Regularity: Regularly occurring
Global Range: Cressy Creek in Smyth County, Virginia.
Comments: The only known natural population was found along the floodplain of a creek at an elevation of about 1160 m. The site is within a narrow strip of second-growth forest that includes many sweet and yellow birches (Betula lenta and B. alleghaniensis). The band of forest is nearly surrounded by agricultural land.
Habitat and Ecology
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 1 - 5
Comments: The single known natural population was rediscovered in 1975. Between 1984 and 1987, twenty populations of 96 seedlings each were planted on USFS lands (Davis 2006). These populations are not yet clearly established. Natural reproduction where a mast year coincides with suitable habitat seems to be very rare (Davis 2006).
Life History and Behavior
National NatureServe Conservation Status
Rounded National Status Rank: N1 - Critically Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G1 - Critically Imperiled
Reasons: First noticed in 1918, this taxon was not seen again until 1975 when the single population (then consisting of 41 trees) was rediscovered in Smyth County, Virginia. Since that time, the number of individuals in the natural, native population has steadily declined from eleven in 1984 to eight in 2003. In the early 1980's an aggressive recovery plan, involving planting greenhouse-grown seedlings at various sites, was implemented. Although vandalism initially threatened the recovery program, in 2003 there were 953 planted individuals alive. Whether these trees will be capable of competing and reproducing successfully remains to be seen. Lack of natural reproduction is a major threat.
IUCN Red List Assessment
Red List Category
Red List Criteria
- Needs updating
- 1997Endangered(Walter and Gillett 1998)
Degree of Threat: High
Comments: Threatened by the absence of forest openings and exposed mineral soil which seem to be requirements for natural reproduction (Davis 2006). This extremely rare species has been affected by over-collecting of seedlings for cultivation and material for research. Vandalism of restoration efforts has also been a factor (Southern Appalachian Species Viability Project 2002). The present availability of greenhouse-grown seedlings has reduced threats from collecting and vandalism (Davis 2006).
Relevance to Humans and Ecosystems
Stewardship Overview: Promote seedling establishment during years of heavy seed production by creating small openings and exposing mineral soil adjacent to adult trees (Davis 2006). Remove nearby Betula lenta to prevent genetic swamping (Davis 2006). Continue to cultivate seedlings.
Betula uber (Virginia Round-leaf Birch) is a rare species of tree in the birch family. One of the most endangered species of North American trees, it is endemic to Smyth County, in the U.S. state of Virginia. It is part of the temperate broadleaf and mixed forests biome.
The tree was first described in 1918 as a variety of Betula lenta, and elevated to species status in 1945. It hybridizes with B. lenta and it has been suggested that it is actually a round-leaved mutant form of that species. Some authorities prefer to treat it as a variety.
After it was first discovered, the tree was not seen again and was thought to be extinct until 1975, when some individuals were located. These 18 adult trees and 23 saplings and seedlings were in a forest along the degraded banks of Cressy Creek on Smyth County, Virginia. The tree was federally listed as an endangered species and conservation efforts were begun. Many seedlings were sprouted in greenhouses and planted in the forest. By 1995 there were 20 populations and it was downlisted to threatened status. The tree was propagated in order to discourage collectors from taking wild specimens, or vandals from destroying them. A recent count estimated 961 individuals in the wild as of 2006. Eight of these are in the original creekside population. The species will not be removed from the endangered species list yet because it has not been observed reproducing sexually, and naturally, more than once. The expansion of its range is limited because the area is surrounded by agricultural land, but the territory on which the tree occurs is not immediately threatened.
This is a tree of moderate size, growing up to 15 meters tall. The crown is compact. The bark is aromatic and dark brown or black in color. The leaf is round or slightly oval with a heart-shaped base and a toothed edge and measures up to 5 centimeters long. The catkin is up to 2.8 centimeters long and contains tiny samaras measuring 2 millimeters in length. The tree is wind-pollinated and reproduces by seed. Seed production is much heavier in some years than in others. The tree's lifespan is around 50 years.
Names and Taxonomy
Comments: Betula uber, known from a single population, differs from the widespread black birch (Betula lenta) in having blunt leaves. It was originally described as a variety of B. lenta (Ashe 1918). Kartesz (1994 checklist and 1999 floristic synthesis) recognizes this as a full species, as does the U.S. Fish and Wildlife Service (formal listing as a threatened species, 1994). Peter Mazzeo, who is familiar with this plant in the field, considers these plants to be best treated as a full species (J.T. Kartesz, pers. comm. to Larry Morse, 25Nov99).