US Forest Service Research & Development
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  • US Forest Service Research & Development
  • 1400 Independence Ave., SW
  • Washington, D.C. 20250-0003
  • 800-832-1355
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 Happy at treeline, collecting whitebark pine cores to study wood energy storage

Jessie M. Godfrey

Research Plant Physiologist
1221 South Main Street
United States

Phone: 510-847-7664
Contact Jessie M. Godfrey

Current Research

I am a postdoc working with Dr. Jeremy Pinto. Our Moscow-based seedling physiology lab is generally posing questions related to conditioning seedlings for ouptlanting in adverse conditions. Specifically, we are gathering data about the potential for nursery interventions like drought treatments and cold storage time or timing to impact wood anatomy, biochemistry (e.g. nonstructural carbohydrates), and physiology (e.g. photosynthesis and stem conductivity) in a way that increases outplanting success. Our overarching goal is to generate information which helps to guide nurseries producing seedlings for dry sites and/or grappling with shifting outplanting windows.

Research Interests

I am interested in the tree structures and functions that extend or define a tree's limits for abiotic stress, ideally joining tree physiology questions of utility that actively contribute to conservation decisions with the whimsical or nagging questions that build from previous work, a conversation, or a walk in the woods.

Past Research

My PhD was divided between two projects linked by living cells in the wood called xylem parenchyma cells. 

In the first project we examined the retrieval of sodium and chloride from the water conduits of pistachio saplings as these elements pass from soil solution through roots and stems and into leaves. This work contributed  to our understanding of how these trees achieve their exceptional salinity tolerance.

In the second project we examined the effects of climate on oaks (3 species) and conifers (12 species) between the hot dry foothills of California's Sierra Nevada and its cold wet treeline, measuring energy storage space in the wood and the seasonal dynamics of energy stored as sugar and starch (nonstructural carbohydrates). Our 72 study sites were randomly distributed within a transect that passes through Yosemite National Park and three adjacent National Forests (Stanislaus, Sierra, and Inyo). Our big questions were related to the influence of climate on our measurements and whether or not energy stored was spatially constrained by energy storage space (parenchyma volume).

As a capstone project for my PhD I led seven colleagues on an expedition up Alaska's haul road north of the Arctic Circle--the focus of the trip was to collect samples for nonstructural carbohydrate analysis as well as gas exchange and light quality data around white spruce canopies around the clock (every 3 hours for 3 days!) to study how trees at arctic treeline cope with continuous light on the solstice. Our big questions were related to how North America's northern-most conifers manage tasks of night like sugar export from their needles in the absence of night.

Why This Research is Important

Tree physiology provides tools for understanding the health of a seedling or a tree much like human physiological measurements like blood pressure provide insights about our own health. Tree physiology is particularly essential to forest health because 1) trees are long-lived 2) tree's can't pick up and move when they are exposed to adverse environmental conditions 3) environmental conditions change not only as we might expect them to from place to place or season to season, but also year to year or century to century 4) environmental conditions are changing especially quickly in the anthropocene 5) tree physiology is the fastest, cheapest way we have of asking a tree how it's doing--there is no "please rate your pain on a scale of 1-10" option there are only physiological measurements like water potential (a measure of drought stress). Much like a human, once a tree is showing visible signs of illness or stress some damage has already occurred.

Also much like a human, the care a tree (seedling) receives early in its life may determine its physiological outcome or even its survival later on. There are loads of questions waiting to be asked about modifications to nursery practice that might improve outplanting success. The answers to these questions are important because nurseries are so critical to natural resource management. Following a disturbance, seedlings are our best tool for advancing the speed at which we can restore the productivity of a landscape and the ecosystem services it provides (e.g. wildlife habitat and water treatment).


  • University of California, Davis, Phd Tree Physiology Horticulture and Agronomy Graduate Group 2019
  • University of California, San Diego, Bachelor Of Science Ecology, Behavior and Evolution (Major) International Studies (Minor) 2008

Professional Experience

  • Owner/ Head Gardener, Godfrey Gardens
    2011 - 2012
  • Agroforestry Extension Specialist, U.S. Peace Corps
    2008 - 2010

Last updated on : 06/10/2021