Minor changes in temperature within montane meadow ecosystems can elicit major responses by flowering plants that provide critical nectar sources to pollinators. These changes can be manifested in terms of phenology, growth patterns, nectar characteristics, or reproduction. We evaluated the responses to experimental warming (timing of flowering, annual height, frost-killed buds, and nectar characteristics) of two dominant flowering plant species in a montane meadow ecosystem in the Rocky Mountains USA. The two forb species included arrowleaf balsamroot (Balsamorhiza sagitatta), an early-season, large-leafed species, and buckwheat (Eriogonum umbellatum), a late-season, small-leaved, semi-woody species. These two forbs are both important to pollinator and nectar-using animal communities and are widely distributed and locally abundant in Western N. America. We used open-sided chambers with a roof of clear polyethylene slats to experimentally increase temperatures. Plant responses were evaluated in plots with and without open-sided chambers.
Results/Conclusions
Warming chambers increased daily minimum temperatures of plant and soil surfaces by approximately 2°C. Warming treatments increased heights of B. sagittata by 20%, reduced frost-killed buds, decreased nectar volume, and increased recruitment of seedlings. Warming had no effects on height in E. umbellatum or seedling recruitment, but it decreased nectar volume and increased sugar concentration of the nectar. Neither species showed changes in timing of flowering. These data suggest that small changes in temperature during critical parts of the growing season may result in changes in plant growth and reproduction as well as the characteristics of the nectar resources available to pollinators in montane meadow ecosystems.