Although it is well recognized that the effect of fire on soil carbon pool is significant (Fig. 9), its long term effect on wetland carbon remains uncertain, since previous studies were limited to a short period (one year or two). The results from our two-year field campaign reveal
that the fire effect varies from one soil carbon form to another. Soil organic carbon (OC) increased in the burned soils in both growing seasons, but the abundances of soil dissolved organic carbon (DOC) and microbial biomass carbon (MBC) increased in the first
post-burning growing season and then returned to the pre-burning levels in the second growing season. The variability in soil MBC and DOC also depends on burning time (spring vs. autumn) and sampling time. In general, spring burnings exerted a larger effect than autumn burnings on soil carbon pool, due in part to the difference in soil water content and the lag between the burning and sampling time Although the impact seems short-lived, the frequent reoccurrence of wildfires may extend the short-term effect to interfere with the longer-term carbon cycling within and outside the burn areas.