Drivers of leaf-out phenology and their implications for species invasions: insights from Thoreau's Concord



This article is corrected by:

  1. Errata: Corrigendum Volume 202, Issue 4, 1413, Article first published online: 28 March 2014


  • To elucidate climate-driven changes in leaf-out phenology and their implications for species invasions, we observed and experimentally manipulated leaf out of invasive and native woody plants in Concord, MA, USA.
  • Using observations collected by Henry David Thoreau (1852–1860) and our own observations (2009–2013), we analyzed changes in leaf-out timing and sensitivity to temperature for 43 woody plant species. We experimentally tested winter chilling requirements of 50 species by exposing cut branches to warm indoor temperatures (22°C) during the winter and spring of 2013.
  • Woody species are now leafing out an average of 18 d earlier than they did in the 1850s, and are advancing at a rate of 5 ± 1 d °C−1. Functional groups differ significantly in the duration of chilling they require to leaf out: invasive shrubs generally have weaker chilling requirements than native shrubs and leaf out faster in the laboratory and earlier in the field; native trees have the strongest chilling requirements.
  • Our results suggest that invasive shrub species will continue to have a competitive advantage as the climate warms, because native plants are slower to respond to warming spring temperatures and, in the future, may not meet their chilling requirements.