The Canadian boreal forest is continuously being renewed by fire, resulting in a range of stand ages and successional dynamics. Most previous studies of net carbon dioxide flux between forests and the atmosphere have concentrated on mature forest stands. We have been supplementing the data from mature stands with data collected over recently burned forests in order to derive forest biome estimates of carbon flux that include all stand ages. Here we report recent data from a three-year-old and a 12-year-old stand located in the Boreal Ecosystem Research and Monitoring Sites (BERMS) area of central Saskatchewan. These sites experienced intense wildfires that killed all of the trees and burned to mineral soils in most locations. Carbon dioxide flux was measured using eddy covariance on towers at each site, with data being collected continuously to derive annual cycles.

The three-year-old site shows net springtime respiration and ecosystem carbon loss until about the end of June. It then becomes a sink until mid-August, becoming carbon neutral for a few weeks and then losing carbon through the autumn and winter. The net fluxes are small with hourly daytime maxima of the order of -5 µmol m^-2 s^-1. The 12-year-old site is a much stronger sink throughout the summer with hourly daytime maxima exceeding -20 µmol m^-2 s^-1. The measurements began in April 2001 and annual carbon fluxes will be derived once a full annual cycle has been achieved. This information will provide parameter values and validation data for carbon budget models of forest environments, especially at hourly to monthly time scales. This adds to the data being collected by the large international flux networks as well as supporting the carbon modeling and accounting initiatives as part of the Kyoto Protocol.