grow.
Figure 7. Close up of S. marginata (blackish-green color) mixed with Scleropodium
obtusifolium (yellow-green color). Photo by Andrea Ruchty.