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Harvard Forest Symposium Abstract 2017

• Title: Timing and local water balance regulate drought impacts on the temperate forest carbon sink
• Primary Author: Loic D'Orangeville (University of New Brunswick)
• Additional Authors: Daniel Bishop (Harvard Forest); Shawn Fraver (University of Maine); Neil Pederson (Harvard Forest); Richard Phillips (Indiana University - Bloomington); Christine Rollinson (Oberlin College)
• Abstract:

  Loïc D’Orangeville, Indiana University, Bloomington, IN, loicdorangeville@gmail.com
  
  Justin Maxwell, Indiana University, Bloomington, IN, maxweljt@indiana.edu
  
  Daniel Kneeshaw, Université du Québec à Montréal, Montreal, Canada, kneeshaw.daniel@gmail.com
  
  Neil Pederson, Harvard Forest, Harvard University, Petersham, MA, neilpederson@fas.harvard.edu
  
  Louis Duchesne, Ministère des Forêts, Montreal, Canada, Louis.Duchesne@mffp.gouv.qc.ca
  
  Travis Logan, Ouranos, Montreal, Canada, logan.travis@ouranos.ca
  
  Daniel Houle, Ministère des Forêts, Montreal, Canada, Daniel.Houle@mffp.gouv.qc.ca
  
  Dominique Arseneault, Université du Québec à Rimouski, Rimouski, Canada, dominique_arseneault@uqar.ca
  
  Colin M Beier, State University of New York College of Environmental Science and Forestry, Syracuse, NY, cbeier@esf.edu
  
  Daniel A. Bishop, Lamont-Doherty Earth Observatory, Palisade, NY, dbishop@fas.harvard.edu
  
  Daniel Druckenbrod, Rider University, Rider, NJ, ddruckenbrod@rider.edu
  
  Shawn Fraver, University of Maine, Bangor, ME, shawn.fraver@maine.edu
  
  François Girard, Université de Montréal, Montreal, Canada, francois.girard@umontreal.ca
  
  Joshua Halman, University of Vermont, Burlington, VT, joshua.halman@vermont.gov
  
  Chris Hanson, University of Vermont, Burlington, VT
  
  Justin L. Hart, University of Alabama, Tuscaloosa, hart013@ua.edu
  
  Henrik Hartmann, Max Planck Institute for Biogeochemistry, Jena, Germany, hhart@bgc-jena.mpg.de
  
  Margot Kaye, Pennsylvania State University, Happy Valley, PA, mwk12@psu.edu,
  
  David Leblanc, Ball State University, Muncie, IN, dleblanc@bsu.edu
  
  Stefano Manzoni, Stockholm University, Stockholm, Sweden, stefano.manzoni@natgeo.su.se
  
  Shelly Rayback, University of Vermont, Burlington, VT, Shelly.Rayback@uvm.edu
  
  Christie Rollinson, Pennsylvania State University, Happy Valley, PA, crollinson@mortonarb.org
  Richard P. Phillips, Indiana University, Bloomington, IN, rpp6@indiana.edu
  
  
  
  Drought can have a significant impact on the terrestrial carbon sink. While theory suggests that the specific hydraulic traits of dominant tree species can determine how forests respond to drought, some evidence suggests environmental drivers might be at in determining forest sensitivity. To test these ideas, we used a network of 10,753 trees across much of the mesic temperate biome of eastern North America (ENA) to determine what might drive the growth of trees. Importantly, our network is composed of 24 species, 452 populations, and collections of trees that might be more representative of the forest in which they grow compared to most studies conducted at this spatial scale. We found that mean evaporative pressure and the timing of drought are stronger drivers of drought sensitivity than soils, stand characteristics, or plant traits across species, time, and space. June is critical over the latitudinal gradient of our network, matching the seasonality of radial growth. Further, trees growing on drier sites (defined by their high summer evapotranspiration, PE) experienced the largest growth reductions during drought. If projected increases in PE increase forest sensitivity to drought, the gross C uptake of ENA’s temperate forest might decline by 5.2-8.2% annually. This increased sensitivity might overwhelm potential benefits of longer growing seasons, land use, rising atmospheric CO2, or nitrogen fertilization.

• Research Category: Regional Studies
  International Research Projects
  Historical and Retrospective Studies
  Forest-Atmosphere Exchange
  Conservation and Management