Daylength helps temperate deciduous trees to leaf-out at the optimal time

Area of Science:

• Ecology
• Phenology
• Climate Change Biology

Background:

• Global warming advances spring leaf-out in temperate deciduous trees.
• The roles of temperature and daylength in this response are not fully understood.
• Accurate models are crucial for predicting forest carbon/energy balances and climate feedbacks.

Purpose of the Study:

• To investigate the interactive effects of daylength and temperature on spring leaf-out timing.
• To understand how these factors influence tree phenology in response to climate change.
• To provide data for improving Earth system models.

Main Methods:

• Analyzed phenological data from six tree species across Europe (2,377 sites).
• Utilized over 30 years of observational data from the Pan European Phenology Network (www.pep725.eu).
• Assessed the relationship between daylength, temperature, chilling, and leaf-out timing.

Main Results:

• Daylength negatively correlates with the heat requirement for leaf-out, independent of chilling.
• In warm springs, shorter days increase the heat requirement, mitigating early leaf-out.
• In cold springs, longer days decrease the heat requirement, preventing delayed leaf-out.

Conclusions:

• Daylength plays a significant, widespread role in modulating the temperature sensitivity of leaf-out phenology in temperate deciduous trees.
• This interaction provides a natural buffer against frost damage from early budding.
• Findings are essential for refining climate models and predicting forest responses to global warming.