Effects of clear-cutting on nitrogen leaching and fine root dynamics in a cool-temperate forested watershed in northern Japan

cutting of understory vegetation, dwarf bamboo (Sasa senanensis), were investigated to understand the effect of these disturbances on biogeochemical processes on forested watershed in northern Japan. Tree-cutting did not cause a significant increase of nitrate (NO3-) concentration in stream water during the growing season after the cutting. Subsequent Sasa-cutting caused significant increase of stream NO3- concentration to ca. 15 mu mol L-1. There was no significant change of stream pH following both cuttings. NO3- concentration in soil solution increased after both cutting, but the change of concentration was higher (> 100 mu mol L-1) after the Sasa-cutting than after the tree-cutting. In a riparian conserved area, on the other hand, NO3- in soil solution remained low after tree-cutting, suggesting the riparian area acted as a NO3- sink after the tree-cutting. There was no significant change in total biomass of fine roots after the tree-cutting because of an increase in Sasa root biomass despite a decrease in tree roots. The subsequent Sasa-cutting caused a 50% decrease of fine root biomass compared to that in the un-cut Sasa site. These results suggested that nitrogen uptake by Sasa was very important in preventing nitrogen leaching after tree-cutting. and decline of this nitrogen uptake after Sasa-cutting lead to marked NO3- leaching to the stream. (c) 2006 Elsevier B.V. All rights reserved.