Temporal variations in soil–atmosphere methane exchange after fire in a peat swamp forest in West Siberia

Abstract

Temporal variations in methane (CH4) exchange between the soil and the atmosphere during a period of 3 years after a forest fire were estimated by combining field measurements of CH4 flux with an analysis of satellite images. The study area was located in a boreal peat swamp forest in the West Siberian plain that experienced a severe fire in the summer of 1998. The surface of the burned area was classified into bare soil, open water and recovered vegetation. In the summers of 1999 and 2000, CH4 fluxes, using a closed-chamber method, and environmental variables, such as soil temperature and soil water content, for each of the three surface types in the burned area and in the unburned area were measured. In general, CH4 fluxes were controlled by the surface moisture in the burned area and by the temperature in the unburned forest. Temporal changes in the areal coverage of soil, water and vegetation in the burned area were investigated using NOAA AVHRR (Advanced Very High Resolution Radiometer) data with subpixel land-cover characterization. Based on the satellite information, temporal changes in the moisture conditions of the burned surface were estimated and temporal variations in the CH4 fluxes for the entire burned area were calculated. The cumulative CH4 emission rates from the entire burned area during the summer (from June to August) were estimated to range from 0.39 to 0.48 g C m−2 during the period from 1999 to 2001. In contrast, unburned forest soils were consistently net CH4 consumers. The cumulative consumption rate during the summer was calculated to be approximately 0.4 g C m−2 based on a reanalysis air temperature dataset. As the surface soil had become extremely wet since the fire, the soil had become a net emitter of CH4 after the fire disturbance, although CH4 oxidation predominated in the unburned forest.