Abstract
CO_2 emission and CH_4 uptake by forest soils were measured in two Hinoki cypress stands (TNG and FMY) in Higashitsuno Village, Kochi, southern Japan. In each stand, control and thinning plots (20×20 m^2) were established adjacent to each other in the spring of 2002. The gas flux was measured by the closed-chamber method every month from August 2002 to March 2003. The means for CO_2 emission rates in the control and thinning plots were 1.24 and 0.91 gC m^<-2>d^<-1> in TNG, and 1.39 and 1.44 gC m^<-2>d^<-1> in FMY. The means for CH_4 uptake rates in the control and thinning plots were 3.20 and 2.13 mgCm^<-2>d^<-1> in TNG, and 2.12 and 2.53 mgCm^<-2>d^<-1> in FMY. The analysis of the repeated measures ANOVA revealed that the thinning plot in TNG had lower CO_2 emission rates (P=0.03) and marginally lower CH_4 uptake rates (P=0.07). In the thinning plot of TNG, lower CH_4 uptake rates may be related to lower soil bulk density due to soil compaction and erosion. In contrast, the thinning in FMY did not significantly affect CO_2 emission, and the interaction of sampling time and plot was significant for CH_4 uptake (P=0.04). The results suggest that the effect of thinning on soil CO_2 emission and CH_4 uptake may differ among Hinoki stands.
