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Harvard Forest Research Project 2022

  • Title: Reaction Wood Tradeoffs: Field Study
  • Principal investigator: Sophie Everbach (severbach@g.harvard.edu)
  • Institution: Harvard University
  • Primary contact: Sophie Everbach (severbach@g.harvard.edu)
  • Team members: Michele Holbrook
  • Abstract:

    Trees are always on the hunt for light. The variety of growth forms seen in the forest is a testament to this photic need; individuals differentially find, occupy, and maintain branches in available light gaps despite the mechanical stressors of gravity and wind. A tree’s structural ability to respond to mechanical stress, while also balancing hydraulic efficiency and resistance to cavitation is therefore key to its resource acquisition success and survival. Yet these mechanical-hydraulic-cavitation tradeoffs are not well understood in reaction wood, a set of tissues that forms in response to mechanical stress. My goal is to characterize the distribution, hydraulic conductance, and cavitation resistance of these stress-modified woods to better understand the biological costs of maintaining productive foraging growth behaviors in forests battling drought, severe storm winds, and other disturbance conditions that have been intensified under global climate change.
    While the development of stress-modified woods is what allows trees to successfully forage for light, the percentage and placement of these woods could greatly impact branch hydraulic capacity. I will determine the amount and distribution of tension wood (TW), the modified wood formed in angiosperms in response to gravity, within mature Acer rubrum and Quercus rubra individuals at Harvard Forest to frame the rest of my TW findings on an organismal level. Through whole-branch sampling and branch increment coring, this work will quantify how much of a branch is composed of TW, if branch angle effects TW density, and where in the branch TW may impact hydraulic conductivity.