OLD - Temperate and Boreal Bog and Fen Formation

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This vegetation formation includes all the nutrient-poor to -medium peatland communities in the temperate and boreal regions of North America – wetlands known as bogs and fens. These saturated vegetation conditions are often referred to as mires or muskeg. Peatlands are, by far, the most common and extensive wetlands in Canada.

Communities in this formation are generally non-forested, but tree species often occur and individual trees can sometimes attain heights greater than 5 m tall. These bog and fen forests or woodlands are included here because they share both floristic and ecological similarity to other non-treed vegetation in this formation.

Peatlands are most common in areas of cool, moist / wet climates where there is adequate precipitation combined with low rates of plant productivity and decomposition. Landscape position also plays a key role in the formation of peatlands; peat accumulation is facilitated by groundwater accumulation in topographic basins with little drainage outflow. Peatlands form in wetland conditions when production rates of plant biomass exceed its decomposition, resulting in a net accumulation of organic substrate materials. This balance is generally the result of low decomposition rates caused by lack of oxygen, high acidity and nutrient availability. Bogs and fens occur along a gradient of these substrate conditions, from very acidic and nutrient-poor (bogs) to nutrient-medium, pH neutral or slightly alkaline (fens). Rich wetlands fall into the swamp and marsh formations.

In Canada, bog and fen peatlands constitute a large proportion of the landscape in the boreal zone, due largely to the cold climate. However, there are areas in the temperate zone that have suitable environmental conditions for peat development, esp. along both the east and west coasts.

Bogs have the poorest nutrient status of any wetlands. They receive most of their water from precipitation and have minimal hydrological contact with surrounding ground water. Most water loss is either to runoff (esp. after the spring thaw) or to evapotranspiration. Bogs are characterized by the dominance of peat mosses (Sphagnum spp.) in both the ground cover and the soil (peat) content. Other common species include Labrador tea (Ledum groenlandicum Oeder), small cranberry (Vaccinium oxycoccus L.), black spruce (Picea mariana (P. Mill.) Britton, Sterns & Poggenb.), bog rosemary (Andromeda polifolia L.), threeleaf false Solomon’s seal (Maianthemum trifolium (L.) Sloboda), cloudberry (Rubus chamaemorus L.), leatherleaf (Chamaedaphne calyculata (L.) Moench), bog laurel (Kalmia polifolia Wang.) and blueberries or lingonberries (Vaccinium spp). Bogs that are transitional to fens (i.e., that are slightly less acidic) tend to also have some glow moss (Aulacomium palustre (Hedw.) Schwaegr.), golden fuzzy fen moss (Tomenthypnum nitens (Hedw.) Loeske), arctic dwarf birch (Betula nana L.) and a greater proportion of graminoids (esp., sedges (Carex spp.). In the boreal zone, transitional bogs contain tamarack (Larix laricina (Du Roi) K. Koch).

Bogs of temperate coastal areas in Canada are of the transitional type. In B.C., various coastal tree species are present, in very stunted form, including shore pine (Pinus contorta var. contorta Dougl. ex Loud.), western red cedar (Thuja plicata Donn ex D. Don) and yellow-cedar (Chamaecyparis nootkatensis (D. Don) Spach). Peat moss and Labrador tea are present, as in boreal bogs, but other species such as tufted clubrush (Trichophorum caespitosum (L.) Hartman), great burnet (Sanguisorba officinalis L.) and deer-cabbage (Nephrophyllidium crista-galli (Menzies ex Hook.) Gilg) are also found. On the east coast, temperate coastal peatlands contain black spruce, as well as rhodora (Rhododendron canadense (L.) Torr.), sheep laurel (Kalmia angustifolia L.), smooth witherod (Viburnum nudum L.), black huckleberry (Gaylussacia baccata (Wangenh.) K. Koch), black chokeberry (Photinia melanocarpa (Michx.) Robertson & Phipps), mountain holly (Nemopanthus mucronatus ((L.) Loes. ), northern bog goldenrod (Solidago uliginosa Nutt.), bog aster (Oclemena nemoralis (Ait.) Greene), cinnamon fern (Osmunda cinnamomea L.), and smooth witherod (Viburnum nudum L.), among other species

Fens are nutrient-medium peatlands. They are richer in nutrients and have higher pH than bogs because of ground water inputs of oxygen and dissolved mineral nutrients. Although fen communities share many plant species with bog communities, they also contain species that are indicators of a more nutrient-rich environment. The degree of difference in floristics increases with nutrient richness. Poor fens (i.e., the transitional bogs mentioned above) have minor species differences to bogs; rich fens have a very different species complement altogether. In general, fens are characterized by high abundance of graminoids (esp. sedges) and 'brown' mosses: i.e., hook-mosses (Drepanocladus spp., Warnstorfia spp.), golden fuzzy fen moss, glow moss, sausage-mosses (Scorpidium spp.), and star-mosses (Campylium spp.). Tamarack  is generally considered a fen tree species, but it is often found in the part of a fen that is transitional to a bog.

Shrub fens may be dominated by willows (Salix spp.), birches (Betula spp.), sweet gale (Myrica gale L.), leatherleaf or meadowsweets (Spiraea spp.). Graminoid fens may be dominated by various grasses (e.g., bluejoint (Calamagrostis canadensis (Michx.) Beauv.)), sedges (Carex spp., Eleocharis spp., Trichophorum spp.) or cotton-grasses (Eriophorum spp.). Other common fen plant species include bog buckbean (Menyanthes trifoliata L.), horsetails (Equisetum spp.) and tall white bog orchid (Platanthera dilitata (Pursh) Lindl. ex Beck).