Effect of shadecloth tree shelters on cold-induced photoinhibition, foliar anthocyanin and growth of Eucalyptus globulus and E-nitens seedlings during establishment

The effects of shadecloth tree shelters on cold-induced photoinhibition, foliar anthocyanin and growth of Eucalyptus globulus Labill. and Eucalyptus nitens (Deane & Maiden) Maiden seedlings were assessed between planting (in early spring) and the age of 23 weeks. The experimental site was at 350 m above sea level (asl), which is considered marginal for establishment of E. globulus (but not E. nitens) plantations in Tasmania because of low mean minimum temperatures. Conditions within 3 weeks of planting induced severe photoinhibition in non-shaded seedlings. This was associated with increased anthocyanin and photodamage in non-shaded E. nitens and E. globulus. As a result, there was 20% mortality in non-shaded E. globulus. In contrast, shaded seedlings of both species had levels of photoinhibition and anthocyanin that were largely similar to those before planting and there was no photodamage. Levels of anthocyanin indicated that its synthesis responded to the severity of photoinhibition. Height growth and levels of mortality indicated that cold-induced photoinhibition, and not frost tolerance alone, determines the range of environments where E. globulus can be successfully planted. In contrast, the tolerance of E. nitens seedlings to cold-induced photoinhibition may be a factor in the demonstrated success of this species as a high-altitude plantation species.