A wetland is a place that has moist conditions and soil is saturated for most of the year. These places are not regional biomes but definable areas of marshes, swamps, bogs, fens, vernal pools, and floodplains. A wetland can have trees and shrubs growing in and does not always have to have water. Water can be present underground or seasonal. Plants in a wetland are adapted for low-oxygen conditions due to frequent and variable periods of inundation.