Some tree species increase fine root production under soil acidification, thus changing the balance of litter input from leaves and roots. Litter leachates released during decomposition may facilitate soil acidification. To test our hypothesis that both the quality and quantity of DOM differ between leaf and root litter, we conducted a 2.5-year laboratory incubation experiment using fine roots and green leaves as litter of two coniferous species. The amount of DOC leached from roots increased and leachate pH declined in the later stage of the decomposition. In contrast, DOC concentrations continued to decrease in leaf leachates during the incubation period, and the pH decrease was not as striking as that of root leachates. The total amount of protons released from roots of the two coniferous species is about 13-18 times higher than that from leaves. These results imply that the increase of fine root biomass may induce a positive plant–soil feedback in acidic soils, affecting soil biogeochemical functions of terrestrial ecosystems.