Effect of fire intensity on active organic and total soil carbon in a Larix gmelinii forest in the Daxing'anling Mountains,Northeastern China

Studying contents and seasonal dynamics of active organic carbon in the soil is an important method for revealing the turnover and regulation mechanism of soil carbon pool. Through 3 years of field sampling and lab analysis, we studied the seasonal variations, content differences, and interrelationships of total organic carbon(TOC), light fraction organic carbon(LFOC), and particulate organic carbon(POC) of the soil in the forest areas burned with different fire intensities in the Daxing'anling Mountains. The mean TOC content in the low-intensity burned area was greater than that in the unburned area,moderate-intensity, and high-intensity burned areas in June and November(P0.05). LFOC and POC in the lowintensity burned area were greater than that in either moderate-intensity or high-intensity burned areas, with significant differences in LFOC in September and November(P 0.05). A significant difference in LFOC between the unburned and burned areas was only found in July(P 0.05). However, the differences in POC between the unburned and burned areas were not significant in all the whole seasons(P 0.05). Soil LFOC and POC varied significantly with the seasons(P 0.05) in the Daxing'anling Mountains. Significant linear relationships were observed between soil TOC, LFOC, and POC, which were positively correlated with soil nitrogen and negatively correlated with soil temperature in the Daxing'anling Mountains.