Onderreed

Onderreed (Dutch for "under reed") is a term used in wetland ecology to describe the submerged components of reed beds, including rhizomes, roots, and the lower portions of stems that remain below the water surface. The concept emphasizes the underwater structure that supports the above-water canopy and overall bed stability.

In typical stands of common reed (Phragmites australis), onderreed comprises the rhizome network and below-water shoots that extend beneath the sediment-water interface. This subterranean and submergent portion of the plant community forms a distinct microhabitat with its own dynamics, contributing to the resilience of the reed bed.

Ecologically, onderreed contributes to sediment stabilization, nutrient cycling, and habitat provision for a range of aquatic organisms, including invertebrates and juvenile fish. It can influence gas exchange between water and atmosphere and affect water clarity by trapping sediments and particulates, thereby shaping the overall functioning of the wetland system.

Onderreed is most commonly observed in temperate wetlands across Europe and parts of Asia, where reed beds occupy floodplains, marsh edges, and ditch networks. Disturbances such as drainage, water level manipulation, and eutrophication can damage the underground structures and alter ecosystem services provided by the bed.

In research and restoration practice, onderreed is considered when designing wetlands and reestablishing reed stands, because healthy rhizome networks are essential for recovery after disturbance. The term is not universally standardized, and some researchers prefer descriptions like "submerged reed components" to avoid regional linguistic assumptions.