Saturday, 15 July 2006

Fluxes of Carbon and Sulfate Dynamics in Salt-Affected Coastal Soils in Northern Germany.

Md. Harunor Rashid Khan1, Hans-Peter Blume2, Tadashi Adachi1, Ulrich Pfisterer3, and Udo Mueller-Thomsen3. (1) Dept of Environmental Management Engineering, Faculty of Environmental Science and Technology, Okayama Univ, Okayama, 700-8530, Japan, (2) Univ of Kiel, Schlieffenallee 28, Kiel, 24105, Germany, (3) Division of Soil Ecology, Res. and Tech. Center-West Coast, Univ of Kiel, 25761 Buesum, Kiel, 24105, Germany

A field study was conducted at Schleswig-Holstein in Germany to evaluate the possible factors controlling carbon and sulfate dynamics along a toposequence ! of daily to seasonally flooded coastal salt marsh soils. The soil at the top end of the salt marsh (with a height of 1.8 m above sea level: a.s.l. and a dense vegetation cover) was salic silty to clayic Typic Sulfaquent (Salzrohmarsh), while the soil at the bottom end (with some salt bushes and a 1.4 m a.s.l.) was sandy to silty Haplic Sulfaquent (Übergangsmischwatt). The mean (depth: 0-100 cm) values of pH were around 7, and of redox potentials (Eh) in the Typic Sulfaquent were ranged from -162 to +104 mV during all the seasons. The average net-emission of CO2 above the vegetation cover was negative (-14.0 g m-2 yr-1) for the Haplic Sulfaquent but highly positive (857 g m-2 yr-1) for Typic Sulfaquent throughout the year. The annual average emissions of CH4 were almost 10 fold higher in Haplic Sulfaquent (0.3 g m-2 yr-1) than that of the Typic Sulfaquent (0.03 g m-2 yr-1). The average maximum concentrations of CO2 were detected within the surface soils at the depth of 20 to 40 cm in both the profiles. The surface soils at depth of 0 to 20 cm, where the concentrations of CO2 were measured relatively low though the values were about 5 to 20 times higher than that of the atmospheric (350 ppmv) concentration. The concentrations of CH4 at different seasons showed almost inverse relationships with the concentrations of CO2. In all the profiles, the concentrations of CH4 were very low and varied significantly (p0.05) with the seasons and depth function. The concentrations of CH4 showed no dependence to temperature. The SO4 contents were observed maximum in the Typic Sulfaquent followed by Haplic Sulfaquent 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 in the soil solution was around 1200 mg SO4 L-1.

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