Potential of two tree shelters to aid the early establishment and growth of three Australian tree species on the Darling Downs, south-east Queensland

Summary

The ability of the commercial tree shelter Growtube® and a perforated sheet metal shelter (Mauri) to improve the growth and survival of seedlings of Casuarina cristata, Eucalyptus moluccana and Melaleuca linariifolia was tested on the Darling Downs in south-east Queensland. The 0.9 m high tree shelters were removed after 2 years and at this time tree survival was unaffected by shelter type for all 3 species. Over a 44-month period, neither shelter improved the height growth of C. cristata or E. moluccana. Growtubes significantly (P < 0.05) increased the height of M. linariifolia and, at the time of shelter removal, trees in Growtubes were 23% taller than control trees. Differences in height decreased after the Growtubes were removed and 18 months later were no longer significant (P > 0.05). The early deterioration of the growtubes would have decreased their ability to create a beneficial microclimate, leading to the absence of any height increases for C. cristata and E. moluccana and small and non-persistent height increases for M. linariifolia. Thus, Growtubes were considered unsuitable for the environment in which they were tested. The cost of establishing a tree without a tree shelter, with a Mauri tree shelter and with a Growtube tree shelter was estimated to be $1.82, $3.08 and $5.12, respectively. During the first two years, a further $1.79 per tree was spent on materials used to replace damaged Growtubes.