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Harvard Forest Symposium Abstract 2008

  • Title: Phenological Differences Within a Forest Community of Woody Species: A Case Study Using the Long-term Harvard Forest Records
  • Primary Author: Andrew Richardson (Northern Arizona University)
  • Additional Authors: John O'Keefe (Harvard Forest)
  • Abstract:

    The timing of phenological events varies both among species, and also among individuals of the same species. Here we use a 12+ year record (data available at of spring and autumn phenology for 33 woody species at the Harvard Forest to investigate these differences. Specifically, we focus on patterns of budburst, leaf expansion, leaf coloration and leaf fall, in the context of differences between canopy and understory species, and between canopy and understory individuals of the same species. Many understory species appear to adopt a strategy of “phenological escape” in spring but not autumn, taking advantage of the high-light period in spring before canopy development. Relationships between canopy and understory conspecifics varied among species, with budburst and leaf fall being earlier in understory individuals of some species, but later in other species. We fit standard models of varying complexity to the bud-burst time series for each species to investigate whether biological responses to environmental cues differed among species. While there was no clear consensus model, Akaike’s Information Criterion (AIC) indicated that a simple two-parameter “Spring warming” model was best supported by the data for more than a third of all species, and well supported by the data for two-thirds of all species. More highly-parameterized models involving various chilling requirements (e.g., Alternating, Parallel or Sequential chilling) were less well supported by the data. Species-specific model parameterization suggested that responses to both chilling and forcing temperatures vary among species. While there were no obvious differences in this regard between canopy and understory species, or between early- and late-budburst species, these results imply that species can be expected to differ in their responses to anticipated future climate change.

  • Research Category: Physiological Ecology, Population Dynamics, and Species Interactions