Mechanistic understanding of the emission, transformation, and exchange of greenhouse gases and aerosol precursors with the terrestrial biosphere is needed to reduce uncertainties in radiative forcing of climate. Measurement of trace gas fluxes from aircraft platforms can be used to verify emission inventories of greenhouse gases and aerosol precursors that are used to initialize and evaluate regional- and global-scale models. Yields of secondary organic aerosols in the atmosphere are highly uncertain and require measurement of gas-phase precursors and their products to understand discrepancies between laboratory and field observations. Aerosol optical properties and CCN activation are influenced by chemical composition and thus, rapid measurement of the molecular composition of secondary organic aerosols in the atmospheric boundary layer (ABL) would improve understanding of organic aerosol formation and their radiative-forcing properties. Fractionation of the stable isotopes of N2O, CH4, CO2, and H2O by biogeochemical processes can be used as a marker for ecosystem transformations. The use of nascent laser-based technologies to measure ecosystem exchange of the stable isotopes of these trace gases offers unique insight into the C, N, and H2O cycles and provides important landscape-scale data for constraining coupled C-N-H2O models of the Community Climate System Model. Approaches for evaluating emission inventories of aerosol precursors and the transformation of secondary organic aerosol precursors in the ABL and for improving the representation of biogeochemical processes in coupled C-N-H2O cycle models will be discussed. sponsored by the Departments of Atmospheric Science and Renewable Resources, and Academic Affairs