EGU2020-20157
https://doi.org/10.5194/egusphere-egu2020-20157
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reduced tree growth in the semiarid United States due to asymmetric responses to intensifying precipitation extremes

Matthew Dannenberg1, Erika Wise2, and William Smith3
Matthew Dannenberg et al.
  • 1Dept. of Geographical and Sustainability Sciences, University of Iowa, Iowa City IA 52242, United States of America (matthew-dannenberg@uiowa.edu)
  • 2Dept. of Geography, University of North Carolina, Chapel Hill NC 27599, United States
  • 3School of Natural Resources and the Environment, University of Arizona, Tucson AZ 85721, United States

Earth’s hydroclimatic variability is increasing, with changes in the frequency of extreme events that may negatively affect forest ecosystems. We examined possible consequences of changing precipitation variability using tree rings in the conterminous U.S. While many growth records showed either little evidence of precipitation limitation or linear relationships to precipitation, growth of some species (particularly those in semiarid regions) responded asymmetrically to precipitation, such that tree growth reductions during dry years were greater than, and not compensated by, increases during wet years. The U.S. Southwest in particular showed both a large increase in precipitation variability coupled with asymmetric responses of growth to precipitation. Simulations suggested roughly a two-fold increase in the probability of large negative growth anomalies across the Southwest resulting solely from 20th century increases in the variability of cool-season precipitation. Models project continued increases in precipitation variability, portending future growth reductions across semiarid forests of the western U.S.

How to cite: Dannenberg, M., Wise, E., and Smith, W.: Reduced tree growth in the semiarid United States due to asymmetric responses to intensifying precipitation extremes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20157, https://doi.org/10.5194/egusphere-egu2020-20157, 2020

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Display material version 1 – uploaded on 03 May 2020
  • AC1: Comment on EGU2020-20157, Matthew Dannenberg, 05 May 2020

    Vincent Humphrey had a good question in chat that I couldn't get to before my time was up: "Do you also identify such asymmetries when using water storage observations (soil moisture, terrestrial water storage) instead of precipitation amounts?"

    I think that this is pretty likely. The asymmetric response of growth to precipitation is likely some combination of nonlinear responses of soil moisture to precipitation and nonlinear responses of tree physiology to soil moisture. We didn't specifically examine the mechanism in this study, but we're currently working on some additional analyses (including both modeling experiments and precipitation exclusion experiments) to try to figure it out.