B. Physical characteristics. 



1. Climate. 



a. Koppen climate classification: Type Dfb, with average January 

 temperature below 0° C (32° F), average temperature of the warmest 

 month above 10° degrees C (50° F) and under 22° C (71.6° F), with 

 no dry season, and the driest month of summer receives more than 3 

 cm (1.2 in.) of rain (Visher, 1954). 



b. Regional microclimate: The closest climatological station located 

 within the range oi Spiranthes diluvialis is in Dillon. Data for the 

 periods 1951-80 and 1961-90 are provided by the U.S. Department of 

 Commerce (NOAA 1982, 1992). At the Dillon Airport (elevation 

 5,216 ft), the mean annual temperature is 13.4° C (56.1 ° F) and the 

 highest mean monthly temperatures are in July at 27.9° C (82.7° F). 

 The annual normal precipitation is 23.8 cm (9.53 inches). Most 

 precipitation falls in May and June. Unlike the regional climate 

 characterization, there is a distinct dry season with hot temperatures. 



Climate regimes in Spiranthes diluvialis settings over the past four 

 years have varied considerably from late season drought in 1994, to 

 season-long coolness and wetness in 1 997 that prevented some local 

 landowners from getting a mature grain crop in nearby fields. 



c Local microclimate: Soils at Spiranthes diluvialis sites remain moist 



through the summer in the shallow wetland settings. Almost all 

 occurrences are in frill sun. The patchy, intermittent shrubs along the 

 border provide negligible shade. The growing season diurnal 

 temperature extremes are at their peak when the plant is flowering. 



2. Air and water quality requirements: The microhabitat is temporarily 

 inundated in spring, often located right below the outer wetland margin. 

 Susbsurface hydrological conditions are ameliorated by high organic content 

 at the surface, and coarse alluvial cobble directly below. Water chemistry as 

 inferred from soils data is moderately alkaline and high in calcium carbonate. 



3. Physiographic province: The Montana occurrences are within the Northern 

 Rockies physiographic region that encompasses western Montana, as mapped 

 by Fenneman (1931). 



4. Physiographic and topographic characteristics: The species is in broad, 

 open intermontane valleys that represent Cenozoic Basins with late 

 Quaternary alluvium in southwestern Montana. The valleys are flat and the 



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