Sulphide as a Soil Phytotoxin: Differential Responses in Two Marsh Species

(1) A glasshouse experiment was conducted to investigate the effects of soil reduction and hydrogen sulphide accumulation on the growth of two marsh species, Spartina alterniflora and Panicum hemitomon. Three treatments were applied to replicated soil cores containing intact vegetation: flooded aerated, flooded non-aerated, and flooded non-aerated with sulphide added. (2) The addition of 1.0 mM sulphide resulted in significantly less total biomass of S. alterniflora and P. hemitomon. Sulphide significantly reduced culm, root and rhizome biomass in P. hemitomon but only root biomass in S. alterniflora. (3) Panicum hemitomon had no significant difference in total biomass between the aerated and non-aerated treatments, but S. alterniflora total biomass was lower in the aerated treatment than in the non-aerated treatment. (4) Redox potential (mV) in the soil cores of both species was highest in the aerated treatment, intermediate in the non-aerated treatment, and lowest in the sulphide treatment. (5) Spartina alterniflora and P. hemitomon soluble interstitial NH4 +and PO4 3-concentrations followed an inverse relationship to redox potential and differences between treatments were highly significant. (6) Root iron concentrations in S. alterniflora were an order of magnitude higher than iron concentrations in leaves of S. alterniflora and roots and leaves of P. hemitomon. The majority of this root iron in S. alterniflora was associated with root coatings.