Environmental Factors Affecting Establishment and Growth of Pedicularis furbishiae, a Rare Endemic of the St. John River Valley, Maine

Abstract

To monitor survival, reproduction, and seedling recruitment of Pedicularis furbishiae S. Wats. (Furbish''s lousewort), a restricted riverbank endemic, we established permanent plots at seven sites. Within sites, plants were concentrated in a horizontal band only 1-2 m wide, which makes the populations vulnerable to local disturbances and suggests that very specific conditions favor Pedicularis growth. Density, percentage of plants in each size class, and the quantities of inflorescences and seeds produced varied considerably among populations. Seedlings emerged from late June through August, except at one site which completely lacked seedlings. Eighty-one percent of the seedlings survived the summer, survival was higher at sites with wetter soil. Seedlings occurred disproportionately on moss rather than on bare soil, gravel, or litter. Flower initiation and number of inflorescences produced were positively correlated with plant size, although dense cover reduced seed output. Disturbance, as ice scour or bank slumping, destroys individual plants and creates conditions inhospitable for immediate colonization, but it seems important in maintaining suitable habitat, since dense vegetation appeared to limit lousewort density. Pedicularis furbishiae''s rarity can be described by its narrow ecological "windows" both in time and in space.