Vegetation and nutrient status of northern Michigan bogs and conifer swamps with a comparison to fens

Abstract

The vegetation and shallow groundwater were sampled at six bog and four conifer swamp sites in northern Lower Michigan in the same manner as at five previously described fen sites.The bogs were characterized by well-developed field (low shrub, herb, and fern), and bryophyte layers and strongly acid waters (pH 3.8–4.3). The most prevalent field-layer plants were Chamaedaphne calyculata and Carex oligosperma while Sphagnum spp. dominated the bryophyte layer. The number of vascular plant species in the field layer was 14 ± 4 (mean ± SD). The conifer swamps were characterized by well-developed tree and field layers and circumneutral waters (pH 7.0–7.4). Thuja occidentalis strongly dominated the tree layer and Mitella nuda, Abies balsamea, and Maianthemum canadense were the most prevalent field layer plants. The number of vascular plant species in the field layer was 57 ± 7 (mean ± SD).The bogs, conifer swamps, and fens are related developmentally (successionally) but differ strongly in floristics, species density, proportion of evergreen species, role of symbiotic nitrogen fixing species, role of Sphagnum spp., and water chemistry. Although these wetland types are often grouped together under the term "bog" or are considered successional stages of "bog," they differ markedly in vegetation and water chemistry, and are best considered as separate but related wetland types.