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

Abstract

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, and determine survival, above- and belowground biomass after 8 weeks of salinity treatment. Both species, Sa. europaea in particular, have much broader salinity tolerances than other plants previously examined, (2) plant survival, above- and belowground biomass have remarkably different responses to salinity, and (3) there is a nonlinear, threshold response of S. salsa to salinity, above which S. salsa survivorship drastically decreases. These results provide multiple important insights. Our study suggests that the potential for using these halophytes to revegetate and restore salt-affected land may be greater than previously thought, and highlights the importance of studying multiple plant responses. Importantly, our study calls for a better integration of thresholds into understanding plant salinity tolerances and their applications.

Keywords: Salicornia europaea; Suaeda salsa; coastal wetlands; nonlinear ecological processes; salt marsh; soil salinity.

Figure 1

Photographs showing Suaeda salsa (a) and Salicorina eutropaea (b) in a hypersaline salt marsh in the Yellow River Delta, northern China. Photo credits: QEcology.org

Figure 2

Effects of 0–100 g/kg salinity treatments on the survivorship of Suaeda salsa and Salicornia europaea. Data are means ± SE (n = 6). Within each species, data points sharing a letter are not significantly different from one another (p > .05)

Figure 3

Effects of 0–100 g/kg salinity treatments on the aboveground (a) and belowground (b) biomass of Suaeda salsa and Salicornia europaea per pot. Data are means ± SE (n = 6). To facilitate comparison between species, biomass data are shown as percentages of plant performance in 0 g/kg salinity treatments. Within each species, data points sharing a letter are not significantly different from one another (p > .05)

Figure 4

Effects of 0–100 g/kg salinity treatments on the aboveground (a), and belowground (b) biomass of Suaeda salsa and Salicornia europaea per survivor. Data are means ± SE. To facilitate comparison between species, biomass data are shown as percentages of plant performance in 0 g/kg salinity treatments. Within each species, data points sharing a letter are not significantly different from one another (p > .05)