Open Peatlands he allure and mystique of peatlands has attracted people for millennia. Well- preserved “bog bodies” up to 8,000 years old have been found in peatlands T from northern Europe to Florida, attesting to an early human relationship to peatlands and revealing religious and cultural practices ranging from human sacrifice to well-organized social structure. In more recent times, naturalists and ecologists have conducted numerous studies of peatland flora, fauna, ecology, and paleoecology. Quite simply, peatlands are wetlands that accumulate peat, a soil type consisting of partially decomposed organic matter. They occur primarily in northern cold-temper- ate and boreal regions of the world, where moist conditions result from annual precipitation exceeding evapotranspiration. Peatlands are permanently saturated with water at or near the soil surface, creating a nearly anaerobic soil environment with limited biological activity. Under these soil conditions, plant growth exceeds plant decomposition, and layers of peat accumulate annually. Two main types of peatlands are commonly distinguished. Bogs are peatlands with slightly raised surfaces that receive most of their water and nutrients from precipitation and are therefore referred to as being ombrotrophic. They have acidic waters that are poor in minerals and nutrients. Bogs are dominated by species of the moss genus Sphagnum, heath shrubs, and in some areas, black spruce. Fens, in contrast, have slightly acidic to slightly basic, mineral-rich waters from groundwater discharge and seepage. Fens may be flat or gently sloping and are dominated by sedges, grasses, and “brown mosses” (non-sphagnum mosses). There is clearly a continuum in the variation between bogs and fens in nature. The following peatland community profiles are presented in an order that roughly reflects this continuum, beginning with ombrotrophic Dwarf Shrub Bog, progressing through several peatland types that receive some mineral enrichment, and ending with Rich Fen, our most enriched peatland type. As mentioned above, decomposition of organic material is generally slow in peatlands due to the cool and nearly anaerobic soil conditions. There is, however, considerable variation in the rate of decomposition and the resulting types of peat found in peatlands along the gradient from Dwarf Shrub Bog to Rich Fen. The acidity or basicity of peatland water is measured using the pH scale. This scale translates hydrogen ion concentration of the water or solution being measured into numbers ranging from 1 to 14, where 7 is neutral, values below 7 are considered acidic, and values above 7 are considered basic. The very acidic waters found in bogs contribute to the slow activity of soil microorganisms and an overall slow rate of peat decomposi- tion. Bog water is usually stagnant, whereas the surface water in fens moves slowly across the peatland surface or through the upper layers of peat. This results in slightly higher oxygen concentrations in fen waters and therefore greater peat decomposition compared to bogs. Another important factor affecting peat types is the vegetation of the OpenIntroduction Peatlands / 311 peatland. Dead sphagnum moss is a dominant component of the poorly decomposed, tan-colored, fibric peat found in bogs. Remains of sedges are prominent in the moder- ately decomposed, dark reddish brown, hemic peat of many fens. Sapric peat is dark brown to black and is so well decomposed that plant remains are not recognizable. A single genus of plants deserves special attention in building an understanding of bogs and fens. There are 29 species of sphagnum moss documented in Vermont. Many of these species are dominant in Dwarf Shrub Bogs and Poor Fens and play many important roles in shaping peatland ecology. Live sphagnum moss and peat derived from sphagnum have an enormous capacity to hold water due to the structure of the leaves and leaf cells. This water holding capacity results in creation of a bog water table raised above the regional water table and contributes to the process of paludification, in which peatlands expand horizontally over time as peat accumulates and impedes drainage. Sphagnum also has the ability to remove mineral cations from solution and release hydrogen ions, thereby acidifying the environment in which it grows. Sphagnum peat is an excellent thermal insulator, and ice may persist in hummocks well into June. The result for many bog plants is a condition of water stress, as their roots may be frozen at the same time that the leaves and stems are functioning under spring and early summer temperatures. The reader is directed to texts by Crum (1988) and McQueen (1990) listed below for a more comprehensive treatment of sphagnum ecology. Peatlands contain an amazing record of past vegetation and climate changes. Vermont’s peatlands have been forming since the retreat of the glaciers some 13,500 years ago. Over this period, each thin layer of annual peat accumulation has stored fragments of plants that grew in the wetland, as well as pollen from peatland