This study integrated CLM4 with a C4 plants discrimination model and a canopy kinetic fractionation model, to simulate regional carbon isotope exchange between land and atmosphere from 2007 to 2009. The model simulated discrimination was compared to the discrimination derived from EC-TDL measurement at two towers with homogeneous underlying surface and a Tall Tower (44°41'19 N, 93°4'22 W, 290m ASL). The land cover data is derived from Landsat 30m resolution data using a hybrid supervised/un-supervised land use classification scheme.
Based on this research we address four climatology questions:
1. What is the relative importance of C3 and C4 species to the regional CO2 budget?
2. How do these different photosynthetic pathways influence the regional biosphere atmosphere isotope discrimination?
3. To what extent do changes in C4 vegetation impact atmospheric isotopic forcing and the isotopic signature of the atmosphere?
4. To what extent do changes in Climate factors impact atmospheric isotopic forcing and the isotopic signature of the atmosphere?