The western prairie fringed orchid (Platanthera praeclara Sheviak & Bowles) was listed as threatened in 1989 by the U.S. Fish and Wildlife Service under the Endangered Species Act. Once widespread and locally common in the mesic to wet-mesic upland tallgrass prairies, today the species persists only in a few, isolated populations in 38 counties across 7 states (USFWS 1994).

 Profound habitat loss is the principal cause of rarity with less than 1% of the original tallgrass prairie remaining. The remaining tallgrass prairie occurs primarily in small isolated patches.

Fragmentation of the once continuous landscape results in the disruption of fire and grazing regimes, and encourages the encroachment of woody vegetation and establishment of exotic species. Further, fragmentation decreases the probability of successful dispersal and may limit pollinator visitation.

Monitoring questions and approach

1. How does the abundance and distribution of flowering individuals change over time?

   • Annual census and mapping of flowering individuals.

2. Is soil moisture correlated with the abundance and distribution of flowering individuals or the density of non-flowering individuals? Soil moisture influences growth and reproduction of the orchid, and below average soil moisture may cause an absence of flowering or the onset of dormancy (Bowles 1983; Sheviak & Bowles 1986).

   • Soil moisture is recorded from two sites in the orchid habitat by an automated weather station.

3. How is the tallgrass prairie habitat changing over time?

   • Prairie plant community monitoring is conducted at four sample sites located in native prairie habitat.

Protocol

• Willson, G.D. 2001. Western prairie fringed orchid monitoring protocol for Pipestone National Monument. U.S. Geological Survey, Northern Prairie Wildlife Research Center, Missouri Field Station, Columbia, MO. 18 pp.

References

• Bowles, M. L. 1983. The tallgrass prairie orchids Platanthera leucophaea (Nutt) Lindl. and Cypripedium candidum Muhl. ex Willd.: some aspects of their status, biology, and ecology, and implications toward management. Natural Areas Journal 3: 14-37.

• Sheviak, C.J. and M.L. Bowles. 1986. The prairie fringed orchids: a pollinator-isolated pair. Rhodora 88: 267-290.

• U.S. Fish and Wildlife Service. 1994. Platanthera praeclara (western prairie fringed orchid) recovery plan. Technical/agency draft. U.S. Fish and Wildlife Service, Ft. Snelling, MN.