The seasonal dynamics of soil microbial biomass of a Larix gmelinii forest after wildfire

Projected changes in the earth's climate have spawned a rush to better understand the global carbon cycle. Understanding the dynamics of soil microbial biomass carbon is important but poorly understood aspect of this cycle. In particular, fires can dramatically alter microbial communities and therefore soil carbon cycles. We took soil samples from Larix gmelinii forests that were burned in two different years (2002 and 2008) and compared them with adjacent unburned area. Soils samples were collected monthly from May to October (2010). We used a fumigation-extraction method (FE) to examine seasonal dynamics of soil microbial biomass carbon (C-mic) and soil microbial biomass nitrogen (N-mic) of the soils burned in different years, and we compared the relationship between C-mic, N-mic and other soil characteristics. There were significant differences in C-mic and N-mic of the soils burned in different years (P<0.01). There were substantial fluctuations in soil microbial biomass and nitrogen within all the sample plots: C-mic peaked in the early spring, fluctuated slightly during the growing season, increased after the growing season, peaked in the autumn, and then began to decline. C-mic and N-mic were positively correlated with soil water content. C-mic was negatively correlated with soil temperature, while N-mic was not significantly correlated with soil temperature. C-mic and N-mic were not significantly correlated with ammonium, pH or nitrate.