Understanding Water and Carbon Dynamics for Improved Prediction of Tropical Tree Function and Demographics

Authors

Nate McDowell¹*([email protected]), Alexandria Pivovaroff², Mizanur Rahman¹, Alfonso Zambrano³, Joe Wright³, Bruno Gimenez⁴, Cristina Santos da Silva⁴, Valdiek da Silva Menezes⁴, Gustavo Spanner⁴, Regison Oliveira⁴, Jeff Warren⁵, Niro Higuchi⁴, Jeffrey Chambers⁶

Institutions

¹Pacific Northwest National Laboratory, Richland, WA; ²Occidental College, Los Angeles, CA; ³Smithsonian Tropical Research Institute, Gamboa, Panama; ⁴National Institute for Amazonian Research, Manaus, Brazil; ⁵Oak Ridge National Laboratory, Oak Ridge, TN; ⁶Lawrence Berkeley National Laboratory, Berkeley, CA

URLs

• https://ngee-tropics.lbl.gov/

Abstract

Understanding and modeling the carbon and water fluxes and stores of tropical trees is critical for improving predictive capacity for forest function under a changing climate. This study investigated the processes regulating plant carbon and water balance in Panama and Brazil with the goals of testing hypotheses and providing parameterization and benchmarking datasets for FATES-Hydro. Resilience of tropical forests to climate perturbations appears to be decreasing globally, with plant hydraulics playing a large role in regulating this resilience.

Hydraulic constraints on photosynthesis become increasingly dependent on vapor pressure deficit as drought worsens, leading to novel constraints on canopy gas exchange. Hydraulic traits and mortality exhibit large shifts over time at Barro Colorado Island, Panama, consistent with climate-driven changes in the most adaptive physiological characteristics. Such shifts in hydraulic traits are also observed over a large precipitation gradient in Panama, suggesting that climate drives adaptive changes in hydraulic traits. Current work is focused on providing sapflow estimates of transpiration along with additional measurements for further tests of the hydraulic mechanisms underlying survival and mortality. This work is ongoing in both Panama and Brazil. ModEx linkages to FATES-Hydro are direct through parameterization and benchmarking of the model, along with conceptual knowledge gains that are incorporated into the model.