(1) Faculty of Agriculture, Iwate University / Graduate School of Bioagrucultural Sciences, Nagoya University
(2) Graduate School of Bioagricultural Sciences, Nagoya University / Frontier Observational Research System for Global Change
(3) Hydrospheric Atmospheric Research Center, Nagoya University
Boreal forest is the major biome that occupies the circumpolar region between 50„a and 70„a north. However, there is scant micrometeorological information on the Siberian boreal forest. A canopy conductance model can be used to determine the characteristics of evapotranspiration in a forest. Although many studies using canopy conductance models have been published for some parts of the world, few have related canopy conductance to the each different climatic characteristic in those areas. This paper examines the characteristics of the energy balance and its seasonal variation above a pine forest canopy in eastern Siberia. Using a canopy conductance model, the parameters for the model were determined and related to latitude.
The study site was a pine forest located at Spasskaya Pad (62„a14'29'' N, 129„a39'2'' E). The average tree height was 6-10 m. The stand density was 2664 trees ha-1, and the average stem diameter was 7.9 cm. The micrometeorological measurements were made from an 18.2-m tower. The turbulent fluxes above the canopy were measured by the eddy correlation method. Using these observations, we examined the characteristics of the energy balance and its seasonal variation. The canopy conductance model used in this study was a Jarvis type.The parameters in the model were determined using a nonlinear least-squares regression analysis. The period for this analysis was from 18 April to 23 August 2000.
The seasonal variation and the magnitude of the latent heat flux (LH) were similar to values for the sensible heat flux (SH), which was maximal in June. Some days after rainfall, LH was very large, and the sum of LH and SH exceeded the net all-wave radiation. Remarkably, in the second half of July, which corresponded to a long rainless period, LH decreased and became smaller than SH. The amount of precipitation was 145 mm from 27 April to 5 September in 2000. The average evapotranspiration above the dry canopy in July was 1.7 mm day-1. Understory evapotranspiration increased in June, and this tendency was similar to the seasonal variation above the canopy. The amount of understory evapotranspiration was about 40% of that above the canopy.
It did not rain from 7 to 20 July, and the daily maximum air temperature and saturation deficit increased during this period. Subsequently, the canopy conductance decreased significantly day by day. During the period of this analysis (from 18 April to 23 August in 2000), the maximum observed canopy conductance was about 30 s-1mm.
We examined the data about parameters from canopy and stomatal conductance models determined in studies carried out throughout the world. There were relationships between latitude and the parameters for temperature and saturation deficit. These results indicate that it is possible to relate the characteristics of evapotranspiration above a canopy to the climatic characteristics in different areas of the world using canopy conductance models.
Submittal Information
Name :
Date :
Shuko HAMADA
30-May-01-17:00:59
Organization :
Theme :
Faculty of Agriculture, Iwate University, Graduate School of Bioagricultural Science, Nagoya University
