Changes in soil organic carbon and aggregate stability following a chronosequence of Liriodendron chinense plantations

The objectives for this study were to determine changes in soil organic carbon (SOC) components and water-stable aggregates for soil profiles from different ages of plantations of Liriodendron chinense and to clarify which organic carbon component is more closely associated with the formation and stability of soil aggregates. Three layers of soil (depths 0-20 cm, 20-40 cm, 40-60 cm) were collected from young, half-mature and mature stages of L. chinense. SOC, readily oxidizable organic carbon, chemically stable organic carbon and aggregate composition were determined. Intermediate stable organic carbon, the microbial quotient and aggregate stability (mean weight diameter) were calculated. SOC and aggregate stability in the L. chinense plantation did not increase linearly with an increase in L. chinense age; rather, they first decreased, then increased with increasing age of L. chinense. The microbial quotient had a negative effect on the level of organic carbon and the stability of aggregates, while chemically stable organic carbon had a positive effect, which explained 55.0% and 19.3% of the total variation, respectively (P < 0.01). Therefore, more attention should be paid of these two indicators in the future.