Chilling outweighs photoperiod in preventing precocious spring development.

Area of Science:

• Plant science
• Ecology
• Forestry

Background:

• Spring phenology is influenced by temperature, but winter chilling and photoperiod also play roles.
• The interplay and relative importance of chilling, photoperiod, and temperature on plant development remain unclear.

Purpose of the Study:

• To investigate the effects of chilling and photoperiod on the spring phenology of 36 woody species.
• To test hypotheses on how species traits influence responses to chilling and photoperiod.
• To elucidate the interactions between chilling, photoperiod, and temperature in regulating budburst.

Main Methods:

• A multispecies climate chamber experiment was conducted.
• The study tested the impact of varying chilling durations and photoperiods on budburst timing.
• Species traits like successional strategy and native climate were analyzed in relation to phenological responses.

Main Results:

• Increased chilling length significantly advanced budburst for most species, with a greater effect than photoperiod.
• Photoperiod advanced budburst in one-third of species, but effects were generally minor and dependent on sufficient chilling.
• Climax species exhibited higher chilling and forcing requirements than pioneer species; invasive species' requirements matched natives.

Conclusions:

• Chilling requirements are a critical factor in spring phenology, more so than photoperiod.
• Warming winters may favor species with lower chilling needs, like pioneer and invasive species, potentially altering forest composition.
• Failure to meet chilling requirements can significantly delay budburst and alter the sequence of species' spring development.