Slow Recovery of Beilschmiedia tawa after Severe Frosts in Inland Taranaki, New Zealand

Extensive damage to native forest followed a prolonged period of severe frosts (12 days; lowest minimum -15°C) in inland Taranaki. In Tangarakau Scenic Reserve, damage was most severe near the boundary between bush and pasture. Some species such as rimu (Dacrydium cupressinum) and miro (Podocarpus ferrugineus) were not affected; others like mamaku (Cyalhea medullaris) recovered within a year. Mahoe (Melicytus ramiflorus) took more than 14 months to recover. Tawa (Beilschmiedia tawa) was the most seriously affected; many trees had most of their leaves killed. By December 1986 (53 months after the frost) affected trees had bare, dead upper branches with new sprouts arising from lower on the tree. Frost-damaged trees produced little radial increment for several years after the frost. The slow recovery of tawa shows that occasional rare events may have an important role in determining forest composition, and that a small change in the frequency of such events could alter the balance between species.