Hail damage in Australian pine plantations I. Nature and extent of damage

Summary

From data gathered on twenty hailstorms which severely damaged pine plantations in various parts of Australia during the past decade, and from a review of the literature, an analysis is presented of the nature and effects of hail damage on Pinus radiata and Pinus elliottii.

Meterorological data from Australia indicate that plantations in this country are likely to experience about two physically damaging hailstorms per 35-year rotation, and scars left by the impact of hailstones tend to confirm this.

Hailstones knocked needle fascicles and thin shoots off the trees and thus caused up to 70% defoliation. They also killed 1–4 cm wide patches of bark and cambium where the bark was thin, i.e. on limbs, and the top 6–12 m of the stem. More serious damage resulted when these physical injuries were followed by shoot dieback associated with infection by Diplodia pinea. Except for vigorous young (<6 yr) plants, all classes of trees were susceptible to the dieback, largely irrespective of dominance, vigour, site quality, stand density and drought stress. Many trees died, but most recovered in about 2 to 4 years. Those that had lost several metres of their leader developed badly deformed stems.

During 1971–80, dieback necessitated the salvage of about 100 000 m⁻¹ of stem wood per year, i.e. about 3.6% of the total harvests.