This Eastern Mud Salamander (Pseudotriton montanus) is resting on sphagnum moss. Sphagnum creates bogs by holding water and creating acidic conditions. Sphagnum itself may be up to 70 percent water.
Bogs are one of North America's most distinctive kinds of wetlands. They are characterized by spongy peat deposits, acidic waters, and a floor covered by a thick carpet of sphagnum moss. Bogs receive all or most of their water from precipitation rather than from runoff, groundwater or streams. As a result, bogs are low in the nutrients needed for plant growth, a condition that is enhanced by acid forming peat mosses.
There are two primary ways that a bog can develop: bogs can form as sphagnum moss grows over a lake or pond and slowly fills it (terrestrialization), or bogs can form as sphagnum moss blankets dry land and prevents water from leaving the surface (paludification). Over time, many feet of acidic peat deposits build up in bogs of either origin. The unique and demanding physical and chemical characteristics of bogs result in the presence of plant and animal communities that demonstrate many special adaptations to low nutrient levels, waterlogged conditions, and acidic waters, such as carnivorous plants.
Carlisle Bog in Alaska. Unlike the rest of the United States, Alaska still has most of its wetlands.
Functions and Values
Bogs serve an important ecological function in preventing downstream flooding by absorbing precipitation. Bogs support some of the most interesting plants in the United States (like the carnivorous Sundew), and provide habitat to animals threatened by human encroachment.
Bogs in the United States are mostly found in the glaciated northeast and Great Lakes regions (northern bogs), but also in the southeast (pocosins). Their acreage declined historically, as they were drained to be used as cropland, and mined for their peat which was used as a fuel and a soil conditioner. Recently, bogs have been recognized for their role in regulating the global climate by storing large amounts of carbon in peat deposits. Bogs are unique communities that can be destroyed in a matter of days, but require hundreds, if not thousands, of years to form naturally.
This bog in Nova Scotia, Canada is dominated by ericaceous dwarf-shrubs, a common family of plants in the peat bogs of the Northeast.
Northern bogs are generally associated with low temperatures and short growing seasons where ample precipitation and high humidity cause excessive moisture to accumulate. Therefore, most bogs in the United States are found in the northern states. Northern bogs often form in old glacial lakes. They may have either considerable amounts of open water surrounded by floating vegetation or vegetation may have completely filled the lake (terrestrialization).
The sphagnum peats of northern bogs cause especially acidic waters. The result is a wetland ecosystem with a very specialized and unique flora and fauna that can grow in these conditions called acidophiles. Nevertheless, bogs support a number of species of plants in addition to the characteristic Sphagnum Moss, including Cotton Grass, Cranberry, Blueberry, Pine, Labrador Tea, and Tamarack. Moose, deer, and lynx are a few of the animals that can be found in northern bogs. The Greater Sandhill Crane, the Sora Rail, and the Great Gray Owl depend on bogs for survival.
The Northern Pitcher Plant (Sarracenia purpurea) overcomes the nutrient deficiencies of bog life by capturing insects in pools of water in its leaves and digesting them with the help of some local bacteria. The Northern Pitcher Plant's flower looks much like the Sweet Pitcher Plant's (see below).
Pocosins are densely vegetated with trees and shrubs. They are subjected to fire about every 10 to 30 years (Photo by Dr. Curtis Richardson/Duke Wetland Center).
The word pocosin comes from the Algonquin Native American word for "swamp on a hill." These evergreen shrub and tree dominated landscapes are found on the Atlantic Coastal Plain from Virginia to northern Florida, though most are found in North Carolina. Usually, there is no standing water present in pocosins, but a shallow water table leaves the soil saturated for much of the year.They range in size from less than an acre to several thousand acres located between and isolated from old or existing stream systems in most instances.
Because pocosins are found in broad, flat, upland areas far from large streams, they are ombrotrophic like northern bogs, meaning rain provides most of their water. Also like the bogs of the far north, pocosins are found on waterlogged, nutrient poor, acid soils. The soil itself is a mixture of peat and sand containing large amounts of charcoal from periodic burnings. These natural fires occur because pocosins periodically become very dry in the spring or summer. The fires are ecologically important because they increase the diversity of shrub types in pocosins.
Pocosins provide large tracks of undisturbed land needed by Black Bears (Ursus americanus).
The most common plants are evergreen trees (Loblolly Bay, Red Bay, and Sweet Bay), and evergreen shrubs (titi, fetterbush, and zenobia). Pocosins provide important habitat for many animals, including some endangered species like the red-cockaded woodpecker. They are especially important as the last refuge for Black Bears in coastal Virginia and North Carolina, and the Red Wolf has recently been reintroduced in North Carolina pocosins.
Sweet Bay (Magnolia virginiana)
Zenobia (Zenobia pulverulenta).
Functions and values
Habitat is the most valuable function of Pocosins. Some pocosins are very large and difficult to develop, and so they remain largely undisturbed. As a result, they are a haven for species adapted to living in unaltered forests. As more and more land is developed in the Eastern United States, pocosins are becoming ever more valuable refuges for wildlife.
The slow movement of water through the dense organic matter in pocosins removes excess nutrients deposited by rainwater. The same organic matter also acidifies the water. This very pure water is slowly released to estuaries, where it helps to maintain the proper salinity, nutrients, and acidity. This process is important to help maintain healthy fish populations important to both commerce and recreation. Pocosins are also sources of valuable timber and fuel, but these uses can harm or destroy pocosins if they are not carried out responsibly.
The Sweet Pitcher Plant (Sarracenia rubra) is one of the carnivorous plants found in pocosins.
About 1,400 square miles of undisturbed pocosins remain today. By comparison, more than 3,000 square miles were drained between 1962 and 1979. Historically, pocosins were mostly threatened by agriculture. Today, timber harvesting, peat mining, and phosphate mining join agriculture as the biggest threats to the remaining undisturbed pocosins.