Plant mortality in coastal ecosystems caused by seawater intrusion due to increasing sea levels has been observed globally. Salinity stress influences water relations and carbon status, subsequently effecting plant growth and survival. Exposure to elevated soil could lead to a reduction in plant water transport capacity, which water use efficiency is expected to increases in individuals even if absolute rates of photosynthesis decline. However, a comprehensive analysis of the effects of salinity stress on plant hydraulic function and carbon balance for coastal ecosystems has not been attempted. We conducted a meta-analysis of coastal soil salinization effects on physiological characteristics associated with hydraulic traits, carbon assimilation and water use efficiency at the global scale. We assessed the responses to higher salinity across multiple plant taxa and hypothesized that salinity stress could have coupled effects on both water and carbon dynamics.
Results/Conclusions
Globally distributed datasets demonstrate that coastal plant mortality in response to seawater exposure occurs regardless of taxa or region. Declines in photosynthetic and increases in water-use efficiency in response to salinity changes are nearly ubiquitous. Analyses of carbon-centric traits such as growth and non-structural carbohydrates concentrations is currently ongoing, as is investigation into key hydraulic traits such as hydraulic conductivity and loss thereof, water potential, transpiration, stomatal conductance, and intrinsic water use efficiency. The responses to salinity stress seen in hydraulic traits in roots, stems and leaves across species will be reported, to best test how seawater exposure causes decreases in hydraulic conductivity and increases the loss of hydraulic conductivity at the whole-plant level. The relationships between relevant hydraulic traits, photosynthetic rate, non-structural carbohydrate and water use efficiency will be analyzed to test our hypothesis that tradeoffs between plant water relations and carbon dynamics are manifest under conditions of seawater exposure. We will also consider the functional trait responses to salinity stress across various plant and climate types, and duration of exposure, and intensity of salinity changes. This study will improve our understanding of underlying physiological responses to salinity stress and will also aid in how we predict plant stress tolerances under projected sea-level rise and saltwater incursion projections.