Influence of salt marsh ecosystem on the concentration and emission of CO2 from the Wadden sea coast soil of northern Germany

Abstract

A field study was conducted to evaluate the possible factors controlling the fluxes of carbon dioxide 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), 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). The mean (depth: 0 -100 cm) values of pH were around 7, and of redox potentials (Eh) in the Typic Sulfaquent ranged from -162 to + 104 mV during all the seasons. The average net-emission of CO 2 (-14.0 g m -2 a -1 ) above the vegetation cover was negative for the Haplic Sulfaquent but highly positive for Typic Sulfaquent round the year (857 g m -2 a -1 ). The average maximum concentrations of CO 2 were detected within the surface soils 20 to 40 cm in both the profiles. In the surface soils of 0 to 20 cm the concentrations of CO 2 measured were relatively low though the values were about 5 to 20 times higher than that of the atmospheric (0.35 g/v) concentration. For the average of two Haplic Sulfaquents, the soil temperatures were almost 2°C higher than that of the Typic Sulfaquent and it was also 2.5°C higher than the mean annual temperature (9.5°C) of the soils. The current results show that the CO 2 fluxes seasonally varied significantly and for certain periods of the year the coastal salt marsh soils can act either as a sink or source for atmospheric CO 2 depending on the physical and chemical properties of the soils.