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

Abstract

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 (Sc; μmol m^-2 s^-1) and sensible and latent heat storage fluxes (Qa and Qw; 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 Sc and Qa 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 Sc in the tropical rainforest, probably mainly due to the difference in nighttime friction velocity at the sites. On the other hand, differences in Qa and Qw were smaller than the difference in Sc, probably because of the smaller nighttime sinks/sources of heat and water vapour.