Incorporating thresholds into understanding salinity tolerance: a study using salt-tolerant plants in salt marshes

Although salinity in many ecosystems such as salt marshes can be extremely high, an asymmetry in salinity range between experimental studies (relatively narrow) and field conditions (potentially broad) has strongly affected current understanding of plant salinity tolerance. To improve understanding, it is thus important to examine plant tolerances over a broad range of salinities and identify potential tolerance thresholds. We examine tolerances of two widely-distributed marsh plants, Suaeda salsa and Salicornia europaea, to salinities ranging from 0 to 100 g kg-1, and determine survival, above- and below-ground biomass after eight weeks of salinity treatment. Both species, especially Sa. europaea, have much broader salinity tolerances than other plants previously examined, 2) plant survival, above- and below-ground biomass have remarkably different responses to salinity, and 3) there is a non-linear, threshold response of S. salsa to salinity, above which S. salsa survivorship drastica...