Methane uptake and nitrous oxide emission in Japanese forest soils and their relationship to soil and vegetation types(Environment)

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To determine the means and variations in CH_4 uptake and N_2O emission in the dominant soil and vegetation types to enable estimation of annual gases fluxes in the forest land of Japan, we measured monthly fluxes of both gases using a closed-chamber technique at 26 sites throughout Japan over 2 years. No clear seasonal changes in CH_4 uptake rates were observed at most sites. N_2O emission was mostly low throughout the year, but was higher in summer at most sites. The annual mean rates of CH_4 uptake and N_2O emission (all sites combined) were 66 (2.9-175)μg CH_4-C m^<-2> h^<-1> and 1.88 (0.17-12.5)μg N_2O-N m^<-2> h^<-1>, respectively. Annual changes in these fluxes over the 2 years were small. Significant differences in CH_4 uptake were found among soil types (P < 0.05). The mean CH_4 uptake rates (μg CH_4-C m^<-2> h^<-1>) were as follows: Black soil (95 ± 39, mean ± standard deviation [SD]) > Brown forest soil (60 ± 27) ≥ other soils (20 ± 24). N_2O emission rates differed significantly among vegetation types (P < 0.05). The mean N_2O emission rates (μg N_2O-N m^<-2> h^<-1>) were as follows: Japanese cedar (4.0 ± 2.3) ≥ Japanese cypress (2.6 ± 3.4) > hardwoods (0.8 ± 2.2) = other conifers (0.7 ± 1.4). The CH_4 uptake rates in Japanese temperate forests were relatively higher than those in Europe and the USA (11-43μg CH_4-C m^<-2> h^<-1>), and the N_2O emission rates in Japan were lower than those reported for temperate forests (0.23-252μg N_2O-N m^<-2> h^<-1>). Using land area data of vegetation cover and soil distribution, the amount of annual CH_4 uptake and N_2O emission in the Japanese forest land was estimated to be 124Gg CH_4-C year^<-1> with 39% uncertainty and 3.3Gg N_2O-N year^<-1> with 76% uncertainty, respectively.

Methane uptake and nitrous oxide emission in Japanese forest soils and their relationship to soil and vegetation types(Environment)

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