with the second hypothesis, regressions of initial lignin content or lignin:N ratio on mass remaining improved (higher R2) from 2 to 4 mo decomposition, while those of N content grew worse, illustrating succession of nitrogen to lignin control of decomposition rate. Reported correlations of the lignin: N ratio with decomposition rate for some litter types arise as aspecial case of this two-phase mechanism of control by nutrients and lignin. For substrates low in lignin, or where abroad range of lignin contents is being considered, the C:N ratio is a better predictor of decomposition rate than the lignin:N ratio.