Comparative Responses to Temperature of the Major Canopy Species of Tasmanian Cool Temperate Rainforest and Their Ecological Significance .I. Foliar Frost-Resistance

Abstract

Foliar frost resistance has been determined using the conductivity method in the rainforest canopy species Nothofagus cunninghamii (Hook.) Oerst., Atherosperma moschatum Labill., Eucryphia lucida (Labill.) Bail]., Phyllocladus aspleniifolius (Labill.) Hook. f. and Athrotaxis selaginoides D. Don in glasshouse experiments and seasonal measurements at Mt Field National Park, Tasmania. Some determinations of frost resistance were also made in Lagarostrobos franklinii (Hook. f.) C. J. Quinn and Nothofagus gunnii (Hook. f.) Oerst. The general trend of foliar frost resistance is in the order A. moschatum < P. aspleniifolius < E. lucida < A. selaginoides < N. cunninghamii. This is consistent with the infrequency of A. moschatum at the higher altitudes, its occupation of the lower canopy in old rainforest and its infrequent establishment on exposed sites. P. aspleniifolius is more common at high altitudes than E. lucida but has a lower foliar frost resistance. A. selaginoides and N. cunninghamii have a high frost resistance consistent with their occurrence at high altitudes and on exposed sites. However, A. selaginoides does not have the superior frost resistance predicted by its occurrence at higher altitudes than N. cunninghamii. The leaves of N. gunnii (winter-deciduous) have a low summer frost resistance relative to the co-occurring evergreen species A. selaginoides and N. cunninghamii. L. franklinii has a higher frost resistance than predicted from its infrequent occurrence at high altitudes.