Source and Sink Strength of Carbon Dioxide, Methane and Distribution of Sulfate in Salt-marsh Soils at the Wadden Sea Coast of Northern Germany

A field study was conducted at Schleswig-Holstein of Kiel in Germany to evaluate the factors controlling carbon and sulfate dynamics along a toposequence of coastal salt marsh soils. The soil at the top end of the salt marsh was salic silty to clayic Typic Sulfaquent (Salzrohmarsh) and the bottom end was sandy to silty Haplic Sulfaquent (Übergangsmischwatt). The mean (depth: 0-100 cm) values of pH and rH were 6.8-6.9; 6.8-7.0 and 17.3-8.1; 15-8.6 for the Typic Sulfaquent (TS) and Haplic Sulfaquent (HS) throughout the year, respectively. The net-emission of CO₂ was negative (-14.0 g m^-2 yr^-1) for the HS but highly positive (857 g m^-2 yr^-1) for the TS throughout the year. The annual emissions of CH4 were almost 10 fold higher in HS (0.3 g m^-2 yr^-1) than that of the TS (0.03 g m^-2 yr^-1). The concentrations of CH4 at different seasons showed almost inverse relationships with the concentrations of CO₂, varied significantly (p≤0.05) with the seasons and depth function, and showed no dependence to temperature. The SO4 contents were observed maximum in the TS than that of HS during all the seasons. There was no noticeable correlation (r=- 0.09) between SO₄ and CH₄ concentrations. Moreover, even CH4 was determined at depths where the SO₄ concentration was about 1200 mg SO₄ L^-1.