Eleocharis wolfii (Gray) Gray ex Britt.
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Basis for Listing
Of all the Minnesota spike-rushes, Eleocharis wolfii may be the rarest and most poorly understood. In fact, it is surprisingly rare for a species with such wide distribution, but it seems to be rare or infrequent throughout its range. Eleocharis wolfii was first collected in Minnesota in 1892 by A. L. Ballard somewhere near Nicollet in Nicollet County. It was next found in 1921 near Lake Traverse in the Red River Valley and again in Norman County in 1967. None of these sites have been relocated since the dates of their original discovery, and it is unknown if any of these populations still survive. In 1998, the Minnesota Biological Survey discovered E. wolfii growing on the margins of ephemeral rainwater pools on Jordan sandstone outcrops along the Minnesota River in Scott County. As of 2008, it had also been located on the margins of rock pools at one location along the Minnesota River in Renville County and in three locations on Sioux quartzite outcrops in Pipestone and Rock counties.
Eleocharis wolfii is a small, grass-like plant that commonly grows in small tufts. It spreads from rhizomes. Stems are 1-4 dm (4-16 in.) long and 1-1.5 mm (0.04-0.06 in.) wide, very flat, furrowed or with numerous parallel horizontal lines, and slightly twisted. Stem sheaths are light brown to straw-colored and end in a thin, translucent tooth that may be split and free from the stem. Floral scales are acute, 4-9 mm (0.16-0.35 in.) long, lance-shaped to ovoid, and arranged in a spiral. They vary from dark red with a broad light green or brown midvein and translucent margin, to straw-colored with a translucent margin, to nearly translucent throughout. The achene is pear shaped, whitish colored, 1 mm (0.04 in.) long, with 9 rounded ribs and numerous transverse partitions. The tubercle is conical, up to 0.1 mm (0.004 in.) long. There are no perianth bristles (Great Plains Flora Association 1986; Gleason and Cronquist 1991).
The preferred habitat of E. wolfii in Minnesota is poorly known, and more research is needed. Historical collections refer to its habitat only as moist places. The site in Norman County was described as mud flats near a stream. Presumably, these were wetlands in the prairie region. The populations in Renville, Scott, Pipestone, and Rock counties were associated with rock outcrops, specifically the margins of bedrock pools that collect or concentrate precipitation run-off.
Biology / Life History
Eleocharis wolfii is a perennial grass-like species that commonly grows in clumps and forms mats. It spreads by well-developed underground stems. Leaves are reduced to bladeless sheaths confined to the base of the plant. Both stems and leaves function as photosynthetic organs. Flowering and fruiting occur from May through July. The species requires high light levels to produce viable seed. Without such light the plants become weakened and elongated, and the seeds abort before maturity (NatureServe 2008).
Conservation / Management
The loss of native grasslands and wetlands in North America is the greatest threat to E. wolfii. Activities such as wetland draining and conversion of native prairie to agricultural crops, residential developments, and road construction are responsible for this loss. Grassland habitats are also sometimes threatened by the overgrowth of woody vegetation that has resulted from the loss of natural fires. Other threats include invasion of non-native plants, soil compaction and trampling by livestock, destructive recreational activities, and herbicide application (NatureServe 2008).
Conservation Efforts in Minnesota
In 2007, the Renville and Redwood County Soil and Water Conservation Districts in association with state and federal agencies coordinated an initiative to compensate interested landowners for permanently protecting the most ecologically intact rock outcrops and associated wetlands in those two counties. A total of 86 ha (212 ac.) were enrolled into perpetual conservation easements as a result of this initiative, and E. wolfii is one of the rock outcrop species most likely to benefit from the program. In 2009, the program was expanded to protect an additional 214 ha (530 ac.) within a five county area of the Upper Minnesota River valley. Conservation plans, which outline conservation practices such as removal of invasive species and livestock exclusion, are being developed for each of the easement sites. Habitat maintenance and improvement measures such as prescribed burning, fencing, rotational grazing, and/or seeding are also included in the plans.
Gleason, H. A., and A. Cronquist. 1991. Manual of vascular plants of northeastern United States and adjacent Canada. Second Edition. New York Botanical Garden, Bronx, New York. 910 pp.
Great Plains Flora Association. 1986. Flora of the Great Plains. University Press of Kansas, Lawrence, Kansas. 1,402 pp.
McKenzie, P. M., C. T. Witsell, L. R. Phillippe, C. S. Reid, M.A . Homoya, S. B. Rolfsmeier, and C.A. Morse. 2009. Status assessment of Eleocharis wolfii (Cyperaceae) in the United States. Journal of the Botanical Research Institute of Texas 3(2):831-854.
NatureServe. 2008. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.0. NatureServe, Arlington, Virginia.