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Abstract:Evaporation from the forest floor (E FF ) in a deciduous broadleaf forest was measured using microlysimeter and closed-chamber systems. The microlysimeter was used at six points in the experimental basin, and measurements gave different E FF values at different points. This could be attributed to the local photoenvironment of each sampling point, rather than to litter conditions, if the spatial variation in air temperature (Ta) or vapour pressure deficit (VPD) at the forest floor was small within this basin. A detachable microlysimeter measured condensation in the litter layer during the night, indicating that the litter layer, as well as the mulch layer, played a role in preventing evaporation from the soil layer. The closed-chamber system made it possible to continuously measure long-term E FF . E FF was closely related to VPD; even during the night, when solar radiation was zero, E FF amounted to 14Ð0% of the daily E FF . The daily E FF was 0Ð20 š 0Ð13 mm day 1 during the study period, with two seasonal peaks: in late spring (0Ð31 mm day 1 in April) and early fall (0Ð22 mm day 1 in September). The former peak has been reported from two deciduous forests in Japan and is strongly related to the solar radiation reaching the forest floor when the trees are dormant.

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