Experimental studies on the drought, waterlogging, and frost tolerance of Ascarina lucida Hook. f (Chloranthaceae) seedlings

Ascarina lucida Hook.f. (Chloranthaceae) is a small tree species endemic to New Zealand. The distribution of A. lucida suggests an inability to survive severe frosts or droughts. Therefore, peaks in the abundance of A. lucida in pollen records have usually been interpreted as indicating periods of mild, moist climates. The environmental tolerance of A. lucida seedlings to climatic extremes was experimentally tested by exposing seedlings to frost, drought, and waterlogged soil conditions. This research confirms the sensitivity of A. lucida to climatic extremes. Ascarina lucida has a similar drought tolerance to Coprosma grandifolia, a species known to be drought intolerant; seedlings had considerable tolerance of waterlogged soils, but exhibited reduced root weights when severely waterlogged; and a frost of -2°C resulted in complete mortality for seedlings sourced from lowland and submontane populations. Peaks in the abundance of A. lucida can be attributed, at least in part, to periods of warm, wet climate. However, the early successional nature of this species also suggests that disturbance regime plays an important role in regulating its distribution and abundance.