Spatiotemporal Ecology of an Imperiled Cushion Plant Assemblage at a North American Rocky Mountain Summit: Implications for Diversity Conservation

Conservation of rare plant species diversity is often found within the context of disturbance and land use planning. In mountainous regions, globally, critical plant conservation issues can occur at esthetically pleasing topoedaphic positions, such as popular mountain summits. Here, we assess the spatiotemporal ecology of an imperiled cushion plant assemblage in such a situation. Plant community dynamics of three rare cushion plant species [scented pussytoes (<i>Antennaria aromatica</i>), Howard’s alpine forget-me-not (<i>Eritrichum howardii</i>), and Shoshone carrot (<i>Shoshonea pulvinata</i>)] were measured at a 2475 m mountain summit near Cody, WY, USA. The survey was conducted in the summer of 2017–2019 using 1 m² quadrats across three macroplots (ranging from 295 to 2250 m² in size) to estimate all vascular plant species abundance. Altitude, canopy height, vegetative cover, standing dead biomass, rock, litter, and bare soil were also measured. We assessed annual changes in abundances, richness (#), evenness (N2/N1), and diversity (H′) and performed a constrained ordination to understand ecological drivers of distribution. Nineteen total plant species were identified, all of which were native perennial species. Five additional species were also noted to be species of conservation concern. For the three rare cushion plants of focus, abundance did not significantly change over the three-year period. Species richness was lower in 2017 than in subsequent years, but there was no difference in evenness or diversity. In the constrained ordination, the first axis explained 56.1% of the variation and was attributed to the rock-to-vegetation gradient of the environment, while the second axis explained an additional 28.7% of the variance and was attributed to altitude. The three rare cushion plants of focus appeared to segregate and occupy differential habitat niches. The popularity of this mountain peak, coupled with the presence of a diverse rare cushion plant community, should facilitate the careful monitoring and management of tourism to ensure the conservation of diversity.