An observational study of the factors that influence interception loss in boreal and temperate forests
2005
Toba, T. | Ohta, T.
This study used same methods to observe interception loss in two boreal forest sites in Siberia and five temperate forest sites in Japan; interception characteristics of the two climate regions were compared. The Siberian sites had high interception ratios of 0.2-0.3. In contrast, the Japanese sites had low interception ratios of ca. 0.15 in coniferous forests and 0.2 in broadleaf forests. Although interception loss generally increases with the plant area index (PAI), our data showed the opposite trend. This suggests that meteorological variables had a greater effect on interception loss than did differences in canopy structure. Rainfall characteristics appeared to be the main meteorological factor affecting interception loss. When mean rainfall intensity exceeded 1 mm h(-1), the interception ratio remained near the upper limit of 0.2 regardless of other rainfall conditions. In contrast, windy and drier atmospheric conditions strongly affected the interception rate when the rainfall intensity dropped below 1 mm h(-1). Japan and Siberia showed significant energy-balance differences related to evaporation from wet canopies. At the Siberian sites, the net all-wave radiation was always larger than the latent heat flux used for interception loss, while Japanese sites often showed the opposite pattern. When the latent heat flux exceeded the net all-wave radiation, the air temperature above the canopy during rainfall events was higher at upper levels than at lower levels, even in the daytime. These results indicate that the sensible heat flux was directed downward and suggest that both net all-wave radiation and sensible heat flux contribute to evaporation from wet canopies during and shortly after rainfall events in Japan.
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