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Harvard Forest Symposium Abstract 2019

  • Title: Comparing the climate signal of annual radial growth and latewood Δ13C across four hardwood species in the Midwestern US
  • Primary Author: Justin Maxwell (Indiana University - Bloomington)
  • Additional Authors: Tessa Mandra (Harvard Forest); Neil Pederson (Harvard Forest)
  • Abstract:

    Tree rings are widely considered to be a reliable proxy record of variations in climate and soil moisture. Recently, studies have shown a deteriorating relationship between radial tree growth and soil moisture that is consistent across multiple species and locations in the Ohio River Valley, United States (US). Here, we examine the climate sensitivity of tree-ring Δ13Cisotopic data derived from the later half of annual growth rings from 1970­–2015 for multiple species across three locations in the Midwest US: Missouri, Indiana, and Michigan USA. We then compare the climate signal of intrinsic water use efficiency (iWUE) to standardized growth chronologies. We find that the deteriorating relationship between soil moisture and tree-growth exists at all three locations. The iWUE data show a similar weakening relationship with summer (June, July, and August) soil moisture at two sites. However, at one site iWUE has a consistent relationship through time with soil moisture. Summer maximum temperature and precipitation both had significant correlations with tree growth with a weaker relationship during the more recent period. For iWUE, maximum summer temperature was generally the strongest correlating climate variable with a consistent relationship through time. These findings provide an example of the benefit of using tree-ring isotopes to better represent the climate signal of trees. Further, these findings indicate that tree-growth and iWUE recorded by tree-rings can be responding to differ aspects of climate variability through time. More research is needed to understand how climate extremes will impact above ground carbon sequestration as radial growth alone represents an incomplete picture.

  • Research Category: Physiological Ecology, Population Dynamics, and Species Interactions; Historical and Retrospective Studies