Fluxes of CO₂, N₂O and CH₄ by ²²²Rn and chamber methods in cold-temperate grassland soil, northern Japan

Figures & data

Figure 1 Concentration profiles of (a) ²²²Rn, (b) CO₂, (c) N₂O and (d) CH₄, observed within northern Japanese grassland aerated soil during the summer and winter seasons. ²²²Rn, CO₂, N₂O, and CH₄ profiles were fitted with exponential curves using the ²²²Rn method (R² > 0.85). Each symbol denotes a sampling date of 1996/97.

Table 1 Calculated diffusion coefficients, relaxation depths, and fluxes of CO₂, N₂O and CH₄ by the ²²²Rn method in grassland aerated soil, northern Japan, during the summer and winter of 1996 and the winter of 1997

Date	Diffusion coefficients			Relaxation depth			Fluxes
in 1996/97	cm^2s^−1			cm			mBqm^2s^−1	mgCm^2h^−1	µgNm^2h^−1	µgCm^2h^−1
(mm-dd)	CO2	N2O	CH4	CO2	N2O	CH4	^222Rn	CO2	N2O	−CH4*
06-22	0.043	0.016	0.047	143	87	149	4.3	43.3	7.6	10.6
07-05	0.078	0.032	0.062	193	123	172	5.7	16.9	4.5	2.0
07-12	0.055	0.022	0.067	162	102	178	7.3	36.2	3.9	8.4
07-21	0.078	0.046	0.083	193	148	199	10.5	46.1	4.4	6.6
08-29	0.086	0.041	0.073	202	140	186	15.7	73.5	2.7	3.0
08-31	0.046	0.026	0.066	148	111	177	5.9	49.6	2.5	4.6
09-20	0.043	NM	0.075	143	NM	189	4.5	40.1	NM	17.6
09-26	0.035	0.019	0.045	129	95	146	4.1	19.8	7.6	6.8
Mean	0.058	0.029	0.065	164	115	175	7.3	40.7	4.8	7.5
12-24	0.021	0.007	0.002	100	240	31	4.1	11.4	7.3	0.35
01-26	0.008	0.002	0.017	62	856	90	5.9	0.8	9.1	0.04
Mean	0.015	0.005	0.010	81	548	61	5.0	6.1	8.2	0.20

NM indicates not measured.

*–CH4 flux denotes the CH₄ uptake to the soil from the atmosphere.

Table 2 The flux ratio of the ²²²Rn method to the chamber method in sandy soil, northern Japan

Date	Flux ratio (FRn/Fchamber)
in 1996 (mm-dd)	CO2	N2O	CH4
06-22	1.27	1.00	1.20
07-05	0.97	0.87	0.57
07-12	1.64	0.90	1.19
07-21	0.84	0.80	0.85
08-29	1.13	1.20	1.18
08-31	1.21	0.70	0.89
09-20	0.88	NM	1.44
09-26	0.95	1.10	0.86
average ± SD*	1.11 ± 0.26	0.92 ± 0.16	1.02 ± 0.28
12-24	1.53	1.00	0.91
01-26**	0.67	0.80	0.59
average ± SD*	1.09 ± 0.60	0.89 ± 0.12	0.78 ± 0.16
Total	1.10 ± 0.31	0.91 ± 0.15	0.98 ± 0.27

NM indicates not measured.

*SD denotes standard deviation.

**The date is January 26, 1997.

Figure 2 Responses from fluxes measured by the ²²²Rn and chamber methods to air temperature (a, b, and c) and soil temperature at 5-cm depth (d, e and f) in aerated grassland soil. Negative CH₄ denotes the oxidation of atmospheric CH₄ to the soil. Solid and dotted lines denote exponential curves for ²²²Rn and chamber methods, respectively. Air and soil temperatures were significant, key factors in determining CO₂ and CH₄ fluxes, measured by ²²²Rn and the chamber method; however, N₂O flux did not depend on temperature.