CHANGES IN SNOWMELT DATE AND SUMMER PRECIPITATION AFFECT THE FLOWERING PHENOLOGY OF ERYTHRONIUM GRANDIFLORUM (GLACIER LILY; LILIACEAE)

Premise of the study : Climate change has affected species worldwide, including alterations in phenology, migration patterns, distribution, and survival. Because Erythronium grandiflorum is an early-season bloomer, alterations in its phenology may have serious implications for many North American Rocky Mountain communities, including changes in resource availability for pollinators and herbivores. Methods : We investigated whether changes in the snowmelt date, summer temperature, and summer precipitation have altered the timing and abundance of flowering in E. grandiflorum by collecting long-term data on floral abundance from 1975-2008 in a series of 2 x 2 m plots at the Rocky Mountain Biological Laboratory (RMBL) in Gothic, Colorado in the United States. Key results: Snowmelt date and mean summer temperature were negatively correlated. Over the 30-yr study, the snowmelt date advanced by 4.14 d/decade, and mean summer temperature increased by 0.38 degrees C/decade. Summer precipitation was variable, showing no change. The first, peak, and last flowering dates of E. grandiflorum advanced an average of 3.2 d/decade. Furthermore, earlier snowmelt and greater summer precipitation in the previous year led to earlier flowering in E. grandiflorum. There was no change in flowering abundance in this species, indicating it may be controlled by a complex set of abiotic and biotic variables. Conclusions : Our study indicates that snowmelt is arriving earlier at the RMBL, which has caused earlier flowering in E. grandiflorum. Because alterations in phenology can disrupt important ecological interactions, information on potential phenological shifts in species that interact with E. grandiflorum is essential in determining the net effect of climate-driven alterations in phenology.