Carex typhina Michx.
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Basis for Listing
In Minnesota, Carex typhina is a highly specialized species that is restricted to mature floodplain forests along the Mississippi River and, to a lesser extent, the St. Croix River. Habitats along the Mississippi River in particular have been fragmented and degraded by a long and ambitious history of dam building, channel dredging, and land clearing, mostly by the U.S. Army Corps of Engineers. Other activities such as road building, agricultural development, and urban expansion have had additional cumulative impacts on the habitat of C. typhina. The current situation for substantial tracts of mature floodplain forests is bleak. Those few acres that have survived are often deprived of regular spring flooding, an event that maintains and rejuvenates them, or they have been dissected by roads or utility corridors. Carex typhina was listed as a special concern species in Minnesota in 1996.
Carex typhina is a perennial clump-forming sedge. The stems are brown or red-brown at the base and rise to a height of 30-80 cm (12-31 in.). The leaves are 3.9-8.7 mm (0.15-0.34 in.) wide and have smooth surfaces. The inflorescence has 2-4 erect spikes; the lateral spikes are usually female and the terminal spike is both male and female, with the female portion positioned above the male portion. The female spikes are cylindrical and densely packed with seeds. The perigynia (the membranous covering of the seed) appears inflated, is round in cross section, 5.5-7.8 mm (0.22-0.31 in.) long, smooth, and has an abrupt slender beak.
In Minnesota, C. typhina appears to be confined to mature floodplain forests along the Mississippi and St. Croix rivers. The canopy of these forests is typically dominated by Populus deltoides (plains cottonwood) and Acer saccharinum (silver maple). Understory shrubs are typically few or absent. The habitat is often flooded by spring meltwater in April or May, which may result in the forest floor appearing devoid of herbaceous vegetation until a few weeks after the waters recede in early or mid summer. At that time, Laportea canadensis (wood nettle) may become very abundant.
Biology / Life History
The flowers of this perennial sedge appear to be wind-pollinated, and the seeds are likely dispersed by floodwaters. By any measure, C. typhina is well adapted to floodplains, where the scouring action of floodwaters can erode sediments and uproot plants, then redeposit them somewhere downstream. Plants that can resist these forces, or turn these forces to their advantage, are relatively few and they tend to be specialists that are not found in other habitats. Carex typhina certainly falls into this category.
Conservation / Management
Carex typhina's floodplain forest habitats are influenced by a number of complex forces, both natural and human-created. On the Mississippi River, the artificial manipulation of water levels for the purpose of maintaining a shipping channel is probably the major factor influencing floodplain forest habitats. Logging is still done, although floodplains do not usually support high-value timber trees. A local land manager has no control over actions of the Army Corps of Engineers, but in most cases logging can and should be prohibited.
Conservation Efforts in Minnesota
Much of the remaining habitat of C. typhina along the Mississippi River has now been incorporated into federal ownership, and is managed by the U.S. Fish and Wildlife Service as a wildlife refuge. Although this is significant for conservation, the benefits to C. typhina are limited by the continued dam operation and maintenance of a shipping channel on the Mississippi River.
Ford, B. A., and A. A. Reznicek. 2002. Carex sect. Squarrosae. Pages 518-519 in Flora of North America Editorial Committee, editors. Flora of North America north of Mexico. Volume 23. Oxford University Press, New York, New York.