INTERANNUAL AND SEASONAL VARIATION OF METHANE FLUX FROM A TEMPERATE PEATLAND AND POSSIBLE ENVIRONMENTAL CONTROLS
This study examined the sub-seasonal, seasonal and interannual variations in net ecosystem CO2 exchange (NEE) and CH4 effluxes and possible links between the two processes in an attempt to determine the environmental controls responsible for the variations. We measured NEEmax, CH4 fluxes, water table level, and meteorological data from the summer (1 May-31 August) for five years (2000-2004) at a temperate peatland in southern New Hampshire. We observed increasing photosynthesis and respiration values as the summer progressed. CH4 fluxes also increased in magnitude and variability due to higher peat temperatures and episodic events as the season progressed. When considering mean seasonal methane flux over the five year period, we found low interannual and spatial variability. However, we found high interannual variability of methane fluxes and relationships between fluxes and variables when we considered instantaneous time scales. Significant differences in methane fluxes were driven by differences in mean monthly methane fluxes. Sedge-dominated sites had the strongest relationships between methane fluxes and measures of plant productivity (NEEmax, photosynthesismax, respiration), as well as environmental variables (air temperature, peat temperature, water table level). This suggests that controls on methane fluxes vary in importance over different timescales and types of vegetation.