Rare Species Guide

  Basis for Listing

Carex xerantica is primarily a species of dry, sandy or gravelly prairies in the northwestern corner of the state. After perhaps a decade of highly directed botanical searches in that region, only a few viable populations of C. xerantica were found, all of which are in rather high quality remnants of native prairie vegetation. At this point in history, remnants are all that remains of a once vast biome that has been fragmented by agriculture over the past 100 years.

In addition to the prairie occurrences, there are two records of C. xerantica from the forested region of the state in the northeast. Both records are from narrow bands of prairie-like vegetation that run along the exposed crest of cliffs in the Rove Slate Formation. The two sites are on different cliff systems but are separated by only about 4.8 km (3 mi.). One was discovered in 1994 and is presumed to still exist. The other was discovered in 1939 (Butters and Abbe 1953), but it has resisted all attempts at rediscovery and its current status is uncertain. Carex xerantica was listed as a special concern species in Minnesota in 1996.

  Description

Carex xerantica is a perennial, clump-forming sedge with stems that rise to a maximum height of about 80 cm (2.6 ft.). The leaves grow to a width of about 3 mm (0.12 in.) and have hairless surfaces. The inflorescence is 2-5 cm (0.75-1.97 in.) long and about 1 cm (0.4 in.) wide, and consists of 3-6 spikes. Each spike is tapered to an acute angle at the apex and the base, is 8-16 mm (0.31-0.63 in.) long, and 3-6 mm (0.12-0.24 in.) wide. The spikes overlap but are not closely aggregated. The perigynia (the membranous covering of the seed) is ovate in outline, 3.8-5.6 mm (0.15-0.22 in.) long, 1.5-2.3 mm (0.06-0.09 in.) wide, and tapered or slightly contracted to a flat, serrulate beak. The surface of the perigynia is more or less veinless or with faint veins on the dorsal surface. Mature, well-developed specimens have a very characteristic whitish or silvery cast to the spikes, which, when present, provides a useful character for field identification. Also notice that the spikes taper to an acutely pointed tip and base, and the stems tend to be stiffly erect.

  Habitat

Carex xerantica occurs in dry, sandy-gravelly prairies on beach ridges in the northwestern counties, and apparently on dry, exposed cliff tops in at least one northeastern county. The vegetation in both these habitats is similar in appearance and structure, and adapted to a dry and sun-baked environment. The vegetation is sparse and dominated by graminoids; clump-forming grasses in the case of the prairies and a mix of shallow-rooted grasses and sedges on the cliff tops. In both cases, there is a scattering of forbs, and possibly a few low-growing woody species. Carex xerantica has the capacity to be a dominant species, at least over a small area, in both habitat types.

  Biology / Life History

The biology of C. xerantica and its ecological role in native Minnesota habitats has not been studied in detail. In general, its floral structure is indicative of a wind-pollinated species, and the lack of specialized dispersal structures on the fruit or seed implies it relies on a variety of dispersal mechanisms. Its fidelity to dry, xeric habitats indicates that it is well adapted to seasonal desiccation. In fact, C. xerantica may rely on periodic drought to maintain a competitive advantage over more opportunistic or more mobile species. It is likely to be fire-adapted, although the sparse vegetation of its habitat may not produce enough fuel to carry a hot fire except in years following a period of higher than average rainfall.

The best time to search for C. xerantica is when the seeds are mature, from early June to mid-July.

  Conservation / Management

It is perhaps too obvious to state that the fate of C. xerantica is tied very closely to the fate of its prairie habitat. In other words, if a habitat that supports a viable population of C. xerantica can be maintained as a full-functioning community of native plants and animals, where the natural ecosystem functions and processes remain intact, then C. xerantica can be expected to thrive. Of course, the challenge to land managers is maintaining (or restoring) these conditions in the tiny habitat remnants that exist in our fragmented landscape. Invasive, non-native species are a constant threat, and this problem will only get worse. The effects of fire-suppression will also need to be evaluated, and ameliorated where possible. Livestock grazing and mowing should be considered incompatible land uses, as should recreational use of OHVs (off highway vehicles).

  Conservation Efforts in Minnesota

No known conservation efforts have been undertaken specifically on behalf of C. xerantica although several populations are located on state managed lands including Felton Prairie Scientific and Natural Area, Lake Bronson State Park, and Huntly and Thief Lake Wildlife Management Areas. In addition, two populations have been documented within the Boundary Waters Canoe Area Wilderness, which may impart some level of protection.

  References and Additional Information

Butters, F. K., and E. C. Abbe. 1953. A floristic study of Cook County, northeastern Minnesota. Rhodora 55:21-55.

Mastrogiuseppe, J., P. E. Rothrock, A. C. Dibble, and A. A. Reznicek. 2002. Carex sect. Ovales. Pages 332-378 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.

Smith, W. R. 2018. Sedges and rushes of Minnesota: the complete guide to species identification. University of Minnesota Press, Minneapolis. 696 pp.