Amplitude and seasonality of storage fluxes for CO2, heat and water vapour in a temperate Japanese cypress forest

Storage fluxes of CO₂, air temperature and relative humidity were measured in a temperate Japanese cypress forest for 3 yr. The 3-yr means of diurnal storage fluxes of CO₂ (S_c), latent heat (Q_a) and sensible heat (Q_w) ranged from –1.3 to 1.2 μmol m^-2 s^-1, –9 to 12 W m^-2 and –2 to 5 W m^-2, respectively. The mean diurnal eddy fluxes of CO₂ (F_c), sensible heat (H) and latent heat (λE) ranged from –13.1 to 2.6 μmol m^-2 s^-1, –37 to 187 and 7 to 146 W m^-2, respectively. The variation and amplitude of diurnal changes in S_c, Q_a and Q_w were generally similar to those reported for other forests. However, the amplitude of diurnal changes in S_c was much smaller than that of tropical rain forests. The amplitudes of diurnal changes in S_c and Q_w in summer were larger than those in winter, although the amplitude of Q_a exhibited no clear seasonal variation. This was likely because of the small seasonal change in the source (sensible heat exchange) in comparison with CO₂ and latent heat exchange.