Influence of topography, bare sand, and soil pH on the occurrence and distribution of plant species in a lacustrine dune ecosystem

Abstract

Dune ecosystems along the Great Lakes shoreline provide essential habitat for specialized plant communities and several state and federal listed rare species. I conducted a vegetation survey in Grand Sable Dunes, Pictured Rocks National Lakeshore, MI, in an effort to investigate the hypothesis that physical dune characteristics influence the distribution of encountered listed species of concern. Three species with concern status were encountered (Cirsium pitcheri, Stellaria longipes, and Tanacetum bipinnatum). Overall plant diversity was negatively correlated with soil pH. Increases in dune aspect and slope resulted in increased abundance of C. pitcheri and S. longipes, while T. bipinnatum decreased in abundance. Increases in species richness and plant density resulted in decreased abundance of C. pitcheri and T. bipinnatum, while S. longipes increased in abundance. These three species rarely co-occurred in quadrats. The gradient of dune stabilization that has naturally occurred within Grand Sable Dunes provides the necessary range of distinct microhabitat necessary for C. pitcheri, S. longipes, and T. bipinnatum to establish and maintain populations. Younger foredunes with less vegetation cover are necessary for C. pitcheri and T. bipinnatum. As dunes stabilize and more species colonize, the microhabitat becomes more suitable for S. longipes. Ensuring a natural range of dune stabilization from active foredunes to stable hind dunes will benefit conservation of endangered, threatened, and species of concern.