The tensile root strength of five emergent coastal macrophytes

The root biomass of emergent macrophytes in coastal wetlands is essential for anchorage and erosion protection. The tensile root strength of these plants is an important component in determining the strength of coastal wetland soils. We made 1449 tensile strength measurements of roots <1.5 mm in diameter for five species of emergent wetland macrophytes (Spartina alterniflora, S.patens, Panicum hemitomon, Schoenoplectus americanus, and Sagittaria lancifolia) collected from six sites in three coastal estuaries. An analysis of variance revealed that the tensile root strength of dead and live roots for all species decreased with depth and that dead roots were stronger than live roots of the same diameter (p < 0.05). There was low variation in the mean tensile root strength among all sites. The S. alterniflora dead roots from the Barataria Basin site, however, were stronger than those from the Lake Pontchartrain site and the S. patens live and dead roots collected from Breton Sound were stronger than those from a nearby site in the same watershed. Wetland root samples exposed to partially-treated sewage effluent were considerably smaller than roots collected from the nearby reference wetland. Further investigation is warranted to ascertain the nature of the factors that causing these variations in tensile root strength with depth, between live and dead roots and with nutrient exposure