Abstract

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 fromLarix 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.

Key words: Wildfire, Larix gmelinii, soil microbial biomass, seasonal dynamics, fumigation-extraction method.