『Abstract
To clarify the reason for the higher CH4
uptake rate in Japanese forest soils, twenty-seven sites were
established for CH4 flux measurement. The
first order rate constant for CH4 uptake
was also determined using soil core incubation at 14 sites. The
CH4 uptake rate had a seasonal fluctuation,
high in summer and low in water, and the rate correlated with
soil temperature at 17 sites. The annual CH4
uptake rates ranged from 2.7 to 24.8 kg CH4
ha-1 y-1, depending on method of calculation),
which is somewhat higher than the uptake rates reported in previous
literature. The averaged CH4 uptake take
correlated closely with the CH4 oxidation
rate of the topsoil (0-5 cm) in the study sites. The CH4
oxidation constant of the topsoil was explained by a multiple
regression model using total pore volume of the soil, nitrate
content, and C/N ratio (p<0.05, R2 = 0.684). This result
and comparison with literature data suggest that the high CH4 uptake rate in Japanese forest soils depends
on the high porosity probably due to volcanic ash parent materials.
According to our review of the literature, the CH4
uptake rate in temperate forests in Europe is significantly different
from that in Asia and North America. A new global CH4
uptake rate in temperate forests was estimated to be 5.4 Tg y-1
(1 SE is 1.1 Tg y-1) on a continental basis.
Keywords: Forest soil; Global methane uptake; Greenhouse gas;
Temperate forest』
Introduction
Materials and methods
Site description
Flux measurement
Soil sampling and analysis
Soil core analysis
Statistical analysis
Results
Seasonal fluctuation of CH4 flux at
each site
Intact soil core incubation analysis
Variation in CH4 flux among the sites and
its relationship with soil properties
Discussion
Factors affecting fluctuation of the methane uptake rate in each
forest
Factors affecting the differences in CH4
uptake rates among the sites
Comparison of CH4 uptake rate with other
reports
Conclusion
Acknowledgments
References