D. Habitat 



1. Associated vegetation: Eriogonum visheri occupies 

 sparsely vegetated settings. At Slim Buttes, these are either 

 dominated by Distichilis stricta , or lacking distinct 

 community development. Other associated species include: 

 Eriogonum paucif lorum , Atriplex dioica , Iva axillaris , 

 Macheranthera canescens and Salsola kali . 



2. Topography: Eriogonum visheri grows on sedimentary rock 

 outcrops that form Badlands topography or localized Badlands 

 features. The settings are barren and highly erodible, most 

 often centered on the outcrop slopes, but also extending into 

 outwash flats. At Slim Buttes, these are localized outcrops 

 of the Hell Creek Formation, one of the few on the District, 

 where two ephemeral streams converge in erodible shale to form 

 a miniature area of Badlands outcrops. 



Almost all of the remains of the previous year's plants were 

 upslope from plants of the current season, indicating a 

 population shift downward in topographic position under the 

 heavy rains of 1993. 



3. Soil relationships: The Slim Butte population is in the 

 largest local area mapped as Cabbart - Rock Outcrop complex 

 (Johnson 1988) . The population occurs mainly on substrate 

 which is classified as Badlands outcrop rather than soil, 

 including shale and bentonite. It extends onto outwash flats 

 that have sandy alluvium mixed in with local parent material. 



E. Population biology and biological interactions 



1. Population size and condition: An estimated 1000 plants 

 made up the Slim Buttes population, within a Badlands area 

 covering less than 5 acres. Most plants of the population 

 were in low density. In one area of upland "pockets", plant 

 densities exceeded 100 plants per square meter, perhaps 

 representing a seed cache that had germinated. 



2. Reproduction: Protandrous, wind-pollinated, and self 

 fertile (Ode 1987) . 



3. Competition: Potential competitors of Eriogonum visheri 

 include Russian thistle ( Salsola kali ) and Kochia ( Kochia 

 scoparia ) , which occupy the same habitat and can grow at high 

 enough densities to crowd it out. In addition, Yellow 

 sweetclover ( Melilotus officinalis ) can contribute to a 

 successional shift which favors these competitors. It is 

 abundant on the south-facing slopes of Slim Buttes above the 

 plains setting, and has the potential to invade the population 

 setting. 



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