Disorder or a new order: how climate change affects phenological variability

Abstract

Advancing spring phenology is a well-documented consequence of anthropogenic climate change, but it is not well understood how climate change will affect the variability of phenology year-to-year. Species' phenological timings reflect adaptation to a broad suite of abiotic needs (e.g. thermal energy) and biotic interactions (e.g. predation and pollination), and changes in patterns of variability may disrupt those adaptations and interactions. Here, we present a geographically and taxonomically broad analysis of phenological shifts, temperature sensitivity, and changes in inter-annual variance encompassing nearly 10,000 long-term phenology time-series representing over 1,000 species across much of the northern hemisphere. We show that early-season species in colder and less seasonal regions were the most sensitive to temperature change and had the least variable phenologies. The timings of leaf-out, flowering, insect first-occurrence, and bird arrival have all shifted earlier and tend to be less variable in warmer years. This has led leaf-out and flower phenology to become moderately but significantly less variable over time. These simultaneous changes in phenological averages and the variation around them have the potential to influence mismatches among interacting species that are difficult to anticipate if shifts in average are studied in isolation.

Stage-mediated priority effects and season lengths shape long-term competition dynamics

“…Temporal variation can play an important role in shaping the outcome of species interactions (Chesson 2000; Adler et al 2006; Barabás et al 2018; Rudolf 2019). In nature, relative arrival time fluctuates across seasons, and this fluctuation of phenology could be increasing with climate change (Parmesan 2006; Diez et al 2012; Post 2013; Wolkovich et al 2014; Pearse et al 2017; but see Stemkovski et al 2022). Our results indicate that seasonal fluctuation in relative arrival time could change competition outcomes, especially when trait-mediated mechanisms are present: periodic arrival times enable either species to harness early arriver competition advantage in alternating seasons, contributing to both equalizing and stabilizing mechanisms in the presence of stage-mediated interspecific competition.…”

Is winter coming? Minor effect of the onset of chilling accumulation on the prediction of endodormancy release and budbreak

“…Interestingly, in the future climate, the annual variability of D BB is expected to be lower. The trend toward more uniform phenology in warm years has already been observed in recent decades for budbreak (Caffarra et al, 2014;Vitasse et al, 2018) and other phenological stages (Stemkovski et al, 2021). It is likely that the response to warm temperature is somewhat saturated with developmental functions reaching a plateau (Caffarra, Donnelly, Chuine, & Jones, 2011a) and eventually declining at even warmer temperature (Schoolfield et al, 1981).…”