WHAT DID THE 2010 EARLY CAREER AWARD ALLOW YOU TO DO?
I received a DOE Early Career Award to study how trees survive and die during drought. This question seems simple at first glance, yet at the beginning of my research period nobody was able to predict vegetation death.
Hence, the fundamental biological question remained: What controls the end of life of plants? This question was particularly relevant to DOE because vegetation plays a major role in the global carbon cycle.
The loss of plants that we are currently witnessing has, therefore, global impact. Without the ability to predict this change, scientists can largely overestimate terrestrial carbon storage because computer models are unable to exhibit the death of plants.
By the end of our work under the Early Career Award, we could predict vegetation mortality in the Southwestern U.S. with accuracy and we generated from those predictions global estimates of conifer tree loss. Based on these estimates, we expect few conifers to remain in the Southwestern U.S. by 2050, with subsequent large conifer loss throughout the northern hemisphere by 2100.
These results are insensitive to challenges associated with atmospheric CO2, landscape variation in mortality, etc. While generating these results, we learned a great deal about how trees die and survive under drought and heat. Ultimately, this research pointed us toward the uncertainties in this challenging carbon flux. While the evidence is now abundant that trees are dying faster than historically, and that this is driven at least in part by rising temperature, we still do not know where, how fast, and how much trees will die across much of the Earth. The consequences of increasing tree mortality are vast, including reductions in carbon storage and biodiversity.
Nathan McDowell is a staff scientist at the U.S. Department of Energy’s Pacific Northwest National Laboratory.
SUPPORTING THE DOE SC MISSION:
The Early Career Research Program provides financial support that is foundational to early career investigators, enabling them to define and direct independent research in areas important to DOE missions. The development of outstanding scientists and research leaders is of paramount importance to the Department of Energy Office of Science. By investing in the next generation of researchers, the Office of Science champions lifelong careers in discovery science.
For more information, please go to the Early Career Research Program.
THE 2010 PROJECT ABSTRACT:
An Integrated Theory on the Mechanisms of Vegetation Survival and Mortality During Drought
The goal of this project is to develop and test a new and improved theory that describes the mortality and survival of vegetation during drought. Research will focus on understanding the impacts of climate change on terrestrial ecosystems with an emphasis on regional scale vegetation mortality during droughts. In particular, the research will attempt to address three significant knowledge gaps, including: 1) improved understanding and resolution of controversy over the specific mechanisms of vegetative mortality, 2) understanding the variability in vegetation mortality that, for unknown reasons, is correlated to plant size and 3) the role of moisture versus temperature as mortality drivers during drought.
Research will use manipulative experiments to generate results and datasets that will be used to develop a new and improved mortality model that will be tested against independent field data. Vegetation will span a range from Arabidopsis to pine trees. Coordination with leading scientists in the molecular, ecological, and dynamic modeling fields will ensure maximum knowledge gain.
N.G. McDowell, A.P. Williams, C. Xu, W.T. Pockman, L.T. Dickman, S. Sevanto, R. Pangle, J. Limousin, J. Plaut, D. Scott Mackay, J. Ogee, J.C. Domec, C.D. Allen, R.A. Fisher, X. Jiang, J. Muss, D.D. Breshears, S. A. Rauscher, and C. Koven, “Multi-scale predictions of massive conifer mortality due to chronic temperature rise.” Nature Climate Change 6, 295 (2015). [DOI: 10.1038/NCLIMATE2873]
N. McDowell and C. Allen, “Darcy’s law predicts widespread forest loss due to climate warming.” Nature Climate Change 5, 669 (2015). [DOI: 10.1038/nclimate2641]
N. McDowell, C.D. Allne, K. Anderson-Teixeira, B.H. Audema, B. Bond-Lamberty, L. Chini, J.S. Clark, M. Dietze, C. Grossiord, A. Hanbury-Brown, G.C. Hurtt, R.B. Jackson, D.J. Johnson, L. Kueppers, J.W. Lichstein, K. Ogle, B. Poulter, T.A.M. Pugh, R. Seidl, M.G. Turner, M. Uriarte, A.P. Walker, and C.Xu, “Pervasive shifts in forest dynamics in a changing world.” Science, 368, 6494 (2020). [DOI: 10.1126/science.aaz9463]
Additional profiles of the 2010 Early Career Award winners can be found at https://www.energy.gov/science/listings/early-career-program.
The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit www.energy.gov/science.
Sandra Allen McLean is a Communications Specialist in the Office of Science, firstname.lastname@example.org.