Ecology of Podocarpus hallii in Central Otago, New Zealand

Abstract

There appears to be no environmental stress severely limiting the growth of established trees of Podocarpus hallii on the Pisa Range in Central Otago. In the sparse stands studied on the Range, trees grow best at their lower limit and, although initiating shoot growth later than the same species in a moist forest environment, achieve comparable though erratic shoot extension for the season. Temperature records during two years indicate that the mean summer isotherm at the trees' upper limit is considerably higher than that recorded for tree lines, either elsewhere in New Zealand or abroad. Since P. hallii does not appear to attain the climatically imposed limits which doubtless exist in the region, it is hardly surprising that the species has proved to be a poor dendroclimatic indicator. Periodic fires probably confine the forest and woodland to their present limits. Extensive log remains and buried charcoals indicate that a mixed forest containing P. hallii, Nothofagus menziesii, and several other species was present up to about the twelfth century A.D. Despite contrary suggestions in the literature, several isolated stands of silver beech which are growing and regenerating well and invading grassland, together with the presence of plentiful totara seedlings, and locally even young trees, suggest that this part of Central Otago is still capable of supporting indigenous forest, given sufficient freedom from fire.