Fig. 4. (a) Log. of observed soil CO2 flux (ln Fco2o) vs. log. of predicted soil CO2 flux (ln Fco2p), and summary statistics; and (b) ln Fco2o and ln Fco2p by position on the transect. ME = mean error (observed – predicted), RMSE = root-mean-square-error, rPM = product-moment correlation, and rMVE = correlation based on a minimum-volume ellipsoid estimate of the covariance matrix (Rousseeuw, 1985).