Winter frost resistance of Pinus cembra measured in situ at the alpine timberline as affected by temperature conditions

Abstract

Winter frost resistance (WFR), midwinter frost hardening and frost dehardening potential of Pinus cembra L. were determined in situ by means of a novel low-temperature freezing system at the alpine timberline ecotone (1950m a.s.l., Mt Patscherkofel, Innsbruck, Austria). In situ liquid nitrogen (LN 2)-quenching experiments should check whether maximum WFR of P. cembra belonging to the frost hardiest conifer group, being classified in US Department of Agriculture climatic zone 1, suffices to survive dipping into LN 2 (-196°C). Viability was assessed in a field re-growth test. Maximum in situ WFR (LT50) of leaves was