Growth and distribution of fine roots closely depend on soil resource availability and affect soil C distribution in return. Understanding of relationships between fine root distribution and soil C can help to predict the contribution of fine root turnover to soil C accumulation.

A study was conducted in a subtropical Cunninghamia lanceolata plantation to assess the fine root mass density (FRMD), fine root C density (FRCD) of different fine root groups as well as their relations with soil C.

The FRMD and FRCD of short-lived roots, dead roots and herb roots peaked in the 0-10 cm soil layer and decreased with soil depth, while FRMD, FRCD of long-lived roots peaked in the 10-20 cm soil layer. Soil C was positively related to FRMD and FRCD of total fine roots (across all three soil layers), dead roots (0-10 cm) and herb roots (10-20 cm) as well as FRCD of short-lived roots (20-40 cm) (P < 0.05).

Soil C was mainly affected by herb roots in upper soil layers and by woody plant roots in deeper soil layers.