Percent uncertainty by diameter at breast height (DBH) class and approach. A. Total live-tree C prediction envelopes by approach for Pseudotsuga menziesii (positive correlation). B. The prediction envelopes, displayed as percent uncertainty (half the width of the prediction envelope expressed as a percentage of the midpoint at each DBH class) for total live-tree C, Pseudotsuga menziesii, by approach for positive correlation only. Abrupt changes in uncertainty occurred where plots of equation predictions crossed, where an equation began or ended, and occasionally when corrections were applied (in the case of approach 3 only).