COMPARISON OF FROST TOLERANCE OF NOTHOFAGUS-SOLANDRI VAR CLIFFORTIOIDES (HOOK F) POOLE AND NOTHOFAGUS-MENZIESII (HOOK F) OERST

Frost tolerance was investigated in both cold-hardened and actively gr owing seedlings of Nothofagus solandri var. cliffortioides and Nothofa gus menziesii in New Zealand. Seedlings of the two species from the sa me geographical origins showed similar tolerances to simulated mid win ter and summer frosts when grown in a common environment. The maximum frost hardiness (LT(50)) ranged from -9.0 +/- 0.8 to -12.1 +/- 0.6 deg rees C in N. solandri, and from -10.0 +/- 0.7 to -12.4 +/- 0.1 degrees C in N. menziesii. Both species exhibited provenance variations in fr ost tolerance that corresponded with variation in long-term means of a nnual minimum temperature and frost days per annum of the seed origins . It is suggested that low temperature may not be a key environmental factor in differentiating the presence of the two species at upper tim berlines in New Zealand.