Pocosins occupy poorly drained higher ground between streams and floodplains. Seeps cause the inundation. There are often perched water tables underlying pocosins. Shrub vegetation is common in a pocosin ecosystem. Pocosins are sometimes called shrub bogs. Pond pines dominate pocosin forests, but loblolly pine and longleaf pine are also associated with pocosins. Additionally, pocosins are home to rare and threatened plant species including Venus flytrap and sweet pitcher plant. A distinction is sometimes made between short pocosins, which have shorter trees, deeper peat, and fewer soil nutrients, and tall pocosins, which have taller trees, shallow peat, and more nutrient-rich soil. Where soil saturation is less frequent and peat depths shallower, pocosins transition into pine flatwoods. A loose definition of "pocosin" can include all shrub and forest bogs, as well as stands of Atlantic white cedar and loblolly pine on the Atlanticcoastal plain. A stricter definition restricts pocosins to shrubby "short pocosins" and pond pine-forested "tall pocosins". Pocosins are formed by the accumulation of organic matter, resembling black muck, that is built up over thousands of years. This accumulation of material causes the area to be highly acidic and nutrient-deficient. The thickness of the organic buildup varies depending on one's location within the pocosin. Near the edges the buildup can be several inches thick but toward the center it can be up to several feet thick. Vegetation on the pocosin varies throughout. At the edges more pond pine is found with an abundance of titi, zenobia, and greenbrier vines. Closer to the center thin, stunted trees are typically found however fewer shrubs and vines are present. Pocosins are very important for birds that live in cold climates during the winter months and migrate southward. The abundance of various types of available berries draws birds from colder areas. Pocosin ecosystems are fire-adapted. Pond pines exhibit serotiny, such that wildfire can create a pond pine seedbed in the soil. Wildfires in pocosins tend to be intense, sometimes burning deep into the peat, resulting in small lakes and ponds. Wildfires occurring about once a decade tend to cause pond pines to dominate over other trees, and cane rather than shrubs to dominate the understory. More frequent fires result in a pyrophytic shrub understory. Annual fires prevent shrub growth and thin the pondpine forest cover, creating a flooded savanna with grass, sedge, and herb groundcover. The word pocosin comes from an Eastern Algonquian word meaning "swamp-on-a-hill", however, a more accurate description of a pocosin would be a "raised bog". The city of Poquoson, Virginia, located in the coastal plain of Virginia, derives its name from this geographic feature.
