Measurement of evaporation from the forest floor in a deciduous forest throughout the year using microlysimeter and closed‐chamber systems

Abstract

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 14·0% of the daily E FF . The daily E FF was 0·20 ± 0·13 mm day −1 during the study period, with two seasonal peaks: in late spring (0·31 mm day −1 in April) and early fall (0·22 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. Copyright © 2008 John Wiley & Sons, Ltd.