Botrychium lanceolatum ssp. angustisegmentum (Pease & Moore) Clausen
Narrow Triangle Moonwort
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Botrychium lanceolatum var. angustisegmentum
Basis for Listing
Botrychium lanceolatum ssp. angustisegmentum (narrow triangle moonwort) was first collected in Minnesota in 1918 in Morrison County. Its status remained a mystery until it was collected again in 1991. Several years of focused searches have provided a clearer idea of this species' distribution and habitat preferences. Botrychium lanceolatum ssp. angustisegmentum seems to occur in only a small percentage of the seemingly suitable forest habitats that were searched. Although still believed to be rare, the number of recent site records indicate this plant may not be as rare as first thought. Perhaps it was overlooked in the past because of its small size and habit of not emerging above ground every year. Nonetheless, many of the locations where it is found are under threat of habitat loss or alteration. Botrychium lanceolatum ssp. angustisegmentum was listed as a threatened species in Minnesota in 1996.
Botrychium lanceolatum ssp. angustisegmentum has a stalk 6-15 cm (2.4-5.9 in.) long, with an unstalked frond. The frond (sterile blade) is dark green, very shinny, glabrous, and deltoid. It has 2-5 pairs of pinnatifid pinnae, the lowest pair much the larger (hence the common name triangle). The bud is enclosed in the stalk base. B. lanceolatum ssp. angustisegmentum can be distinguished from B. matricariifolium (matricary grapefern) by the deltoid, usually sessile, blade with both sterile and fertile blades reflexed in bud. The variety of B. lanceolatum (S.G. Gmelin) in Minnesota is var. angustisegmentum Pease & Moore.
In Minnesota, B. lanceolatum ssp. angustisegmentum prefers moist, shady, mature northern hardwood forests, particularly in low areas. It usually occurs with Acer saccharum (sugar maple), Betula alleghaniensis (yellow birch), Fraxinus pennsylvanica (green ash), Fraxinus nigra (black ash), Quercus rubra (red oak), Tilia americana (basswood), and sometimes Thuja occidentalis (northern white cedar). The understory can be rather open and the ground cover often sparse with Athyrium angustum (lady fern) and other Botrychium species, especially B. matricariaefolium. Botrychium lanceolatum ssp. angustisegmentum populations often occur as a few scattered individuals, but occasionally 50 or more can be found in a single site.
Biology / Life History
It takes up to seven years for a B. lanceolatum ssp. angustisegmentum spore to develop into a plant that produces an above-ground leaf. Even though the plant usually produces one leaf each year, that leaf may not emerge above ground. Leaves of this species emerge in the spring and are divided into a sterile photosynthetic portion and a fertile spore-bearing portion. Spores of the fertile portion mature slowly through the summer, changing to a noticeable gold color by late summer. The aboveground portion of the plant is killed by frost in the fall, sometimes as late as October.
Conservation / Management
Botrychium lanceolatum ssp. angustisegmentum appears to be very sensitive to disturbances within its forest habitat, more sensitive than most Botrychium species. The most often cited problems result from: loss of the humus layer caused by non-native earthworms, damage caused by timber harvesting, the effects of road building, and land use changes that affect drainage. In general, any activity that results in the creation of significant gaps in the overstory canopy would likely be deleterious to this species and its habitat. The term significant gap, in this case, means anything greater in extent or more frequent in time than single tree gap phase dynamics, which is part of the normal range of variability in mature forests. Significant gaps can result from timber management activity, even selection harvesting. This can increase solar energy reaching the forest floor, thereby warming and drying the soil. This could result in a major shift in floristic composition, which will likely not favor B. lanceolatum ssp. angustisegmentum. Small local populations of fewer than ten individuals may be particularly at risk (U.S. Forest Service 2000).
Best Time to Search
The presence of sporangia is not needed to confirm the identification of B. lanceolatum ssp. angustisegmentum; the shape of the sterile portion of the leaf is usually enough. For this reason, searches can be conducted anytime from early June to mid-August.
Conservation Efforts in Minnesota
While a number of B. lanceolatum ssp. angustisegmentum populations occur on State Forest lands and county-owned lands, they may be threatened by intensive logging. A cooperative monitoring project is currently underway in Aitkin County, which may offer valuable insights on management needs.
Ownbey, G. B., and T. Morley. 1991. Vascular plants of Minnesota: a checklist and atlas. University of Minnesota Press, Minneapolis, Minnesota. 320 pp.
Peck, J. H. 1982. Ferns and fern allies of the driftless area of Illinois, Iowa, Minnesota, and Wisconsin. Milwaukee Public Museum Press, Contributions in Biology and Geology Book 53, Milwaukee, Wisconsin. 140 pp.
U.S. Forest Service. 2000. Population viability assessment in forest plan revision. Questions for plant population viability assessment panel: Botrychium lanceolatum. United States Forest Service, Region 9, Duluth, Minnesota.
Wagner, W. H., Jr., and F. S. Wagner. 1993. Botrychium. Pages 86-101 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 2. Oxford University Press, New York.