Frost hardiness of Nothofagus procera and Nothofagus obliqua in Britain

Abstract

The frost hardiness of four seedlots of Nothofagus proccra and six seedlots of Nothofagus obliqua was measured experimentally during three winters. Shoots were taken from saplings growing at the Bush Estate in Scotland. All seedlots set buds in late September, hardened very slowly in the autumn, were damaged to some extent by temperatures below -14°C in mid-winter, and dehardened during frosty weather in February/March prior to budburst in mid to late April. The range of mid-winter temperatures giving 0%, 50% and 100% kill (LT0, LT50 and LT100) were 8-14°C, 13%20°C and 14-22°C, respectively. By contrast, British Fagus sylvatica hardened off rapidly in September, was undamaged by frosts well below -20°C in mid-winter, and did not deharden until late April, prior to budburst at the end of May.Nothofagus seedlots from Nuble in Chile (the most Equatorial source) were the most frost susceptible: unfortunately, seed of this origin was supplied to many British nurseries between 1976 and 1W9. Seedlots from Neuquen in Argentina, and from mature trees of Malleco (Chile) origin growing in Britain, were the most host hardy. N. procera tended to be hardier than N. obliqua, and the trees became hardier with age.Past temperature records for Britain suggested that all the Nothofagus seedlots had a high risk of suffering severe frost damage at least once during a timkr rotation in all but mild coastal regions. Spring and autumn frosts may be more damaging than winter frosts. However, if it were possible to select individuals within populations that were 3-6°C more frost hardy than the population means, such trees would be sufficiently hardy to avoid frost damage in most lowland regions. © 1986 Oxford University Press.