Dissolved and particulate carbon dynamics in a cool-temperate forested basin in Northern Japan

Abstract

When evaluating forest functions and their responses to climate change, it is important to clarify carbon dynamics in forested basins. Carbon fluxes in litter fall, throughfall, soil solution, groundwater and stream water were determined from November 1997 to October 1998 for a forest stream ecosystem in a cool-temperate forested basin in the Tomakomai Experimental Forest, Hokkaido University, northern Japan. The annual carbon input to the stream by litter fall was 0.23 gC m-2 year-1, with the greatest flux in the autumn. Owing to biological decomposition of litter in the stream, the carbon concentration in stream particulate organic matter (>0.45 μm) decreased as particle size decreased. The upstream carbon flux was 1.9 gC m-2 year-1, and the annual carbon output in stream water was 7.6 gC m-2 year-1, mainly as dissolved inorganic carbon (DIC), resulting in net carbon output in stream water of 5.7 gC m-2 year-1. The mean dissolved organic carbon (DOC) concentration in soil solution was higher than that in throughfall and stream water. The estimated annual carbon flux from soil in deep (about 1.5 m) soil solution was 4.4 gC m-2 year-1. About 40% of DOC in soil solution was decomposed and converted to DIC in groundwater. These results indicate that carbon dynamics in the forest stream were affected strongly by decomposition of organic matter in the soil-groundwater-stream continuum and by the hydraulic conditions, which are characterized by a large pool of groundwater and high soil permeability. Copyright © 2001 John Wiley & Sons, Ltd.