Variation in timing and abundance of flowering by Delphinium barbeyi Huth (Ranunculaceae): the roles of snowpack, frost, and La Niña, in the context of climate change

Abstract

Delphinium barbeyi is a common herbaceous wildflower in montane meadows at 2,900 m near the Rocky Mountain Biological Laboratory, and its flowers are important nectar resources for bumblebees and hummingbirds. During the period 1977-1999 flowering was highly variable in both timing (date of first flower ranged from 5 July to 6 August, mean=17 July) and abundance (maximum open flowers per 2×2-m plot ranged from 11.3 to 197.9, mean=82). Time and abundance of flowering are highly correlated with the previous winter's snowpack, as measured by the amount of snow remaining on the ground on 15 May (range 0-185 cm, mean=67.1). We used structural equation modeling to investigate relationships among snowpack, first date of bare ground, first date of flowering, number of inflorescences produced, and peak number of flowers, all of which are significantly correlated with each other. Snowpack depth on 15 May is a significant predictor of the first date of bare ground (R =0.872), which in turn is a significant predictor of the first date of flowering (R=0.858); snowpack depth is also significantly correlated with number of inflorescences produced (R =0.713). Both the number of inflorescences and mean date of first flowering are significant predictors of flowers produced (but with no residual effect of snowpack). Part of the effect of snowpack on flowering may be mediated through an increased probability of frost damage in years with lower snowpack - the frequency of early-season "frost events" explained a significant proportion of the variance in the number of flowers per stem. There is significant reduction of flower production in La Niña episodes. The variation in number of flowers we have observed is likely to affect the pollination, mating system, and demography of the species. Through its effect on snowpack, frost events, and their interaction, climate change may influence all of these variables.

Landscape genetics of alpine-snowbed plants: comparisons along geographic and snowmelt gradients

“…In addition, breeding system of individual species may be important to understand the relationship between landscape features and spatial pattern of genetic variation, although further studies are needed (see Ingvarsson and Giles, 1999). Recently, the effects of global climate change on alpine ecosystems have raised concerns not only from the viewpoint of vegetational change over the geographic range (eg Grabherr et al, 1994) but also the reproductive characteristics of individual species (Inouye and McGuire, 1991;Inouye et al, 2002). If global temperature changes alter snowmelt patterns in alpine regions, the flowering phenology of alpine plants will be highly influenced, resulting in changes in patterns of gene flow and/or the intensity of selective forces and thus the spatial pattern of genetic variation.…”

Habitat‐specific responses in the flowering phenology and seed set of alpine plants to climate variation: implications for global‐change impacts

“…Acceleration of snowmelt time often decrease the survival, growth and reproductive activity of alpine plants in the early-melt habitat when early exposure from the protection by snow-cover enhances the risk of frost damage and water stress for plants (Walker et al 1995;Inouye et al 2002;Saavedra et al 2003). It is reported that an evergreen cushion plant Diapensia lapponica abruptly decreased the biomass by 22% and the flower production by 55% due to frost damage caused by the extremely early snowmelt during the last three years in the early-melt habitat, while plants in the late-melt habitat had little or no damage in the subarctic alpine of northern Sweden (Molau 1996).…”

Coevolutionary Dynamics and the Conservation of Mutualisms

“…However, we can offer one suggestion of a likely situation in which such a development may have already started. It has recently been shown that elevated CO 2 levels and global warming can alter flowering phenology and flower nectar volumes in certain plant species (Erhardt and Rusterholz 1997;Ahas et al 2002;Fitter and Fitter 2002;Inouye et al 2002;Dunne et al 2003). Phenologies of different species appear to be shifting to different degrees, and in different directions: for example, Fitter and Fitter (2002) report that while 16% of British flowering plants are flowering significantly earlier than in previous decades (with an average advancement of 15 days in a decade), another 3% of species are flowering significantly later than they once did.…”