Surface energy balances of Canadian boreal forests following fire

Fire is an important stand renewing event in boreal forests that drastically changes the surface characteristics of the forest. As forests go through various stages of succession following fire, the surface energy fluxes will change. Data obtained from eddy covariance measurements at three post-fire boreal sites in central Saskatchewan of ages 27 years, 15 years, and 6 years were used to quantify the energy balances. Located in close proximity to one another, the sites are exposed to similar climate and weather conditions. Monitoring began at the site burned in 1989 (F89) and the site burned in 1998 (F98) in the spring of 2001. The site burned in 1977 (F77) has been monitored since the spring of 2003. Net radiation, sensible heat flux, latent heat flux, and soil heat flux were measured at all sites. Additional meteorological measurements were also taken. Significant differences among sites were observed in all fluxes during 2001 and 2002. By 2004, the fluxes at all sites became more similar. Latent heat flux best illustrates the changes in site characteristics that take place with time after fire. Summertime daily latent heat fluxes are twice as high at the F77 and F89 sites compared to the F98 site. This difference is likely due to the abundance and maturity of the vegetation at the two older sites compared to F98 where the vegetation is small and sparse. The amount of bare ground at F98 has a significant impact on soil heat flux which is illustrated during the summer and winter months when F98 has the highest soil heat flux. Understanding how the energy balance changes with time following disturbance is also important for predicting the effects that the possible increase in forest fires that may accompany climate change could have on local, regional and global climates.