Agrometeorological conditions of grassland vegetation in central Mongolia and their impact for leaf area growth

[1] The long-term observation of surface heat and water budget and hydrometeorological elements has been carried out over a grassland site at Arvaikheer (46.23� N, 102.82� E) in central Mongolia as the framework of the GEWEX Asian Monsoon Experiment-Asian Automatic Weather Station Network (GAME-AAN). The purpose of this study is to clarify the relationship between vegetation and climate using long-term data (1982–2000) of satellite-derived leaf area index (LAI) and climatic data observed at Arvaikheer. Furthermore, we aimed to reveal physical process by comparing soil moisture and heat and water budgets in 1999 and 2000 as a case study of good and poor vegetation growth. Significant positive correlations with 99% confidence levels were found for July precipitation (P) and the LAI in July (0.538), August (0.826), and September (0.564). Composite analysis for five highest (H5) and lowest (L5) LAI years showed the significant positive anomalies of P in July and LAI in July and August for H5. In June and July 1999, soil moisture and P values were higher than values in 2000; this pattern was reversed in August and September. The mean LAI during the 1999 growing season (1.0) was about twice that of 2000 (0.6). In 1999 the ratio of evapotranspiration (ET) to P (ET/P) and change of stored soil moisture (DW )t o P( DW/P) were 0.79 and 0.15, respectively. In 2000, ET/P and DW/P were 0.94 and 0.0, respectively. These results suggest that the P and DW before July had the most influent on grass growth in central Mongolia. INDEX TERMS: 1818 Hydrology: Evapotranspiration; 1866 Hydrology: Soil moisture; 3309 Meteorology and Atmospheric Dynamics: Climatology (1620); 3322 Meteorology and Atmospheric Dynamics: Land/ atmosphere interactions; 3360 Meteorology and Atmospheric Dynamics: Remote sensing; KEYWORDS: Mongolia, grassland, leaf area index, soil moisture, rainfall, evapotranspiration

[1]  Inhomogeneity of the Land Surface and Problems in theParameterization of Surface Fluxes in Natural Conditions , 1998 .

[2]  Ranga B. Myneni,et al.  Estimation of global leaf area index and absorbed par using radiative transfer models , 1997, IEEE Trans. Geosci. Remote. Sens..

[3]  Xuhui Lee,et al.  On micrometeorological observations of surface-air exchange over tall vegetation , 1998 .

[4]  C. Potter,et al.  Analysis of a multiyear global vegetation leaf area index data set , 2002 .

[5]  T. Yasunari,et al.  Interannual Variations of Summer Precipitation in the Arid/semi-arid Regions in China and Mongolia : , 1995 .

[6]  Lawrence B. Flanagan,et al.  Seasonal and interannual variation in evapotranspiration, energy balance and surface conductance in a northern temperate grassland , 2002 .

[7]  Kenji Tanaka,et al.  Surface Energy Budget at Amdo on the Tibetan Plateau using GAME/Tibet IOP98 Data. , 2001 .

[8]  T. Yasunari,et al.  Trends and Decadal-Scale Fluctuations of Surface Air Temperature and Precipitation over China and Mo , 1994 .

[9]  O. Tsukamoto,et al.  Heat Budget and Evapotranspiration at an Oasis Surface Surrounded by Desert , 1995 .

[10]  E. A. Vostokova,et al.  Vegetation Dynamics of Mongolia , 1999, Geobotany.

[11]  Wilfried Brutsaert,et al.  Daily evaporation over a region from lower boundary layer profiles measured with radiosondes , 1991 .

[12]  Larry Mahrt,et al.  Flux Sampling Errors for Aircraft and Towers , 1998 .

[13]  J. D. Merritt,et al.  Testing energy balance closure with GOES‐retrieved net radiation and in situ measured eddy correlation fluxes in BOREAS , 1999 .

[14]  W. Brutsaert.  Evaporation into the atmosphere , 1982 .

[15]  Peter D. Blanken,et al.  Energy balance and canopy conductance of a boreal aspen forest: Partitioning overstory and understory components , 1997 .

[16]  Stephen K. Cox,et al.  PROCEDURES FOR IMPROVING PYRGEOMETER PERFORMANCE. , 1977 .

[17]  J. Blair,et al.  Rainfall Variability, Carbon Cycling, and Plant Species Diversity in a Mesic Grassland , 2002, Science.

[18]  J. Ni,et al.  Plant functional types and climate along a precipitation gradient in temperate grasslands, north-east China and south-east Mongolia , 2003 .

[19]  Daqing Yang,et al.  Accuracy of tretyakov precipitation gauge: Result of wmo intercomparison , 1995 .

[20]  T. W. Horst,et al.  How Far is Far Enough?: The Fetch Requirements for Micrometeorological Measurement of Surface Fluxes , 1994 .

[21]  K. Musiake,et al.  Observations of Energy Fluxes and Evapotranspiration over Terrestrial Complex Land Covers in the Tropical Monsoon Environment , 2002 .

[22]  J. Norman,et al.  Correcting eddy-covariance flux underestimates over a grassland , 2000 .

[23]  Tsutomu Watanabe,et al.  Testing of the bandpass eddy covariance method for a long-term measurement of water vapour flux over a forest , 2000 .

[24]  N. Saigusa,et al.  Seasonal variations of the exchange of CO2 and H2O between a grassland and the atmosphere: An experimental study , 1998 .

[25]  C. Tucker,et al.  Climate-Driven Increases in Global Terrestrial Net Primary Production from 1982 to 1999 , 2003, Science.

[26]  Hydrological regime analysis of the Selenge River basin, Mongolia , 2003 .

[27]  Rikie Suzuki,et al.  West–east contrast of phenology and climate in northern Asia revealed using a remotely sensed vegetation index , 2003, International journal of biometeorology.

[28]  Different scale measurements of soil moisture on the ground , 2000, IGARSS 2000. IEEE 2000 International Geoscience and Remote Sensing Symposium. Taking the Pulse of the Planet: The Role of Remote Sensing in Managing the Environment. Proceedings (Cat. No.00CH37120).

[29]  W. Oechel,et al.  Energy balance closure at FLUXNET sites , 2002 .