Basis for Listing

Eleocharis rostellata is chiefly an inhabitant of salt marshes along the Atlantic Coast with rare inland occurrences in localized habitats. It also occurs in scattered alkaline regions in the West and in South America. The range map for E. rostellata is rather generalized and incorrectly implies a continuous distribution across North America. In fact, several coastal states such as Maine, Virginia, North Carolina, and Florida consider it to be rare. In its inland range, it is considered rare in Minnesota, Wisconsin, Illinois, Ontario, and Pennsylvania.

The presence of this species in Minnesota is somewhat of an anomaly considering its geographic distribution. Minnesota populations are widely disjunct from other populations, probably because E. rostellata has very specific habitat requirements. This species appears to be confined to calcareous seepage fens and spring fens in acid peatlands, both very rare habitats in the region. In fact, E. rostellata was first collected in Minnesota in 1980 when these unique habitats were just beginning to be recognized.

As of 2008, there were 12 known locations for E. rostellata in Minnesota. In the Minnesota River valley and in the Glacial Lake Agassiz beach ridges in the prairie region, E. rostellata occurs strictly in calcareous fens. Some of the populations in Becker and Mahnomen counties are rather substantial, but they are probably remnants of much larger, continuous populations that existed before their habitat was fragmented by agricultural development. Despite intensive surveys in the 1990s, E. rostellata is known from only 3 sites in the Minnesota River valley. The most interesting finds are perhaps those in north-central Minnesota in Koochiching County, where plants occur in a highly specialized microhabitat within large, low-nutrient, acidic peatlands. Eleocharis rostellata was listed as a threatened species in Minnesota in 1984.

  Description

Eleocharis rostellata is a very distinctive species. Like other members of the Eleocharis genus, it produces only 1 spikelet (flower cluster) at the tip of the culm (the stem of a grass or sedge). This species can be identified in general by its formation of dense tussocks; its long, firm, flattened culms; and the presence of sterile (non-flowering) culms that may be more than 1 m (3.3 ft.) long and which may arch back to the ground and take root at the tip. This vegetative feature may not always be present so the spikelet is necessary for positive identification. Scales of the spikelet are leathery, drab or brownish, and the tip comes to a broad triangle (obtuse angle). The 3-sided achene (one-seeded fruit) has a pyramidal cap (tubercle) that is flush (confluent) with the sides of the achene and not broadened (Svenson 1934).

  Habitat

All known Minnesota populations of E. rostellata occur in fens that are maintained by the surface discharge of calcareous or circumneutral groundwater. This habitat type is rare compared with the other wetland types in the prairie region and in the vast expanses of acidic, mineral-poor peatlands in the forested region. Acid peatlands typically receive only mineral-poor surface water or rainwater. The habitat type that harbors E. rostellata has been described as a calcareous fen in the prairie region and as a spring fen in the northern forested region of Minnesota. Calcareous fens are generally more calcareous and mineral-rich than the spring fens, but intermediate examples are found along the prairie-forest border. In all cases, these specialized areas are wet, sunny habitats dominated by low-growing sedges and mosses.

  Biology / Life History

Eleocharis rostellata is a member of the sedge family. It is a perennial plant that forms persistent clumps. In addition to producing normal flowering culms, it may produce special, sterile (non-flowering) shoots that can assist in the vegetative spread of the plant by rooting at the tip and forming a new green shoot.

The best time to search for E. rostellata is when the achenes are ripe, from early July to late August.

  Conservation / Management

The conservation of E. rostellata in Minnesota is tied to the conservation of its specialized fen habitat. A typical calcareous fen may be only 2 ha. (5 ac.) in size, but the recharge area that maintains its groundwater supply may cover thousands of hectares. Spring fens similarly are recharged over thousands of acres of peatland. Without safeguarding the hydrologic settings of these fens, the security of this species' habitat is in doubt. Activities that could affect hydrologic systems include upslope gravel mining and withdrawal of large volumes of water from the aquifers that feed the fens. There have been significant losses recently, especially in the prairie region, resulting from diverted groundwater flows.

After years of fire suppression, shrub cover in some fens may become so dense that it threatens populations of E. rostellata. The restoration of a dormant-season fire regime that mimics natural wildfires may not be enough to control shrubs. In such cases, physical shrub removal may be the best alternative. Woody encroachment should be controlled by hand, preferably after the ground is frozen. Because of the fragile nature of the peat layer that fosters the unique conditions of fens, use of tracked vehicles or other mechanized equipment should be avoided.

  Conservation Efforts in Minnesota

Understanding the distribution and habitat preferences of E. rostellata has been greatly enhanced by recent systematic inventories of calcareous fens conducted by Minnesota DNR botanists. These inventory efforts have been ongoing since about 1990 and built upon a cursory study of Minnesota's northern peatlands, including areas of spring fens, that was conducted in the 1980s. Two of the populations of E. rostellata in spring fens are in a state Scientific and Natural Area, and several of the calcareous fen populations are on public land. However, no formal mechanism exists to assure the hydrologic integrity of aquifers that feed the majority of these areas. The broader challenge remains understanding how land use changes outside the boundaries of protected areas may affect critically important hydrologic conditions within the protected areas.

  References and Additional Information

Glaser, P. H. 1983. Eleocharis rostellata and its relation to spring fens in Minnesota. The Michigan Botanist 22:19-21.

Smith, G. S., J. J. Bruhl, M. S. González-Elizondo, and F. J. Menapace. 2002. Eleocharis. Pages 60-120 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York.

Smith, S. G., J. J. Bruhl, M. S. González-Elizondo, and F. J. Menapace. 2002. Eleocharis. Pages 60-120 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

Svenson, H. K. 1934. Monographic studies in Eleocharis 3. Rhodora 36:377-389.