Future Climate Doubles the Risk of Hydraulic Failure in a Wet Tropical Forest
Authors
Zachary Robbins1* (zjrobbins@lanl.gov), Jeffrey Chambers2,6, Rutuja Chitra-Tarak1, Bradley Christoffersen3, Turin Dickman1, Rosie Fisher4, Alex Jonko1, Lara Kueppers2, Charles Koven2, Nate McDowell5, Ryan Knox2, Chonggang Xu1
Institutions
1Los Alamos National Laboratory, Los Alamos, NM; 2Lawrence Berkeley National Laboratory, Berkeley, CA; 3The University of Texas of Rio Grande Valley, Edinburg, TX; 4CICERO Centre for International Climate Research, Oslo, Norway; 5Pacific Northwest National Laboratory, Richland, WA; 6University of California–Berkeley, CA
URLs
Abstract
Global changes drive conflicting responses in forest biomass, with rising carbon dioxide (CO2) increasing productivity while rising vapor pressure deficit increases tree mortality. The net effect of these drivers is poorly understood, particularly in tropical forests. Hydraulic traits and water use strategies are critical in determining mortality risk under climate change. In this study, the team used a dynamic vegetation model with plant hydrodynamics (Functionally Assembled Terrestrial Ecosystem Simulator–Hydro) to simulate the response of gross primary productivity and hydraulic failure to future climate in a wet tropical forest. Researchers calibrated the model for Barro Colorado Island in Panama and selected plant trait ensemble members that performed well against observations. Selected members were run with temperature and precipitation anomalies from Coupled Model Intercomparison Project Phase 6 models for two greenhouse gas emission scenarios (SSP2-45 and SSP5-85) and two CO2 levels (contemporary and anticipated). The simulations project productivity increases by 22% under SSP2-4.5 and by ~48% under SSP5-8.5. In simulations where CO2 is held at contemporary levels, productivity decreases by ~25% under both scenarios in 2100. The risk of hydraulic failure increased from 4% to ~10% under each climate scenario, with or without elevated CO2. The team further analyzed the variance in productivity, evapotranspiration, and hydraulic failure due to climate scenarios, CO2, and plant traits. Results suggest that rising mortality rates through hydraulic failure may offset increases in future productivity due to increasing CO2 levels.