Statistical design required for the proposed tree improvement programme for E. deglupta

narrow (1.08, 1.12, 1.03, 1.08, 0.99, 1.05, 1.02, 1.07, 1.16 mm for trees KT1 – 9 a range of 0.99 to 1.16 mm). Thus the combination of a non-representative breast height sample and the lack of any possibility of significant improvement of fibre length through breeding caused meto relegate selection of individual trees based on fibre length to a secondary role.

Of the nine trees in the preliminary investigation, and if they had been candidates for selection for a breeding programme (they were not), I would have been inclined to reject only the one tree that had a weighted whole tree fibre length of slightly less than 1 mm (0.99 mm).

Statistical design required for the proposed tree improvement programme for E. deglupta

While in Canberra the opportunity was taken to discuss with several experts the statistical design required for selection of superior trees in the Keravat plantations for breeding purposes.

The outcome was that three populations would be required to be identified and assessed: 1. A random population of 125 or more trees representing the routine unimproved plantation trees involved at Keravat. This would be the lowest level in the hierarchy of populations. Also called a base population by some workers. It would serve also for gene conservation, storing genes of the unimproved population which may be lost during later generations of tree breeding, but which may be required to fall back on in later if breeding is required for a different purpose. It could be a suitable backcross source destination to reverse any severe inbreeding depression that might develop in succeeding generations of the breeding population. 2. A candidate tree population of 150 to 200 trees for the current tree improvement programme based (i) on external morphological appearance of a number of characters of relevance to selection of superior individuals (including bole straightness, bole cylindricity, minimal buttressing and bole fluting), and (ii) on superior growth based on total height and diameter at breast height, determined by comparison with total height and diameter at breast height of the 5 nearest neighbor trees. 3. A breeding population of not less than 150 trees resulting from selection of the best trees from among the candidates in regard to rate of growth and external morphological appearance. No. 1 was also used to establish that individual stand and tree variables in the Keravat plantations were normally distributed and not skewed and to serve as a reference to which the selected populations could be compared. A program called SCREEN was written by me for screening data under pre-set conditions, taking the sub-set satisfying the conditions and calculating several basic statistics such as the mean, median, standard deviation, confidence limits, skewness, kurtosis and the Kolmogorov-Smirnov