Turbulent spectra and cospectra of momentum, heat, water and carbon dioxide over two mixed hardwood forests will be presented from long-term (3-4 years) eddy-covariance measurements at two AmeriFlux sites in the Midwest of the US (University of Michigan Biological Station in northern lower Michigan and Morgan-Monroe State Forest in south-central Indiana). Spectral characteristics are discussed in terms of stability, measurement height (ranging from 1.3 to 2.1 times mean tree height, roughness layer), canopy morphology and seasonality, and in comparison with well-known spectra and cospectra characteristics observed over flat surfaces. Spectral correction of carbon dioxide and water vapor fluxes due to the long-tube damping of the closed-path IRGA systems and its implication on measured net ecosystem exchange will also be discussed.