Tobias, V.D. and Nyman, J.A., 2017. Leaf tissue indicators of flooding stress in the above- and belowground biomass of Spartina patens.Many factors, such as rising sea levels and human alterations, threaten coastal wetlands in the United States and around the world. To reverse some wetland loss, dredge material, tidal flow, or river flow can be used to create new wetlands, or existing wetlands can be managed to increase plant productivity. Identifying the causes of limited production can improve management plans by suggesting possible remedies. Managing and restoring marshes depends on understanding which stress factors limit growth of key marsh-building plants. Spartina patens is a common marsh-building species of grass in brackish marshes along the Gulf of Mexico and Atlantic coasts of North America, and it is often the target of management and restoration plans. Spartina patens was grown under six flooding levels in a field experiment. Spartina patens plants grown at lower elevations had consistently lower biomass, in contrast to Spartina alterniflora, which has been shown to exhibit peak biomass at intermediate levels of flooding. Critical values of elemental concentrations in plant tissue are widely used to diagnose mineral deficiencies in agricultural crops and are just beginning to be developed to aid wetland management and restoration. For leaf tissue harvested in summer, [Mn] < 256 ppm and [Ca] < 0.3% indicated that plants grew at lower elevations and had limited biomass. The results suggest that concentrations of Mn and Ca in the leaf tissue of S. patens could form part of an indicator to monitor belowground productivity of marshes. Although low concentrations of these elements were associated with the smaller root and shoot biomass of plants grown at low elevations, variability in the relationship suggests that additional factors may need to be considered. Marsh managers should monitor soil elevation loss carefully if they choose to drain marshes to increase plant production to prevent excessive loss of soil elevation.