Evaporation of intercepted precipitation based on an energy balance in unlogged and logged forest areas of central Kalimantan, Indonesia

The effect of logging practices on rainfall interception loss has been investigated in a humid tropical rainforest of central Kalimantan. The traditional volume balance method was used to measure throughfall, stemflow and interception loss. The evaporation rate during and after rainfall has ceased in canopy-saturated conditions was calculated by an energy balance method, which relied on the modified Penman equation using directly determined microclimatic and canopy structure variables as inputs. The results obtained showed that the evaporation from wet canopies in this research area is driven more by advected energy than by radiative energy. In the unlogged plot, advective energy accounted for 0.38 mmh(-1) of the 0.51 mm h(-1) of evaporation, whereas radiative energy accounted for only 0.13 mm h(-1). A similar relationship between the major driving variables and the rate of evaporation was also found in the logged plot and this implies that logging activities did not change the proportion of energy used for interception loss. The Priestley-Taylor equation was found to be a poor model for evaporation of intercepted water in tropical forests because advected energy is very important at the canopy scale. (C) 1998 Elsevier Science B.V. All rights reserved.