plants and nearby forests. By taking cores of peat, paleoecologists are able to date the time at which specific layers were deposited and analyze the peat composition to determine what plants grew in the vicinity at that time. Understanding the ecology of individual species identified provides a basis for interpreting the vegetation and climate at a particular time. These paleoecological records have revealed that Vermont was first colonized by tundra, followed by the spread of black spruce and birch forests begin- ning about 11,000 years ago. Northern Hardwood species began colonizing the lower elevations of the area approximately 8,000 years ago. There is also strong evidence that there was a period of much warmer climate about 6,000 years ago that is reflected by abundant oak pollen in the paleoecological record. Selected References and Further Reading Johnson, C. 1985. Bogs of the Northeast. University Press of New England, Hanover. Crum, H. 1988. A Focus on Peatlands and Peat Mosses. University of Michigan Press, Ann Arbor. McQueen, C. 1990. Field Guide to the Peat Mosses of Boreal North America. University Press of New England, Hanover. Damman, A. and T. French. 1987. The ecology of peat bogs of the glaciated northeastern United States: a community profile. U.S. Fish and Wildlife Service Biological Report 85. 312 / Wetland, Woodland, Wildland HOW TO IDENTIFY Peatland Natural Communities Read the short descriptions that follow and choose the community that fits best. Then go to the page indicated and read the full community profile to confirm your decision. Dwarf Shrub Bog: These bogs are open, acid peatlands dominated by heath shrubs (leatherleaf, bog laurel, sheep laurel, and Labrador tea) and sphagnum moss. Scattered, stunted black spruce and tamarack trees cover less than 25 percent of the ground. Found in cold climate areas. Deep sphagnum peat is permanently saturated. Go to page 314. Black Spruce Woodland Bog: Stunted black spruce trees cover 25 to 60 percent of the ground over heath shrubs and sphagnum moss. Found in cold climate areas. Peat is deep and dominated by remains of sphagnum moss. Go to page 318. Pitch Pine Woodland Bog: Pitch pine forms an open canopy (25 to 60 percent cover) over rhodora, heath shrubs, and sphagnum moss. This community is known only from Maquam Bog at the mouth of the Missisquoi River. Go to page 321. Alpine Peatland: This community is found only on the highest peaks of the Green Mountains (above 3,500 feet). It has characteristics of both bog and poor fen, but is distinguished by its high elevation and presence of alpine bilberry, black crowberry, Bigelow’s sedge, and deer-hair sedge. Peat is shallow over bedrock. Go to page 324. Poor Fen: These fens are open, acid peatlands dominated by sphagnum mosses, sedges, and heath shrubs. There is some mineral enrichment of surface waters in the hollows, as indicated by the presence of bog bean, mud sedge, white beakrush, and hairy-fruited sedge. Peat is deep and made up of sphagnum moss and sedge remains. Go to page 327. Intermediate Fen: These fens are open, slightly acid to neutral peatlands dominated by tall sedges, non-sphagnum mosses, and a sparse to moderate cover of shrubs. Hairy-fruited sedge is typically dominant and water sedge, twig rush, bog-bean, and sweet gale are characteristic. The peat is deep, saturated, and composed of sedge remains. Go to page 330. Rich Fen: These fens are similar to Intermediate Fen but typically have shallower sedge peat and more mineral-enriched surface waters. A gentle slope of the peatland may be evident. Sedges and non-sphagnum mosses dominate, including inland sedge, porcupine sedge, yellow sedge, and the moss starry campylium. Red-osier dogwood, shrubby cinquefoil, and alder-leaved buckthorn are characteristic shrubs. Go to page 333. Spruce-Fir Northern Hardwood ForestOpen FormationPeatlands / 313 DWARF SHRUB BOG ECOLOGY AND PHYSICAL SETTING Entering a bog for the first time is likely to be a long- remembered experience. There is an otherworldly character to bogs that is unlike any other part of our Vermont landscape. They are quiet places with soft, spongy ground underfoot and typically have dense conifer forests surround- ing them. Bogs are open but may have a few scattered, highly stunted trees. Early summer can bring a profusion of flowers on the low shrubs and songs of birds commonly found much farther north. Insectivorous plants, like pitcher plant and sundew, are well adapted to the low nutrient environments of bogs and are a common occurrence. Dwarf Shrub Bogs are open peatlands with acidic water (pH of 3.5 to 5.0) that is very low in dissolved minerals and nutrients. Bogs are referred to as being ombrotrophic if they receive water and nutrients only from precipitation. DISTRIBUTION/ABUNDANCE Ombrotrophic bogs have a slightly raised peat surface and Dwarf shrub bogs a water table that generally remains just below the peat occur throughout Vermont surface but elevated above the local water table of sur- but are more common in rounding wetlands or uplands.