Fig. 1
Warming, measurement and snow-covered periods during 2007–2011.
Fig. 2
Relationship between soil temperature (T s) and soil CO2 efflux (F c) after outlier detection by eqs. (1) and (2) with three cases for their threshold value (β=0.1, 0.3 and 0.6). Efflux data without outlier detection are also plotted. Data obtained from April to August 2008 at Chamber no. 10 are used.
Fig. 3
Inter-annual variation of (a) soil temperature at 5-cm depth (T s) and temperature difference between unwarmed and warmed treatments (T s dif.), (b) soil CO2 efflux (F c) and daily-average air temperature (T a), (c) Q 10, and (d) basal respiration rate at 10°C (R 10). Thick lines are the average of five daily averages and the standard deviation is shown as shades for two trenched treatments. For undisturbed control treatment, only average values are shown as dot lines. The temperature difference is shown as the difference between daily averages of five chambers.
Table 1
Inter-annual variation of micrometeorology
Table 2
F values of repeated-measures ANOVA on the effects of warming, month and their interaction on monthly averages of soil temperature at 5-cm depth (T s), soil CO2 efflux (F c), Q 10 and basal respiration rate at 10°C (R 10)
Table 3
Seasonal average (each measurement period for each year) and the standard deviation of soil temperature at 5-cm depth (T s) and soil CO2 efflux (F c)
[i] Seasonal sums of F c are also shown for each measurement period of each year and for the same days of the year (180 days from 13 May to 8 November) overlapping during the four seasons from 2008 to 2011 (parentheses). Seasonal average difference in the soil temperature between unwarmed and warmed treatments (T s dif.), seasonal average enhancement ratio of F c by warming (ER), and seasonal average ratio of unwarmed-trenched F c to control F c (HR) are also shown. Four-season averages during 2008–2011 are also shown for each parameter.
Fig. 4
Monthly averages of soil CO2 efflux (F c), Q 10 and basal respiration rate at 10°C (R 10). The standard deviation is shown as vertical lines.
Fig. 5
Inter-annual variation of monthly average ratio of efflux rate in unwarmed-trenched chambers to total soil CO2 efflux (open circles), the residual (total – unwarmed-trenched) to total efflux (closed circles) and monthly average enhancement ratio of trenched efflux by warming (open squares).
Fig. 6
Relationship between daily-average soil CO2 efflux (F c) and soil temperature at 5-cm depth (T s) in 2011 (n=5). Regression equations in the figure were obtained by the least-squares method using eq. (3).
Fig. 7
Relationship between temperature-normalised daily-average F c and the soil water content (SWC). See text for the determination of temperature-normalised F c.
Table 4
Seasonal average (each measurement period for each year) and standard deviation of Q 10 and basal respiration rate at 10°C (R 10)