2024 Abstracts

Linking Function and Life History Strategy to Soil Water Access in Panamanian Forests


Jeffrey Warren1* (warrenjm@ornl.gov), Cynthia Wright2, Rutuja Chitra-Tarak3, Alex Neild1, Alfonso Zambrano4, Nate McDowell5, Robinson Negron-Juarez6, Chonggang Xu3, Joe Wright4, Jeffrey Chambers6,7


1Oak Ridge National Laboratory, Oak Ridge, TN; 2USDA Forest Service, Knoxville, TN; 3Los Alamos National Laboratory, Los Alamos, NM; 4Smithsonian Tropical Research Institute, Panama City, Panama; 5Pacific Northwest National Laboratory, Richland, WA; 6Lawrence Berkeley National Laboratory, Berkeley, CA; 7University of California–Berkeley, CA



Soil water potential and effective root water sourcing depth are key factors that determine the availability of soil water to plants. Plant water uptake is further controlled by edaphic and environmental conditions and root, hydraulic, and stomatal characteristics that vary with plant-water use strategies. Understanding this variation is central to assessing vegetation responses to drought. Stable isotopes of water (δ18O and δ2H) can be powerful tracers to investigate effective tree rooting depth when combined with site- and species-specific information. Yet, such studies are limited in the humid tropics due to logistics and difficulty in timing water isotope sampling, which needs to occur during a significant dry-down period that allows evaporative isotopic separation of water within the soil profile. Furthermore, foundational studies conducted in the tropics have generally relied on only one isotope tracer, thereby limiting Bayesian and other mixing-model frameworks aimed at quantifying source water contributions. Here, the team reports findings on differential plant-water sourcing depths based on δ18O and δ2H, stem δ13C, and soil and plant water dynamics. These data were collected in 2022 from tree species with a range of ecological strategies and plant functional types at two forest sites in Panama: Parque Natural Metropolitano (PNM) and Barro Colorado Island, which include a range of growth-survival and stature-recruitment trade-off strategies. Data are being applied to test an inverse rooting model and results used to inform the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), FATES-Hydro land models, and their simulations of tropical forest response to drought. In 2023 to 2024, there was a major El Niño-Southern Oscillation (ENSO) event that affected the neotropics, and additional samples were collected in PNM, the typically wetter San Lorenzo site in Panama, and the ZF2 Research Forest in Brazil. Preliminary data from the ENSO will also be presented.