Canadian Forest Service Publications

Bud break responds more strongly to daytime than night-time temperature under asymmetric experimental warming. 2017. Rossi, S.; Isabel, N. Global Change Biol. 23 : 446-454.

Year: 2017

Issued by: Laurentian Forestry Centre

Catalog ID: 37706

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: 10.1111/gcb.13360

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Global warming is diurnally asymmetric, leading to a less cold, rather than warmer, climate. We investigated the effects of asymmetric experimental warming on plant phenology by testing the hypothesis that daytime warming is more effective in advancing bud break than night-time warming. Bud break was monitored daily in Picea mariana seedlings belonging to 20 provenances from Eastern Canada and subjected to daytime and night-time warming in growth chambers at temperatures varying between 8 and 16 °C. The higher advancements of bud break and shorter times required to complete the phenological phases occurred with daytime warming. Seedlings responded to night-time warming, but still with less advancement of bud break than under daytime warming. No advancement was observed when night-time warming was associated with a daytime cooling. The effect of the treatments was uniform across provenances. Our observations realized under controlled conditions allowed to experimentally demonstrate that bud break can advance under night-time warming, but to a lesser extent than under daytime warming. Prediction models using daily timescales could neglect the diverging influence of asymmetric warming and should be recalibrated for higher temporal resolutions.

Plain Language Summary

In this study, the researchers confirmed the hypothesis that the budding process in black spruce is more greatly enhanced by a rise in daytime temperatures than a rise in nighttime temperatures.

The increase in spring temperatures caused by climate change, accelerates budbreak in black spruce. This temperature increase is asymmetrical in that minimum night temperatures have increased two-fold compared with maximum day temperatures; therefore, the overall climate is warmer.

Current budbreak forecasting models do not take into account this temperature asymmetry. These models should be recalibrated in order to improve their accuracy and results.