Water and energy exchanges in the larch and the pine forest, Eastern Siberia
Takeshi OHTA (1), Tetsuya HIYAMA (1), Trofim C. MAXIMOV (3)
(1) Nagoya University, FORSGC
(3) IBPC
Siberian taiga is one of the most extensive forests on Earth. Little is known about the Siberian taiga on water and energy cycles, or their seasonal variation, especially in eastern Siberia. This report presents the preliminary results obtained from 1996 to 2000.
Two observation sites are located about 20 km north of Yakutsk City. One is a larch forest site. The other is a pine forest site.
Each year, the sensible heat flux was maximal at the end of May, just after the snowmelt season. The flux decreased, while the net all-wave radiation increased until the end of June. The latent heat flux increased quickly when the sensible heat flux dropped (Ohta et al., in press). These results suggest that plant physiological activity strongly affects the energy balance above the canopy.The amount of precipitation from May to August obtained by a heat pilse method was 81.5 and 235.7 mm in 1998 and 1999, respectively. Consequently, there was a significant difference in the soil moisture in the thawing layer between these two years. After the middle of July, soil moisture was always higher in 1999 than in 1998. On the other hand, the daily transpiration rates were larger in 1998 than in 1999 during this period, which suggests that soil moisture did not control the transpiration rates in the observed range.
In the pine forest, the sensible heat flux increased rapidly just after the snowmelt season, as in the larch forest, but a high flux density was maintained until the middle of August. Consequently, the sensible heat flux above the larch forest was 80% of that above the pine forest just after the melting season, and the percentage decreased to 40% by the middle of August. The latent heat flux was quite higher than that in the larch forest in the early spring. The differce of thawing depth of permafrost between the two forest might cause the high latent heat flux in the pine forest.
Submittal Information
Name :
Date :
Takeshi OHTA
24-May-01-10:08:32
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Graduate School of Bioagricultural Sciences, Nagoya University
