Increased exposure to chilling advances the time to budburst in North American tree species

Abstract

The phenology of trees is highly susceptible to changing global temperatures. Leaf budburst advances with increasing spring temperatures, but can also be delayed when warmer winters reduce chilling exposure. Results from long-term observations show that increasing temperatures have triggered advanced budburst in the past decades, but some studies also show that budburst advance has slowed recently. Here, we conducted an experiment with five temperate deciduous tree species (Acer rubrum L., Larix laricina (Du Rois) K. Koch, Populus tremuloides Michx., Quercus ellipsoidalis E. j. Hill, Betula papyrifera Marsh.) and one invasive species (Rhamnus cathartica L.) in Minnesota, USA, to assess the impact of chilling on the timing of leaf budburst. We collected twigs over two winter seasons (2011/2012 and 2012/2013) on a biweekly basis and exposed them to spring-like temperatures of 21 °C/16 °C day and night, long day photoperiod (16 h). We found a significant relationship of advanced budbreak with increased chilling for all species tested (P < 0.001) and significant differences in the timing to budburst among all species (P < 0.001). Acer rubrum responded strongly to chilling, showing a very steep linear decline in days to budburst with increased exposure to chilling. On the other end of the spectrum, L. laricina responded least to increases in chilling. These results suggest that rising global temperatures will likely have diverse impacts on tree species with potential implications for species interactions such as competition.

Ecological genomics of variation in bud‐break phenology and mechanisms of response to climate warming in Populus trichocarpa

“…These results are not completely unexpected (e.g. Nanninga et al ., ) and poplars tend to have strong responses to warm temperatures, acting as ‘opportunistic’ species (Caffarra & Donnelly, ). Greater forcing temperature also strongly reduced genotypic differences in timing of bud‐break due to the steep trajectory of heat sum accumulation (Fashler & El‐Kassaby, ).…”

“…Picea , Vitis , Quercus , Populus , Salix , Betula ) have shown that the timing of bud‐break also is strongly influenced by spring temperatures, as a certain heat sum is needed to trigger growth (Heide, ; Saxe et al ., ; Caffarra & Donnelly, ). For woody plants in temperate and boreal environments, it is critical to understand how modified temperatures stemming from climate change are expected to affect both overwintering and spring flush‐out processes (Arora et al ., ; Nanninga et al ., ). Although plasticity has broadly been observed through warmer temperatures advancing the spring date of bud‐break (Menzel & Fabian, ; Wolkovich et al ., ), the ability of different species (or populations) to respond to fluctuating conditions may be determined by the complexity of the genetic architecture underlying spring bud‐break.…”

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“…Additionally we found that increased exposure to chilling temperatures led to less forcing temperatures required prior to reproductive budburst, similar to other studies of vegetative and reproductive phenology (Harrington, Gould & St.Clair, 2010;Nanninga et al, 2017;Prevéy, Harrington & St. Clair, 2018). Thus, even if winter temperatures become warmer in the future, increasing temperatures in spring may still result in advancing budburst dates.…”

Effectiveness of winter temperatures for satisfying chilling requirements for reproductive budburst of red alder (Alnus rubra)

“…Multiple studies indicate that exposure to increased chilling temperatures reduces the amount of forcing temperatures needed for reproductive budburst in spring (Harrington, Gould & St.Clair, 2010; Nanninga et al, 2017). Thus, a "possibility-line" can be modeled that predicts the amount of forcing needed for reproductive budburst based on the amount of chilling a tree has received (Harrington, Gould & St.Clair, 2010;Prevéy, Harrington & St. Clair, 2018).…”