Modeling CO2 sources, sinks, and fluxes within a forest canopy

A practical method to infer CO2 sources, sinks, and fluxes from measured me an concentration profiles is proposed and field-tested in a uniform pine fo rest using eddy covariance measurements. The proposed method computes the v elocity statistics from a second-order closure model and uses these statist ics to infer profiles of scaler fluxes using a scalar-flux budget. The mode l input requirements are leaf area density profile, mean sheer stress at th e canopy top, and measured concentration profiles within and just above the canopy, In contrast to the localized near-field (LNF) theory the model doe s not assume zero vertical velocity skewness, negligible advective effects, and local vertical homogeneity in the near-field concentration. The model results compared well with eddy covariance CO2 flux measurements inside the canopy and reproduced qualitatively much of the physiologically known dayt ime evolution of the CO2 source-sink profile.