Advancing Model Predictions of Tropical Forest Response to Droughts

Authors

Rutuja Chitra-Tarak¹* ([email protected]), Jeffrey Warren², Chonggang Xu¹, Cynthia Wright³, Zachary Robbins¹, Nate McDowell⁴, Joe Wright⁵, Robinson Negron-Juarez⁶, Adam Collins¹, Stuart Davies⁵, Daniel Zuleta⁵, Alfonso Zambrano⁵, Niro Higuchi⁷, Charles Koven⁶, Jeffrey Chambers^6,8

Institutions

¹Los Alamos National Laboratory, Los Alamos, NM; ²Oak Ridge National Laboratory, Oak Ridge, TN; ³USDA Forest Service, Washington, DC; ⁴Pacific Northwest National Laboratory, Richland, WA; ⁵Smithsonian Tropical Research Institute, Washington, DC; ⁶Lawrence Berkeley National Laboratory, Berkeley, CA; ⁷National Institute of Amazonian Research, Manaus, Amazonas, Brazil; ⁸University of California–Berkeley, CA

URLs

https://ngee-tropics.lbl.gov

Abstract

In a demonstration of model-experiment (ModEx) success, the Next-Generation Ecosystem Experiments (NGEE) Tropics project is using diverse co-located datasets to advance understanding of tropical forest function and the predictive ability of global vegetation models. For example, via a complex data-model integration in Panama, the team found that if vegetation demography models (VDMs) are to correctly represent drought resilience of tropical forests, they must account for trees’ rooting depths (drought avoidance) and not merely hydraulic vulnerability traits (drought resistance). Researchers found that deeper-rooted tree species were more hydraulically vulnerable but survived through several droughts compared to shallow-rooted trees. Thus, without accounting for rooting depths, VDMs would kill the wrong plant functional types, leading to misleading predictions of changes in forest function.

The large set of co-located measurements collected by NGEE Tropics—from hydrology and tree demography to water-sourcing depths, hydraulic traits, and other carbon- and water-related responses across sites in Brazil and Panama—are being used for DOE’s E3SM–Functionally Assembled Terrestrial Ecosystem Simulator (E3SM-FATES; -Hydro) model improvements. Here, the team summarizes current and planned hypotheses tests to quantify whole-plant drought resilience strategies and their coordination with other stress axes (light, nutrients, heat, fire) across representative pantropical forest communities along climatic, edaphic, water table, and disturbance gradients. This will enable representation of the true diversity and resilience of tropical forest response and feedback to carbon dioxide, climatic, and land-use change in E3SM.