rivers have low gradient in these settings though they are fed by mountain 

 tributaries. The 130 km (80 mile) length of valleys supporting the species 

 have elevation ranges from 1224-1485 m (4080-4950 ft). The valleys are app. 

 5-8 km (3-5 miles) wide, with nearly-level floodplains across much of the 

 valley width. Intermittent segments contain alkaline flats having wetland 

 soils. In these flats it is restricted to meandered wetland channels and 

 meadow-filled swales that represent alluvial fans. In the meandered 

 wetlands, it is restricted to discrete bands in segments and zones with seeps or 

 at least subsurface moisture through the summer. The wetland complexes are 

 referred to as "alluvial fans" (Boast and Shelito 1989) and they are in areas 

 that appear to have structural/tectonic interference (Locke pers. comm.), 

 schematically presented by Reichmuth (1986). 



Abandoned meandered wetlands represent one of two floodplain settings for 

 the species in the rest of its range, the other being successional river corridor 

 banks and backwaters (Jennings 1989, U.S. Fish & Wildlife Service 1992.) 



5. Edaphic factors: Soils are loamy calcareous wetland soils, with gley 

 features. 



Orchid ecology is often closely linked with edaphic factors and mycorrhizal 

 fimgi (Wells 1981), so this study included collection of soils data to refine the 

 habitat description. Edaphic conditions were documented by collecting soil 

 samples at five of the sites that represent the array of habitats and includes 

 the three largest populations in Montana. There was no replicate sampling 

 but multiple samples were taken at two sites where Spiranthes diluvialis 

 occupied different microhabitats. Soils were collected during the August 

 flowering period to a depth of 10 cm, air-dried and color was recorded using 

 the Munsell color chart. Analysis of texture, pH (buffered 7.0), organic matter 

 (%), conductivity (mmhos/cm), cation exchange capacity (cmol/kg), and 

 nutrients in ppm (ammonia, nitrate, excess lime, potassium. Bray 

 phosphorus, zinc, iron, manganese, copper, sodium) were conducted by the 

 University of Nebraska Soils Testing Service in conjunction with soil sample 

 tests collected from Spiranthes diluvialis sites in Nebraska and Wyoming. 

 Results were compared with soils sample results previously compiled from 

 Spiranthes diluvialis sites in Colorado and Utah (Arft 1995a). Results are 

 summarized in Table 2 as reprinted from the report by Hildebrand (1998), 

 and the raw data for Montana sites is included in Appendix F. 



Soils at Spiranthes diluvialis sites in general are high in micronutrients and 

 organic matter, but are low in phosphorus compared to average values for 

 agricultioral soils. The Montana soils generally overiap with the Nebraska and 

 Wyoming soils in having high potassium concentrations, and low zinc, 

 copper, and ammonia concentrations relative to the Colorado and Utah sites. 



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