Distribution Characteristics of Labile Soil Organic Carbon in Longmenshan Seismic Fault Zone, Sichuan Province.

Understanding the distribution characteristics and influencing factors of labile soil organic carbon (LSOC) and its factors in seismic fault zones are important for understanding the changes of soil carbon balance in the region. Soil samples were collected to a depth of 50 cm in the northern part of the Longmenshan seismic fault zone as the research object, to investigate the profile distribution of LSOC and its relative proportion in soil organic carbon (SOC). The results showed that the effects of pH and soil water content (SWC) on SOC and its components were related to soil depth. The content of SOC and LSOC were negatively correlated with soil pH and positively correlated with SWC. Significant differences in the contents of SOC and LSOC were found between horizons. The content of SOC and LSOC decreased with soil depth within 50 cm soil profiles; while the proportion of LSOC to SOC increased. Oxidation stability coefficient (KOS) of SOC were significantly different between different soil layers and decreased with soil depth. The significant correlations between SOC and LSOC suggested that correlations between hot water extractable organic carbon (HEOC), cold water extractable organic carbon (CEOC), dissolved organic carbon (DOC), oxidizable organic carbon fraction (ROC), microbial biomass carbon (MBC) and SOC varied with soil depth. Notably, SOC in topsoil and bottom soil was highly correlated with HEOC and CEOC, respectively. LSOC and SOC in Longmenshan seismic fault showed obvious vertical distributions and the relationship between LSOC and SOC was related to soil depth. Besides, the correlation of SWC and pH with LSOC also varied with soil depth. [ABSTRACT FROM AUTHOR]