Dissolved organic carbon (DOC) input to the soil: DOC fluxes and their partitions during the growing season in a cool-temperate broad-leaved deciduous forest, central Japan

Dissolved organic carbon (DOC) plays an important role in C cycling in forest ecosystems. Here we measured the concentrations and fluxes of DOC in a cool-temperate broad-leaved deciduous forest (Takayama Forest) to quantify the contribution of DOC from different forest water flux conditions. Mean DOC concentration during the growing season increased in the sequence from bulk precipitation (2.98 +/- 0.45 mg L-1), throughfall above dwarf bamboo (6.84 +/- 0.45 mg L-1), throughfall below dwarf bamboo (7.08 +/- 0.42 mg L-1), stemflow (15.05 +/- 0.98 mg L-1), and litter leachate (21.33 +/- 1.01 mg L-1). Litter leachate DOC concentration, being high in spring and autumn, which was fairly correlated with the amount of litterfall of bamboo and trees. In stemflow, the DOC concentration was high during early summer and gradually decreased, in addition, it also showed dramatic variation among different plant species. Litter leachate (72.5%) accounted for most of the DOC input to the soil during the growing season (311.5 kg C ha(-1) 7 months(-1)), while stemflow (1.6%) contributed the least. A great quantity of precipitation at the study site was associated with a subsequent high atmospheric contribution of DOC flux (8.6%), which was more than half of throughfall (16.5%). The high input of DOC to the soil and andisol soil characteristics at the Takayama Forest suggest that the DOC fluxes are vital to the soil carbon sequestration. Therefore, DOC fluxes should be taken into account when the carbon balance is assessed at forest ecosystems.