Leaf litter contributes more to soil organic carbon than fine roots in two 10-year-old subtropical plantations

Although many reports assume a strong relationship between plant litter inputs and soil organic carbon (SOC) accumulation, there is limited experimental evidence in support of this relationship. The Detritus Input and Removal Transfer (DIRT) experiment was conducted in two subtropical plantations, an Acacia crassicarpa monoculture (AC) and a Eucalyptus urophylla monoculture (EU), to assess the importance of leaf litter and fine roots for SOC content over a 6-year period. The SOC content in 0–10 cm soil layer was significantly reduced by litter removal (NL) or by removal of both litter and roots (NI), but the influence of root removal (NR) was only marginal. The AC forest had a much higher annual rate of litter production and a lower decomposition rate than the EU forest, but carbon release from plant litter did not significantly differ between the two forests. These results help explain why the SOC content did not differ between the two forests. Our findings suggest that plant leaf litter is more important than roots in maintaining the balance of the SOC pool in subtropical forest plantations.