Large cranberry - short sedge moss lawn (S3)
The large cranberry - short sedge moss lawn community is widespread in
This community differs from intermediate fens (e.g., those with sweet gale, or dominated by robust sedges) by a number of important factors. These include abundant aquatic peat mosses; a relatively sparse, dwarfed shrub layer; a higher frequency of “bog” plants such as tawny cotton-grass and pitcherplant; a lower frequency of robust Carex species; a higher frequency of short sedges (Carex, Dulichium, and Rhynchospora); and an absence of Sphagnum lescurii.
Characteristic vegetation: Large cranberry (Vaccinium macrocarpon), spatulate-leaved sundew (Drosera intermedia), and short sedges such as three-way sedge (Dulichium arundinaceum), white beak-rush (Rhynchospora alba), and silvery sedge (Carex canescens) are common. These species are more frequent and abundant than in either Sphagnum rubellum - small cranberry moss carpet or liverwort - horned bladderwort fen, indicating slightly higher nutrient levels in this community. Sweet gale (Myrica gale) may be common in low to moderate abundance. Quagmire sedge (Carex limosa), swamp candles (Lysimachia terrestris), marsh St. John’s-wort (Triadenum virginicum), and mud rush (Juncus pelocarpus) are occasional to frequent. Leatherleaf (Chamaedaphne calyculata) is frequent and sometimes abundant, but dwarfed. Pitcher plant (Sarracenia purpurea), tawny cotton-grass (Eriophorum virginicum), and other common bog plants may also be present. Some combination of Sphagnum torreyanum, S. cuspidatum, and S. pulchrum dominate the moss layer. Robust Carex species [wire sedge (Carex lasiocarpa), bottle-shaped sedge (C. utriculata), and few seeded sedge (C. oligosperma)] are infrequent.
Variants: Three variants are described based largely on the dominant peat moss and minor shifts in species composition.
1. Sphagnum cuspidatum variant:
Sphagnum cuspidatum is dominant and Drosera intermedia (spatulate-leaved sundew) and white beak rush are frequent. Robust sedges and sweet gale are rare (more frequent in the other variants). Sphagnum angustifolium, S. fimbriatum, and S. fallax are infrequent. The average pH is 4.2 and hummocks are moderately small (average hummock height 0.11 m; average maximum hummock height 0.20 m). Peat is moderately well decomposed in the upper 0.5 m. Dwarf shrub height averages 0.29 m. One example is dominated by the coastal plain sedge inflated sedge (Carex bullata) and Sphagnum cuspidatum. Overall, the floristic composition is indicative of slightly more oligotrophic conditions than in the S. torreyanum variant.
2. Sphagnum torreyanum variant:
Sphagnum torreyanum is abundant to dominant, S. papillosum is occasional, and S. affine, S. pulchrum, and S. cuspidatum are infrequent. Mud rush (Juncus pelocarpus), spatulate-leaved sundew (Drosera intermedia), pitcherplant (Sarracenia purpurea), and tawny cotton-grass (Eriophorum virginicum) are occasional. Podgrass (Scheuchzeria palustris), wire sedge (Carex lasiocarpa), bottle-shaped sedge (C. utriculata), few seeded sedge (C. oligosperma), and quagmire sedge (C. limosa) are infrequent. Average pH is 4.3. Hummocks are moderately small (average 0.14 m) and range to an average maximum height of 0.29 m. Peat is moderately well decomposed within the upper 0.5 m. Dwarf shrub height averages 0.42 m.
3. Sphagnum pulchrum - quagmire sedge variant:
This variant corresponds to open moss lawns or pools dominated by Sphagnum pulchrum and sparse cover of vascular plants. It occurs as small pools with loose Sphagnum, or occasionally as extensive carpets or lawns associated with large lake border peatlands (e.g., peatlands around
Good examples can be seen at
Large cranberry - short sedge moss lawns often occur as part of larger medium level fen systems or patterned fen systems, and sometimes as part of kettle hole bog systems or poor level fen/bog systems.
Large cranberry - short sedge moss lawn in Madison (photo by Ben Kimball)