I. Introduction: What is a Bog?
The word "bog," from the old Gaelic "bogach," is commonly used to refer to any stretch of waterlogged, swampy ground. The words, fen, moor, muskeg, peatland, and mire are also used to describe these areas, which can lead to some confusion over terminology. Specifically, a bog is "a peat accumulating wetland that has no significant inflows or outflows and supports acidophilic mosses, particularly sphagnum" (Gosselink and Mitsch 1993). The vast majority of bogs are located in the moist, cool boreal regions of North America and Eurasia. Bogs are also called "peatlands" because of the peat they accumulate, but "peatland" is a more general term that includes "minerotrophic" and "transition" peatlands. These wetlands also accumulate peat, but they differ topographically and hydrologically from bogs. True bogs (ombrotrophic peatlands) are characterized by peat layers higher than their surroundings; they are often called "raised bogs." They also receive nutrients and minerals exclusively by precipitation, i.e. they are hydrologically isolated (Gosselink and Mitsch 1993 p.374). They form in a variety of ways, but once ombrotrophic (rain-nourished) peatlands develop they are stable under "fairly wide environmental fluctuation" (Gosselink and Mitsch 1993 p.372). This discussion will be limited to the true bogs, and they will be referred to as bogs or peatlands.
II. Peat Soils and Carbon Mineralization
Peat is the name for the soil that forms in bogs and other peatlands. It is an organic soil (Histosol), composed almost entirely of partially decayed plant matter. The high percentage of organic fibers in peat makes it a fibrist, which is a Histosol containing less than one third decayed organic matter (USDA 1975 p.66). Peat soils are typically dark brown in color and very acidic (pH= 2.6-4.0). The hydrologic isolation of bog peats causes them to be deficient in nitrogen and other nutrients, limiting the species of plants that can thrive in these soils. Plants that can survive in bogs have evolved to take advantage of other sources of nitrogen; sundews and pitcher plants are two of the more spectacular examples of these adaptations.
One of the important factors necessary for bogs to develop is a surplus of peat production over decomposition, which will be explained later (Gosselink and Mitsch 1993 p.372). This surplus allows undecomposed peat to build up in increasingly thick layers, creating a raised bog and acting as a "sink" for organic carbon. Because of this carbon storage, bogs and other peatlands are important reservoirs in the global carbon cycle. Some researchers estimate that all northern peatlands now store 1.5-4.5 X 1015 kg of carbon (Siegel et al. 1995). As concern grows over the role of carbon in global climate change, knowing the fate of this stored carbon is becomes vitally importance.
Like other waterlogged soils, bog peats are characterized by strongly reducing conditions (Singer and Munns...