Complex sentence: Peatlands, particularly bogs, are the primary source of peat, although less common wetlands including fens, pocosins, and peat swamp forests also deposit peat.
Split into simpler sentences: Peatlands, particularly bogs, are the most important source of peat. That said, other less common wetland types, including fens, pocosins, and peat swamp forests, also deposit peat.