Effects of salinity and sulfide on the distribution of Phragmites australis and Spartina alterniflora in a tidal saltmarsh.

摘要

In laboratory studies, the short-term response of Phragmites australis and Spartina alterniflora to root immersion in solutions of different salinity and sulfide concentration was measured as the rate of ammonium depletion (a proxy for root uptake)from an initial concentration of 20 鍹. From 0 to 20 ppt in the absence of sulfide, ammonium uptake as a function of dry root weight decreased for both Phragmites (from 29.7 ?3.5 s.e. to 8.2 ?1.5 鎚ol N g-1 h-1) and Spartina (from 25.5 ?3.5 to 9.0 ?1.5 鎚ol N g-1 h-1). With an average sulfide concentration of 582 鍹 at 20 ppt, the rate of ammonium uptake for Spartina (10.9 ?2.2 鎚ol N g-1 h-1) was not significantly different from the rate in the absence of sulfide. In contrast, the rate of ammoniumuptake was significantly lower for Phragmites when the average sulfide concentration was increased from 0 to 375 鍹 (1.7 ?1.6 鎚ol N g-1 h-1). In a tidal salt marsh, the average pore water sulfide concentration in Phragmites australis stands (124 ?206鍹) was almost an order of magnitude lower than that measured in stands of Spartina alterniflora (989 ?166 鍹). These field and laboratory results support the notion that increased sulfide in the rhizosphere reduces the ability of Phragmites to take upnutrients relative to species such as Spartina that are better-adapted to sulfidic soil conditions, thus restricting the distribution of Phragmites in tidal salt marshes.