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

Abstract

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 (Fc), 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 Sc, Q_a and Q_w were generally similar to those reported for other forests. However, the amplitude of diurnal changes in Sc 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.