Seasonal frost hardiness ofNothofagus solandriseedlings from two altitudinally diverse sites in Canterbury, New Zealand

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Abstract
Seasonal variation in frost hardiness was evaluated in beech (Nothofagus solandri) seedlings from sites in North Canterbury at 460 m near the lower altitude limit, and at 1100 m near timberline. Both 1-. 2-year old seedlings were lifted on five occasions through the year and exposed to a range of controlled frosts. Visual frost damage was measured four weeks later as the percentage of foliage damaged, and frost hardiness determined as that temperature causing an average of 50% foliage damage. Low-altitude seedlings achieved a maximum midwinter frost hardiness of-4.5°C and about-l°C in summer whereas the high-altitude seedlings were respectively hardy to -11.5. -3.5°C. From a conditioning experiment, and in keeping with the differences in seasonal variation in frost hardiness high-altitude seedlings apparently have an inherently greater capacity to develop frost hardiness than low-altitude seedlings. Consideration of temperatures at timberline indicated that frost hardiness of seedlings would be regularly exceeded by the frost temperatures particularly in spring and early summer. This supports earlier reports that altitudinal variations in mountain beech timberlines mainly reflect frost hardiness limits of seedlings.