NAME =  Dr. Shin Miyazaki  
ORGANIZATION =  Institute of Industrial Science, University of Tokyo / Japan Science and Technology Agency  
ADDRESS =  4-6-1 KOMABA, MEGURO-KU, Tokyo 153-8505, Japan  
COUNTRY =  Japan  
PHONE =  +81-3-5452-6382  
FAX =  +81-3-5452-6383  
E-MAIL =  miyashin@iis.u-tokyo.ac.jp  
POSTER_ONLY =  no  
THEME =  T1  
DATE =  28-Jul-04-18:01:22  
ABSID = T1DSM28Jul04180122 
TITLE = Hydrometeorological conditions of grassland vegetation in Central Mongolia and their impact for leaf area growth 
AUTHOR_1 = Shin Miyazaki 
INSTITUTION_1 = Institute of Industrial Science, University of Tokyo /Japan Science and Technology Agency  
PRESENTER = AUTHOR_1 
AUTHOR_2 = Tetsuzo Yasunari 
INSTITUTION_2 = Hydrospheric Atmospheric Research Center, Nagoya University 
AUTHOR_3 = Tadashi Miyamoto 
INSTITUTION_3 = Nomura Research Institute 
AUTHOR_4 = Ichirow Kaihotsu 
INSTITUTION_4 = Faculty of Integrated Arts and Sciences, Hiroshima University 
AUTHOR_5 = Gambo Davaa 
INSTITUTION_5 = Institute of Meteorology and Hydrology of Mongolia 
AUTHOR_6 = Dambarajaa Oyunbaatar 
INSTITUTION_6 = Institute of Meteorology and Hydrology of Mongolia 
AUTHOR_7 = Lubsan Natsagdorj 
INSTITUTION_7 = Institute of Meteorology and Hydrology of Mongolia 
AUTHOR_8 = Taikan Oki 
INSTITUTION_8 = Institute of Industrial Science, University of Tokyo 
ABSTRACT =  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.