Plant phenological responses to experimental warming—A synthesis

Abstract

Although there is abundant evidence that plant phenology is shifting with climatic warming, the magnitude and direction of these shifts can depend on the environmental context, plant species, and even the specific phenophase of study. These disparities have resulted in difficulties predicting future phenological shifts, detecting phenological mismatches and identifying other ecological consequences. Experimental warming studies are uniquely poised to help us understand how climate warming will impact plant phenology, and meta‐analyses allow us to expose broader trends from individual studies. Here, we review 70 studies comprised 1226 observations of plant phenology under experimental warming. We find that plants are advancing their early‐season phenophases (bud break, leaf‐out, and flowering) in response to warming while marginally delaying their late‐season phenophases (leaf coloration, leaf fall, and senescence). We find consistency in the magnitude of phenological shifts across latitude, elevation, and habitat types, whereas the effect of warming on nonnative annual plants is two times larger than the effect of warming on native perennial plants. Encouragingly for researchers, plant phenological responses were generally consistent across a variety of experimental warming methods. However, we found numerous gaps in the experimental warming literature, limiting our ability to predict the effects of warming on phenological shifts. In particular, studies outside of temperate ecosystems in the Northern Hemisphere, or those that focused on late‐season phenophases, annual plants, nonnative plants, or woody plants and grasses, were underrepresented in our data set. Future experimental warming studies could further refine our understanding of phenological responses to warming by setting up experiments outside of traditionally studied biogeographic zones and measuring multiple plant phenophases (especially late‐season phenophases) across species of varying origin, growth form, and life cycle.

Drivers of phenological changes in southern Europe

“…Temperature is regarded as the main driver of the onset of phenological phases (Cleland et al 2007;Sanz 2005, 2010). Increasing temperatures usually cause strong advances in spring during leaf unfolding and flowering, while advances are less pronounced during fruiting and a small delay of senescence occurs (Gordo and Sanz 2009;Menzel et al 2020;Penuelas et al 2002;Piao et al 2019;Stuble et al 2021). This is in line with our findings indicating a negative correlation between temperature and the onset of leaf unfolding, flowering and fruiting.…”

“…Global warming particularly affects early phenophases, while the influence on later phases is less pronounced, sometimes even undetectable and generally a higher variance is observed for these phases (Piao et al 2019;Spano et al 2013;Sparks and Menzel 2002;Stuble et al 2021). This can potentially be attributed to the interplay of several factors which play a role here (Gallinat et al 2015).…”

Proposal and extensive test of a calibration protocol for crop phenology models

“…Plant phenology is a major aspect of plant response to environment, and a major determinant of plant response to climate change. This includes phenology of natural vegetation, which is a dominant aspect of plant ecology (Cleland et al, 2007) and has been shown to be affected by warming (Menzel et al, 2020; Piao et al, 2019; Stuble et al, 2021) and phenology of cultivated crops. For the latter, phenology must be taken into account for crop management (Sisheber et al, 2022), choice of cultivar or cultivar characteristics adapted to a particular region (Zhang et al, 2022) and for evaluating the impact of climate change on crop production (Rezaei et al, 2018).…”

Ecosystems at Glacier Margins Can Serve as Climate‐Change Laboratories

“…Because of these unprecedented changes, case studies that describe how this accelerated warming event will impact Earth's ecosystems have become quite valuable. Much of the ecological research on this topic has focused on plot‐level warming experiments (Stuble et al., 2021), but this approach is logistically intensive and inherently restricted in spatial and temporal scope. Currently, environmental scientists lack real‐world bioclimatic situations for conducting retrospective studies of how ecological communities responded to climate changes that occurred in the recent past (the last several centuries) at rates and with magnitudes similar to those predicted for the current century.…”