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 (R-2 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 (R-2 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 (R-2 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 (R-2 of 0.81).