though the associations differ. By contrast, the nearest out-of-state sites in 

 Idaho they have steep canyon conifer communities and cottonwoods lining 

 the riparian corridor where the species occurs. 



3. Frequently associated species: In the immediate vicinity of Spiranthes 



diluvialis, the graminoid vegetation is often markedly short in height (less 

 than 20 cm) and with less than complete canopy cover (40-80%) exposing 

 more bare soil or litter compared to the surrounding wetland plant 

 associations. The local dominants and abundant species vary between sites, 

 but the species at Montana sites with cover of 10% or greater, include: 

 Agrostis stolonifera, Carex simulata, Eleocharis pauciflora, Elymus 

 trachycaulus, Juncus balticus, Muhlenbergia asperifolia, Muhlenbergia 

 filiformis, and Juncus longistylis. 



Carex simulata distribution has the highest correlation with Spiranthes 

 diluvialis distribution within the study area. The relatively widespread exotic 

 species, Agrostis stolonifera, was also found with high consistency at 

 Spiranthes diluvialis occurrences. The plant associations dominated by Carex 

 simulata and Eleocharis pauciflora were at the short and sparse extreme in 

 vegetation structure. Juncus balticus is ubiquitous and other species of rush 

 are locally common compared to surrounding wetlands. Other species that 

 tend to be highly localized and associated with Spiranthes diluvialis at two or 

 more of the documented sites include: Castillej exilis, Primula incana, 

 Triglochin maritima, Sphenopholis obtusata, Habenaria hyperborea, and 

 Phlox kelseyi var. kelseyi. 



At one extreme, it occurred in a relatively well-developed peatland setting 

 that included Triglochin palustre. Aster juncifor mis, and Salix Candida amid 

 pools of Chara spp. (in one segment of EO#004; the aforementioned bum 

 site). At the other extreme, it was in associations made up of relatively 

 widespread graminoids like Elymus trachycalus, Carex praegracilis and 

 Calamagrostis inexpansa (EO#001) as a wetland band that is preferentially 

 grazed to short heights early in the growing season. 



Five sites were sampled in 1 x 1 m areas of relatively Spiranthes diluvialis 

 density to refine the vegetation description. The microplots appeared to 

 represent more extensive, repeating plant associations but were not expanded 

 because of the microhabitat discontinuity. In addition, two sites had two 

 samples representing two different associations, for a total of seven 

 microplots. Finally, a pair of microplots were sampled directly above and 

 below a Spiranthes diluvialis plot to profile the major shifts in wetland 

 vegetation composition over the short distance of three contiguous meters of 

 the moisture gradient (Figure 7). Canopy cover was estimated in 1 0% 

 increment categories for all vascular species within the area, and soil surface 



24 



