Better information regarding the spatial variability of height, Diameter at Breast Height (DBH) and stocking could improve inventory estimates at the operational Planning Unit since these parameters are used extensively in allometric equations, including stem volume, biomass and carbon calculations. In this study, the influence of stand stocking on height and DBH of two even aged radiata pine (Pinus radiata D. Don) stands were investigated using airborne Light Detection and Ranging (LiDAR) data at a study site in New South Wales, Australia. Both stands were characterized by irregular stocking due to patchy establishment and self-thinning in the absence of any silvicultural thinning events. For the purpose of this study, a total of 34 plots from a 34 year old site and 43 plots from a nine year old site were established, from which a total of 447 trees were sampled. Within these plots, DBH and height measurements were measured and their relationships with stocking were evaluated. LiDAR was used for height estimation as well as stem counts in fixed plots (stocking). The results showed a significant relationship between stem DBH and stocking. At both locations, trees with larger diameters were found on lower stocking sites. Height values were also significantly correlated with stocking, with taller trees associated with high stocking. These results were further verified of additional tree samples, with independent field surveys for DBH and LiDAR-derived metrics for height analysis. This study confirmed the relationship between P. radiata tree heights and stem diameter with stocking and demonstrated the capacity of LiDAR to capture sub-compartment variation in these tree-level attributes.

The aim of this study was to determine whether diameter at breast height (DBH, at 1.3 m) and total height of radiata pine (Pinus radiata D. Don) trees showed any significant relationships with microsite estimates of solar radiation. A total of 77 plots were established in two even-aged stands of radiata in Nundle State Forest, New South Wales, Australia. Within these plots, tree DBH and height measurements were recorded and their relationships with solar radiation evaluated. Airborne light detection and ranging (LiDAR) data were processed to generate a high resolution digital elevation model (DEM), and the DEM was used for calculating the incoming solar radiation. Overall, at both study sites, taller and larger trees were found on areas with lower solar radiation, possibly due to a lower loss in soil moisture. The findings of this study suggest that LiDAR-derived DEM estimates of solar radiation are significantly correlated with DBH and height variation, and therefore suitable for use as a sub-compartment stratification variable as well as for possible inclusion in fine-scale estimates of P. radiata growth and productivity.