The effects of salinity and soil drying on nutrient uptake and growth of Spartina alterniflora in a simulated tidal system

Abstract

A study quantifying the role of the interactive effects of salinity and soil drying on nutrient uptake in Spartina alterniflora was conducted in a climate-controlled greenhouse. The experiment consisted of three levels of salinity (3–5 g/L, L; 15–20 g/L, M; 35–38 g/L, H) as well as three dynamic water levels: drought (water level maintained at least 20 cm below the soil surface at high tide, D), intermediate soil drying (water level maintained between 20 cm below the soil surface at low tide and 10 cm below the soil surface at high tide, I), and flooding (water level maintained 3–5 cm above the soil surface at high tide and 10 cm below the soil surface at low tide, F). Survival, shoot and root dry matter production, and concentrations of Al, Ca, Fe, Mg, N, P, K, Na, and S were measured along with soil conditions of redox potential and water potential. Contrary to expectations, the interactive effects of salinity and soil drying were not additive on plant nutrient uptake or biomass. However, both salinity and soil drying significantly impacted root and shoot dry weights. In addition, significant decreases were seen in all nutrients in response to increases in salinity and/or soil drying. High salinity in conjunction with drought (HD) decreased survival to 71%, whereas survival was 100% for all other treatments. Furthermore, leaf chlorosis and browning occurred in plants under increased salinity and drought conditions (HD and MD). Therefore, it appears that drought may magnify the adverse effects of salinity on plant nutrient status. Although the combined effects of increased salinity and soil drying did not appear to be detrimental to this species, significant decreases in nutrient uptake seen in response to the combined effects at severe levels (HD), if continued over an extended period, may be detrimental enough to cause large-scale marsh browning as noted in the field.