INTRODUCTION 



This report describes a sensitive plant survey at the southern end of 

 the Elkhorn Mountains on lands administered by the Bureau of Land 

 Management (BLM) . The purpose of this work was to locate and evaluate 

 populations of plant species proposed for designation as sensitive by 

 the BLM (USDI BLM 1993) in keeping with the Endangered Species Act of 

 1973 and agency policy. A secondary goal of this project was the 

 development of a preliminary floristic list for the study area. 



Baseline sensitive species surveys have been conducted in the Elkhorns 

 on the Helena National Forest (Poole and Heidel 1993) and on the 

 Limestone Hills to the east administered by the Bureau of Land 

 Management (Heidel 1994) . There has been little sensitive species 

 survey in the southern end of the Elkhorn Mountains, which represents 

 the most extensive calcareous outcrop in the Elkhorn Mountains 

 vicinity. More sensitive species in Montana are restricted to 

 limestone substrates than any other parent material, with the possible 

 exception of sensitive species on peatland histosols. These factors 

 taken together made the southern end of the Elkhorn Mountains a high 

 priority for baseline sensitive species survey. 



Prior to this study, no sensitive species were known from the area, 

 although Townsendia spathulata is known from the Limestone Hills 

 (Heidel 1994), and Cirsium lonqistylum had been found in the Elkhorn 

 Mountains (Poole and Heidel 1993) . This study represents an extension 

 of previous limestone habitat surveys in Montana, mainly on BLM lands, 

 out of which emerges a new picture of species' status and collective 

 biogeography (e.g., Lesica and Achuff 1992, Vanderhorst and Lesica 

 1994, Vanderhorst 1995). 



STUDY AREA 



The Elkhorn Mountains are located in Broadwater and Jefferson County, 

 Montana. Much of the montane and some of the foothill settings are on 

 public land, administratively coordinated between Helena National 

 Forest, Deerlodge National Forest, and the Bureau of Land Management 

 (BLM) - Headwaters Resource Area. The largest expanse of foothills on 

 public land are on the southern flanks of the Elkhorn Range, making up 

 the core study area. 



The study area is made up of Madison Group formations that mantle the 

 Boulder Batholiths making up the core of the Elkhorn Mountains (Ross 

 et al. 1955). These calcareous formations are in discontinuous bands 

 across the state and have in common distinct vegetation and floristic 

 attributes. The vegetation of the study area is a separate study 

 (Cooper in prep.). In general, there are exceptionally well-developed 

 mountain mahogany ( Cercocarpus ledifolius ) stands, and shrub 

 communities of black sage ( Artemisia novum ) which are restricted to 

 this substrate in Montana. Many of the common species as well as the 

 rare species are calciphiles, e.g., Pentaphylloides floribunda, Ivesia 

 gordonii , Senecio canus and Delphinium bicolor ssp. novum. 



