Effects of birch encroachment, water table and vegetation on methane emissions from peatland microforms in a rewetted bog.

This study investigated the influence of vegetation and microforms on methane (CH) balances of a rewetted bog in north-west Germany. The two study sites are in close proximity on the same former peat extraction area, one dominated by Sphagnum-mosses and the other one by a dense Betula pubescens stand with a high Eriophorum vaginatum cover. The contribution of microforms (hummocks/hollows) to CH emissions and the effect of Betula encroachment has been studied. Transparent and opaque chambers were used to measure CH fluxes every 3-4 weeks during daytime for one year. For the estimation of annual balances, three methods were compared and the method using water level and soil temperature as explanatory variables was selected. Fluxes were scaled to the site level. The annual emissions per site are and 7.1 ± 1.5 g CH-C m year at the treed site and 36.1 ± 3.5 g CH-C m year at the open site, mainly controlled by higher water levels. Highest annual emissions originated from hollows at the open site, but in the vegetation period, hummock emissions tend to be higher. At the tree site, emission differences between the microforms were less pronounced. There were no differences between fluxes from transparent and opaque chambers.