Concordance of long‐term shifts with climate warming varies among phenological events and herbaceous species

Abstract

Many temperate herbs now flower earlier than a few decades ago. Little is known about other phenological events, despite the importance of life history integration for plant fitness. This study addresses the hypothesis that temporal shifts of multiple phenological events in herbs are concordant with temporal changes in weather. Explicitly showing that changes in timing of annual life cycle events are correlated with changes in weather-predicting variables provides support for the hypothesis that a phenological shift is concordant with climate change. Observations of six phenological events and five phenophases were made yearround for 25 yr for herb species in a deciduous forest fragment, Trelease Woods in Illinois, USA. Dates for 43 species were analyzed by linear mixed-effects models for events and phenophases and were compared to weather data from a nearby station. For early species, emergence was delayed by 1.5 d/decade, while end expansion advanced by 3.8 d/decade and begin dormancy advanced by 2.5 d/decade. For late species, end expansion advanced by 6.7 d/decade, while begin senescence delayed by 17.7 d/decade. Begin flowering and end flowering advanced similarly for both seasonal groups, at 3.8 to 4.2 d/decade. Some events showed no temporal change. Species differed greatly in the degree or direction of change, related to seasonality of event or length of phase. Overall, for a given species, most events are advancing (68.4%) and most durations are shortening (74.4%). In 12 of 13 cases, inter-annual variation in event date was predicted by a temperature-event-season combination variable, but in only six cases did both event date shift and weather variable warm through time. This finding supports the hypothesis that climate change is associated with changes in some, but not all, phenological events. This first long-term, multi-phase study of a community of temperate herb species indicates little temporal coherence of responses of multiple phases. Changes in date are event specific, phase specific, and species specific. This complexity of responses among species and uneven responses within a species' integrated annual cycle events has implications for evolutionary responses and more immediate interactions among plant, animal, and microbe species in this community.

Long‐term surveys support declines in early season forest plants used by bumblebees

“…The declining abundance of G. maculatum has been documented in other studies in Illinois (Augspurger & Buck, 2017;Burkle et al, 2013) and New York (Greller et al, 1990). Notably, the understorey herb flowering in central Illinois has advanced by >1 week in the last 20 years (Augspurger & Zaya, 2020), compounding the effects of resource loss by potentially increasing the asynchrony between plant flowering and pollinator emergence. Except for the most recent sampling period, the loss of resources in forests appears to be driven by a decline in plant cover (Figure 2a), not species richness (Figure 2b), consistent with evidence that species richness of plant communities lags behind trends in abundance (Price et al, 2018).…”

Snow melt timing acts independently and in conjunction with temperature accumulation to drive subalpine plant phenology

“…Temperature accumulation was the sole cue of phenological changes in only two out of nine cases (Figure 4: timing and duration of fruiting in Delphinium ), and temperature accumulation worked in tandem with other drivers in an additional two cases (Figure 4: timing of flowering in Delphinium and Valeriana ). Temperature accumulation as a phenological cue may be less important in ecosystems with seasonal snow cover compared to those where temperature is the main climate driver (Augspurger & Zaya, 2020).…”

“…Here we study the timing, duration, and success of flowering and fruiting in three subalpine wildflower species. The timing and length of events such as flowering and fruiting are important because they can affect interactions with pollinators, herbivores, other plants (via co‐flowering overlap), and season length (Augspurger & Zaya, 2020; Forrest et al, 2010; Inouye et al, 2003; Li et al, 2016). We factorially crossed warming with early snow melt within a subalpine plant community in the Colorado Rocky Mountains to answer the following questions.…”

Siberian plants shift their phenology in response to climate change

“…Our current understanding of how phenology is responding to climate change is based nearly exclusively on data from temperate Europe and North America, where most phenological studies have been conducted (Augspurger & Zaya, 2020; König et al, 2018; Menzel et al, 2020). The few existing regional studies in other biomes (Bjorkman et al, 2015; Mo et al, 2017; Park & Schwartz, 2015) suggest that the magnitude and, in some cases, even the direction of phenological shifts may depend on plant adaptations to regional and local climatic parameters.…”

“…advance in leaf out and delay in senescence), with some species showing divergent patterns, because mechanisms underlying phenological timing (e.g. responsiveness to climate; Badeck et al, 2004; Basler & Körner, 2012; Rathcke & Lacey, 1985) are likely to differ from species to species (Augspurger & Zaya, 2020; Ovaskainen et al, 2013; Panchen & Gorelick, 2017; Sherry et al, 2007). For the same reason, we also expect the species with advanced leaf out, flowering and fruiting, and delayed senescence to differ in the magnitude of shifts over time, among these events. Are these species‐specific phenological responses related to plant growth forms (i.e.…”