Methane emission from West Siberia tundra mires
Beside carbon dioxide and water vapor, methane is one of the most important greenhouse gases. Mires are the largest natural source of methane. West Siberia tundra zone gains the especial importance in this regard as the greatly paludified region with the mire area of 29% of this territory. Nevertheless, the information about methane fluxes in tundra is still incomplete and need to be advanced. For this purpose detailed investigation of methane emission at 2 key sites in West Siberia tundra zone was organized. About 300 methane emissions varied from small negative values to several mgC-CH 4·m -2·h -1 were measured by a static chamber method. It was confirmed that frozen hillocks, bogs and shallow ponds had the lowest methane fluxes (1 st/2 nd/3 rd quartiles are -0.04 /0.01 /0.07 mgC-CH 4·m -2·h -1 for frozen hillocks, -0.01 / 0.03 / 0.28 mgC-CH 4·m -2·h -1 for bogs and 0.15 / 0.27 / 0.57 mgC-CH 4·m -2·h -1 for ponds). Larger emissions were character for fens (0.76 / 0.96 / 1.53 mgC-CH 4·m -2·h -1) and poor fens (0.41 /1.42 / 3.38 mgC-CH 4·m -2·h -1). Maximal rate of methane emission were observed in peat mats (0.99 / 2.42 / 3.24 mgC∙m ‑2∙h ‑1). Cluster analysis was used to reveal the main ecological factors influencing on the methane emission. As a result, 5 classes distinguished by water table level, trophicity and the peat layer strength were described. Water table level and peat layer strength accounted for the most variability inside the clusters while trophicity affects the most between ones. Analysis makes possible the detection of probably degrading wetlands with the unfavorable conditions for methanogenesis, too. All emission data were generalized into the spatial emission model (the model is based upon a fractional area coverage map of mire micro-landscapes, methane flux probability distributions for each micro-landscape type and methane emission period). Version Bc8 of this model estimates methane flux from West Siberia tundra mires at 110 kTC-CH 4·yr -1 that accounts for about 4% of the total methane emission from all West Siberia mires. Fens were revealed as the most significant methane source from tundra mires contributing for about 99% of the regional flux from this territory. Unfavorable thermal conditions, short period of biological activity, shallow permafrost bedding and low peat layer strength appear to be the reasons for such insignificant role of tundra mires.