National Geographic : 1987 Mar
Wetland worlds RAISED BOG B OG, MARSH, SWAMP-poetically used as synonyms-scientifically describe strikingly different wetlands (below left). Swamps are dominated by trees, marshes by grasses, and bogs by sphagnum mosses and heaths. Found on all continents except Antarctica,bogs are most common in northernlatitudes where retreating glaciers left moist, depressed landwith poor drainage.Precipitationis their only water source. If fed by other waters, usually springs, bogs are called fens. Climate and terraindetermine bog type (above). Waterloggingfirst lowers oxygen levels and slows plant decay. Dead vegetation settles and becomes peat, a precursorof coal. Swamps and some marshes also producepeat. But accumulationis most dramaticin bogs, where sphagnum mosses excrete antibioticsand raise water acidity. In some parts of New England,glacier melt kettle holes may simply fill in with peat and vegetation. In areassuch as central Ireland,they may climax as raised bogs. Blanket bogs spread acrosspoorly drained landscapes, most often in northern coastal regions. A bog bouquet on a block of sphagnum moss (left) gathersplants adapted to this deceptively hostile environment.Water abounds, but anaerobicconditions limit bacteriaand fungi from breaking down nutrients in the peat. The thick leaves of leatherleaf1 and bog rosemary 2 help conserve nutrientsfrom photosynthesis. Acid-lovingfungi in the roots of the arethusa3 releasepeat nutrients to the orchid.Amid hardy sedges 4, the carnivorouspitcherplant 5 and sundew 6 catch theirown nourishinginsect meals. American Indians brewed the leaves of Labradortea 7 and used the cranberry8 for medicine and dye as well as food. Folk remediesfor arthritisprescribe the roots of false Solomon's seal 9. Able to absorbmany times its weight in water, sphagnum moss (below) is valued in horticulture as a soil conditioner.Dried, the fluffy moss once diaperedIndian children and served as a surgicaldressingduringWorld War I.