Vertical profiles and storage fluxes of CO₂, heat and water in a tropical rainforest at Pasoh, Peninsular Malaysia

Ambient CO₂ concentration, air temperature and relative humidity were measured intermittently for a 3-year period from the floor to the canopy top of a tropical rainforest in Pasoh, Peninsular Malaysia. Mean diurnal CO₂ storage flux (S_c; μmol m^-2 s^-1) and sensible and latent heat storage fluxes (Q_a and Q_w; W m^-2) ranged from -12.7 to 3.2 μmol m^-2 s^-1, -15 to 27 W m^-2 and -10 to 20 W m^-2, respectively. Small differences in diurnal changes were observed in S_c and Q_a between the driest and wettest periods. Compared with the ranges of mean diurnal CO₂ eddy flux (-14.7 to 4.9 μmol m^-2 s^-1), sensible eddy flux (-12 to 169 W m^-2) and latent eddy flux (0 to 250 W m^-2), the contribution of CO₂ storage flux was especially large. Comparison with summertime data from a temperate Japanese cypress forest suggested a higher contribution of S_c in the tropical rainforest, probably mainly due to the difference in nighttime friction velocity at the sites. On the other hand, differences in Q_a and Q_w were smaller than the difference in S_c, probably because of the smaller nighttime sinks/sources of heat and water vapour.