Regeneration status of some New Zealand conifers, with particular reference to Libocedrus bidwillii in Westland National Park

Abstract

High-altitude stands of Libocedrus bidwillii in Westland National Park are deficient in trees less than 30 cm in diameter, and extrapolation from a limited number of increment corings indicates that this results from failure to regenerate after about 1600 A.D. Similar degeneration of stands has been reported from other localities.

The paper also discusses the recent dying out of L. bidwillii trees on Banks Peninsula, and of Podocarpus hallii through much of Westland. For Dacrydium cupressinum the deficiency in smaller-size classes characteristic of certain sites was confirmed in Westland National Park.

Successional processes or death through pathogens and other causes can account for imbalanced representation of size classes in many stands of conifers, but there are other stands, especially on hill slopes, where paucity of young plants cannot be readily explained in these terms. It is concluded that there is prima facie evidence for a period of reduced regeneration of some native conifers on sensitive sites coinciding with cooler temperatures during recent centuries.