Non-destructive assessment of green density and moisture condition in plantation-grown radiata pine (Pinus radiata D. Don.) by increment core measurements

A novel protocol for non-destructive assessment of green density and moisture content via increment cores was validated for young (8–10 years) and mature trees (36 years) of radiata pine (Pinus radiata D. Don.). Initial procedures involved comparing 5- and 12-mm cores with fresh disks taken from young trees at breast height and felled during the winter, as well as methods for rehydrating the wood cores. Subsequently, the best method (12-mm cores) was validated with material collected in summer from both young and mature trees. The protocols developed require separate processing of sapwood and heartwood, and soaking the sapwood for 24 h to replace the moisture lost while coring. For young trees, bark-to-pith 12-mm cores accounted for between 64% and 66% of variation in green density of sapwood and between 51% and 72% of saturation percentage, as measured by destructively sampled disks. For mature trees, the average of two sides of 12-mm bark-to-bark cores accounted for 73% of variation in green density of sapwood, and 56% of saturation percentage as measured by destructive wedges. One or both sides of a bark-to-bark core accounted for between 72% and 80% of variation in whole-section green density, and between 70% and 79% of variation in sapwood percentage. The number of heartwood rings was better predicted from the average of two sides of the cores (R2 of 0.71). Whole-tree values (lower two logs) for sapwood green density and saturation were better predicted from the average of both sides of the bark-to-bark core (R2 of 0.76 and 0.57, respectively). Whole-tree values for whole-section green density could be predicted either by one side or two sides of the cores (R2 for 1 or 2 sides of 0.77 and 0.81). Finally, whole-tree sapwood volumetric percent was better predicted by the average of two sides of the cores (R2 of 0.81).