Evaporation of intercepted precipitation in unlogged and logged forest areas of central Kalimantan, Indonesia

The effect of logging practices on rainfall interception loss was monitored for 12 months and related to vegetation and rainfall characteristics at the Wanariset Sangai, Central Kalimantan. The results show that evaporation of intercepted rainfall is higher in the unlogged forest (11% of total gross rainfall) than in the logged forest (6%). These results were closely associated with the reduction in number of trees per hectare from 581 in the unlogged plot to 278 (52%) in the logged plot, or a reduction in terms of basal area from 38.6 to 13.8 m(2) ha(-1) (65%). 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 mm h(-1) of the 0.50 mm h(-1) of evaporation, whereas radiative energy accounted for only 0.13 mm h(-1).