Contrasting survival strategies for seedlings of two northern conifer species to extreme droughts and floods.

This article investigates how lowland northern white-cedar (Thuja occidentalis L.) and balsam fir (Abies balsamea (L.) Mill.) seedlings respond to experimental drought and flood stress of varying durations. The study found that cedar employs a strategy of stress resistance and resilience, surviving moderate drought and flooding with partial canopy browning and recovering growth, whereas fir tends to avoid drought and flood stress, exhibiting threshold responses that lead to either survival with minimal damage or mortality. Cedar experienced more rapid water use and lower water potentials during drought but tolerated these conditions better than fir, which maintained higher water potentials through conservative water use. Flooding caused higher mortality in fir, with 50% mortality reached after 7.4 days of flooding compared to 23.1 days for cedar, indicating greater flood tolerance in cedar. These findings highlight species-specific hydraulic and physiological traits that influence regeneration and survival under variable moisture regimes, informing conservation and management of lowland cedar-fir forests amid climate change.