Blechnum spicant: Habitat and Vigor of Optimal, Marginal, and Disjunct Populations, and Field Observations of Gametophytes

Species composition and abundance values for vascular plants were determined for four forest stands at Olympic Peninsula, Washington, and a stand in northern Idaho where the homosporous fern Blechnum spicant occurred. Vegetative vigor and reproductive vitality for B. spicant were estimated. Sterile frond length ranged from 47.9 cm at Twanoh to 19.0 cm at the Hoh Stand. Spore germination approached zero m the Hoh and Mason Mountain populations. The optimum habitat for B. spicant, represented by the Twanoh Stand, was wetter than mean sites in the Tsuga heterophylla zone, where Oplopanax horridum and Lysichitum americanum were abundant, Oxalis oregana was absent, and Polystichum munitum was uncommon. Species composition, density, and phenology were determined for mixed fern gametophyte populations at Lake Quinault. Gametophytes were first found in early fall, grew vigorously over the winter, and produced sporophytes through late spring. Female, bisexual, and male gametophytes occurred in mixedspecies populations at densities up to 4.5 cm-2. Sporophytes appeared shortly after development of archegonia on bisexual and female gametophytes. Polyembryony did not occur. As almost all archegoniate plants bore sporophytes in dense populations, competition among gametophytes was thought to be minimal. Dense populations of young sporophytes later occupied sites sufficient for single perennating sporophytes. I hypothesized that strong competition occurs between young sporophytes and that gametophyte reproductive mechanisms that increase heterozygosity will be selected in dense populations.