Shifts in flowering phenology reshape a subalpine plant community

Abstract

Phenology-the timing of biological events-is highly sensitive to climate change. However, our general understanding of how phenology responds to climate change is based almost solely on incomplete assessments of phenology (such as first date of flowering) rather than on entire phenological distributions. Using a uniquely comprehensive 39-y flowering phenology dataset from the Colorado Rocky Mountains that contains more than 2 million flower counts, we reveal a diversity of species-level phenological shifts that bring into question the accuracy of previous estimates of long-term phenological change. For 60 species, we show that first, peak, and last flowering rarely shift uniformly and instead usually shift independently of one another, resulting in a diversity of phenological changes through time. Shifts in the timing of first flowering on average overestimate the magnitude of shifts in the timing of peak flowering, fail to predict shifts in the timing of last flowering, and underrepresent the number of species changing phenology in this plant community. Ultimately, this diversity of species-level phenological shifts contributes to altered coflowering patterns within the community, a redistribution of floral abundance across the season, and an expansion of the flowering season by more than I mo during the course of our study period. These results demonstrate the substantial reshaping of ecological communities that can be attributed to shifts in phenology.growing season | no-analogue community | phenological mismatch | phenology curve | species interactions P henology, the timing of biological events, is intimately tied to the reproduction and survival of organisms (1). Phenological events generally are occurring earlier in temperate environments in accordance with climate change, although several recent studies have emphasized species-specificity in the direction and magnitude of change (2-5). The great majority of these longterm datasets contain a single measure of phenology for individual species, most often the first day on which a biological event is observed (i.e., "phenological firsts" such as first flowering) (Fig. 1A). In addition to phenological firsts, basic components of an entire phenological response include the timing of the ending of a biological event and details of intermediate stages, such as the timing and magnitude of peak abundance or activity (Fig. 1A). Given that phenological firsts represent the early tail of a population-level response, most assessments of phenological change to date may provide an incomplete view of the magnitude of change, the number of responsive species, and how species-level shifts contribute to change at higher levels of biological organization.We have amassed a unique long-term record of flowering phenology that allows us to investigate complete phenological responses for a plant community. Over a 39-y period , we have sampled a montane site (2,900 m elevation) in Colorado, USA, counting the total number of flowers of 121 plant species across a series of permanent...

Impact of Climate Change on Flowering and Fruiting Times of Nunavut Arctic Plants

“…I found a wide range of flowering time temperature-sensitivity among the seven species, with mountain avens being the most temperature-sensitive. The diversity of flowering time temperature-sensitivity in my elevation gradient study concurs with my herbarium specimen study findings and further supports my hypothesis of altered Arctic ecological community structure with climate change (CaraDonna et al, 2014). As with the Tanquary Fiord long-term phenology monitoring study, I found that the flowering time temperature-sensitivity of mountain avens was twice that of purple saxifrage, and that seed dispersal times of mountain avens showed temperature-sensitivity, while those of purple saxifrage did not.…”

“…For each species separately, I ran a regression analysis of the flowering time records with the associated June mean temperature over the last 70 years (1946 -2015) to determine the flowering time temperature-sensitivity of each of the 23 plant species. I found great diversity in the flowering time temperature-sensitivity of the 23 species (Panchen and Gorelick, in press), and I suggested that the interspecific variation in responsiveness to climate change could lead to altered Arctic ecological community competition, pollinator interactions, and ultimately Arctic ecological community composition (Hegland et al, 2009;McKinney et al, 2012;CaraDonna et al, 2014). The flowering time temperature-sensitivity also varied within a species: for example, plants from the Nunavut archipelago (includes the Boothia and Melville Peninsulas, as well as islands north of Hudson Bay) were more temperature-sensitive than their conspecifics from mainland Nunavut farther south (includes islands with similar latitude and climate), and within the Nunavut archipelago, plants from Baffin Island were more temperature-sensitive than their conspecifics from Ellesmere Island.…”

Effects of Road Dust on the Pollination and Reproduction of Wildflowers

“…During the peak summer season in July, which corresponds roughly to the peak in density of wildflowers of all species (CaraDonna et al 2014), the counts must greatly exceed these averages, since the averages include periods of much lower use in spring and autumn. A noticeable plume of dust trails each vehicle ( fig.…”

Relatively stable response of fruiting stage to warming and cooling relative to other phenological events

“…2011;Cook et al 2012;Wolkovich et al 2012;Wang et al 2014a). Plants may face trade-offs between the adjustment of one phenological event to temperature and the timing of subsequent events during the growing season (Post et al 2008;Sherry et al 2007Sherry et al , 2011 Haggerty and Galloway 2011; Dorji et al, 2013;CaraDonna et al 2014;Wang et al 2014b). This is illustrated by Fig.…”