Effects of thinning on aboveground carbon and nitrogen dynamics at a sugi (Cryptomeria japonica) plantation in northern Kanto region, eastern Japan.

This study examined effects of thinning on aboveground carbon (C) and nitrogen (N) dynamics of a 40-yearold sugi (Cryptomeria japonica) plantation in Ibaraki prefecture, Japan. In this study, aboveground C and N storage and deposition of C and N through litterfall were estimated in 2003–2005. Allometric equations were established to estimate C and N storage in aboveground biomass using six sample trees. A thinning practice was conducted in December 2003, in which the aboveground biomass decreased by ~30%. In 2004–2005, Aboveground C and N storage in the thinned plots (~80 Mg C ha -1 and ~360 kg N ha -1 ) were ~70% of those in the unthinned control, whereas the increment of C and N storage in the thinned plots (~3.5 Mg C ha -1 yr -1 and ~14 kg N ha -1 yr -1 ) were similar to those in the unthinned control. Deposition of C and N through litterfall in the thinned plots (~1.6 Mg C ha -1 yr -1 and ~33 kg N ha -1 yr -1 ) was ~60% of those in the unthinned control. These results suggested that the thinning practice decreased aboveground C and N storage, and C and N deposition through litterfall, but the effects on C and N accumulation in the aboveground biomass was less evident in this study.