Effects of Snowpack on Timing and Abundance of Flowering in Delphinium nelsonii (Ranunculaceae): Implications for Climate Change

Abstract

Delphinium nelsonii is an early-blooming herbaceous perennial of montane western North America, which we studied in dry subalpine meadows in the Colorado Rocky Mountains. We examined the effects of variation in annual snowfall between 1973 and 1989 on the timing and abundance of flowering. During years of lower snow accumulation, D. nelsonii plants experienced colder temperatures between the period of snowmelt and flowering. Also, flowering was delayed, floral production was lower, and flowering curves were more negatively skewed; damage during floral development probably occurred in years of low snowfall. If climate change results in decreased mean annual snowfall for the Rocky Mountains, then the seed production of D. nelsonii will probably be adversely affected. Decreased snowfall may also indirectly lower the seed production of later-blooming species by decreasing populations of bumblebees and hummingbirds that forage on D. nelsonii flowers. Decreased snowfall has the potential to reduce the number and relative proportions of species in the herbaceous flora in our study area.