Fig. 1
Location of Takayama site (36°09′N, 137°25′E, 1420 m a.s.l., TKY) in central Japan.
Fig. 2
Relationships between δ(O2/N2) and CO2 concentration obtained from (a) soil chamber and (b) branch bag measurements. Solid lines denote the regression lines fitted to the data.
Fig. 3
δ(O2/N2) and CO2 concentration observed at heights of 8.8 (red dots) and 27 m (blue dots) for the period 4 August–4 September 2012. Smoothing spline curves fitted to the observed data and their 24-hour running mean values are also shown. Δδ(O2/N2) (ΔCO2), representing the difference of the smoothing spline curve of the δ(O2/N2) (CO2 concentration) at 8.8 m from that at 27 m, is also plotted by black (orange) line, together with air temperature (black line) and PAR (green line) at 25 and 19.5 m heights, and 24-hour running mean values of air temperature are also plotted.
Fig. 4
Relationships between the daily mean values of δ(O2/N2) and CO2 concentration observed at 8.8 (open circles) and 27 m (closed circles).
Fig. 5
Schematic vector diagram representing the contributions to O2 and CO2 budgets in a forest ecosystem.
Fig. 6
(a) Diurnal cycles of δ(O2/N2) and CO2 concentration observed at 8.8 and 27 m in the forest canopy on 23 August 2012 (circles), together with their best-fit curves (solid lines). (b) Relationships between δ(O2/N2) and CO2 concentration shown in (a). Solid lines denote the regression lines fitted to the data.
Fig. 7
(a) Plots of diurnal cycle component values of δ(O2/N2) and CO2 concentration observed at 8.8 and 27 m heights for the period 4 August–4 September 2012, and their best-fit curves, and (b) relationships between the best-fit curves of the two variables. In (b), the colour scale denotes the time of the day, and black solid, dashed and dotted lines indicate the relationships derived from the data for the periods 6:00–13:00 and 18:00–24:00 and expected from the exchange ratio of 1.00, respectively.
Fig. 8
Calculated average ERF values (red lines) and average observed ERatm values (black solid lines) for the time intervals of 6:00–13:00 and 18:00–24:00 at 8.8 m height for the period 4 August–4 September 2012. Average diurnal variations of GPP, RE, NEP (blue, brown, green solid lines), Md(O2)dt −1 and Md(CO2)dt −1 (grey solid and dashed lines) are also shown in lower part of the figure. The time-varying ERF values (red solid line) are calculated using eqs. (3) and (4) and the average diurnal variations of GPP, RE, Md(O2)dt −1 and Md(CO2)dt −1. The daily mean ERF value (red dashed line) is the ratio of the daily-integrated net turbulent O2 and CO2 fluxes calculated from eqs. (3) and (4) (see text).