An analysis of the surface energy budget above the worldʹs tallest angiosperm forest

Eddy covariance measurements were conducted over the worlds’ tallest angiosperm forest (>90 m) for the first time at an old-growth Eucalyptus regnans (Mountain Ash) site at Wallaby Creek, Victoria, Australia. At this challenging site we examined half-hourly exchanges of the turbulent energy balance components between the surface and atmosphere over an 18-month period. Detailed estimates of the storage flux components were made, with emphasis on the biomass heat flux components. Near complete closure was attained for the site, with the best surface energy balance (SEB) closure occurring in summer and poorest in autumn, 0.96 and 0.84, respectively. The addition of storage fluxes significantly improved closure by 6–10%. Storage of heat within the vegetation and air column were found to be the two largest components of the total storage flux. The ‘ensemble block’ time averaging analysis, together with cospectral and Ogive analysis suggested that a 30-min averaging period was sufficient in capturing the majority of the turbulent fluxes, though an averaging period of 60-min may be more suitable for this site.