Modeling the characteristics of interception loss in forests of eastern Siberia and Japan
Tae TOBA (1), Takeshi OHTA (2)
(1) Graduate School of Bioagricultural Sciences, Nagoya University
(2) Graduate School of Bioagricultural Sciences, Nagoya University, Frontier Observational Research System for Global Change
Interception loss is an important component in forest hydrological cycles. The aim of this study was to construct a model of interception loss based on field measurements of canopy structure, precipitation measured beneath canopies and gross precipitation in open sites, both in Siberia and JapanD
Six forest sites were selected for data collection. One pine and two larch stands were located 20 km north of Yakutsk City, Siberia, and three pine stands were located 25 km west of Morioka City, Japan. The parameters observed in these forests were throughfall, stemflow, gross precipitation in open-canopy sites, meteorological variables, and plant area indices (PAI). We also measured the heat pulse velocity for four or five trees, to estimate the timing when canopies dry out. PAI, which was estimated from fish-eye photos, ranged from 2.27 to 4.44 during the summer in these six forests.
The ratios of precipitation measured beneath canopies to gross precipitation measured in open sites ranged from 66 % to 86 %. The relationships between y-intercepts in these linear functions and the values of PAI are suggest that a forest with larger values of PAI has a larger capacity to collect precipitation.
The interception loss model is based on a tank-model. This model is composed of two tanks. The T tank represents a canopy and the S tank represents trunks. Water that overflows from the T tank divides according to the dividing rate of the throughfall and the incoming water to the S tank, if the water depth exceeds the depth of the T tank . The water flowing into the S tank moves according to the same algorithm as in the T tank. Total evaporation from the canopy is calculated using the Penman-Monteith formula. The model parameters, e.g., the height of a hole, the depth of the tanks, and the dividing rates, were chosen based on results obtained from field observations.
The agreement of interception losses estimated by the model and those obtained from field observations is good. We compared model estimates with field observations of when the canopies had dried out. The times when the water levels in the T tank become zero are coincidental to dried canopies. The heat pulse velocity might increase when the canopy dries out after a precipitation event. We compared the times when the water in the T tank had completely evaporated to times when the heat pulse velocity rose in the observations. The two times agreed well with each other.
@@ The results obtained by the simulation for interception loss were as follows: 1) Interception loss increased with an increase in PAI; 2) the effect of meteorological conditions on interception losses was reduced as precipitation intensity increased; and 3) when the intensity of precipitation increased, the effect of PAI on interception losses become smaller.
Submittal Information
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Tae TOBA
30-May-01-08:56:47
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Graduated School of Bioagricultural Sciences, Nagoya University
