Extreme temperatures help in identifying thresholds in phenological responses

Aim: To investigate temperature drivers of the spring phenology of 12 flowering events and 6 leafing events. Boreal phenology has previously exhibited only a modest response to temperature but record breaking temperatures in March 2020 led to some extreme phenological timing and provided the opportunity for a more rigorous look at the nature and complexity of the relationship between temperature and phenology.

Location: Boreal habitat in the Tatarstan Republic of Russia

Time period: 1989-2020

Major taxa studied: 18 plant species

Methods: We examined for changes over time in the timing of phenological events and the relationship with temperature drivers using a range of regression techniques. Extreme temperatures caused some extreme phenology and visually suggested temperature thresholds which were investigated using segmented regression (broken stick models). The performance of these models was subsequently compared to more complex alternatives based on accumulated daily tem...