Methane emission rates from a northern wetland; response to temperature, water table and transport

Static chamber measurements of CH ₄ flux were made from a range of micro-environments in an area of blanket bog in Northern Scotland. CH ₄ flux covered a wide range, the largest rate of CH ₄ emission, at 175.6 μmol m ^-2 h ^-1, was observed in pool areas through the vascular plant Menyanthes trifoliata. Investigations into the response of net CH ₄ emission rates to temperature and water table were carried out under semi-natural conditions on 45 large peat monoliths, maintained in open-top chambers, over a three-year period. The mean rate of CH ₄ emission at 10°C was an order of magnitude larger from pool monoliths (surface water table) at 78.0 μmol m ^-2 h ^-1, than from hummock monoliths (water table 15 cm below surface) at 8.4 μmol m ^-2 h ^-1. Rates of CH ₄ emission showed a positive linear response to increasing temperature from pool and lawn monoliths with activation energies of 74.3 and 79.5 kJ mol ^-1 and Q₁₀ values of 3.0 and 3.3, respectively. When conditions of temperature, water table, light and humidity were controlled pool cores showed an exponential increase in CH ₄ emission rates between 5 and 30°C.