Soil erodibility differs according to heritable trait variation and nutrient-induced plasticity in the salt marsh engineer Spartina alterniflora

ABSTRACT: Use of landform engineers for habitat restoration has often resulted in unanticipated outcomes. It is possible that departures from expectation arise because applications do not adequately account for the influence of heritable and non-heritable phenotypic variation on ecosystem attributes. In this study, we performed a common garden greenhouse experiment to determine whether soil shear strength—a characteristic linked to erosion resistance—varies according to heritable and plastic trait expression in Spartina alterniflora grown under contrasting nutrient regimes. We detected heritable variation across a broad spectrum of functional traits, including nutrient uptake. We also found that S. alterniflora exhibited trait-specific differences in nutrient-induced phenotypic plasticity. Heritable trait differences and plasticity together explained approximately 70% of the observed variation in soil shear strength. Soil shear strength increased when plants received more nutrients, but the influence of heritable variation on soil shear strength was equal to or larger than that of nutrient-induced plasticity. These findings illustrate that heritable and non-heritable trait expression can potentially govern the fate of marsh ecosystems, which suggests that consideration should be given to both factors when deploying landform engineers for coastal restoration.