Abstracts for the 6th International GAME Conf.
3-5 December 2004
Kyoto Japan
Hydrometeorological conditions of grassland vegetation in Central Mongolia and their impact for leaf area growth
Shin Miyazaki (1), Tetsuzo Yasunari (2), Tadashi Miyamoto (3), Ichirow Kaihotsu (4), Gambo Davaa (5), Dambarajaa Oyunbaatar (5), Lubsan Natsagdorj (5), Taikan Oki (8)
(1) Institute of Industrial Science, University of Tokyo /Japan Science and Technology Agency
(2) Hydrospheric Atmospheric Research Center, Nagoya University
(3) Nomura Research Institute
(4) Faculty of Integrated Arts and Sciences, Hiroshima University
(5) Institute of Meteorology and Hydrology of Mongolia
(8) Institute of Industrial Science, University of Tokyo
In this study, we investigated the impacts of seasonal and interannual variability on vegetation as well as soil moisture and evapotranspiration over a grassland at Arvaikheer, central Mongolia. Correlations were determined for 19 years (1982-2000) of monthly mean leaf area index (LAI) and climate data. The largest and significant correlation was found for precipitation (P) in July with LAI in July, which continued until September. Furthermore, significant correlation showed for P in May and LAI in June, P in June and LAI in June. In the composite analysis of highest five years of LAI in August (H5) and lowest five years (L5), the significant positive anomalies of P (77.0 mm) in July and LAI (0.8) in August were found, which was corresponded to the correlation analysis. It implies that the P in July had the largest impact for grass growth.
To study the physical processes of grass growth, we conducted a case study using energy and water budget data with hydro-meteorological elements from 1999 and 2000. In both 1999 and 2000, total precipitation during growing season (GS) was almost same about 130 mm. However, the intra-seasonal distribution of rainfall was different. P in 1999 before July was about 70% of total P during GS while P in 2000 before July was about 40%. These intra-seasonal distribution of P caused the difference of the intra-seasonal variation of surface soil moisture. The soil moisture in upper 20cm in June and July 1999 was higher than in 2000. The LAI from June to September in 1999 was always larger than in 2000. These differences of surface conditions were closely related with the average evapotranspiration (ET) between 1999 (1.3mm/day) and 2000 (0.7mm/day). In 1999, averaged ET/P and temporal change of stored soil moisture (deltaW)/P during the growing season were 0.79 and 0.15, respectively. In contrast, ET/P and deltaW/P during the growing season were 0.94 and 0, respectively. There was almost no stored water in the soil in 2000 because of low P frequency and the small P amounts in June and July 2000.
The results of this study suggest that grass growth in central Mongolia is influenced by P and deltaW before July. High amounts of P, provided after August, did not contribute to grass growth. Although this study focused on one site, it is the first study to examine physical processes related to seasonal rainfall variation and its impact on grass growth in central Mongolia. To generalize our results, we are conducting further analyses using LAI data and data from other stations.
Submittal Information
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Institute of Industrial Science, University of Tokyo / Japan Science and Technology Agency | |
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4-6-1 KOMABA, MEGURO-KU, Tokyo 153-8505, Japan | |
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miyashin@iis.u-tokyo.ac.jp | |