administered by the Bureau of Land Management and are subject to 

 livestock grazing (Lesica and Elliott 1987a) . 



Previous studies have indicated that inflorescence predation 

 and seed predation by insects may be adversely affecting A. 

 scaphoides fecundity (Lesica and Elliott 1987a, 1989) . Lowered 

 fecundity is thought to be the cause of local rarity in a number 

 of plant species (Greig-Smith and Sagar 1981, Hester and 

 Mendelssohn 1987, Cabin et al. 1991). Here I report the results 

 of an eight-year demographic monitoring study of A^ scaphoides at 

 two sites. I use stage-based transition matrix models and 

 elasticity analysis (Caswell 1989, de Kroon et al. 1986) to 

 examine population stability and predict the effects predation, 

 especially livestock grazing on this rare species. 



METHODS 



Study Sites 



The Sheep Corral Gulch population occurs in southern 

 Beaverhead County, Montana on a gentle south-facing slope at 

 6,300 ft (T8S R12W S16). Mean July and January temperatures at 

 Dillon, 20 miles to the northwest at 5,400 ft, are 66.2° and 

 20.1°F respectively. Mean annual precipitation is 9.5 in. 

 Vegetation is dominated by Artemisia tridentata and Agropyron 

 spicatum . Aster scopulorum and Phlox hoodii are common f orbs . 

 Evidence of heavy spring grazing by livestock was observed in 

 1989, 1990 and 1993. 



The Haynes Creek population is in central Lemhi County, 

 Idaho, approximately 30 miles west of Sheep Corral Gulch. It 

 occurs on a moderate southeast-facing slope at 5,100 ft (T19N 

 R23E S2). Mean July and January temperatures at Salmon, 15 miles 

 northwest at 3,900 ft, are 61.3° and 19.8°F respectively. Mean 

 annual precipitation is 9.93 in. Vegetation is dominated by 

 Artemisia tridentata . Agropyron spicatum and Bromus tectorum. 

 This site was not grazed by livestock before early July during 

 the course of my study. 



Field Methods 



Two permanent monitoring transects were established at each 

 of the study sites in early July, 1986 following methods outlined 

 in Lesica (1987). Transects were located subjectively to 

 represent the populations. At each site the transects were 

 parallel to each other and the slope and separated by ca. 30 ft. 

 Procedures for reading the monitoring transects are outlined in 

 Lesica and Elliott (1987a) and Lesica (1987) . Each transect 

 consisted of 50 l-m^ quadrats placed along the transect line. 

 The position of each A^. scaphoides plant encountered in the 

 quadrats was mapped and classified for three traits: size. 



