Abstracts for the 6th International GAME Conf.
3-5 December 2004
Comparison of water and heat balance on grassland and forest in Central Yakutia, East Siberia.
Hironori Yabuki (1), Yoshiyuki Ishii (2), Tetsuo Ohata (3)
(1) Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology
Siberian region is an area dominated by taiga forest but the percentage of it is 70%, other being bare land, grassland and water bodies such as rivers and lakes. These regions were underlain by permafrost. Especially, in right bank of the Lena River region which is the opposite side of the Yakutsk City, there are many concave landform called "alas". An alas is formed after the forest has been cleared by natural collapse and forest fire, cultivation in an area where the ice content of permafrost was high. The alas occupying up to 20% of this area. Most alas have lakes and marshes near the center, and the surround of lake is covered in the grassland. When we consider the water and heat circulation of this region, it is necessary to clarify water and heat characteristics of the forest and grassland. In this study, the water and heat flux observation was carried out in the forest and grassland area, and the water and heat balance characteristics was compared. Until now, the simultaneous measurement of sensible heat and latent heat fluxes in forest and grassland was little, where weather condition seemed to be almost similar.
Observation site in the right bank of the Lena River is called "Ulakhan Sykkhan", located 50km north east part of the Yaktusk city. The field observation was carried out from April to September 2000. In forest site, we install observation tower in a flat larch forest. The stand density was 4200 tree ha-1. The mean basal diameter of tree was 7.6cm. The mean stand height was 7.6m. The maximum stand height was 17.3m. In grassland site, we installed observation mast in the center of alas. This alas has oval shape and 0.64km2 area including a 0.1km2 lake at the center. The tower and mast were used 1-D scale flux observations of forest canopy and grassland, respectively. Both sites have separated as a distance about 2km. Air temperature and humidity were measured at 22m and 17m in forest site, and 2m and 0.5m in grassland site, respectively. We measured the downward and upward short-wave/long-wave radiation on top of tower and upward short-wave/long-wave radiation at grassland. Latent heat and sensible heat fluxes were obtained by the BOWEN ratio method. And those flues were compared with between forest and grassland sites.
At the grassland the sensible heat flux was smaller and latent heat flux larger than those at the forest site. PAI in forest and grassland were 3.5 and 3.2, respectively, this value of the grassland was smaller than that of the forest site. However, the area of trunk and branch at forest were big, LAI of the forest which contributes to the evapotranspiration was 2.0, this value was smaller than grassland. The difference of this LAI seems to appear the difference in the latent heat of the forest and the grassland.
(2) Institute of Low Temperature Science, Hokkaido University
(3) Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology / Institute of Low Temperature Science, Hokkaido University
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Institute of Observational Research for Global Change, Japan Agency for Marine-Earth Science and Technology
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3173-25 Showa-machi Kanazawa-ku Yokohama-city Kanagawa, 236-0001
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