title: Bud break responds more strongly to daytime than night-time temperature under asymmetric experimental warming.
abstract: 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.
authors.affiliation: Département des Sciences Fondamentales, Université du Québec à Chicoutimi, 555 boulevard de l'Université, Chicoutimi, QC, G7H 2B1, Canada.|Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, 723 Xingke Road, Tianhe District, Guangzhou, 510650, China.|Provincial Key Laboratory of Applied Botany, South China Botanical Garden, Chinese Academy of Sciences, 723 Xingke Road, Tianhe District, Guangzhou, 510650, China.
authors.forename: Sergio
authors.initials: S
authors.lastname: Rossi
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 rue du P.E.P.S., Québec, QC, G1V4C7, Canada.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Isabel
mesh_terms: D002170:Canada; D002980:Climate; D057232:Global Warming; D028222:Picea / Q000254:growth & development*; D012621:Seasons; D013696:Temperature
keywords: 
  Picea mariana
  ; bud burst; climate change; ecotype; maximum temperature; minimum temperature; phenology