Gains in mean stem volume from selection of the top 10% of hybrid clones over the best performing pure species ranged between 40 and 45%.
Results confirmed that the positive effects of thinning on mean stem volume is due more to the higher diameter increment than to different height growth.
These hybrids exhibited heterosis under saline irrigated conditions, with the mean stem volume of hybrids at 85 months exceeding the best pure species parent by 140 252%.
The combination of mean stem volume and number of stems provides stand-level volume estimates.
Conversely, the proportion of useable cells for calculating mean stem volume was stable for all cell sizes.
where ( overline{x} ) is the estimated mean stem volume and t is a Student's t-test value.
It is interesting to compare these results with those of Gordon and Pont (2015), who tested a number of different sampling methods to estimate the mean stem wood volume of individual trees in five populations of plantation Pinus radiata in New Zealand.
Values of RMSE for the final models of mean top height, green crown height, stem volume, mean diameter, basal area and stand density were, respectively, 1.02 m, 0.427 m, 20.2 m3 ha-1, 13.9 mm, 3.81 m2 and 355 stems ha-1.
Models were developed using SAS software (SAS Institute Inc. 2008), to estimate mean top height, green crown height, total stem volume, mean diameter, basal area and total stand density.
The positive linear relationships between LiDAR metrics and mean top height, green crown height, total stem volume, mean diameter and basal area had respective coefficients of determination (R2) of 0.85, 0.71, 0.83, 0.74 and 0.72.
The final models constructed for mean top height, green crown height, total stem volume, mean diameter, basal area, and stand density had R2 values of 0.85, 0.79, 0.86, 0.86, 0.84 and 0.55, respectively, with root mean square errors of 1.02 m, 0.427 m, 20.2 m3 ha-1, 13.9 mm, 3.81 m2 ha-1 and 355 stems ha-1, respectively.
