Large gaps in plantations and their effect on height, diameter, volume and branchiness of radiata pine.  G. Minko and G. Hepworth.  July 1986.  8pp. (unpubl.)

SUMMARY

Effects of gaps exceeding 100 m² in area, resulting from seedling mortality, on height, diameter, form and branch size of the gap-edge and non-edge trees in radiata pine plantations were examined at Myrtleford, North-eastern Victoria.

The trees around gaps 6 m in radius (area 113 m²) varied little from the trees further into the stand. For gaps 9 m or greater in radius (area > 254 m²), distance from the gap centre had no effect on tree height, but, up to a distance of 3 trees from the gap edge, was negatively and significantly related to diameter (p < 0.05) and volume (p < 0.05).

Trees located on the 'sunny'^† side of gaps had significantly greater diameter (p < 0.01) and volume (p < 0.05) than trees on the 'shady'^†† side. Edge trees had significantly larger diameter (p < 0.001), volume (p < 0.01) and more branches with diameter above 2.5 cm (p < 0.01) than trees inside the stands. Edge trees also contained significantly (p < 0.05) fewer trees with forked stems than trees away from the gap edge.

These results indicate that during the establishment phase of plantations, replacement of dead seedlings is unnecessary if the gaps are not greater than 100 m². When larger gaps are involved, renewal planting is justified. If dead seedlings are not replaced, pruning of edge trees appears necessary to maintain log quality where the gap area approaches or exceeds 250 m².

^†    Edge trees facing north or west.

^††  Edge trees facing south or east.

Also published:

Minko, G. and Hepworth, G. (1990)  Growth effects of large gaps in Pinus radiata plantations.  N.Z. J. For. Res. 20(1): 22-28.