Changes of active soil organic carbon under different growing stages of Chinese fir plantation

Active soil organic carbon (ASOC) has been proposed as a sensitive indicator of early changes in soil organic carbon (SOC) under different management practices because it can reflect micro change of soil quality more sensitively than SOC. In this study, changes of ASOC, such as water soluble organic carbon (WSOC), microbial biomass carbon (MBC), hot water-extractable C (HWC) and hot water-extractable carbohydrate-C (HWcC), during the growth and development of Chinese fir plantation (PCF) were researched. The results showed that SOC was accumulated. At the beginning of development of PCF, the concentrations of most C pools declined except for WSOC. The changes were reversed during development of Chinese fir plantation into maturation period. In the depth of 0-10 cm, the efficiency of WSOC to soil microorganism was the highest among of ASOC and there was negative significant correlation between WSOC and MBC. However, that of HWcC was the highest in the depth of 10-20 cm due to increase of recalcitrant of SOC and there was positive significant correlation between HWcC and MBC.