However, because the character of a wetland area depends heavily upon its water source, there may be great variation within these categories. Marshes contain nonwoody emergent plants. There may be different zones within one marsh which vary with respect to the relationship between the height of the soil and the height of the water. Different plant species may inhabit these different zones. Marshes may have either salt water or fresh water and soil may vary greatly in mineral and organic quality.
Swamps contain large amounts of trees or shrubs.
They may vary greatly in salinity and nutrient content of soil. Peatlands are special types of wetlands. Plantlife in these areas emerges more quickly than they are able to fully decay. Partially decomposed plant material, called peat, accumulates in these ecosystems. This peat forms a rich, organic soil which promotes the growth of certain plants.