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Hydroclimatic relationships and stable isotopic analysis in baldcypress tree rings

Published Article

United States

Publication date: October 25, 2025

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Instrumental climate records are too short to capture long‑term hydroclimatic extremes, making new paleoproxies essential. This study evaluates δ18O in baldcypress latewood from the Choctawhatchee River Basin as an indicator of southeastern U.S. drought, pluvial events and tropical‑cyclone rainfall. Tree‑ring δ18O showed strong correlations with precipitation, streamflow, drought indices and summer temperature, with major depletions reflecting tropical‑cyclone rainfall. Compared with longleaf pine, baldcypress δ18O was more sensitive to drought, highlighting its value for multivariate climate reconstructions. Findings demonstrate the promise of baldcypress δ18O as a powerful proxy for understanding past hydroclimatic extremes and improving future risk assessments.

Subject Tags

  • Climate resilience
  • Forest
  • Climate impacts

Abstract

Instrumental records of hydroclimatic extremes (e.g., drought, pluvial flooding, tropical cyclones) are temporally and spatially limited, making long-term assessments of the drivers of these events difficult. Paleo-reconstructions of these extreme events are therefore essential in understanding and evaluating future risk, especially within vulnerable coastal communities. In dendrochronology, δ18O (18O/16O) is a known proxy for reconstructing various hydroclimatic parameters (i.e., temperature, atmospheric humidity, streamflow). The tree takes up δ18O in source water for the development of woody tissue, with the isotopic ratio stored within the α-cellulose of annual tree rings. However, cellulose-derived δ18O from baldcypress (Taxodium distichum), the longest-lived species in the region, has never been investigated in studies of hydroclimate. In this exploratory study, we evaluate the use of δ18O-depletion in baldcypress latewood as a proxy for various southeastern hydroclimatic extremes to the comparable instrumental period. Results of baldcypress latewood δ18O over the Choctawhatchee River Basin were then compared to various climate indices and the instrumental tropical cyclone record, with correlations of varying strength expressed between the produced δ18O time series and precipitation, streamflow, self-calibrated Palmer Drought Severity Index, and maximum summer temperature. Large decreases in baldcypress δ18O latewood are determined to be reflective of regional TC precipitation. In direct interspecies comparisons, baldcypress δ18O is shown to be more sensitive to drought conditions than nearby longleaf pine (Pinus palustris) δ18O. Results of these comparisons reveal the future potential of the proxy in multivariate climate reconstructions.

Citation

Friedman, J. M., Elliott, E. A., Tucker, C. S., Bregy, J. C., Therrell, M. D., & Pearl, J. K. (2025). Hydroclimatic relationships and stable isotopic analysis in baldcypress tree rings. Science of the total environment, 1001, 180392. https://doi.org/10.1016/j.scitotenv.2025.180392

TNC Authors