11 



important features of nearly all known sites 

 appears to be semi-permanent water seepage near 

 the surface. Orchis rotund! folia is often found 

 on moist, mossy hummocks in these seepage zones. 

 The soil environment of the species is described 

 by Luer (1975) as follows: "(o)n the cold open 

 tundra or limestone barrens of the far North, 

 this. . .species grows dwarfed but abundantly in 

 full exposure, but. .. southward, it becomes 

 increasingly rare in increasingly sheltered 

 habitats. Plants of cold coniferous forests and 

 at moderate elevations in the West may thrive in 

 the humus of dry spruce needles, but farther south 

 plants are restricted to shaded bogs where. . .moist 

 beds of sphagnum moss offer (cool microhabitats) . 

 Good drainage of a constant water supply over 

 sufficient lime is essential for the frail roots, 

 which can tolerate neither heat nor acid." 



4. REGIONAL CLIMATE: The climate of northwestern 

 Montana west of the Continental Divide can 

 generally be classified as moist and temperate, 

 while the Front Range is more likely to be 

 influenced by cold, dry continental air masses. 

 For the distributional area of O. rotundifolia in 

 Montana, the nearest climatological stations are 

 located at Gibson Dam (1399 m. (4590 ft.)) and 

 Hungry Horse Dam (963 m. (3160 ft.)). Data for 

 the period 1951-1980 are provided by the U.S. 

 Department of Commerce (1982) . At Gibson Dam, the 

 mean annual precipitation was 47.04 cm. (18.52 

 in.); the mean annual temperature was 5.4 °C 

 (41.7°F), the mean January minimum was -11.6°C 

 (11.2°F), and the mean July maximum was 25.5''C 

 (77. 9 "F). At Hungry Horse Dam, the mean annual 

 precipitation was 85.09 cm. (33.50 in.); the mean 

 annual temperature was e.l'C (43.0°F), the mean 

 January minimum was -9.7*C (14.6°F), and the mean 

 July maximum was 26.8°C (80.2°F). 



F. POPULATION DEMOGRAPHY AND BIOLOGY 



1. PHENOLOGY: In Montana, O. rotundifolia typically 

 begins blooming during the second week of June; 

 peak flowering was observed at the end of the 

 third week in June. Some flowers persist until 

 mid-July, but the species then goes out of bloom 

 rapidly. Fruiting extends from late June into 

 late July or early August. 



2. POPULATION SIZE AND CONDITION: In Montana, 

 populations of Orchis rotundifolia range in size 

 from 35 to approximately 3000 individuals; these 

 contain from one to seven subpopulations. The 



