Status of the Lake Huron Tansy at the Grass Bay Preserve: a preliminary report on stem densities in different dune habitats.

Abstract

This preliminary report is an analysis of the distribution and density of the Lake Huron tansy (Tanacetum huronense Nutt.) based on three years of monitoring data from dune habitats in The Nature Conservancy's Grass Bay Preserve in northern Michigan. It represents a first step towards identifying critical managment issues for the species. The hypotheses tested are (1) The density of tansies in each habitat type are the same; and (2) the number and density of stems per transect are the same between years. Preliminary results suggest that the relative proportion of different dune habitats present is highly variable between years, and that the tansy stems are patchily distributed with the density of stems varying widely from patch to patch. Although none of the habitat types sampled had densities of tansy stems that were consistently signficantly different in distribution than any other habitat type, the results suggest that protection of primary ridge and primary hindunce habitats should be a conservation priority at Grass Bay.