Vegetation and nutrient status of northern Michigan fens

Abstract

The vegetation, selected characteristics of shallow groundwater, and depth to water were examined in five fens in northern Lower Michigan. The field layer was the dominant stratum in all five fens and contained a total of 85 vascular species with a mean density of 30 vascular species per stand. Carex lasiocarpa was the most prevalent dominant plant and attained a frequency–presence index (FPI) of 8000 of a possible 10 000 and a mean importance value of 33 of a possible 200. Other common dominants in decreasing order of FPI were Carex aquatilis (6640), Myrica gale (4636), and Andromeda glaucophylla (2000). Common subordinates were Hypericum virginicum (2639), Muhlenbergia glomerata (2466), and Campanula aparinoides (1400). The vegetation was relatively homogeneous as indicated by a homogeneity index of 58%.The shallow groundwaters were minerotrophic with pH values ranging from 5.7 to 7.0 and calcium concentrations of 11.0 to 75.0 mg/ℓ. Four of the fens were on floating mats and had relatively stable water levels while the fifth was on a grounded mat and was subject to substantial water level fluctuation.Three previously described alkaline lake-edge kettle-hole 'bog' communities were found to be similar to the fens in species composition and water chemistry.