New Zealand Journal of Forestry (1981) 26(1): 55–69
©New Zealand Institute of Forestry
Blanking plantations of radiata pine.
C. G. R. Chavasse , J. M. Balneaves and G. P. Bowles
A series of trials was laid down between 1963 and 1978 to determine the effect on the original planting of blanking small gaps (from single-tree gaps of 17 m2 minimum, to gaps approximately 100 m2 in extent). The earlier trials were in stands with the then conventional spacing of 2.4 X 1.8 m but the final trial, at Ashley Forest in Canterbury, was in a crop spaced at 3.6 X 1.8 m. The trials were terminated at the time of second pruning, when crop trees were about 8 m tall.
It was shown that blanking radiata pine stands in the summer or winter following planting had no measurable effect on the original crop in terms of height, d.b.h., or branch sizes where pruning was carried out on time to 1.8 and 3.7 m. In all stands, the difference in size between the blanking stock and the original crop was highly significant. Only rarely were blanking stock selected for either first or second pruning, and then only because of toppling and the inferior form of the original stocks.
Larger blanking stock (IV2/O and 2/0) was marginally better than small (1/0) stock. Delaying pruning for 1 year, even for the largest gap size, had only a minor effect on branch sizes.
It was concluded that, for the sizes of gap studied, blanking in summer or winter following original planting is of little use, except perhaps for gaps of 100 m2, which would accommodate one final-crop tree, where full stocking is the aim. It is preferable to achieve full stocking in the first place by applying appropriate techniques.