Relationships between Vegetation Succession, Pore Water Chemistry and CH4 and CO2 Production in a Transitional Mire of Western Siberia (Tyumen Oblast)

Wertebach T-M, Knorr K-H, Lordieck M, Tretiakov N, Blodau C, Hölzel N, Kleinebecker T

Abstract

We present data on a transitional mire in South-Western Siberia that evolved from early thermokarst lake succession. The vegetation of the mire shows a remarkable zonation from the edges to the center. Vegetation, peat characteristics, pH and electric conductivity were recorded at 10 sites along a transect of 1.5 km. At two of the transect points with contrasting vegetation and succession stage (floating mat vs. birch forest) pore water peepers were inserted once for 3 weeks and pore waters of the upper 60 cm were analyzed for major anions and cations, and dissolved CO2 and CH4 concentrations. Pore waters substantially differed between the floating mat and the birch forest regarding base cation chemistry and pH whilst nutrient availability was comparable. Compared to literature, depth integrated productions (DIPs) of CH4 and CO2 were high for both sites but three times higher for the floating mat (CH4 10.89 mmol m−2 d−1, CO2 34.19 mmol m−2 d−1). Along with other reasons, the higher DOC input at this location seems to be responsible for the higher DIP by fueling higher microbial activity. We discuss driving factors for biogeochemical differences between both sites and draw conclusions on CH4 production during mire evolution.