Tree Maladaptation Under Mid-Latitude Early Spring Warming and Late Cold Spell: Implications for Assisted Migration

Area of Science:

• Forestry
• Ecology
• Climate Change Biology

Background:

• Global warming trends suggest longer growing seasons but also increased extreme climate events like late-spring frosts.
• Mid-latitude forests face heightened risks from intensified climate variability, impacting tree phenology and survival.
• Intraspecific variation in frost tolerance and local adaptation are poorly understood in the context of climate change.

Purpose of the Study:

• To assess frost damage in white spruce (Picea glauca) seed sources during an extreme late-spring frost event.
• To investigate the role of local adaptation and seed origin climate on frost tolerance in assisted migration trials.
• To provide recommendations for managing plantation productivity amidst increasing climate instability.

Main Methods:

• Evaluated frost damage on 5,376 white spruce trees from various seed sources across three bioclimatic zones in Quebec, Canada.
• Assessed damage severity following a late-spring frost after an early spring warming advanced bud flush.
• Analyzed frost damage rates, severity, and apical growth cancellation in relation to site, seed source latitude, and tree height.

Main Results:

• A near-total frost damage rate (99.8%) was observed across all sites and seed sources.
• Frost damage severity varied by site, with northern sites experiencing higher damage than central and southern sites.
• Damage severity was inversely related to tree height, and apical growth cancellation differed significantly among sites but not seed sources.

Conclusions:

• White spruce seed sources, including local ones, exhibited maladaptation to extreme spring frost events, challenging assisted migration strategies.
• Lack of local adaptation to climate instability poses significant risks to the productivity of spruce plantations.
• Recommendations are provided for seed transfer models and plantation management to mitigate losses from unpredictable spring climate anomalies.