Vegetation Mortality in the Kaimai Ranges, North Island, New Zealand

Abstract

Areas of vegetation mortality have been recognized in the upland forests of the Kaimai Ranges, North Island, New Zealand. The mortality is not confined to any particular vegetation type, but occurs above a critical altitude that differs at different points along the ranges. The mortality is episodic and has occurred at intervals over a period of several hundred years, with severe droughts implicated as the causative factor. The numerous mortality events have resulted in forests of many age classes where trees do not reach potential maturity. The coincidence between the occurrence of cloud and the mortality is suggested to make the forests drought-sensitive through poorly developed root systems caused by prolonged soil waterlogging.