PARENT SESSION
Organized Oral Session 5: Biome and Coastal Models for Local Sites and Biosphere Regions
Organized by: JS Olson and D Ojima
Friday, August 8. 9:00 AM to 12:00 PM, SITCC Meeting Room 106.

Shared templates for modeling carbon eddy flux and nitrogen cycling on Asian and American grasslands.

Ojima, Dennis^*,1, Lee, G-J², Saliendra, N.³, Johnson, D.A.^{3, 4}, Tang, Y-H⁵, Akshalov, K.⁶, Chuluun, Togtohyn⁷, ¹ Colorado State University, Fort Collins, CO² Tsukuba University, Tsukuba, Japan, Japan³ Utah State University, Logan, UT⁴ USDA-ARS Forage and Range Research Lab, Logan, UT⁵ National Institute of Environmental Sciences, Tsukuba, Japan, Japan⁶ Barayev Kazakh Research Institute of Grain Farming, Shortandy, Kazakhstan, Kazakhstan⁷ Mongolian Academy of Sciences, Ulaanbaatar, Mongolia, Mongolia

ABSTRACT- Ecologists and atmospheric scientists are concerned with understanding how biospheric characteristics of the land surface are being modified in response to changing climate, CO₂ concentrations, and land use. Our understanding of the biological controls of carbon fluxes between the atmosphere and the land surface (referring to the soil, vegetation, water system) is critical to our estimation of net terrestrial carbon fluxes. Recent advances in modeling and observation systems of surface fluxes of CO₂ and other trace gases have improved our ability to understand seasonal and interannual dynamics of the biosphere. These technologies are proving to be important for cross continental comparisons of carbon and other biogeochemical fluxes. Data from US, Asian, and Central Asian grasslands will be presented, along with analyses of the climate and land use effects on the biosphere and atmosphere interactions. The Century model of Great Plains short and tall grass prairie can be compared with SimCYCLE Eddy for central Japanese (Tsukuba) meadow and northern and southern Chinese steppes. A recent assessment indicated that salinization of soils due to the drop of the Aral Sea level occurred over 4.9 million hectares, having an adverse impact on the regional economy and human health. The 30-year study of carbon balance of the chernozem soils in northern Kazakhstan conducted at the Barayev Institute of Grain Farming (Shortandy, Kazakhstan) indicated a 25 to 30 percent reduction of humus reserves due to cultivation. Cumulative daily net CO₂ fluxes during measurement periods (174-237 days) for three years (1998-2000) indicated that Central Asian rangelands were sinks for atmospheric CO₂ in this order: Shortandy (1.58±0.26) > Karnap (1.36±0.55) > Karrykul (0.32±0.43 t C ha-1 season-1).

Key words: nitrogen cycling, terrestrial carbon fluxes